project presettable digital timer(down counter)

Fred, nice job.

Was this a college project that you had hanging around ?

I think everyone who went to school in the 60's and 70's did this type of thing.

Brings back memories of long nights with graph paper and timing charts.

Donald

The timer is complicated because for the seconds count it has to rollover to 59 instead of 99 and the 74LS192 is difficult to work with from that perspective, but the timing is easy at 1Hz. The trick is to activate the 10's digit counter /LOAD when its /BORROW is low on the rising edge of the 1's digit CTR CLK, and to maintain /LOAD active past the 1's digit counter /BORROW rising edge which is used to clock it, ensuring minimum /LOAD pulsewidths are met and the load operation is clean. The LCE does this by waiting for the coincidence of 10's CTR /BORROW and 1's CTR CLK high state, which means the CTR's are due to transition out of the 00 state. It then activates the 10's CTR /LOAD so that '5' propagates into the 10's digit, which causes 10's CTR /BORROW into high state. The high state on 10's /BORROW enables the AND gate to pass the high 1's CTR CLK. This forces the 1's CTR /BORROW into the high state and decrements the 1's CTR simultaneously. The LCE sense 1's CTR /BORROW high and removes the 10'S CTR /LOAD about three gate delays later (NAND+OR+NAND in the LCE), ensuring that the positive going edge on its CLK due to 1's /BORROW does not corrupt the '5' that has just been /LOAD'ed. From this time on the CTR's operate as simple decade counter cascade as the manufacturer intended until the next 00 state. This operation is not required for the minutes counters. The minutes

10's CTR /BORROW low state indicates that the whole CTR group is in state 00:00 and CLK is low, so it's time to STOP. This is done by using 10's minutes /BORROW to zero the seconds CLK input AND gate, stopping the down count while the CLK is still in the low state. This situation must be adjusted when you go to set the timer for another count because the DOWN input must be high to enable the individual UP counts, hence the other signals from the SSSE module. Just to give an idea of what you're up against, I have included the schematic of presettable down counter with range from 1 second to 99 minutes and 99 seconds. Press START, it counts down, and then shuts off. To set it, press STOP/SET, and then press the UP switches for each digit in the display. Press START to begin the countdown. The timebase is a 32.768KHz oscillator using the 74HCT4060 14-stage binary counter with oscillator section. It is best to maintain consistency and use 74LS parts throughout. If you want to time in 100th's of seconds, then the oscillator has to be changed to a 200Hz frequency, remove the LCE from the SDC, make it identical to the MDC in other words, the counters will roll over to 99, and change the display colon to a decimal point. View in a fixed-width font such as Courier.

. . COUNTDOWN TIMER . . MINS SECS . ------------------------------------------ . | ---- ---- ---- ---- | . | | | | | | | | | | . | | | | | O | | | | | . | ---- ---- ---- ---- | . | | | | | O | | | | | . | | | | | | | | | | . | ---- ---- ---- ---- | . ------------------------------------------ . | | | | . /4 / 4 /4 /4 . | | | | . \\---------\\----. \\---------\\----------, . | | . ,---------------------------------. | . | | | | . | .-------------------------------------------------, . | | | | | | . | | | | | | . | | ----MDC----- | | ----SDC----- | | . +------|-|CLR -----| | '--|CLR -----| | | . | | | BO10M|---. | BO10S|------+ . --- .--|-|UP1M | | | .-------|UP1S | | | . /// | | | | | | | | | | | . |.-|-|UP10M | | | |.------|UP10S | | | . || | | | | | || | | | | . || '-|CLKM MIN1S|/| | || .-|CLKS SEC1S|/| | . || |--- | | | || | |--- | | | . || .-|CLK MIN10|/ | || .---|CLK SEC10|/ | . || | ------------ | || | | ------------ | . ||--- | || | | -----74LS00----- | . ||/// | || | | | | | . -SSE-- || | || | | | __ / |---' . | | || | || | | / |------o G2| . | ___| || | || | '--o G1| \\__|---. . | CLK|--------------------------------' \\__|-- | . | | || | || | | | | . | CLK|--------------------------------------| \\ | | | . | ___| || | || |G3 o------| \\ | . | SSR|-. || --TSE--- '------------|__/ | |G4 o--' . | | | || | | || | +----|__/ | . ------ | '--------|UPMIN1S | || | | | . | | | | || ----------------- . | '-------|UPMIN10S| || | . | | | || | . | | UPSEC1S|------'| | . | | | | | . | |UPSEC10S|-------' | . | -------- | . '------------------------------------------' . . . . . ****************** LOGIC MODULES ****************************** . . . . . . . . (SSSE) . . -----------------START/STOP/SET ELEMENT----------------- . | | . | VCC | . | | | . | +----------------------+ | . | | | | . | o o | . | -| STOP/SET -| START | . | o 74LS14 o 74LS14 | . | | |\\ | |\\ | . | +-[560]-+-| o-+ +-[560]-+-| o-+ | . | | +| |/ | | +| |/ | | . | [330] === | [330] === | | . | | 100u| | | 100u| | | . | +-------+ | +-------+ | | . | | | | | | . | --- | --- | | . | /// | /// | | . | | | | . | +--------------------------------------+ | . | | | |___ . | | +--+----------------------------------|SSR . | | VCC | | . | | | | | . | | +--------|-------------------------+ | . | | | | | | . | | | | | | . | | | | | | . | | | -------------------74LS112-------------- | . | | | | | | | | . | | | | +--------+ +--------+ | | . | | | | | --- | | --- | | | . | | | | | PRE | | PRE | | |--- . | | +--|-|J Q |---+ +--------|J Q |---|--|CLK . | | | | |-- | | | |-- | | | . | | +--|-|CK | | | +--|CK | | | . | | | | | FF1 | | | | | FF2 | | | . | | | | | - | | | | | - | | | . | | +--|-|K Q |-+ | | +-----|K Q |---|--|CLK . | | | | | --- | | | | | | | --- | | | . | | | | | CLR | | | | | | | CLR | | | . | | | | +--------+ | | | | | +--------+ | | . | | | | | | | | | | | | | . | | | ---------------------------------------- | . | | | | | | | | | | | . | | +--------|------------+--+ | | | . | | | | | | | | . | +------------+ +------------------+ | . | | | | . | | | | . | | | | . | ------------- | | . | +----| RESET | | | . | | | | | | . | ----- | 2HZ 0SC | | | . | 32.768K | 32.768KHZ | | | . | ----- | XYSTAL | | | . | | | | | | . | +----| Q14|--+ | . | | | | . | --74HCT4060-- | . | | . | | . | | . -------------------------------------------------------- . . . (TSE) . . ---------------------TIMER SET ELEMENT--------------- . | VCC VCC | . | | | | . | | | | . | | | | . | o o | . | -| SWSEC1S -| SWSEC10S | . | o 74LS14 o 74LS14 | . | | |\\ | |\\ | . | +-[560]-+-| o---+ +-[560]-+-| o-----|UPSEC10 . | | +| |/ | | +| |/ | . | [330] === | [330] === | . | | 100u| | | 100u| | . | +-------+ | +-------+ | . | | | | | . | --- | --- | . | /// | /// | . | +-------------------------------|UPSEC1S . | | . | | . | +-------------------------------|UPMIN1S . | | | . | | | . | VCC | VCC | . | | | | | . | | | | | . | | | | | . | o | o | . | -| SWMIN1S | -| SWMIN10S | . | o 74LS14 | o 74LS14 | . | | |\\ | | |\\ | . | +-[560]-+-| o---+ +-[560]-+-| o-----|UPMIN10 . | | +| |/ | +| |/ | . | [330] === [330] === | . | | 100u| | 100u| | . | +-------+ +-------+ | . | | | | . | --- --- | . | /// /// | . ----------------------------------------------------- . . . . (SDC) . . -----------------SECONDS DOWN COUNTER-------------- . | |----- . | +-------------------------|BO10S . | | | . | +---------------------------------------------+ | . | | | | | . | | -----PDCE----- | ------LCE------ | | . | | | ---| | |--- ---- | | | . | | | BO1|-------|BO1 LOAD |--+ | . CLR|--|---|CLR | | | | | . | | | ----| | |---- | | . | | | BO10|---+---|BO10 | | . UP1S|--|---|UP1 | | | | . | | | | |--- | | . UP10S|- |---|UP10 | +---|CLK | | . | | | | | --------------- | . | | |---- | | | . | +---|LOAD 1S_DIGIT|-----------/4----------------|SEC1S . | | | | | . CLKS|------|DOWN 10S_DIGIT|-----------/4----------------|SEC10S . | -------------- | | . ---| | | . CLK|-------------------------+ | . --------------------------------------------------- . . . . (MDC) . . -----------------MINUTES DOWN COUNTER-------------- . | | . | | . | VCC | . | | -----PDCE----- | . | | | ----| | . | | | BO1S| | . CLR|--|---|CLR | | . | | | -----| |----- . | | | BO10S|-----------------------------|BO10M . UP1M|--|---|UP1 | | . | | | | | . UP10M|--|---|UP10 | | . | | | | | . | | |---- | | . | +---|LOAD 1S_DIGIT|-----------/4----------------|MIN1S . | | | | . CLKM|------|DOWN 10S_DIGIT|-----------/4----------------|MIN10S . | -------------- | . | | . | | . --------------------------------------------------- . . . (PDCE) . . --------------PRE-SETTABLE DOWN COUNT ELEMENT-------------- . | | . | VCC---+----+----+-+-+-+--------------+----+---+ | . | | | | | | | | | | | . | +--------------------------+ | | | | . | | | | | | | | | | | | | . | | +----------------------------------------------------+ | . ---| | | | | | | | | | | | | | | . BO1|--+ | +----------------------------+ | | +-|-+---+ | | . | | | | | | | | | | | | | | | | | | | . ----| | | | +-------------+ | | +-------------+ --- | | . BO10|----+ | | |VCC A B C D| | | |VCC A B C D| /// | | . | | | | | | | | | | | . | | | | --| | | | --| | | . CLR|------+----|CLR BO|---+ +-|CLR BO|-----+ | . | | | __| | | __| | . | | | CO| | | CO| | . UP1|-----------|UP 74LS192 | | +-----|UP 74LS192 | | . | | | CTR1 | | | | CTR2 | | . | | | | | | | | | . DOWN|-----------|DOWN QA|\\ +-------|DOWN QA|\\ | . | | | | | | | | | | . | | | QB|\\| | | QB|\\| | . UP10|-----+ | |---- | | | |---- | | | . | | +--|LOAD QC|\\| | +-|LOAD QC|\\| | . ----| | | | | | | | | | | . LOAD|--+ | | QD|\\| | | | QD|\\| | . | | | |GND | | | | |GND | | | . | | | +- -----------+ | | | +-------------+ | | . | | | | | | | | | | . | | | --- | | | --- | | . | | | /// | | | /// | | . | | +---------------------|---+ | | | . | +------------------------|-------+ | | . | | | | . ----------------------------------------------------------- . | | . /4 /4 . | | . . 1S_DIGIT 10S_DIGIT . . . . . (LCE) . . -------------------LOAD CONTROL ELEMENT------------ . | | . | +------------------------------------+ | . | | +--------------------------------+ | | . | | | | | | . | | | ----------74LS00--------- | | | . | +-----|--------+ +--------|--+ | | . | | | | __ | | __ | | | . | | | | / |-+ +-| \\ | | | . | +-------|--o G3| |G1 o--|--+-|--+ | . | | | | | \\__|-+ +-|__/ | | | | | . ---| | | | | | | | | | | | . BO1|-------------|--------+ +--------|--|-+ | | . | | | | | | | | | | . | | +-----|--------+ +--------|--+ | | | . | | | | __ | | __ | | | | . | | | | / |-+ +-| \\ | | | | . | | +-----|--o G4| |G2 o--|----+ | | . | | | | | \\__|-+ +-|__/ | | | | . ----| | | | | | | | | | | . BO10|---+---------|--------+ +--------|--+ | | | . | | | | | ------------------------- | | | | . ----| | | | | | | | | . LOAD|-----------------------------------------------+ | . | | | | | | | | . | | | | | -----------74LS32--------- | | | . | | | +----|---------+ +--------|-------+ | . | | | | | __ | | __ | | | | | . | | | | | / /-+ +-\\ \\ | | | | | . | | | +--|--< G7| |G5>--|--+ | | | . | | | | \\ __\\-+ +-/__/ | | | | . | | | | | | | | | | . | | +------|---------+ +--------|-+ | | | . | | | | | | | | . | +--------|---------+ +--------|----+ | | . | | __ | | __ | | | | | . | | / /-+ +-\\ \\ | | | | | . | +----|--< G8| |G6>--|-+ | | | . | | | \\ __\\-+ +-/__/ | | | | . | | | | | | | | | . | | +--|---------+ +--------|-+ | | | . | | | -------------------------- | | | | . | | +----------------------------------+ | | . | | | | | . | +---------------------------------------+ | . ---| | | . CLK|-----------------------------------------+ | . --------------------------------------------------- .

*********************** END MODULES ****************************

PART NO QTY

74LS00 2 74LS14 1 74LS32 1 74LS112 1 74LS192 4 74HCT4060 1 100UF10WVDC 4 560R1/4w 4 330R1/4W 4 32.768KXSTL 1 SW MOMON 6 0.01UF50V 12 DISPLAY 1 22PF 2

Heheh- it took me back 20 years:-) I drew it up on the fly- was fun chasing those Tpds, Tmins, and Trecovery's again, and got caught up in the old hangup of using every single gate of every chip:-)

Fixing some administrivia and adding a buzzer: View in a fixed-width font such as Courier.

. . COUNTDOWN TIMER . . MINS SECS . ------------------------------------------ . | ---- ---- ---- ---- | . | | | | | | | | | | . | | | | | O | | | | | . | ---- ---- ---- ---- | . | | | | | O | | | | | . | | | | | | | | | | . | ---- ---- ---- ---- | . ------------------------------------------ . | | | | . /4 / 4 /4 /4 . | | | | . \\---------\\----. \\---------\\----------, . | | . ,---------------------------------. | . | | | | . | .-------------------------------------------------, . | | | | | | . | | | | | | . | | ----MDC----- | | ----SDC----- | | . +------|-|CLR -----| | '--|CLR -----| | | . | | | BO10M|---. | BO10S|------+ . --- .--|-|UP1M | | | .-------|UP1S | | | . /// | | | | | | | | | | | . |.-|-|UP10M | | | |.------|UP10S | | | . || | | | | | || | | | | . || '-|CLKM MIN1S|/| | || .-|CLKS SEC1S|/| | . || | | | | || | |--- | | | . || | MIN10|/ | || .---|CLK SEC10|/ | . || ------------ | || | | ------------ | . || | || | | -----74LS00----- | . || | || | | | | | . -SSSE- || | || | | | __ / |---' . | | || | || | | / |------o G2| . | ___| || | || | '--o G1| \\__|---. . | CLK|--------------------------------' \\__|-- | . | | || | || | | | | . | CLK|--------------------------------------| \\ | | | . | ___| || | || |G3 o------| \\ | . | SSR|-. || --TSE--- +------------|__/ | |G4 o--' . | | | || | | | || | +----|__/ | . ------ | '--------|UPMIN1S | | || | | | . | | | | | || ----------------- . | '-------|UPMIN10S| | || | . | | | | || | . | | UPSEC1S|------'| | . | | | | | | . | |UPSEC10S|-------' | . | -------- | | . '------------------------------------------' . | . | . | VCC . | | + 10U . | +---[1K]--+---||--+ . | | | | . | | |< | . '-[1.2K]-+-------| 2N4403 | . |\\ | . | | . BUZZER | . | | . +-------+ . | . --- . /// . . . ****************** LOGIC MODULES ****************************** . . . . . . . . (SSSE) . . -----------------START/STOP/SET ELEMENT----------------- . | | . | VCC | . | | | . | +----------------------+ | . | | | | . | o o | . | -| STOP/SET -| START | . | o 74LS14 o 74LS14 | . | | |\\ | |\\ | . | +-[560]-+-| o-+ +-[560]-+-| o-+ | . | | +| |/ | | +| |/ | | . | [330] === | [330] === | | . | | 100u| | | 100u| | | . | +-------+ | +-------+ | | . | | | | | | . | --- | --- | | . | /// | /// | | . | | | | . | +--------------------------------------+ | . | | | |___ . | | +--+----------------------------------|SSR . | | VCC | | . | | | | | . | | +--------|-------------------------+ | . | | | | | | . | | | | | | . | | | | | | . | | | -------------------74LS112-------------- | . | | | | | | | | . | | | | +--------+ +--------+ | | . | | | | | --- | | --- | | | . | | | | | PRE | | PRE | | |--- . | | +--|-|J Q |---+ +--------|J Q |---|--|CLK . | | | | |-- | | | |-- | | | . | | +--|-|CK | | | +--|CK | | | . | | | | | FF1 | | | | | FF2 | | | . | | | | | - | | | | | - | | | . | | +--|-|K Q |-+ | | +-----|K Q |---|--|CLK . | | | | | --- | | | | | | | --- | | | . | | | | | CLR | | | | | | | CLR | | | . | | | | +--------+ | | | | | +--------+ | | . | | | | | | | | | | | | | . | | | ---------------------------------------- | . | | | | | | | | | | | . | | +--------|------------+--+ | | | . | | | | | | | | . | +------------+ +------------------+ | . | | | | . | | | | . | | | | . | ------------- | | . | +----| RESET | | | . | | | | | | . | ----- | 2HZ 0SC | | | . | 32.768K | 32.768KHZ | | | . | ----- | XYSTAL | | | . | | | | | | . | +----| Q14|--+ | . | | | | . | --74HCT4060-- | . | | . | | . | | . -------------------------------------------------------- . . . (TSE) . . ---------------------TIMER SET ELEMENT--------------- . | VCC VCC | . | | | | . | | | | . | | | | . | o o | . | -| SWSEC1S -| SWSEC10S | . | o 74LS14 o 74LS14 | . | | |\\ | |\\ | . | +-[560]-+-| o---+ +-[560]-+-| o-----|UPSEC10 . | | +| |/ | | +| |/ | . | [330] === | [330] === | . | | 100u| | | 100u| | . | +-------+ | +-------+ | . | | | | | . | --- | --- | . | /// | /// | . | +-------------------------------|UPSEC1S . | | . | | . | +-------------------------------|UPMIN1S . | | | . | | | . | VCC | VCC | . | | | | | . | | | | | . | | | | | . | o | o | . | -| SWMIN1S | -| SWMIN10S | . | o 74LS14 | o 74LS14 | . | | |\\ | | |\\ | . | +-[560]-+-| o---+ +-[560]-+-| o-----|UPMIN10 . | | +| |/ | +| |/ | . | [330] === [330] === | . | | 100u| | 100u| | . | +-------+ +-------+ | . | | | | . | --- --- | . | /// /// | . ----------------------------------------------------- . . . . (SDC) . . -----------------SECONDS DOWN COUNTER-------------- . | |----- . | +-------------------------|BO10S . | | | . | +---------------------------------------------+ | . | | | | | . | | -----PDCE----- | ------LCE------ | | . | | | ---| | |--- ---- | | | . | | | BO1|-------|BO1 LOAD |--+ | . CLR|--|---|CLR | | | | | . | | | ----| | |---- | | . | | | BO10|---+---|BO10 | | . UP1S|--|---|UP1 | | | | . | | | | |--- | | . UP10S|- |---|UP10 | +---|CLK | | . | | | | | --------------- | . | | |---- | | | . | +---|LOAD 1S_DIGIT|-----------/4----------------|SEC1S . | | | | | . CLKS|------|DOWN 10S_DIGIT|-----------/4----------------|SEC10S . | -------------- | | . ---| | | . CLK|-------------------------+ | . --------------------------------------------------- . . . . (MDC) . . -----------------MINUTES DOWN COUNTER-------------- . | | . | | . | VCC | . | | -----PDCE----- | . | | | ----| | . | | | BO1S| | . CLR|--|---|CLR | | . | | | -----| |----- . | | | BO10S|-----------------------------|BO10M . UP1M|--|---|UP1 | | . | | | | | . UP10M|--|---|UP10 | | . | | | | | . | | |---- | | . | +---|LOAD 1S_DIGIT|-----------/4----------------|MIN1S . | | | | . CLKM|------|DOWN 10S_DIGIT|-----------/4----------------|MIN10S . | -------------- | . | | . | | . --------------------------------------------------- . . . (PDCE) . . --------------PRE-SETTABLE DOWN COUNT ELEMENT-------------- . | | . | VCC---+----+----+-+-+-+--------------+----+---+ | . | | | | | | | | | | | . | +--------------------------+ | | | | . | | | | | | | | | | | | | . | | +----------------------------------------------------+ | . ---| | | | | | | | | | | | | | | . BO1|--+ | +----------------------------+ | | +-|-+---+ | | . | | | | | | | | | | | | | | | | | | | . ----| | | | +-------------+ | | +-------------+ --- | | . BO10|----+ | | |VCC A B C D| | | |VCC A B C D| /// | | . | | | | | | | | | | | . | | | | --| | | | --| | | . CLR|------+----|CLR BO|---+ +-|CLR BO|-----+ | . | | | __| | | __| | . | | | CO| | | CO| | . UP1|-----------|UP 74LS192 | | +-----|UP 74LS192 | | . | | | CTR1 | | | | CTR2 | | . | | | | | | | | | . DOWN|-----------|DOWN QA|\\ +-------|DOWN QA|\\ | . | | | | | | | | | | . | | | QB|\\| | | QB|\\| | . UP10|-----+ | |---- | | | |---- | | | . | | +--|LOAD QC|\\| | +-|LOAD QC|\\| | . ----| | | | | | | | | | | . LOAD|--+ | | QD|\\| | | | QD|\\| | . | | | |GND | | | | |GND | | | . | | | +- -----------+ | | | +-------------+ | | . | | | | | | | | | | . | | | --- | | | --- | | . | | | /// | | | /// | | . | | +---------------------|---+ | | | . | +------------------------|-------+ | | . | | | | . ----------------------------------------------------------- . | | . /4 /4 . | | . . 1S_DIGIT 10S_DIGIT . . . . . (LCE) . . -------------------LOAD CONTROL ELEMENT------------ . | | . | +------------------------------------+ | . | | +--------------------------------+ | | . | | | | | | . | | | ----------74LS00--------- | | | . | +-----|--------+ +--------|--+ | | . | | | | __ | | __ | | | . | | | | / |-+ +-| \\ | | | . | +-------|--o G3| |G1 o--|--+-|--+ | . | | | | | \\__|-+ +-|__/ | | | | | . ---| | | | | | | | | | | | . BO1|-------------|--------+ +--------|--|-+ | | . | | | | | | | | | | . | | +-----|--------+ +--------|--+ | | | . | | | | __ | | __ | | | | . | | | | / |-+ +-| \\ | | | | . | | +-----|--o G4| |G2 o--|----+ | | . | | | | | \\__|-+ +-|__/ | | | | . ----| | | | | | | | | | | . BO10|---+---------|--------+ +--------|--+ | | | . | | | | | ------------------------- | | | | . ----| | | | | | | | | . LOAD|-----------------------------------------------+ | . | | | | | | | | . | | | | | -----------74LS32--------- | | | . | | | +----|---------+ +--------|-------+ | . | | | | | __ | | __ | | | | | . | | | | | / /-+ +-\\ \\ | | | | | . | | | +--|--< G7| |G5>--|--+ | | | . | | | | \\ __\\-+ +-/__/ | | | | . | | | | | | | | | | . | | +------|---------+ +--------|-+ | | | . | | | | | | | | . | +--------|---------+ +--------|----+ | | . | | __ | | __ | | | | | . | | / /-+ +-\\ \\ | | | | | . | +----|--< G8| |G6>--|-+ | | | . | | | \\ __\\-+ +-/__/ | | | | . | | | | | | | | | . | | +--|---------+ +--------|-+ | | | . | | | -------------------------- | | | | . | | +----------------------------------+ | | . | | | | | . | +---------------------------------------+ | . ---| | | . CLK|-----------------------------------------+ | . --------------------------------------------------- . . . *********************** END MODULES **************************** . . . . PART NO QTY . . 74LS00 2 . 74LS14 1 . 74LS32 1 . 74LS112 1 . 74LS192 4 . 74HCT4060 1 . 100UF10WVDC 6 . 560R1/4w 6 . 330R1/4W 6 . 32.768KXSTL 1 . SW MOMON 6 . 0.01UF50V 12 . DISPLAY 1 . 22PF 2 . 5VPS 1 . BUZZER 1 . 10U10WVDC 1 . 1KR1/4W 1 . 1.2KR1/4W 1 . .

I'm top-posting, because, well, Geez, look at this thing!

Just wanted to say, ROFL!

Thanks! Rich

Fred, do you get paid to do these kids' homework for them? ;-P

Cheers! Rich

Or a detonator?

Sure- you would want to add a removable shunt w/indicator at output for ckt status + continuity test on the firing ckt, and make the display + TSE + switches in SSSE portions removable with pull-up resistors left behind with counter portion.

PCB are done, parts have been ordered, manuals have been written and are at the printers. Plastic cases are NRE and on order as well.

Then the marketing guy comes along and wonders if the diagram will completely change.

:-)

donald

74LS192?

thanks for diagram you gave it will help me a lot in my project hehehe....:) But how can i change the timer set element. Instead of using pushbuttons, logic gates and components, i preferred to use 4 thumbwheel coonnecting them in the A,B,C,D preset inputs of 74192. If I use this will the diagram completely change?

In that case you need to use a 2:1 mux at each ABCD input of the most significant digit (MSD) of each time unit, this would be 2x quad 2:1 mux ICs, so that in count down mode the mux sets the inputs as shown in the diagram, and in SET mode the mux loads the thumbwheel pattern. The /LOAD inputs of the MSD of each time unit pair are used for down counting, so you will have to work your SET loading in with that- an AND gate of existing /LOAD with a low going signal from your new SET circuitry. The thumbwheels can go into the least digits (LSD) ABCD directly and the /LOAD is not used so you can also trigger that directly.

This is along the lines of what you need: View in a fixed-width font such as Courier.

. . COUNTDOWN TIMER . . MINS SECS . ------------------------------------------ . | ---- ---- ---- ---- | . | | | | | | | | | | . | | | | | O | | | | | . | ---- ---- ---- ---- | . | | | | | O | | | | | . | | | | | | | | | | . | ---- ---- ---- ---- | . ------------------------------------------ . | | | | . /4 / 4 /4 /4 . | | | | . \\---------\\----. \\---------\\----------, . | | . ,---------------------------------. | . | | | | . | .-------------------------------------------------, . | | | | | | . | | | | | | . | | ----MDC----- | | ----SDC----- | | . +------|-|CLR -----| | '--|CLR -----| | | . | | | BO10M|---. | BO10S|------+ . --- +---|SET_MD | | | +--------|SET_MD | | | . /// | | |______ | | | | |______ | | | . +------|SET_LD | | | | +----- |SET_LD | | | . | | | | | | | | | | | | | . | | '-|CLKM MIN1S|/| | | | .-|CLKS SEC1S|/| | . | | | | | | | | | |--- | | | . | | | MIN10|/ | | | .---|CLK SEC10|/ | . | | ------------ | | | | | ------------ | . -SSSE- +--|----+-------------------+ | | -----74LS00----- | . | | | | | | | | | | | . |SET_MD|----+--------------------|-+ | | | __ / |---' . | | | | | | / |------o G2| . | ___| | | | '--o G1| \\__|---. . | CLK|--------------------------------' \\__|-- | . | | | | | | | | . | CLK|--------------------------------------| \\ | | | . | ___| | | |G3 o------| \\ | . | SSR|-. | --TSE--- +------------|__/ | |G4 o--' . | | | | | | | | +----|__/ | . ------ | | | | | | | | . | | |______ | | ----------------- . | +--|SET_LD | | | . | | | | | . | | | | | . | | | | | . | | | | | . | -------- | | . '------------------------------------------' . | . | . | VCC . | | + 10U . | +---[1K]--+---||--+ . | | | | . | | |< | . '-[1.2K]-+-------| 2N4403 | . |\\ | . | | . BUZZER | . | | . +-------+ . | . --- . /// . . . ****************** LOGIC MODULES ****************************** . . . . . . . . (SSSE) . . -----------------START/STOP/SET ELEMENT----------------- . | | . | VCC | . | | | . | +----------------------+ | . | | | | . | o o | . | -| STOP/SET -| START | . | o 74LS14 o 74LS14 | . | | |\\ | |\\ | . | +-[560]-+-| o-+ +-[560]-+-| o-+ | . | | +| |/ | | +| |/ | | . | [330] === | [330] === | | . | | 100u| | | 100u| | | . | +-------+ | +-------+ | | . | | | | | | . | --- | --- | | . | /// | /// | | . | | | | . | +--------------------------------------+ | . | | | |___ . | | +--+----------------------------------|SSR . | | VCC | | . | | | | | . | | +--------|-------------------------+ | . | | | | | | . | | | | +----------------|-----------|SET_MD . | | | | | | | . | | | -------------------74LS112-------------- | . | | | | | | | | | . | | | | +--------+ | +--------+ | | . | | | | | --- | | | --- | | | . | | | | | PRE | | | PRE | | |--- . | | +--|-|J Q |---+ +--------|J Q |---|--|CLK . | | | | |-- | | | |-- | | | . | | +--|-|CK | | | +--|CK | | | . | | | | | FF1 | | | | | FF2 | | | . | | | | | - | | | | | - | | | . | | +--|-|K Q |-+ | | +-----|K Q |---|--|CLK . | | | | | --- | | | | | | | --- | | | . | | | | | CLR | | | | | | | CLR | | | . | | | | +--------+ | | | | | +--------+ | | . | | | | | | | | | | | | | . | | | ---------------------------------------- | . | | | | | | | | | | | . | | +--------|------------+--+ | | | . | | | | | | | | . | +------------+ +------------------+ | . | | | | . | | | | . | | | | . | ------------- | | . | +----| RESET | | | . | | | | | | . | ----- | 2HZ 0SC | | | . | 32.768K | 32.768KHZ | | | . | ----- | XYSTAL | | | . | | | | | | . | +----| Q14|--+ | . | | | | . | --74HCT4060-- | . | | . | | . | | . -------------------------------------------------------- . . . (TSE) . . ---------------------TIMER SET ELEMENT--------------- . | VCC | . | | | . | | | . | | | . | o | . | -| SWSEC10S | . | o 74LS14 | . | | |\\ |------ . | +-[560]-+-| o-----|SET_LD . | | +| |/ | . | [330] === | . | | 100u| | . | +-------+ | . | | | . | --- | . | /// | . | | . | | . | | . | | . | | . | | . | | . | | . | | . | | . | | . ----------------------------------------------------- . . (SDC) . . -----------------SECONDS DOWN COUNTER-------------- . | |----- . | +------------+ +-------------------------|BO10S . | | __ | | | . | | 74ls08/ |-+ | | . | +--------< | | | . | | | \\__|--------------------------------+ | . | | | | | | . | | | -----PDCE----- | | | . | | | | | | | | . SET_MD|------|SET_MD | | | | . ------| | | | | | ------LCE------ | | . SET_LD|----+-|SET_LD ---| | |--- ---- | | | . | | | BO1|-------|BO1 LOAD |--+ | . CLR|------|CLR | | | | | . | | | ----| | |---- | | . | | | BO10|---+---|BO10 | | . | | | | | | | . | | | | |--- | | . | | | | +---|CLK | | . | | | | | --------------- | . | | |---- | | | . | +---|LOAD 1S_DIGIT|-----------/4----------------|SEC1S . | | | | | . CLKS|------|DOWN 10S_DIGIT|-----------/4----------------|SEC10S . | -------------- | | . ---| | | . CLK|-------------------------+ | . --------------------------------------------------- . . . . . . . (MDC) . . -----------------MINUTES DOWN COUNTER-------------- . | | . | | . | | . | | . | | . | -----PDCE----- | . | | | | . SET_MD|------|SET_MD | | . | | | | . | +---|SET_LD ---| | . | | | BO1| | . CLR|--|---|CLR | | . | | | ----| |----- . | | | BO10|-----------------------------|BO10M . | | | | | . | | | | | . | | | | | . | | | | | . ------| | |---- | | . SET_LD|--+---|LOAD 1S_DIGIT|-----------/4----------------|MIN1S . | | | | . CLKM|------|DOWN 10S_DIGIT|-----------/4----------------|MIN10S . | -------------- | . | | . | | . --------------------------------------------------- . .

(PDCE)

--------------PRE-SETTABLE DOWN COUNT ELEMENT-------------- | | | | | 1'S | | 10'S | | THMBWHL | | +-------+ THMBWHL | | | | | | | VCC +-------+ | | | | | | | | | | | | | | | +-------+ +---+ | | | | | | | | | | | | | +-------+ | | +--------------------------------------+---+ | | | | | | | | | | | | | | | | | | | | | | | | | | +------------------+ | | | | | | | | A0 A2 B0 B2 | | | | | | | | |_ A1 A3 B1 B3| | SET_MD|--------------------------------------|A/B | | | | | | | | | | | | | | | | | |_ Y1 Y3 | | | +----------------------------------|G Y0 Y2 | | . | | | | | | +-------+----74LS157 | . | --- | | | | | | | | | . | /// | | | | | | | | | . ------| | | | | | | | | | . SET_LD|--------+ | | | | | | | | | . | | | | | | | | | | | . | +--------------------------+ | | | | | . | | | | | | | | | | | | | . | | +----------------------------------------------------+ | . ---| | | | | | | | | | | | | | | . BO1|--+ | +----------------------------+ | | | | | | . | | | | | | | | | | | | | | | | . ----| | | | +-------------+ | | +-------------+ | | . BO10|----+ | | | A B C D| | | | A B C D| | | . | | | | | | | | | | | . | | | | --| | | | --| | | . CLR|------+----|CLR BO|---+ +-|CLR BO|-----+ | . | | | __| | | __| | . | | | CO| | | CO| | . | VCC-+-----|UP 74LS192 | | +-----|UP 74LS192 | | . | | | | CTR1 | | | | CTR2 | | . | | | | | | | | | | . DOWN|-----|-----|DOWN QA|\\ +-------|DOWN QA|\\ | . | | | | | | | | | | | . | | | | QB|\\| | | QB|\\| | . | | | |---- | | | |---- | | | . | | +--|LOAD QC|\\| | +-|LOAD QC|\\| | . ----| | | | | | | | | | | . LOAD|--+ | | QD|\\| | | | QD|\\| | . | | | |GND | | | | |GND | | | . | | | +- -----------+ | | | +-------------+ | | . | | | | | | | | | | . | | | --- | | | --- | | . | | | /// | | | /// | | . | | +---------------------|---+ | | | . | +------------------------|-------+ | | . | | | | . ----------------------------------------------------------- . | | . /4 /4 . | | . . 1S_DIGIT 10S_DIGIT . . . . . (LCE) . . -------------------LOAD CONTROL ELEMENT------------ . | | . | +------------------------------------+ | . | | +--------------------------------+ | | . | | | | | | . | | | ----------74LS00--------- | | | . | +-----|--------+ +--------|--+ | | . | | | | __ | | __ | | | . | | | | / |-+ +-| \\ | | | . | +-------|--o G3| |G1 o--|--+-|--+ | . | | | | | \\__|-+ +-|__/ | | | | | . ---| | | | | | | | | | | | . BO1|-------------|--------+ +--------|--|-+ | | . | | | | | | | | | | . | | +-----|--------+ +--------|--+ | | | . | | | | __ | | __ | | | | . | | | | / |-+ +-| \\ | | | | . | | +-----|--o G4| |G2 o--|----+ | | . | | | | | \\__|-+ +-|__/ | | | | . ----| | | | | | | | | | | . BO10|---+---------|--------+ +--------|--+ | | | . | | | | | ------------------------- | | | | . ----| | | | | | | | | . LOAD|-----------------------------------------------+ | . | | | | | | | | . | | | | | -----------74LS32--------- | | | . | | | +----|---------+ +--------|-------+ | . | | | | | __ | | __ | | | | | . | | | | | / /-+ +-\\ \\ | | | | | . | | | +--|--< G7| |G5>--|--+ | | | . | | | | \\ __\\-+ +-/__/ | | | | . | | | | | | | | | | . | | +------|---------+ +--------|-+ | | | . | | | | | | | | . | +--------|---------+ +--------|----+ | | . | | __ | | __ | | | | | . | | / /-+ +-\\ \\ | | | | | . | +----|--< G8| |G6>--|-+ | | | . | | | \\ __\\-+ +-/__/ | | | | . | | | | | | | | | . | | +--|---------+ +--------|-+ | | | . | | | -------------------------- | | | | . | | +----------------------------------+ | | . | | | | | . | +---------------------------------------+ | . ---| | | . CLK|-----------------------------------------+ | . --------------------------------------------------- . . . *********************** END MODULES **************************** . . . . PART NO QTY . . 74LS00 2 . 74LS14 1 . 74LS32 1 . 74LS112 1 . 74LS192 4 . 74HCT4060 1 . 100UF10WVDC 6 . 560R1/4w 6 . 330R1/4W 6 . 32.768KXSTL 1 . SW MOMON 6 . 0.01UF50V 12 . DISPLAY 1 . 22PF 2 . 5VPS 1 . BUZZER 1 . 10U10WVDC 1 . 1KR1/4W 1 . 1.2KR1/4W 1 . 2N4403 1 . THUMBWHEELS 4 74LS157 2 74LS08 1

I like this one better- adds a disable to the SET load switch in the down count mode: View in a fixed-width font such as Courier.

. . COUNTDOWN TIMER . . MINS SECS . ------------------------------------------ . | ---- ---- ---- ---- | . | | | | | | | | | | . | | | | | O | | | | | . | ---- ---- ---- ---- | . | | | | | O | | | | | . | | | | | | | | | | . | ---- ---- ---- ---- | . ------------------------------------------ . | | | | . /4 / 4 /4 /4 . | | | | . \\---------\\----. \\---------\\----------, . | | . ,---------------------------------. | . | | | | . | .-------------------------------------------------, . | | | | | | . | | | | | | . | | ----MDC----- | | ----SDC----- | | . +------|-|CLR -----| | '--|CLR -----| | | . | | | BO10M|---. | BO10S|------+ . --- +---|SET_MD | | | +--------|SET_MD | | | . /// | | |______ | | | | |______ | | | . +------|SET_LD | | | | +----- |SET_LD | | | . | | | | | | | | | | | | | . | | '-|CLKM MIN1S|/| | | | .-|CLKS SEC1S|/| | . | | | | | | | | | |--- | | | . | | | MIN10|/ | | | .---|CLK SEC10|/ | . | | ------------ | | | | | ------------ | . -SSSE- +--|----+-------------------+ | | -----74LS00----- | . | | | | | | | | | | | . |SET_MD|----+--------------------|-+ | | | __ / |---' . | | | | | | | / |------o G2| . | ___| | | | | '--o G1| \\__|---. . | CLK|--------------------------------' \\__|-- | . | | | | | | | | | . | CLK|--------------------------------------| \\ | | | . | ___| | | | |G3 o------| \\ | . | SSR|-. | | --TSE--- +------------|__/ | |G4 o--' . | | | | | | | | | +----|__/ | . ------ | | | | | | | | | . | | | |______ | | ----------------- . | | +--|SET_LD | | | . | | | | | | . | +-------|SET_MD | | | . | | | | | . | | | | | . | -------- | | . '------------------------------------------' . | . | . | VCC . | | + 10U . | +---[1K]--+---||--+ . | | | | . | | |< | . '-[1.2K]-+-------| 2N4403 | . |\\ | . | | . BUZZER | . | | . +-------+ . | . --- . /// . . . ****************** LOGIC MODULES ****************************** . . . . . . . . (SSSE) . . -----------------START/STOP/SET ELEMENT----------------- . | | . | VCC | . | | | . | +----------------------+ | . | | | | . | o o | . | -| STOP/SET -| START | . | o 74LS14 o 74LS14 | . | | |\\ | |\\ | . | +-[560]-+-| o-+ +-[560]-+-| o-+ | . | | +| |/ | | +| |/ | | . | [330] === | [330] === | | . | | 100u| | | 100u| | | . | +-------+ | +-------+ | | . | | | | | | . | --- | --- | | . | /// | /// | | . | | | | . | +--------------------------------------+ | . | | | |___ . | | +--+----------------------------------|SSR . | | VCC | | . | | | | | . | | +--------|-------------------------+ | . | | | | | | . | | | | +----------------|-----------|SET_MD . | | | | | | | . | | | -------------------74LS112-------------- | . | | | | | | | | | . | | | | +--------+ | +--------+ | | . | | | | | --- | | | --- | | | . | | | | | PRE | | | PRE | | |--- . | | +--|-|J Q |---+ +--------|J Q |---|--|CLK . | | | | |-- | | | |-- | | | . | | +--|-|CK | | | +--|CK | | | . | | | | | FF1 | | | | | FF2 | | | . | | | | | - | | | | | - | | | . | | +--|-|K Q |-+ | | +-----|K Q |---|--|CLK . | | | | | --- | | | | | | | --- | | | . | | | | | CLR | | | | | | | CLR | | | . | | | | +--------+ | | | | | +--------+ | | . | | | | | | | | | | | | | . | | | ---------------------------------------- | . | | | | | | | | | | | . | | +--------|------------+--+ | | | . | | | | | | | | . | +------------+ +------------------+ | . | | | | . | | | | . | | | | . | ------------- | | . | +----| RESET | | | . | | | | | | . | ----- | 2HZ 0SC | | | . | 32.768K | 32.768KHZ | | | . | ----- | XYSTAL | | | . | | | | | | . | +----| Q14|--+ | . | | | | . | --74HCT4060-- | . | | . | | . | | . -------------------------------------------------------- . . . (TSE) . . --------TIMER SET ELEMENT--------------- . | | . | | . | VCC | . | | | . | +---[1K]----+ | . | | | | . | | |< | . | +---------| 2N3904 | . | | |\\ | . | | | | . | | | | . | | | | . | [4.7K] | | . | | o | . | | -| SET_SW | . | | o 74LS14| . | | | |\\ |------ . | | +-[560]-+-| o--|SET_LD . | | | +| |/ | . | 74LS14 | [330] === | . | |\\ | | 100u| | . SET_MD |------| o----+ | | | . | |/ +-------+ | . | | | . | --- | . | /// | . | | . ---------------------------------------- . . (SDC) . . -----------------SECONDS DOWN COUNTER-------------- . | |----- . | +------------+ +-------------------------|BO10S . | | __ | | | . | | 74ls08/ |-+ | | . | +--------< | | | . | | | \\__|--------------------------------+ | . | | | | | | . | | | -----PDCE----- | | | . | | | | | | | | . SET_MD|------|SET_MD | | | | . ------| | | | | | ------LCE------ | | . SET_LD|----+-|SET_LD ---| | |--- ---- | | | . | | | BO1|-------|BO1 LOAD |--+ | . CLR|------|CLR | | | | | . | | | ----| | |---- | | . | | | BO10|---+---|BO10 | | . | | | | | | | . | | | | |--- | | . | | | | +---|CLK | | . | | | | | --------------- | . | | |---- | | | . | +---|LOAD 1S_DIGIT|-----------/4----------------|SEC1S . | | | | | . CLKS|------|DOWN 10S_DIGIT|-----------/4----------------|SEC10S . | -------------- | | . ---| | | . CLK|-------------------------+ | . --------------------------------------------------- . . . . . . . (MDC) . . -----------------MINUTES DOWN COUNTER-------------- . | | . | | . | | . | | . | | . | -----PDCE----- | . | | | | . SET_MD|------|SET_MD | | . | | | | . | +---|SET_LD ---| | . | | | BO1| | . CLR|--|---|CLR | | . | | | ----| |----- . | | | BO10|-----------------------------|BO10M . | | | | | . | | | | | . | | | | | . | | | | | . ------| | |---- | | . SET_LD|--+---|LOAD 1S_DIGIT|-----------/4----------------|MIN1S . | | | | . CLKM|------|DOWN 10S_DIGIT|-----------/4----------------|MIN10S . | -------------- | . | | . | | . --------------------------------------------------- . .

(PDCE)

--------------PRE-SETTABLE DOWN COUNT ELEMENT-------------- | | | | | 1'S | | 10'S | | THMBWHL | | +-------+ THMBWHL | | | | | | | VCC +-------+ | | | | | | | | | | | | | | | +-------+ +---+ | | | | | | | | | | | | | +-------+ | | +--------------------------------------+---+ | | | | | | | | | | | | | | | | | | | | | | | | | | +------------------+ | | | | | | | | A0 A2 B0 B2 | | | | | | | | |_ A1 A3 B1 B3| | SET_MD|--------------------------------------|A/B | | | | | | | | | | | | | | | | | |_ Y1 Y3 | | | +----------------------------------|G Y0 Y2 | | . | | | | | | +-------+----74LS157 | . | --- | | | | | | | | | . | /// | | | | | | | | | . ------| | | | | | | | | | . SET_LD|--------+ | | | | | | | | | . | | | | | | | | | | | . | +--------------------------+ | | | | | . | | | | | | | | | | | | | . | | +----------------------------------------------------+ | . ---| | | | | | | | | | | | | | | . BO1|--+ | +----------------------------+ | | | | | | . | | | | | | | | | | | | | | | | . ----| | | | +-------------+ | | +-------------+ | | . BO10|----+ | | | A B C D| | | | A B C D| | | . | | | | | | | | | | | . | | | | --| | | | --| | | . CLR|------+----|CLR BO|---+ +-|CLR BO|-----+ | . | | | __| | | __| | . | | | CO| | | CO| | . | VCC-+-----|UP 74LS192 | | +-----|UP 74LS192 | | . | | | | CTR1 | | | | CTR2 | | . | | | | | | | | | | . DOWN|-----|-----|DOWN QA|\\ +-------|DOWN QA|\\ | . | | | | | | | | | | | . | | | | QB|\\| | | QB|\\| | . | | | |---- | | | |---- | | | . | | +--|LOAD QC|\\| | +-|LOAD QC|\\| | . ----| | | | | | | | | | | . LOAD|--+ | | QD|\\| | | | QD|\\| | . | | | |GND | | | | |GND | | | . | | | +- -----------+ | | | +-------------+ | | . | | | | | | | | | | . | | | --- | | | --- | | . | | | /// | | | /// | | . | | +---------------------|---+ | | | . | +------------------------|-------+ | | . | | | | . ----------------------------------------------------------- . | | . /4 /4 . | | . . 1S_DIGIT 10S_DIGIT . . . . . (LCE) . . -------------------LOAD CONTROL ELEMENT------------ . | | . | +------------------------------------+ | . | | +--------------------------------+ | | . | | | | | | . | | | ----------74LS00--------- | | | . | +-----|--------+ +--------|--+ | | . | | | | __ | | __ | | | . | | | | / |-+ +-| \\ | | | . | +-------|--o G3| |G1 o--|--+-|--+ | . | | | | | \\__|-+ +-|__/ | | | | | . ---| | | | | | | | | | | | . BO1|-------------|--------+ +--------|--|-+ | | . | | | | | | | | | | . | | +-----|--------+ +--------|--+ | | | . | | | | __ | | __ | | | | . | | | | / |-+ +-| \\ | | | | . | | +-----|--o G4| |G2 o--|----+ | | . | | | | | \\__|-+ +-|__/ | | | | . ----| | | | | | | | | | | . BO10|---+---------|--------+ +--------|--+ | | | . | | | | | ------------------------- | | | | . ----| | | | | | | | | . LOAD|-----------------------------------------------+ | . | | | | | | | | . | | | | | -----------74LS32--------- | | | . | | | +----|---------+ +--------|-------+ | . | | | | | __ | | __ | | | | | . | | | | | / /-+ +-\\ \\ | | | | | . | | | +--|--< G7| |G5>--|--+ | | | . | | | | \\ __\\-+ +-/__/ | | | | . | | | | | | | | | | . | | +------|---------+ +--------|-+ | | | . | | | | | | | | . | +--------|---------+ +--------|----+ | | . | | __ | | __ | | | | | . | | / /-+ +-\\ \\ | | | | | . | +----|--< G8| |G6>--|-+ | | | . | | | \\ __\\-+ +-/__/ | | | | . | | | | | | | | | . | | +--|---------+ +--------|-+ | | | . | | | -------------------------- | | | | . | | +----------------------------------+ | | . | | | | | . | +---------------------------------------+ | . ---| | | . CLK|-----------------------------------------+ | . --------------------------------------------------- . . . *********************** END MODULES **************************** . . . . PART NO QTY . . 74LS00 2 . 74LS14 1 . 74LS32 1 . 74LS112 1 . 74LS192 4 . 74HCT4060 1 . 100UF10WVDC 6 . 560R1/4w 6 . 330R1/4W 6 . 32.768KXSTL 1 . SW MOMON 6 . 0.01UF50V 12 . DISPLAY 1 . 22PF 2 . 5VPS 1 . BUZZER 1 . 10U10WVDC 1 . 1KR1/4W 1 . 1.2KR1/4W 1 . 2N4403 1 . THUMBWHEELS 4 74LS157 2 74LS08 1

I am satisfied with this one- gets rid of the SET load switch altogether. When you press STOP/SET switch the counters are all in continuous LOAD mode, so just dial the new time into the thumbwheels and they are displayed immediately. Then press START and it starts count down... I used the spare 74LS14's to put a delay on the SET_MD signal so that it falls after /SET_LD lifts by a safe margin- for a clean load. The first DOWN clock edge will not arrive for another second so no problem from that. View in a fixed-width font such as Courier.

. . COUNTDOWN TIMER . . MINS SECS . ------------------------------------------ . | ---- ---- ---- ---- | . | | | | | | | | | | . | | | | | O | | | | | . | ---- ---- ---- ---- | . | | | | | O | | | | | . | | | | | | | | | | . | ---- ---- ---- ---- | . ------------------------------------------ . | | | | . /4 / 4 /4 /4 . | | | | . \\---------\\----. \\---------\\----------, . | | . ,---------------------------------. | . | | | | . | .-------------------------------------------------, . | | | | | | . | | | | | | . | | ----MDC----- | | ----SDC----- | | . +------|-|CLR -----| | '--|CLR -----| | | . | | | BO10M|---. | BO10S|------+ . --- +---|SET_MD | | | +--------|SET_MD | | | . /// | | |______ | | | | |______ | | | . +------|SET_LD | | | | +----- |SET_LD | | | . | | | | | | | | | | | | | . | | '-|CLKM MIN1S|/| | | | .-|CLKS SEC1S|/| | . | | | | | | | | | |--- | | | . | | | MIN10|/ | | | .---|CLK SEC10|/ | . | | ------------ | | | | | ------------ | . -SSSE- +--|----+-------------------+ | | -----74LS00----- | . | | | | | | | | | | | . |SET_MD|----+--------------------|-+ | | | __ / |---' . | | | | | | / |------o G2| . | ___| | | | '--o G1| \\__|---. . | CLK|--------------------------------' \\__|-- | . | | | | | | | | . | CLK|--------------------------------------| \\ | | | . | | | | |G3 o------| \\ | . |______| | +------------|__/ | |G4 o--' . |SET_LD|---------+ | | +----|__/ | . | | | | | | . | | | ----------------- . | ___| | | . | SSR|-. | | . | | | | | . ------ | | | . | | | . | | | . '------------------------------------------' . | . | . | VCC . | | + 10U . | +---[1K]--+---||--+ . | | | | . | | |< | . '-[1.2K]-+-------| 2N4403 | . |\\ | . | | . BUZZER | . | | . +-------+ . | . --- . /// . . . ****************** LOGIC MODULES ****************************** . . . . . . . . (SSSE) . . -----------------START/STOP/SET ELEMENT----------------- . | | . | VCC | . | | | . | +----------------------+ | . | | | | . | o o | . | -| STOP/SET -| START | . | o 74LS14 o 74LS14 | . | | |\\ | |\\ | . | +-[560]-+-| o-+ +-[560]-+-| o-+ | . | | +| |/ | | +| |/ | | . | [330] === | [330] === | | . | | 100u| | | 100u| | | . | +-------+ | +-------+ | | . | | | | | | . | --- | --- | | . | /// | /// | | . | | | | . | +--------------------------------------+ | . | | | |___ . | | +--+----------------------------------|SSR . | | VCC | |\\ |\\ |\\ |\\ | . | | | | +----| o---| o---| o---| o---|SET_MD . | | | | |/ |/ |/ |/ | . | | | | | 74LS14 | . | | +--------|-------------------------+ | . | | | | | | | . | | | -------------------74LS112-------------- | . | | | | | | | | | . | | | | +--------+ | +--------+ | | . | | | | | --- | | | --- | | | . | | | | | PRE | | | PRE | | |--- . | | +--|-|J Q |---+ +--------|J Q |---|--|CLK . | | | | |-- | | | |-- | | | . | | +--|-|CK | | | +--|CK | | | . | | | | | FF1 | | | | | FF2 | | | . | | | | | - | | | | | - | | | . | | +--|-|K Q |-+ | | +-----|K Q |---|--|CLK . | | | | | --- | | | | | | | --- | | | . | | | | | CLR | | | | | | | CLR | | | . | | | | +--------+ | | | | | +--------+ | | . | | | | | | | | | | | | | . | | | ---------------------------------------- | . | | | | | | | | | | | . | | +--------|------------+--+ | | | . | | | | | | | |______ . | +------------+ +------------------+-----------|SET_LD . | | | | . | | | | . | | | | . | ------------- | | . | +----| RESET | | | . | | | | | | . | ----- | 2HZ 0SC | | | . | 32.768K | 32.768KHZ | | | . | ----- | XYSTAL | | | . | | | | | | . | +----| Q14|--+ | . | | | | . | --74HCT4060-- | . | | . | | . | | . -------------------------------------------------------- . . . . . (SDC) . . -----------------SECONDS DOWN COUNTER-------------- . | |----- . | +------------+ +-------------------------|BO10S . | | __ | | | . | | 74ls08/ |-+ | | . | +--------< | | | . | | | \\__|--------------------------------+ | . | | | | | | . | | | -----PDCE----- | | | . | | | | | | | | . SET_MD|------|SET_MD | | | | . ------| | | | | | ------LCE------ | | . SET_LD|----+-|SET_LD ---| | |--- ---- | | | . | | | BO1|-------|BO1 LOAD |--+ | . CLR|------|CLR | | | | | . | | | ----| | |---- | | . | | | BO10|---+---|BO10 | | . | | | | | | | . | | | | |--- | | . | | | | +---|CLK | | . | | | | | --------------- | . | | |---- | | | . | +---|LOAD 1S_DIGIT|-----------/4----------------|SEC1S . | | | | | . CLKS|------|DOWN 10S_DIGIT|-----------/4----------------|SEC10S . | -------------- | | . ---| | | . CLK|-------------------------+ | . --------------------------------------------------- . . . . . . . (MDC) . . -----------------MINUTES DOWN COUNTER-------------- . | | . | | . | | . | | . | | . | -----PDCE----- | . | | | | . SET_MD|------|SET_MD | | . | | | | . | +---|SET_LD ---| | . | | | BO1| | . CLR|--|---|CLR | | . | | | ----| |----- . | | | BO10|-----------------------------|BO10M . | | | | | . | | | | | . | | | | | . | | | | | . ------| | |---- | | . SET_LD|--+---|LOAD 1S_DIGIT|-----------/4----------------|MIN1S . | | | | . CLKM|------|DOWN 10S_DIGIT|-----------/4----------------|MIN10S . | -------------- | . | | . | | . --------------------------------------------------- . .

(PDCE)

--------------PRE-SETTABLE DOWN COUNT ELEMENT-------------- | | | | | 1'S | | 10'S | | THMBWHL | | +-------+ THMBWHL | | | | | | | VCC +-------+ | | | | | | | | | | | | | | | +-------+ +---+ | | | | | | | | | | | | | +-------+ | | +--------------------------------------+---+ | | | | | | | | | | | | | | | | | | | | | | | | | | +------------------+ | | | | | | | | A0 A2 B0 B2 | | | | | | | | |_ A1 A3 B1 B3| | SET_MD|--------------------------------------|A/B | | | | | | | | | | | | | | | | | |_ Y1 Y3 | | | +----------------------------------|G Y0 Y2 | | . | | | | | | +-------+----74LS157 | . | --- | | | | | | | | | . | /// | | | | | | | | | . ------| | | | | | | | | | . SET_LD|--------+ | | | | | | | | | . | | | | | | | | | | | . | +--------------------------+ | | | | | . | | | | | | | | | | | | | . | | +----------------------------------------------------+ | . ---| | | | | | | | | | | | | | | . BO1|--+ | +----------------------------+ | | | | | | . | | | | | | | | | | | | | | | | . ----| | | | +-------------+ | | +-------------+ | | . BO10|----+ | | | A B C D| | | | A B C D| | | . | | | | | | | | | | | . | | | | --| | | | --| | | . CLR|------+----|CLR BO|---+ +-|CLR BO|-----+ | . | | | __| | | __| | . | | | CO| | | CO| | . | VCC-+-----|UP 74LS192 | | +-----|UP 74LS192 | | . | | | | CTR1 | | | | CTR2 | | . | | | | | | | | | | . DOWN|-----|-----|DOWN QA|\\ +-------|DOWN QA|\\ | . | | | | | | | | | | | . | | | | QB|\\| | | QB|\\| | . | | | |---- | | | |---- | | | . | | +--|LOAD QC|\\| | +-|LOAD QC|\\| | . ----| | | | | | | | | | | . LOAD|--+ | | QD|\\| | | | QD|\\| | . | | | |GND | | | | |GND | | | . | | | +- -----------+ | | | +-------------+ | | . | | | | | | | | | | . | | | --- | | | --- | | . | | | /// | | | /// | | . | | +---------------------|---+ | | | . | +------------------------|-------+ | | . | | | | . ----------------------------------------------------------- . | | . /4 /4 . | | . . 1S_DIGIT 10S_DIGIT . . . . . (LCE) . . -------------------LOAD CONTROL ELEMENT------------ . | | . | +------------------------------------+ | . | | +--------------------------------+ | | . | | | | | | . | | | ----------74LS00--------- | | | . | +-----|--------+ +--------|--+ | | . | | | | __ | | __ | | | . | | | | / |-+ +-| \\ | | | . | +-------|--o G3| |G1 o--|--+-|--+ | . | | | | | \\__|-+ +-|__/ | | | | | . ---| | | | | | | | | | | | . BO1|-------------|--------+ +--------|--|-+ | | . | | | | | | | | | | . | | +-----|--------+ +--------|--+ | | | . | | | | __ | | __ | | | | . | | | | / |-+ +-| \\ | | | | . | | +-----|--o G4| |G2 o--|----+ | | . | | | | | \\__|-+ +-|__/ | | | | . ----| | | | | | | | | | | . BO10|---+---------|--------+ +--------|--+ | | | . | | | | | ------------------------- | | | | . ----| | | | | | | | | . LOAD|-----------------------------------------------+ | . | | | | | | | | . | | | | | -----------74LS32--------- | | | . | | | +----|---------+ +--------|-------+ | . | | | | | __ | | __ | | | | | . | | | | | / /-+ +-\\ \\ | | | | | . | | | +--|--< G7| |G5>--|--+ | | | . | | | | \\ __\\-+ +-/__/ | | | | . | | | | | | | | | | . | | +------|---------+ +--------|-+ | | | . | | | | | | | | . | +--------|---------+ +--------|----+ | | . | | __ | | __ | | | | | . | | / /-+ +-\\ \\ | | | | | . | +----|--< G8| |G6>--|-+ | | | . | | | \\ __\\-+ +-/__/ | | | | . | | | | | | | | | . | | +--|---------+ +--------|-+ | | | . | | | -------------------------- | | | | . | | +----------------------------------+ | | . | | | | | . | +---------------------------------------+ | . ---| | | . CLK|-----------------------------------------+ | . --------------------------------------------------- . . . *********************** END MODULES **************************** . . . . PART NO QTY . . 74LS00 2 . 74LS14 1 . 74LS32 1 . 74LS112 1 . 74LS192 4 . 74HCT4060 1 . 100UF10WVDC 6 . 560R1/4w 6 . 330R1/4W 6 . 32.768KXSTL 1 . SW MOMON 6 . 0.01UF50V 12 . DISPLAY 1 . 22PF 2 . 5VPS 1 . BUZZER 1 . 10U10WVDC 1 . 1KR1/4W 1 . 1.2KR1/4W 1 . 2N4403 1 . THUMBWHEELS 4 74LS157 2 74LS08 1

This should do it- got rid of the 74LS08 by rearranging some control signals. View in a fixed-width font such as Courier.

. . . COUNTDOWN TIMER . . MINS SECS . ------------------------------------------ . | ---- ---- ---- ---- | . | | | | | | | | | | . | | | | | O | | | | | . | ---- ---- ---- ---- | . | | | | | O | | | | | . | | | | | | | | | | . | ---- ---- ---- ---- | . ------------------------------------------ . | | | | . /4 / 4 /4 /4 . | | | | . \\---------\\----. \\---------\\----------, . | | . ,---------------------------------. | . | | | | . | .-------------------------------------------------, . | | | | | | . | | | | | | . | | ----MDC----- | | ----SDC----- | | . +------|-|CLR -----| | '--|CLR -----| | | . | | | BO10M|---. | BO10S|------+ . --- +---|SET_MD | | | +--------|SET_MD | | | . /// | | |______ | | | | |______ | | | . +------|SET_LD | | | | +----- |SET_LD | | | . | | | | | | | | | | | | | . | | '-|CLKM MIN1S|/| | | | .-|CLKS SEC1S|/| | . | | | | | | | | | |--- | | | . | | | MIN10|/ | | | .---|CLK SEC10|/ | . | | ------------ | | | | | ------------ | . -SSSE- +--|----+-------------------+ | | -----74LS00----- | . | | | | | | | | | | | . |SET_MD|----+--------------------|-+ | | | __ / |---' . | | | | | | / |------o G2| . | ___| | | | '--o G1| \\__|---. . | CLK|--------------------------------' \\__|-- | . | | | | | | | | . | CLK|--------------------------------------| \\ | | | . | | | | |G3 o------| \\ | . |______| | +------------|__/ | |G4 o--' . |SET_LD|---------+ | | +----|__/ | . | | | | | | . | | | ----------------- . | ___| | | . | SSR|-. | | . | | | | | . ------ | | | . | | | . | | | . '------------------------------------------' . | . | . | VCC . | | + 10U . | +---[1K]--+---||--+ . | | | | . | | |< | . '-[1.2K]-+-------| 2N4403 | . |\\ | . | | . BUZZER | . | | . +-------+ . | . --- . /// . . . ****************** LOGIC MODULES ****************************** . . . . . . . . (SSSE) . . -----------------START/STOP/SET ELEMENT----------------- . | | . | VCC | . | | | . | +----------------------+ | . | | | | . | o o | . | -| STOP/SET -| START | . | o 74LS14 o 74LS14 | . | | |\\ | |\\ | . | +-[560]-+-| o-+ +-[560]-+-| o-+ | . | | +| |/ | | +| |/ | | . | [330] === | [330] === | | . | | 100u| | | 100u| | | . | +-------+ | +-------+ | | . | | | | | | . | --- | --- | | . | /// | /// | | . | | | | . | +--------------------------------------+ | . | | | |___ . | | +--+----------------------------------|SSR . | | VCC | |\\ |\\ |\\ | . | | | | +------------| o---| o---| o---|SET_MD . | | | | |/ |/ |/ | . | | | | | 3x 74LS14 | . | | +--------|-------------------------+ | . | | | | | | | . | | | -------------------74LS112-------------- | . | | | | | | | | | . | | | | +--------+ | +--------+ | | . | | | | | --- | | | --- | | | . | | | | | PRE | | | PRE | | |--- . | | +--|-|J Q |---+ +--------|J Q |---|--|CLK . | | | | |-- | | | | |-- | | | . | | +--|-|CK | | | | +--|CK | | | . | | | | | FF1 | | | | | | FF2 | | | . | | | | | - | | | | | | - | | | . | | +--|-|K Q |-+ | | +-----|K Q |---|--|CLK . | | | | | --- | | | | | | | --- | | | . | | | | | CLR | | | | | | | CLR | | | . | | | | +--------+ | | | | | +--------+ | | . | | | | | | | | | | | | | . | | | ---------------------------------------- | . | | | | | | | | | | | . | | +--------|------------+--+ | | | . | | | | | | | |______ . | +------------+ +------------------+-----------|SET_LD . | | | | . | | | | . | | | | . | ------------- | | . | +----| RESET | | | . | | | | | | . | ----- | 2HZ 0SC | | | . | 32.768K | 32.768KHZ | | | . | ----- | XYSTAL | | | . | | | | | | . | +----| Q14|--+ | . | | | | . | --74HCT4060-- | . | | . | | . | | . -------------------------------------------------------- . . . . . (SDC) . . -----------------SECONDS DOWN COUNTER-------------- . | +------------+ |----- . | |74LS14 __ | +-------------------------|BO10S . | | /| / |-+ | | . | +----o |-o G3| | | . | | | \\| \\__|--------------------------------+ | . | | | 74LS00 | | | . | | | | | | . | | | -----PDCE----- | | | . | | | | | | | | . SET_MD|------|SET_MD | | | | . ------| | | | | | ------LCE------ | | . SET_LD|----+-|SET_LD ---| | |--- ____ | | | . | | | BO1|-------|BO1 LOAD |--+ | . CLR|------|CLR | | | | | . | | | ----| | |---- | | . | | | BO10|---+---|BO10 | | . | | | | | | | . | | | | |--- | | . | | | | +---|CLK | | . | | | | | --------------- | . | | |---- | | | . | +---|LOAD 1S_DIGIT|-----------/4----------------|SEC1S . | | | | | . CLKS|------|DOWN 10S_DIGIT|-----------/4----------------|SEC10S . | -------------- | | . ---| | | . CLK|-------------------------+ | . --------------------------------------------------- . . . . . . . (MDC) . . -----------------MINUTES DOWN COUNTER-------------- . | | . | | . | | . | | . | | . | -----PDCE----- | . | | | | . SET_MD|------|SET_MD | | . | | | | . | +---|SET_LD ---| | . | | | BO1| | . CLR|--|---|CLR | | . | | | ----| |----- . | | | BO10|-----------------------------|BO10M . | | | | | . | | | | | . | | | | | . | | | | | . ------| | |---- | | . SET_LD|--+---|LOAD 1S_DIGIT|-----------/4----------------|MIN1S . | | | | . CLKM|------|DOWN 10S_DIGIT|-----------/4----------------|MIN10S . | -------------- | . | | . | | . --------------------------------------------------- . . . . . . . . . . (PDCE) . . --------------PRE-SETTABLE DOWN COUNT ELEMENT-------------- . | | . | | . | 1'S | . | 10'S | . | THMBWHL | . | +-------+ THMBWHL | . | | | | | | VCC +-------+ | . | | | | | | | | | | | | | . | +-------+ +---+ | | | | | | . | | | | | | | +-------+ | . | +--------------------------------------+---+ | | | | | . | | | | | | | | | | | | | | | . | | | | | | +------------------+ | . | | | | | | | A0 A2 B0 B2 | | . | | | | | | |_ A1 A3 B1 B3| | . SET_MD|--------------------------------------|A/B | | . | | | | | | | | | . | | | | | | |_ Y1 Y3 | | . | +----------------------------------|G Y0 Y2 | | . | | | | | | +-------+----74LS157 | . | --- | | | | | | | | | . | /// | | | | | | | | | . ------| | | | | | | | | | . SET_LD|--------+ | | | | | | | | | . | | | | | | | | | | | . | +--------------------------+ | | | | | . | | | | | | | | | | | | | . | | +----------------------------------------------------+ | . ---| | | | | | | | | | | | | | | . BO1|--+ | +----------------------------+ | | | | | | . | | | | | | | | | | | | | | | | . ----| | | | +-------------+ | | +-------------+ | | . BO10|----+ | | | A B C D| | | | A B C D| | | . | | | | | | | | | | | . | | | | --| | | | --| | | . CLR|------+----|CLR BO|---+ +-|CLR BO|-----+ | . | | | __| | | __| | . | | | CO| | | CO| | . | VCC-+-----|UP 74LS192 | | +-----|UP 74LS192 | | . | | | | CTR1 | | | | CTR2 | | . | | | | | | | | | | . DOWN|-----|-----|DOWN QA|\\ +-------|DOWN QA|\\ | . | | | | | | | | | | | . | | | | QB|\\| | | QB|\\| | . | | | |---- | | | |---- | | | . | | +--|LOAD QC|\\| | +-|LOAD QC|\\| | . ----| | | | | | | | | | | . LOAD|--+ | | QD|\\| | | | QD|\\| | . | | | |GND | | | | |GND | | | . | | | +- -----------+ | | | +-------------+ | | . | | | | | | | | | | . | | | --- | | | --- | | . | | | /// | | | /// | | . | | +---------------------|---+ | | | . | +------------------------|-------+ | | . | | | | . ----------------------------------------------------------- . | | . /4 /4 . | | . . 1S_DIGIT 10S_DIGIT . . . . . (LCE) . . -------------------LOAD CONTROL ELEMENT------------ . | | . | +------------------------------------+ | . | | +--------------------------------+ | | . |*used | | | | | . | in | | ----------74LS00--------- | | | . | SDC | | |--------+ +--------|--+ | | . | | | | __ | | __ | | | . | | | | * / |-+ +-| \\ | | | . | | | |--o G3| |G1 o--|--+----+ | . | | | | \\__|-+ +-|__/ | | | | | . | | | | | | | | | | | . | | | |--------+ +--------|--|-+ | | . ---| | | | | | | | | . BO1|-------------|--------+ +--------|--+ | | | . | | | | __ | | __ | | | | . | | | | / |-+ +-| \\ | | | | . | | +---|--o G4| |G2 o--|----+ | | . | | | \\__|-+ +-|__/ | | | | . ----| | | | | | | | | . BO10|---+ +-----|--------+ +--------|--+ | | | . | | ------------------------- | | | | . ____| | | | | | . LOAD|-----------------------------------------------+ | . | | | | | . | | -----------74LS32--------- | | | . | | +-|---------+ +--------|-------+ | . | | | | __ | | __ | | | | | . | | | | / /-+ +-\\ \\ | | | | | . | | | |--< G7| |G5>--|--+ | | | . | | | | \\ __\\-+ +-/__/ | | | | . | | | | | | | | | | . | | VCC-+-|---------+ +--------|-+ | | | . | | | | | | | | . | +--------|---------+ +--------|----+ | | . | | __ | | __ | | | | | . | | / /-+ +-\\ \\ | | | | | . | +----|--< G8| |G6>--|-+ | | | . | | | \\ __\\-+ +-/__/ | | | | . | | | | | | | | | . | | +--|---------+ +--------|-+ | | | . | | | -------------------------- | | | | . | | +----------------------------------+ | | . | | | | | . | +---------------------------------------+ | . ---| | | . CLK|-----------------------------------------+ | . --------------------------------------------------- . . . *********************** END MODULES **************************** . . . . PART NO QTY . . 74LS00 2 . 74LS14 1 . 74LS32 1 . 74LS112 1 . 74LS192 4 . 74HCT4060 1 . 100UF10WVDC 2 . 560R1/4w 2 . 330R1/4W 2 . 32.768KXSTL 1 . SW MOMON 2 . 0.01UF50V 12 . DISPLAY 1 . 22PF 2 . 5VPS 1 . BUZZER 1 . 10U10WVDC 1 . 1KR1/4W 1 . 1.2KR1/4W 1 . 2N4403 1 . THUMBWHEELS 4 74LS157 2

After fiddling around with gate reallocation and worst case timing I am settled on this one- which will only needs the one MUX because minutes are not cascaded: View in a fixed-width font such as Courier.

. . . COUNTDOWN TIMER W/THUMBWHEELS . . MINS SECS . ------------------------------------------ . | ---- ---- ---- ---- | . | | | | | | | | | | . | | | | | O | | | | | . | ---- ---- ---- ---- | . | | | | | O | | | | | . | | | | | | | | | | . | ---- ---- ---- ---- | . ------------------------------------------ . | | | | . /4 / 4 /4 /4 . | | | | . \\---------\\----. \\---------\\----------, . | | . ,---------------------------------. | . | | | | . | .-------------------------------------------------, . | | | | | | . | | | | | | . | | ----MDC----- | | ----SDC----- | | . +------|-|CLR -----| | '--|CLR -----| | | . | | | BO10M|---. | BO10S|------+ . --- | | | | | | | | | . /// | |______ | | | |______ | | | . .----|SET_LD | | | .------|SET_LD | | | . | | | | | | | | | | | . | '-|CLKM MIN1S|/| | | .-|CLKS SEC1S|/| | . | | | | | | | |--- | | | . | | MIN10|/ | | .---|CLK SEC10|/ | . | ------------ | | | | ------------ | . -SSSE- +-------------------------' | | -----74LS00----- | . | | | | | | | | | . | | | | | | | __ / |---' . | | | | | | / |------o G2| . | ___| | | | '--o G1| \\__|---. . | CLK|---|----------------------------' \\__|-- | . | | | | | | | | . | CLK|---|----------------------------------| \\ | | | . | | | | |G3 o------| \\ | . |______| | +------------|__/ | |G4 o--' . |SET_LD|---' | | +----|__/ | . | | | | | | . | | | ----------------- . | ___| | | . | SSR|--------------------------------------------' . | | | . ------ | VCC . | | + 10U . | +---[1K]--+---||--+ . | | | | . | | |< | . '-[1.2K]-+-------| 2N4403 | . |\\ | . | | . BUZZER | . | | . +-------+ . | . --- . /// . . . . . . . . . ****************** LOGIC MODULES ****************************** . . . . . . . . (SSSE) . . -----------------START/STOP/SET ELEMENT----------------- . | | . | VCC | . | | | . | +-------------------------+ | . | | | | . | o o | . | -| STOP/SET -| START | . | o 74LS14 o 74LS14 | . | | |\\ | |\\ | . | +-[560]-+-| o-+ +-[560]-+-| o-+ | . | | +| |/ | | +| |/ | | . | [330] === | [330] === | | . | | 100u| | | 100u| | | . | +-------+ | +-------+ | | . | | | | | | . | --- | --- | | . | /// | /// | | . | | | | . | +------------|-------------------------+ | . | | | |___ . | | +-------------------------------------|SSR . | | VCC | | . | | | | | . | | | | | . | | | | | . | | +--------|-------------------------+ | . | | | | | | . | | | -----|-------------74LS112-------------- | . | | | | | | | | . | | | | +--------+ +--------+ | | . | | | | | --- | | --- | | | . | | | | | PRE | | PRE | | |--- . | | +--|-|J Q |---+ +--------|J Q |---|--|CLK . | | | | |-- | | | |-- | | | . | | +--|-|CK | | | +--|CK | | | . | | | | | FF1 | | | | | FF2 | | | . | | | | | - | | | | | - | | | . | | +--|-|K Q |-+ | | +-----|K Q |---|--|CLK . | | | | | --- | | | | | | | --- | | | . | | | | | CLR | | | | | | | CLR | | | . | | | | +--------+ | | | | | +--------+ | | . | | | | | | | | | | | | | . | | | ---------------------------------------- | . | | | | | | | | | | | . | | +--------|------------+--+ | | | . | | | | | | | |______ . | +------------+ +------------------+-----------|SET_LD . | | | | . | | | | . | | | | . | ------------- | | . | +----| RESET | | | . | | | | | | . | ----- | 2HZ 0SC | | | . | 32.768K | 32.768KHZ | | | . | ----- | XYSTAL | | | . | | | | | | . | +----| Q14|--+ | . | | | | . | --74HCT4060-- | . | | . | | . | | . -------------------------------------------------------- . . . . . (SDC) . . -----------------SECONDS DOWN COUNTER-------------- . | |----- . | +-------------------------|BO10S . | | | . | | | . | +---------------------------------------------+ | . | | | | | . | | | | | . | | -----PDCE_S--- | | | . | | | | | | | . | | | | | | | . ------| | |______ | | ------LCE------ | | . SET_LD|------|SET_LD ---| | |--- ____ | | | . | | | BO1|-------|BO1 LOAD |--+ | . CLR|------|CLR | | | | | . | | | ----| | |---- | | . | | | BO10|---+---|BO10 | | . | | | | | | | . | | | | |--- | | . | | | | +---|CLK | | . | | | | | --------------- | . | | |---- | | | . | +---|LOAD 1S_DIGIT|-----------/4----------------|SEC1S . | | | | | . CLKS|------|DOWN 10S_DIGIT|-----------/4----------------|SEC10S . | -------------- | | . ---| | | . CLK|-------------------------+ | . --------------------------------------------------- . . . . (PDCE_S) . . --------------PRE-SETTABLE DOWN COUNT ELEMENT SECONDS------ . | | . | | . | | . | | . | 10'S | . | THMBWHL | . | VCC +-------+ | . | | | | | | | | . | +---+ | | | | | | . | | | +-------+ | . | +----||------+-------+---+ | | | | | . | | 1N | | | | | | | | | | . | | | +------------------+ | . | | | | A0 A2 B0 B2 | | . ------| |\\ | |\\ |\\ | |_ A1 A3 B1 B3| | . SET_LD|--------+--| o-[220]-+--| o---| o-----|A/B | | . | | |/ |/ |/ | | | | . | | 3x 74LS14 | |_ Y1 Y3 | | . | | +---|G Y0 Y2 | | . | | 1'S THMBWHL | +------------74LS157 | . | | +-------+ --- | | | | | . | | | | | | | /// | | | | | . | | | | | | | | | | | | . | | +-------+ | | | | | . | | | | | | | | | | | . | +--------------------------+ | | | | | . | | | | | | | | | | | | | . | | +----------------------------------------------------+ | . ---| | | | | | | | | | | | | | | . BO1|--+ | +----------------------------+ | | | | | | . | | | | | | | | | | | | | | | | . ----| | | | +-------------+ | | +-------------+ | | . BO10|----+ | | | A B C D| | | | A B C D| | | . | | | | | | | | | | | . | | | | --| | | | --| | | . CLR|------+----|CLR BO|---+ +-|CLR BO|-----+ | . | | | __| | | __| | . | | | CO| | | CO| | . | VCC-+-----|UP 74LS192 | | +-----|UP 74LS192 | | . | | | | CTR1 | | | | CTR2 | | . | | | | | | | | | | . DOWN|-----|-----|DOWN QA|\\ +-------|DOWN QA|\\ | . | | | | | | | | | | | . | | | | QB|\\| | | QB|\\| | . | | | |---- | | | |---- | | | . | | +--|LOAD QC|\\| | +-|LOAD QC|\\| | . | | | | | | | | | | | | . | | | | QD|\\| | | | QD|\\| | . | | | |GND | | | | |GND | | | . | | | +- -----------+ | | | +-------------+ | | . | | | | | | | | | | . | | | --- | | | --- | | . | | | /// | | | /// | | . | +--|------------------|---+ | | | . | | | | | | . | | * from LCE | | | | | | 74LS00 | | | | | | __ | | | | | +--| \\ |\\ | | | | ----| |G3 o----| o------------+ | | LOAD|-----------|__/ |/ | | | | 74LS14 | | | | | | | | | | | | | | | . ----------------------------------------------------------- . | | . /4 /4 . | | . . 1S_DIGIT 10S_DIGIT . . . (MDC) . . -----------------MINUTES DOWN COUNTER-------------- . | | . | | . | | . | | . | | . | -----PDCE_M--- | . | | | | . | | | | . | |______ | | . | +---|SET_LD ---| | . | | | BO1| | . CLR|--|---|CLR | | . | | | ----| |----- . | | | BO10|-----------------------------|BO10M . | | | | | . | | | | | . | | | | | . | | | | | . ------| | |---- | | . SET_LD|--+---|LOAD 1S_DIGIT|-----------/4----------------|MIN1S . | | | | . CLKM|------|DOWN 10S_DIGIT|-----------/4----------------|MIN10S . | -------------- | . | | . | | . ---------------------------------------------------

. . (PDCE_M) . . --------------PRE-SETTABLE DOWN COUNT ELEMENT MINUTES------ . | | . | | . | | . | | . | 1'S 10'S | . | | . | THMBWHL THMBWHL | . | +-------+ +-------+ | . | | | | | | | | | | | | . | | | | | | | | | | | | . | +-------+ +-------+ | . | | | | | | | | | | . ------| | | | | | | | | | . SET_LD|--------+ | | | | | | | | | . | | | | | | | | | | | . | | | | | | | | | | | . | | | | | | | | | | | . | +----------------------------------------------------+ | . | | | | | | | | | | | | | . | | +----------------------------+ | | | | | | . | | | | | | | | | | | | | | | . ----| | | | +-------------+ | +-------------+ | | . BO10|----+ | | | A B C D| | | A B C D| | | . | | | | | | | | | | . | | | | --| | | --| | | . CLR|------+----|CLR BO|---+ +-|CLR BO|-----+ | . | | | __| | | __| | . | | | CO| | | CO| | . | VCC-+-----|UP 74LS192 | | +-----|UP 74LS192 | | . | | | | CTR3 | | | | CTR4 | | . | | | | | | | | | | . DOWN|-----|-----|DOWN QA|\\ +-------|DOWN QA|\\ | . | | | | | | | | | | | . | | | | QB|\\| | | QB|\\| | . | | | |---- | | | |---- | | | . | | +--|LOAD QC|\\| | +-|LOAD QC|\\| | . ----| | | | | | | | | | | . LOAD|--+ | | QD|\\| | | | QD|\\| | . | | | |GND | | | | |GND | | | . | | | +-------------+ | | | +-------------+ | | . | | | | | | | | | | . | | | --- | | | --- | | . | | | /// | | | /// | | . | | +---------------------|---+ | | | . | +------------------------|-------+ | | . | | | | . ----------------------------------------------------------- . | | . /4 /4 . | | . . 1S_DIGIT 10S_DIGIT . . . (LCE) . . -------------------LOAD CONTROL ELEMENT------------ . | | . | +-------------------------------------+ | . |* | +---------------------------------+ | | . |used | | | | | . |in | | ----------74LS00--------- | | | . |PDCE_S| | |--------+ +--------|--+ | | . | | | | __ | | __ | | | . | | | | * / |-+ +-| \\ | | | . | | | |--o G3| |G1 o--|-------+ | . | | | | \\__|-+ +-|__/ | | | | . | | | | | | | | | | . | | | |--------+ +--------|----+ | | . | | | | | | | | . | +------|--------+ +--------|----|--+ | . | | | __ | | __ | | | | . | | | / |-+ +-| \\ | | | | . | | +--|--o G4| |G2 o--|----+ | | . | | | | \\__|-+ +-|__/ | | | | . ---| | | | | | | | | | . BO1|-------------|--------+ +--------|--+ | | | . | | | ------------------------- | | | | . ____| | | | | | | . LOAD|----------+------------------------------------+ | . | | | | | | . | | | -----------74LS32--------- | | | . | | +-|---------+ +--------|-------+ | . | | | | __ | | __ | | | | | . | | | | / /-+ +-\\ \\ | | | | | . | +---|--< G7| |G5>--|--+ | | | . | | | \\ __\\-+ +-/__/ | | | | . | | | | | | | | | . | +-|---------+ +--------|-+ | | | . ----| | | | | | | . BO10|------------|---------+ +--------|----+ | | . | | __ | | __ | | | | | . | | / /-+ +-\\ \\ | | | | | . | +----|--< G8| |G6>--|-+ | | | . | | | \\ __\\-+ +-/__/ | | | | . | | | | | | | | | . | | +--|---------+ +--------|-+ | | | . | | | -------------------------- | | | | . | | +----------------------------------+ | | . | | | | | . | +---------------------------------------+ | . ---| | | . CLK|-----------------------------------------+ | . --------------------------------------------------- . . . *********************** END MODULES **************************** . . . PART NO QTY . . 74LS00 2 . 74LS14 1 . 74LS32 1 . 74LS112 1 . 74LS192 4 . 74HCT4060 1 . 100UF10WVDC 2 . 560R1/4w 2 . 330R1/4W 2 . 32.768KXSTL 1 . SW MOMON 2 . 0.01UF50V 12 . DISPLAY 1 . 22PF 2 . 5VPS 1 . BUZZER 1 . 10U10WVDC 1 . 1KR1/4W 1 . 1.2KR1/4W 1 . 2N4403 1 . THUMBWHEELS 4 . 74LS157 1 . 220R1/4W 1 . 0.001U50V 1 .