I wish to take digital clock seconds "00 to 59" and translate the segments into 0 to 60 incrementing LED'S. IOW the digital display converted to "analog" ring of LED's around the clock face. Thus my digital clock display's "hh:mm" and a ring of LED's (60 for each second). They must start at the 12 O-Clock position when seconds makes 00.
Looking at the MAX 7219 to drive the individule LEDs. How can I decode this?
Largo
If I understand what you need to do, drive 60 individual LEDs, the minimum drive line count is 16 (8 x 8 matrix). PIC16F870 has enough lines plus some for I/O. Matrix LED anodes on Port-B, cathodes on Port-C. Drive 1 line high, and one low from each port. Float the rest. Then move on to the next line for a count of 60.
The PIC's all have 25ma current limit so resistors are not needed. This is a 'one chip' solution.
-- Luhan Monat: luhanis(at)yahoo(dot)com http://members.cox.net/berniekm "Any sufficiently advanced magick is indistinguishable from technology."
Spehro Pefhany wrote: snip
It's probably easier to make a whole clock with a PIC than to decode the digits...
-- ------------------------------------------- Tim Wescott Wescott Design Services http://www.wescottdesign.com
9 port lines are enough to directly drive 60 LEDs.
I think I'd like to see 9 current limiting resistors in there. The maximum current is not well defined.
But converting the drive from two digits of an existing digital clock into unary sounds pretty unpleasant.
Best regards, Spehro Pefhany
-- "it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
How do you do 60 LEDs with 9 lines?
-- Luhan Monat: luhanis(at)yahoo(dot)com
antiparallel ???
Could you please post a simple schematic.
I don't get it.
Spehro Pefhany wrote:
I pondered this myself for use with a WWVB clock.
Reset a 60-long shift-register at 00, then clock it at one second intervals.
MAYBE smaller, use counters and decoding logic.
...Jim Thompson
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I love to cook with wine. Sometimes I even put it in the food.
Connect two antiparallel LEDs betwen each unique pair of lines (series resistor on each line assumed). The maximum number of LEDs with n lines is thus n*(n-1) for n>=2. To drive a single LED you tristate all but two lines, on those two you make one high and the other low. The antiparallel LED is turned on by reversing the polarity, of course. Only one LED can be on at once, but that's okay for this application (and multiplexing can increase the number that visually appear to be lit, within reason).
Best regards, Spehro Pefhany
-- "it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Okay, sounds like dinner's almost ready, let's see if I can get it done and scanned.. ah, in the nick of time:
This is an example of driving 12 LEDs from 4 port lines.
Best regards, Spehro Pefhany
-- "it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Google for charlieplexing.
-- Thanks, Frank. (remove \'q\' and \'invalid\' when replying by email)
You are most exactly correct on this. I'll keep it in mind next time I need to run a shitload of LED's from just a few line.
-- Luhan Monat: luhanis(at)yahoo(dot)com http://members.cox.net/berniekm "Any sufficiently advanced magick is indistinguishable from technology."
And, on the input end, de-multiplexing the digit data (most likely) and level-shifting the LED drive (assuming it's an LED clock)- maybe a bunch of comparators.
I did something like this ages ago using a few 4051s to mux static
3-1/2 digit LED drive into a single comparator. Plus some magic to synchronize with updates. Unpleasant.Best regards, Spehro Pefhany
-- "it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
I think the Velleman design is a sub-optimal variation that, in return, for the extra port lines, allows an inexpensive single-sided PCB layout
Best regards, Spehro Pefhany
-- "it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
In article , Spehro Pefhany wrote: [....]
To make the design easier you can:
Do it in two steps. The first could be a PROM look up table with 128 elements, 10 of which will ever be addressed. From there it is a simple decode.
Since this is only got to work at 1Hz like time frames: you could just make a table of LED states and search down the list for one that matches the clock's output. There could be a second table that gives the port state for the LED drive.
-- -- kensmith@rahul.net forging knowledge
Several electronics stores (in Europe at least) sell kits made by a company called Velleman. One of their kits is a roulette wheel, which uses a PIC to drive 36 LEDs. The circuit for it is here:
It's the same principle as Spehro's, just taken a few stages further (and so far as I can see, still a fair bit of room for expansion). Very cunning! Mike
Spehro Pefhany wrote in sci.electronics.design:
Nice drawing :)
It could also be arranged in a matrix with diodes across each crossing except the main diagonal, all the same orientation. The port lines are connected to both the rows and the columns of the matrix. That are n^2 - n = n*(n - 1) diodes. To light the diode at i,k (i != k), make line i high, line k low, and make all other lines hi-z.
Anno
An amp? With _one_ _6AQ5A_?
Might as well plug high-impedance phones right into the guitar jack.
Good Luck! Rich
Looks like the DSP6 strobe is going to be several KHz- so scratch that idea. Why don't you learn how to re-program the PIC- or ask the kit maker to do it, so that RC0-RC6 output a 4-bit BCD instead of 7-segment when addressing DSP5,6- then 2x 4-bit latches capture the data and drive the 74HC42 circuit.
Why can't you?
How many suggestions do you need? Do you want to maintain the 7-segment, and _add_ the seconds roulette wheel?
Then you'll either need 8x 8-bit shift registers, 4X 4-to-16 decoders, or a matrix.
Or another PIC, which means you'll have to learn to program a PIC anyway.
Do you want a strictly hardware solution to this, without any programming involved _at all_? Then be prepared to spend about a couple of hundred bucks on discrete logic and perfboards.
Good Luck! Rich
The last two digits to go away, then add the roulette wheel, as you say, run off the seconds digits logic. Or if possible, program this into the PIC--unfortunately like Steve Ciarcia say's "My favorite programming language is solder"
I'll need to absorb all these great suggestions. Thanks for your patients.
No way. Largo
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