latching LED array
latching LED array
(OP)
I am in need of a simple circuit that will latch on an LED after a momentary digital signal is produced (dry contact), and stay on until power is removed. I need an array of 60 of these, so the simplest/smallest footprint/least wiring possible is desired. One or more of these LEDs is expected to light per use.
The ideal device as far as I can tell would be something like a light-emitting SCR (LESCR, SCLED, Thyristor LED?), however there does not appear to be such a device. An SCR in series is another option, but a multiple channel IC would be preferred instead of an additional device per LED.
I haven't seen anything higher than a 4-channel S/R latch IC (e.g. 4043/4044), and besides, the reset function is superfluous (although could be used instead of removing power entirely). Is there anything out there either with more channels, or with a single reset for all channels?
The LEDs will be arranged in a 6x10 grid, so I am also considering the idea of turning on a row & column to activate these. However, with multiple activations there will be one or more extra LEDs lit, which will add confusion.
So what are my options? Thanks for your help!
The ideal device as far as I can tell would be something like a light-emitting SCR (LESCR, SCLED, Thyristor LED?), however there does not appear to be such a device. An SCR in series is another option, but a multiple channel IC would be preferred instead of an additional device per LED.
I haven't seen anything higher than a 4-channel S/R latch IC (e.g. 4043/4044), and besides, the reset function is superfluous (although could be used instead of removing power entirely). Is there anything out there either with more channels, or with a single reset for all channels?
The LEDs will be arranged in a 6x10 grid, so I am also considering the idea of turning on a row & column to activate these. However, with multiple activations there will be one or more extra LEDs lit, which will add confusion.
So what are my options? Thanks for your help!





RE: latching LED array
Dan - Owner
http://www.Hi-TecDesigns.com
RE: latching LED array
TTFN

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RE: latching LED array
IRstuff - not something I had considered, I'll look into that; but again, trying to find an elegant solution that does not have superfluous features.
RE: latching LED array
If so, hands down, a large pin count microcontroller. Say, something in a 100 or 120 pin count region. Perhaps something off this list:
List of micros
You can get a free compiler for this little job.
Use a couple of pins to scan ALL the buttons and then directly drive all the LEDs from the raft of remaining pins. You're talking a regulator a single chip and a handful of resistors.
Keith Cress
kcress - http://www.flaminsystems.com
RE: latching LED array
If you plan on adding a bunch of functionality, high-pin count micros are likely better, assuming you can program.
If you can only wire together chips, latching ICs is best.
Dan - Owner
http://www.Hi-TecDesigns.com
RE: latching LED array
If you multiplex the buttons (6x10 is a logical way of doing it - then your "data processing" will be very simple) then you only need 2x(6+10)=32 pins. Not unheard of and available in most micro families.
Even more reduction of pin counts if you use one set of outputs to scan both inputs and outputs. You will then need 10+6+6=22 pins. Sounds like you will be using a small and simple micro.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: latching LED array
In the hobbiest Arduino world, there are plenty of cheap LED arrays andcrelated drivers available. Whatever you're doing could probably be built from scratch in an evening or two using the building block modules readily available from the Arduino sellers.
RE: latching LED array
RE: latching LED array
You would still have to do the circuit to drive them, but another potential solution
RE: latching LED array
Actually, there may not be any electronics needed at all. Just connect the input switch to the "show" terminal. Then tie all "unshow" terminals together and reset wit a simple contact closure. Sooo simple.
Of course, it depends on the length of your input signal. Microseconds won't work. But ten or twenty milliseconds may work and 100 ms will work fine.
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.
RE: latching LED array
Its close, but not quite there, as the flip-dots appear to require at least 250mA to drive them, and my switches are limited to 10mA. I have so far been unable to find a good IC driver solution, and discrete drivers are no better than discrete SCR/LEDs.
Also, at 250mA and 5V that comes out to 75W total to drive 60 of these, which seems like a lot.
RE: latching LED array
TTFN

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RE: latching LED array
Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.