Need help with intermittent circuit failures - JK Flip Flops

---

1. A 4059 is a programmable counter, not an inverter.

1. The reed switch should _not_ be used to supply power to the 555. The 555 should be connected across the power rails and the reed switch should only be used to do the triggering.

2. Your triggering polarity is wrong. It should be a short negative-going spike. Here's how the 555 should be wired: (View in Courier)

+12V-+---------+---+----+-------+------+ | | | | |8 | [10K] [10K] +->[POT] +---+---+ | | | | 2|_ Vcc _|4 | +-[0.1µF]-+--------|--O|T R|O-+ | | 6| |3 | O +---|TH OUT|------ | O | 7|_ |5 SW1| +--O|D VC|----+ | +| | GND | | | [10µF] +---+---+ [0.1µF] | | |1 | GND>-+------------------+-------+--------+

1. The motor drive logic is bad because when the 555 times out its output will go low, driving U2-2 high. This will toggle the JK and send power to the motor at the same time. Unfortunately, power will be sent to the motor before the direction relay has a chance to toggle, so the motor will be starting to spin up when the relay opens, cutting off power to the motor and then, when it closes on the other set of contacts, plugging the motor. OUCH!

To keep that from happening, what you need to do is cut power to the motor first, when the reed relay triggers the 555, then, when the motor stops spinning, toggle the relay, and then reapply power to the motor, like this:

|-->T1

--
Oops, I misread the "4069" as "4059"...

On Fri, 09 Jun 2006 11:56:41 -0500, John Fields wrote:

--- Here ya go. Since you had half of the JK left over, and some inverters as well, I made a debouncer out of the JK and split the drivers into two sections; one for the relay and one for motor power. Make sure you disconnect R2 from U2-2 and/or U3-3 if you use my circuit. Following the schematic is a partly fleshed out LTSPICE simulation. Enough to see that the logic and the noise filter / debouncer works. Enjoy! :-)

+12V>-+-------+ | | U3B O [0.1µF] 4027 | | 9+-------+15 SW1| 1 R1|---------+ | |10| | | GND +--|J1 | [2.2µF] |11| _ |14 | +--|K1 Q1|---+ GND | +-------+ | GND | | +12V>--+--[10K]--+-----[0.1µF]---+ | | +---------|------+-------+------+ | | | U1 |8 | [1N4148] | [1MR] +---+---+ | | | | 2|_ Vcc _|4 | +---------+------|--O|T R|O-+ U2 | | 6| |3 1| \\ 2 | +---|TH OUT|-----O| >---> TO U3-3 | | 7|_ |5 | / | +--O|D VC|----+ | +| | GND | | | [1.2µF] +---+---+ [0.1µF] | | |1 | GND>-------------|------+-------+--------+ | | | | +12v>------------|------+-------+------+ | | U4 | | | [1MR] +---+---+ | | | |_ Vcc _|4 | +------|--O|T R|O-+ U2 | | |3 | \\ +---|TH 0UT|-----O| >---> TO R2 | |_ | | / +--O|D VC|----+ +| | GND | | [1.5µF]+---+---+ [0.1µF] | | | GND---------------------+-------+--------+

Version 4 SHEET 1 1972 1056 WIRE -1280 400 -1280 -80 WIRE -1280 544 -1280 480 WIRE -1280 592 -1280 544 WIRE -1168 400 -1168 144 WIRE -1168 544 -1280 544 WIRE -1168 544 -1168 480 WIRE -1072 400 -1072 240 WIRE -1072 544 -1168 544 WIRE -1072 544 -1072 480 WIRE -976 544 -1072 544 WIRE -976 544 -976 288 WIRE -928 240 -1072 240 WIRE -928 288 -976 288 WIRE -880 144 -1168 144 WIRE -880 224 -880 144 WIRE -880 352 -880 304 WIRE -880 432 -880 352 WIRE -880 544 -976 544 WIRE -880 544 -880 512 WIRE -816 -80 -1280 -80 WIRE -816 -32 -816 -80 WIRE -816 80 -816 32 WIRE -816 352 -880 352 WIRE -816 352 -816 80 WIRE -768 224 -768 176 WIRE -768 544 -880 544 WIRE -768 544 -768 224 WIRE -720 176 -768 176 WIRE -720 224 -768 224 WIRE -640 80 -816 80 WIRE -640 128 -640 80 WIRE -640 384 -640 272 WIRE -496 176 -560 176 WIRE -496 272 -496 176 WIRE -496 384 -640 384 WIRE -496 384 -496 352 WIRE -496 432 -496 384 WIRE -496 544 -768 544 WIRE -496 544 -496 496 WIRE -464 224 -544 224 WIRE -384 -80 -816 -80 WIRE -384 48 -384 -80 WIRE -384 224 -400 224 WIRE -384 224 -384 112 WIRE -304 -80 -384 -80 WIRE -304 32 -304 -80 WIRE -304 224 -384 224 WIRE -304 224 -304 112 WIRE -224 288 -224 -320 WIRE -160 -320 -224 -320 WIRE -160 224 -304 224 WIRE -160 224 -160 -128 WIRE -128 544 -496 544 WIRE -128 544 -128 160 WIRE -96 -368 -96 -480 WIRE -48 -368 -96 -368 WIRE -48 -320 -96 -320 WIRE -48 -80 -304 -80 WIRE -48 -32 -48 -80 WIRE -48 352 -48 48 WIRE -48 432 -48 352 WIRE -48 464 -48 432 WIRE -48 544 -128 544 WIRE -48 544 -48 528 WIRE -16 160 -128 160 WIRE -16 224 -160 224 WIRE -16 288 -224 288 WIRE -16 352 -48 352 WIRE 32 -416 32 -448 WIRE 32 -224 32 -272 WIRE 160 -448 32 -448 WIRE 160 -224 32 -224 WIRE 160 -224 160 -448 WIRE 160 -192 160 -224 WIRE 192 -480 -96 -480 WIRE 192 -320 128 -320 WIRE 192 -320 192 -480 WIRE 272 -368 112 -368 WIRE 272 -320 272 -368 WIRE 272 -192 272 -240 WIRE 272 224 208 224 WIRE 272 288 208 288 WIRE 272 288 272 224 WIRE 272 320 272 288 WIRE 336 -80 -48 -80 WIRE 336 160 208 160 WIRE 336 160 336 -80 WIRE 336 192 336 160 WIRE 336 320 272 320 WIRE 336 320 336 272 WIRE 336 352 336 320 WIRE 336 544 -48 544 WIRE 336 544 336 416 WIRE 464 -128 -160 -128 WIRE 464 224 464 -128 WIRE 464 320 464 288 WIRE 464 544 336 544 WIRE 464 544 464 400 WIRE 560 432 -48 432 WIRE 560 432 560 352 WIRE 592 544 464 544 WIRE 592 544 592 160 WIRE 656 160 592 160 WIRE 656 224 464 224 WIRE 656 288 464 288 WIRE 656 352 560 352 WIRE 944 -80 336 -80 WIRE 944 160 880 160 WIRE 944 160 944 -80 WIRE 944 224 880 224 WIRE 944 288 880 288 WIRE 944 288 944 224 WIRE 944 320 944 288 WIRE 1008 160 944 160 WIRE 1008 192 1008 160 WIRE 1008 320 944 320 WIRE 1008 320 1008 272 WIRE 1008 352 1008 320 WIRE 1008 544 592 544 WIRE 1008 544 1008 416 FLAG -1280 592 0 FLAG 160 -192 0 FLAG 272 -192 0 SYMBOL Misc\\\\NE555 96 256 R0 SYMATTR InstName U1 SYMBOL voltage -1072 384 R0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR Value PULSE(0 5 1 1e-6 1e-6 1 0 1) SYMATTR InstName V1 SYMBOL voltage -1280 384 R0 WINDOW 123 0 0 Left 0 WINDOW 3 24 104 Invisible 0 SYMATTR Value 5 SYMATTR SpiceLine Rser=0 SYMATTR InstName V2 SYMBOL res 320 176 R0 SYMATTR InstName R2 SYMATTR Value 1e6 SYMBOL cap 320 352 R0 SYMATTR InstName C1 SYMATTR Value 1.2e-6 SYMBOL Misc\\\\NE555 768 256 R0 SYMATTR InstName U2 SYMBOL res 992 176 R0 SYMATTR InstName R4 SYMATTR Value 1e6 SYMBOL cap 992 352 R0 SYMATTR InstName C2 SYMATTR Value 1.5e-6 SYMBOL cap -400 208 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C6 SYMATTR Value .1e-6 SYMBOL res -320 16 R0 SYMATTR InstName R6 SYMATTR Value 10k SYMBOL diode -368 112 R180 WINDOW 0 43 30 Left 0 WINDOW 3 25 -6 Left 0 SYMATTR InstName D2 SYMATTR Value 1N4148 SYMBOL res 448 304 R0 SYMATTR InstName R7 SYMATTR Value 1000 SYMBOL Digital\\\\dflop 32 -416 R0 SYMATTR InstName A1 SYMATTR SpiceLine trise 1e-6 tfall 1e-6 vhigh 5v SYMBOL Digital\\\\inv -160 -384 R0 SYMATTR InstName A2 SYMATTR SpiceLine trise 1e-6 tfall 1e-6 vhigh 5v SYMBOL Digital\\\\dflop -640 128 R0 SYMATTR InstName A3 SYMATTR SpiceLine trise 1e-6 tfall 1e-6 vhigh 5v SYMBOL res -896 416 R0 WINDOW 0 -40 35 Left 0 WINDOW 3 -46 62 Left 0 SYMATTR InstName R5 SYMATTR Value 100K SYMBOL sw -880 320 M180 WINDOW 0 -55 143 Left 0 WINDOW 3 -81 109 Left 0 SYMATTR InstName S2 SYMATTR Value MYSW SYMBOL res -512 256 R0 WINDOW 0 -43 40 Left 0 WINDOW 3 -35 71 Left 0 SYMATTR InstName R8 SYMATTR Value 1e6 SYMBOL cap -512 432 R0 WINDOW 0 -43 32 Left 0 WINDOW 3 -62 62 Left 0 SYMATTR InstName C4 SYMATTR Value 2e-6 SYMBOL res 256 -336 R0 SYMATTR InstName R9 SYMATTR Value 10k SYMBOL voltage -1168 384 R0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR Value PULSE(0 5 0 1e-7 1e-7 .001 .002) SYMATTR InstName V3 SYMBOL cap -832 -32 R0 SYMATTR InstName C3 SYMATTR Value 1E-7 SYMBOL cap -64 464 R0 WINDOW 0 36 34 Left 0 WINDOW 3 24 60 Left 0 SYMATTR InstName C5 SYMATTR Value 1E-7 SYMBOL res -64 -48 R0 WINDOW 0 -53 35 Left 0 WINDOW 3 -67 62 Left 0 SYMATTR InstName R1 SYMATTR Value 100K TEXT -1178 -160 Left 0 !.tran 0 3s 0 TEXT -1184 -128 Left 0 !.model MYSW SW(Ron=1 Roff=1Meg Vt=.5 Vh=-.4)

-- John Fields Professional Circuit Designer

+12V>-+-------+ | | U3B O [0.1µF] 4027 | | 9+-------+15 SW1| 1 R1|---------+ | |10| | | GND +--|J1 | [2.2µF] |11| _ |14 | +--|K1 Q1|---+ GND | +-------+ | GND | | +12V>--+--[10K]--+-----[0.1µF]---+ | | +---------|------+-------+------+ |K | | U1 |8 | [1N4148] | [1MR] +---+---+ | | | | 2|_ Vcc _|4 | +---------+------|--O|T R|O-+ U2 | | 6| |3 1| \\ 2 | +---|TH OUT|-----O| >---> TO U3-3 | | 7|_ |5 | / | +--O|D VC|----+ | +| | GND | | | [1.2µF] +---+---+ [0.1µF] | | |1 | GND>-------------|------+-------+--------+ | | | | +12v>------------|------+-------+------+ | | U4 | | | [1MR] +---+---+ | | | |_ Vcc _|4 | +------|--O|T R|O-+ U2 | | |3 | \\ +---|TH 0UT|-----O| >---> TO R2 | |_ | | / +--O|D VC|----+ +| | GND | | [1.5µF]+---+---+ [0.1µF] | | | GND---------------------+-------+--------+

--
Oops... The cathode of the 1N4148 should go to +12V, as shown.

I can't find it either. Ed

In addition to John's reply, another change is needed: you're not driving Q1 hard enough. Lower the value of R2 from 10K to 1K.

Ed

Noted. Thanks Ed =)

Thanks guys heaps. You been a great help. I haven't had a chance yet to try your schematic John (Petrus and ehsjr, I have noted your observations and advice as well), but I'll let you know as soon as I've totally rewired my breadboard...ugh.

However, do I really need to add another IC to my board (the 2nd 555)? This board has to be as small as possible... I didn't think I'd need so much electronics to do this simple task. Maybe 1x 556 (dual 555 IC) instead of

2x 555 would save a little more space??

By the way - in relation to the way I configured the monostable.... is it still a bad thing to want to be able to trigger the monostable at power on (ignoring the reed switch for arguments sake)? Assume pins 1 and 8 were connected directly to the supply rails... so when power is turned on, the monostable triggers automatically (due to C2). I understand the correct method of triggering pin 2 with a negative pulse, but then I would need a separate circuit to achieve that as well - the negative pulse. That is the only reason why I connected the reed relay the way I did - When the magnet comes into contact with the reed, it triggers the 555, doesn't matter how long the reed is in contact with the magnet for. In my circuit, if I made it so that the reed switch triggers pin 2, the 555 would freeze (on 'high') because the motor would have turned off and stopped right in front of the magnet indefinately. I was just wondering that's all.

The two 15V zener diodes across the motor opposite each other is critical yeah? Is my Q1 transistor overheating because these are absent? Or because of the motor reactivating too soon before the relay switches over??? The Q1 is rated 0.8A.

P.S: John, I really appreciate your schematics... makes it a lot easier to understand what you are talking about =).

Ta Jason.

*** Further to this, I have redone my schematic. Please check if everything is correct as I may have missed something or misunderstood a bit here n there.

Try this direct link :

... or find it manually by going to

then clicking 'PHOTOS', 'Electronics', and clicking top (most recent) image, "schemtaic_SL_v2".

I am yet to rewire my breadboard.

Regards,

Jason.

On Thu, 08 Jun 2006 19:00:26 GMT, in message , Rich Grise scribed:

Irfan V. 3.80 for Windows does the trick nicely. I don't like the newer versions. And, um, thanks for the info about .gif vs. .jpg. Now it's off to the forest to take some photos of hot babes!

--
The second 555 isn\'t necessary.  After thinking about it for a
while, Petrus\' suggestion to use unused gates to get the delay
turned out to be a good one, so that\'s what I did.  I\'ve posted a
new schematic for you on abse which has that change (as well as
others) on it.  After looking the schematic over, if you need a
circuit description I\'ll be happy to post one here.

--------- Hi John, I don't see the new schematic on adse =( Remember how you couldn't see mine? Looks like the same thing is happening. Please, I would like to see it =) If I could get away without the need for an additional IC, I'd be happy. But if I need it I need it... but I'll probably end up somehow wiring up a

556 rather than two separate 555's. That'd be alright wouldn't it?

John, please confirm the correct wiring of these zeners on my schematic if your new schematic doesn't include this section of the circuit. I'm not

100% if I understood what you meant by, "connect two 15V Zener diodes in series opposition across the motor".

Jason.

--- OK, I've emailed it to you.

If you don't have access to abse it's probably because your ISP doesn't carry abse. If you want it, let them know and maybe they'll start carrying it.

BTW, I'm working on a version of the circuit with _no_ 555s which looks pretty good. I'll post it to abse and email you a schematic when I'm done. Sometime today, I think.

-- John Fields Professional Circuit Designer

On Sun, 11 Jun 2006 07:45:09 -0500, John Fields wrote:

--- Better than that, an LTSPICE simulation follows that uses only two chips for the logic, a "D" type flip-flop and a NOR. I used a MOSFET bridge instead of a relay for the motor rotation reversal, but if you want to use a relay you can hook it up like you've shown on your schematic. Same thing for the power ON-OFF to the motor.

Version 4 SHEET 1 2564 1056 WIRE -2304 112 -2304 -624 WIRE -2304 480 -2304 112 WIRE -2304 624 -2304 560 WIRE -2304 672 -2304 624 WIRE -2192 480 -2192 224 WIRE -2192 624 -2304 624 WIRE -2192 624 -2192 560 WIRE -2096 112 -2304 112 WIRE -2096 480 -2096 320 WIRE -2096 624 -2192 624 WIRE -2096 624 -2096 560 WIRE -2000 624 -2096 624 WIRE -2000 624 -2000 368 WIRE -1952 320 -2096 320 WIRE -1952 368 -2000 368 WIRE -1904 224 -2192 224 WIRE -1904 304 -1904 224 WIRE -1904 432 -1904 384 WIRE -1904 512 -1904 432 WIRE -1904 624 -2000 624 WIRE -1904 624 -1904 592 WIRE -1840 112 -2032 112 WIRE -1840 432 -1904 432 WIRE -1840 432 -1840 112 WIRE -1792 304 -1792 256 WIRE -1792 624 -1904 624 WIRE -1792 624 -1792 304 WIRE -1744 256 -1792 256 WIRE -1744 304 -1792 304 WIRE -1664 112 -1840 112 WIRE -1664 208 -1664 112 WIRE -1664 464 -1664 352 WIRE -1664 512 -1664 464 WIRE -1664 624 -1792 624 WIRE -1664 624 -1664 576 WIRE -1632 464 -1664 464 WIRE -1520 144 -1520 112 WIRE -1520 256 -1584 256 WIRE -1520 256 -1520 208 WIRE -1520 464 -1552 464 WIRE -1520 464 -1520 256 WIRE -1408 112 -1520 112 WIRE -1408 464 -1408 112 WIRE -1408 512 -1408 464 WIRE -1408 624 -1664 624 WIRE -1408 624 -1408 576 WIRE -1328 464 -1408 464 WIRE -1328 496 -1328 464 WIRE -1328 624 -1408 624 WIRE -1328 624 -1328 576 WIRE -1184 112 -1408 112 WIRE -1184 208 -1184 112 WIRE -1184 304 -1184 272 WIRE -1184 368 -1184 336 WIRE -1184 480 -1184 432 WIRE -1184 512 -1184 480 WIRE -1184 624 -1328 624 WIRE -1184 624 -1184 576 WIRE -1152 208 -1184 208 WIRE -1152 272 -1184 272 WIRE -1152 368 -1184 368 WIRE -1152 432 -1184 432 WIRE -1152 480 -1184 480 WIRE -1040 -464 -1040 -592 WIRE -1040 256 -1088 256 WIRE -1040 256 -1040 -416 WIRE -1040 288 -1184 336 WIRE -1040 288 -1040 256 WIRE -1040 336 -1184 304 WIRE -1040 416 -1088 416 WIRE -1040 416 -1040 336 WIRE -1040 480 -1072 480 WIRE -1040 480 -1040 416 WIRE -992 -464 -1040 -464 WIRE -992 -416 -1040 -416 WIRE -912 -512 -912 -560 WIRE -912 -320 -912 -368 WIRE -912 -224 -912 -320 WIRE -864 112 -1184 112 WIRE -864 208 -864 112 WIRE -864 304 -864 272 WIRE -864 368 -864 336 WIRE -864 480 -864 432 WIRE -864 512 -864 480 WIRE -864 624 -1184 624 WIRE -864 624 -864 576 WIRE -832 208 -864 208 WIRE -832 272 -864 272 WIRE -832 368 -864 368 WIRE -832 432 -864 432 WIRE -832 480 -864 480 WIRE -784 -560 -912 -560 WIRE -784 -320 -912 -320 WIRE -784 -320 -784 -560 WIRE -736 -592 -1040 -592 WIRE -736 -416 -816 -416 WIRE -736 -416 -736 -592 WIRE -736 -176 -736 -416 WIRE -736 80 -736 -176 WIRE -720 256 -768 256 WIRE -720 288 -864 336 WIRE -720 288 -720 256 WIRE -720 336 -864 304 WIRE -720 416 -768 416 WIRE -720 416 -720 336 WIRE -720 480 -752 480 WIRE -720 480 -720 416 WIRE -672 -176 -736 -176 WIRE -672 80 -736 80 WIRE -624 -192 -624 -256 WIRE -624 -48 -624 -96 WIRE -624 0 -624 -48 WIRE -624 144 -624 96 WIRE -528 256 -720 256 WIRE -512 -48 -624 -48 WIRE -480 -624 -2304 -624 WIRE -480 -256 -624 -256 WIRE -480 -256 -480 -624 WIRE -480 144 -624 144 WIRE -480 176 -480 144 WIRE -480 368 -480 272 WIRE -336 -256 -480 -256 WIRE -336 -192 -336 -256 WIRE -336 -48 -432 -48 WIRE -336 -48 -336 -96 WIRE -336 0 -336 -48 WIRE -336 144 -480 144 WIRE -336 144 -336 96 WIRE -240 -464 -832 -464 WIRE -240 -176 -288 -176 WIRE -240 -176 -240 -464 WIRE -240 80 -288 80 WIRE -240 80 -240 -176 FLAG -2304 672 0 FLAG -912 -224 0 FLAG -480 368 0 SYMBOL voltage -2096 464 R0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR Value PULSE(0 5 .1 1e-6 1e-6 .01 2s) SYMATTR InstName V1 SYMBOL voltage -2304 464 R0 WINDOW 123 0 0 Left 0 WINDOW 3 24 104 Invisible 0 SYMATTR Value 12 SYMATTR SpiceLine Rser=0 SYMATTR InstName V2 SYMBOL res -1056 464 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R2 SYMATTR Value 1e6 SYMBOL cap -1200 512 R0 SYMATTR InstName C1 SYMATTR Value .4e-6 SYMBOL cap -1536 144 R0 SYMATTR InstName C6 SYMATTR Value .1e-6 SYMBOL res -1344 480 R0 SYMATTR InstName R6 SYMATTR Value 10k SYMBOL diode -1392 576 R180 WINDOW 0 43 30 Left 0 WINDOW 3 25 -6 Left 0 SYMATTR InstName D2 SYMATTR Value 1N4148 SYMBOL Digital\\\\dflop -1664 208 R0 SYMATTR InstName A3 SYMATTR SpiceLine trise 1e-6 tfall 1e-6 vhigh 12v SYMBOL res -1920 496 R0 WINDOW 0 -40 35 Left 0 WINDOW 3 -46 62 Left 0 SYMATTR InstName R5 SYMATTR Value 100K SYMBOL sw -1904 400 M180 WINDOW 0 -51 9 Left 0 WINDOW 3 -76 -15 Left 0 SYMATTR InstName S2 SYMATTR Value MYSW SYMBOL res -1536 448 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R8 SYMATTR Value 1e6 SYMBOL cap -1680 512 R0 WINDOW 0 -43 32 Left 0 WINDOW 3 -62 62 Left 0 SYMATTR InstName C4 SYMATTR Value .3e-6 SYMBOL voltage -2192 464 R0 WINDOW 3 24 104 Invisible 0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR Value PULSE(0 12 0 1e-6 1e-6 1e-3 2e-3) SYMATTR InstName V3 SYMBOL cap -2032 96 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C3 SYMATTR Value 1E-7 SYMBOL Digital\\\\dflop -912 -512 R0 SYMATTR InstName A1 SYMATTR SpiceLine trise 1e-6 tfall 1e-6 vhigh 12V SYMBOL Digital\\\\or -1120 176 R0 WINDOW 0 -10 110 Left 0 SYMATTR InstName A9 SYMATTR SpiceLine trise 1e-6 tfall 1e-6 vhigh 12V SYMBOL res -736 464 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R1 SYMATTR Value 1e6 SYMBOL cap -880 512 R0 SYMATTR InstName C5 SYMATTR Value .5e-6 SYMBOL Digital\\\\or -800 176 R0 WINDOW 0 -10 112 Left 0 SYMATTR InstName A2 SYMATTR SpiceLine trise 1e-6 tfall 1e-6 vhigh 12V SYMBOL Digital\\\\or -800 336 R0 SYMATTR InstName A4 SYMATTR SpiceLine trise 1e-6 tfall 1e-6 vhigh 12V SYMBOL Digital\\\\or -1120 336 R0 SYMATTR InstName A10 SYMATTR SpiceLine trise 1e-6 tfall 1e-6 vhigh 12V SYMBOL pmos -288 -96 R180 SYMATTR InstName M3 SYMATTR Value FDS6575 SYMBOL pmos -672 -96 M180 SYMATTR InstName M1 SYMATTR Value FDS6575 SYMBOL nmos -672 0 R0 SYMATTR InstName M5 SYMATTR Value FDS6680A SYMBOL nmos -288 0 M0 SYMATTR InstName M6 SYMATTR Value FDS6680A SYMBOL nmos -528 176 R0 SYMATTR InstName M2 SYMATTR Value FDS6680A SYMBOL ind -528 -32 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 5 56 VBottom 0 SYMATTR InstName L1 SYMATTR Value .1 SYMATTR SpiceLine Rser=10 TEXT -2258 680 Left 0 !.tran 0 30s 0 TEXT -2280 648 Left 0 !.model MYSW SW(Ron=1 Roff=1Meg Vt=.5 Vh=-.4) TEXT -2192 208 Left 0 ;BOUNCE / NOISE TEXT -2096 304 Left 0 ;REED SWITCH TEXT -1792 184 Left 0 ;DEBOUNCE TEXT -1176 152 Left 0 ;SPINDOWN TEXT -1152 176 Left 0 ;TIMER TEXT -848 152 Left 0 ;POWER TEXT -840 176 Left 0 ;TIMER TEXT -1024 -536 Left 0 ;FWD/REV

-- John Fields Professional Circuit Designer

[snip]

Hi again John, Thanks, I received your email with your PDF attachment. I have also added this to my website so everybody else can see what you have posted to me, if that's ok.

Click this link to view the schematic John Fields emailed to me :

.

I rewired my breadboard and the attached circuit works quite well, although I couldn't hook up the gearhead motor because I broke one of its terminals =S ... I'll have to pull it apart and resolder it. Besides, I don't have any 15V zeners on me at the moment, so I don't want to pop another BC338! But at least I can tell what is happening by the 3 LED's, "Motor On", "Direction A" and "Direction B". So it appears now there is that extra delay before the motor turns back on.

I've noticed a potential problem though!!! You know how this thing pans 180 degrees and then changes direction shortly after the reed switch is magnetized? This thing would break on me if it was left the way it is (not the circuit, but the outer structure because it's not designed to spin beyond 180 degrees).

- I'll give you an example: Imagine the motor is turning in Direction "A", and the reed switch just made contact with the magnet. Then I shut down the whole circuit intentionally (at this stage, it has already panned 180 degrees, which is the max). If you then turn the circuit back on, *sometimes* the motor starts to spin in the same direction (A) it was before - when it should be turning the opposite direction (B) straight away. So somehow the circuit will need to know that it reached the end from the previous time and should be turning in the correct direction. I'm not sure how this will need to be hooked up, but maybe a second reed switch is needed (one for each direction)???

Other than that it seems to be working fine. I can't wait to see your next version John.... no 555!

Regards Jason.

--
Yes.

John! Thanks for the once-again modified schematic. Fantastic to see less IC's ... from three down to only one single IC now, the 74HC02 NOR gate! As you know, IC's take a lot of room on a board, and my board needs to be as small as possible. I haven't got some of the parts readily available to modify my breadboard prototype, but when I get my hands on them (within the next couple of days) I will try it out and see what happens! I'll get back to you to let you know how I went. Fingers crossed it won't need any more mods =)

I will include your mod on my website incase anyone wants to see it (for those who can't access it via ABSE like I can't).

Thanks Jason.

Hi John,

I built your latest schematic on my breadboard. Works really well, except for one thing.... There is no 1 sec delay for the motor before the relay switches over. So what it's doing is turning off the motor and switching relay contacts at the same time, then half a second later the motor turns back on.

Regards Jason.

--- Good!, that's how it's supposed to work. :-)

The reason the relay switches over when the motor stops is because there's no reason for it not to and it saves a timer.

Think about it... once power to the motor is cut off, all you need is the delay for the motor to stop turning before you supply power to the motor again, so when the direction-reversing relay switches over is immaterial.

If you need some extra time before power is again applied to the motor just adjust R10.

-- John Fields Professional Circuit Designer