Author Topic: Help with momentary to latching array  (Read 254 times)

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Offline hydrolisk1792

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Help with momentary to latching array
« on: December 08, 2018, 06:47:58 am »
I have attempted to make a 16 button momentary to latching array with 8 556 timers. When I power up the board all is well, but when I go to trigger one of the timers, all of the outputs go high. Also when I go to turn one of them back off, the respective one goes off, however when I trigger a different one, the previous one (s) turn back on...

Is there a better solution out there for this kind of thing? My control panel is wired as all buttons are commoned together and one wire from each button is the trigger wires.

Offline Ian.M

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Re: Help with momentary to latching array
« Reply #1 on: December 08, 2018, 08:12:21 am »
My first reaction to that probelm would be to use an Arduino (or  other 8 bit MCU) rather than effectively 16x 555 timers, even though the Arduino would need extra transistors to drive the relay coils, and a resistor ladder to put multiple buttons on each of the few remaining input pins.

However, you've madea start with the 8x 556 chips, so to give us a chance to figure out what's going wrong, we need to see the  schematic, + good photos of the project - an overall view so we can see the general layout and what's hooked up where, and a closeup of each sde of the circuit board.

I suspect that your decoupling or layout is inadequate so when one timer pulls a current spike as it switches, its glitching all the others.  However that's pure speculation until we've seen the schematic and photos.

Online Zero999

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Re: Help with momentary to latching array
« Reply #2 on: December 09, 2018, 12:15:03 am »
Yes, it's probably bad layout and decoupling.

There are also plenty of alternatives to 555 timers. The first thing you could try is replacing them with the '7556. They're less sensitive to poor decoupling and have the same pin-out as the '556, there's no need to change the rest of the circuit.

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