I would like to make a this switch but am unsure how to make it work.

Thread Starter

TofuNinja

Joined May 11, 2017
6
I know this is an old post but I would like to make a this switch but am unsure how to make it work. I am using a Sparkfun benchtop breakout board in a ATX tower case and would like to use the case power button.

This is the breakout board I am using:

https://www.sparkfun.com/products/12867

I tried this Pololu board for the switch but it didn't work and I was told it was because it switches to + and I need a switch that switches to -

https://www.pololu.com/product/2808

So will this do what I want and if so how to I connect it to my Sparkfun bard that has 3 pin on-off switch?



Moderator's Note:
Please don't hijack other member's thread, now you have your own.
This thread was split from --
Circuit to turn a momentary pushbutton into a latched on/off toggle
https://forum.allaboutcircuits.com/threads/circuit-to-turn-a-momentary-pushbutton-into-a-latched-on-off-toggle.73811/#post-1130081
 

Thread Starter

TofuNinja

Joined May 11, 2017
6
Sorry the rules said to search for similar questions and I thought what I wanted to do was similar to what was in that thread that was why I posted there.
 

Reloadron

Joined Jan 15, 2015
4,508
I tried this Pololu board for the switch but it didn't work and I was told it was because it switches to + and I need a switch that switches to -
No it doesn't. On a 24 Pin ATX form factor PSU Pin 16 (Green Wire) is the PWR_ON pin and is placed at a Logic Low to start the PSU, exactly as shown in the drawing. On the earlier 20 Pin connector it would be Pin 14 and still the Green wire. So it does matter if you have a newer 24 pin or older 20 pin main power connector. If you look at the drawing it clearly shows a On-Off-ON switch with NC (No Connection) and a Ground. You connect it exactly as shown in this drawing. If you want a quick check just connect the green wire in the harness to ground. A good PSU will start. I have used a simple paper clip to jump the PS_ON pin to ground and started the PSU.

Ron
 

Tonyr1084

Joined Sep 24, 2015
3,578
I'm not sure I understand what the OLD post was trying to accomplish. Was he/she wanting to push a single button and turn something on then push the same button again and turn it off? If so then a simple flip-flop circuit would do just fine. All you'd have to do is add a little capacitance to the button input to prevent switch bounce so that your circuit only sees a single command to turn on or off. When a switch bounces it can send several if not dozens of clock pulses as the contacts finally come to rest. Capacitance (don't ask me what value) will buffer the bounce so that the clock signal looks like a single pulse. The flip flop - if wired properly will interpret each clock pulse as a single push of the button. If Q is in the ON state then pushing the button will send it into the OFF state. With the next push of the button - from OFF to ON. With each button push it will flip flop states. That's why it's called a flip flop.
 
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