Thread: Anyone know how to rework circuitry?

Originally Posted by Curiosity

Yep. Well, not really a large variety. TMR-3 would work fine. It can start the timer when power is applied to it, has an adjustable number of seconds before it pulses and you can set the number of pulses. So you could push the button any number of times.

How would i apply the TMR-3 to what I am trying to do?

Originally Posted by Curiosity

You would tap into the 12V power that runs the DQP and connect the 2 output wires to the button connection. So 4 wires total. When the power goes on it waits 1 second and pulses the output.

After it pulses the output, does the unit shut off?

Originally Posted by Curiosity

Yes

OK, I'll go ahead and buy one then and see how it goes. Its only $20.00 dollars so not a big waste of money if i can not get it to work.

Originally Posted by dandydanny

It's probably difficult to reverse-engineer and trying to modify the original board's power-on behavior (as it's preprogrammed into the onboard microcontroller).

Rather than using discrete analog ICs like 555, why not use a simple 8-pin 8-bit PIC / AVR / BASIC Stamp microcontroller? Program it to simulate (pull up / pull low the pin connected to the switch) a button press. A 1-second delay can be implemented as a loop, and the MCU itself can perform switching much faster than a relay can. Most MCUs can sink / drain few 10's of mA easily, and more with an additional FET.

I've only built one MCU-based project so far; best to ask other people on the forum with more experience. The drawback with this approach is the chip itself needs to be programmed, and it's not cost / time effective to purchase / build one just for this particular task.

Of course, this really depends on the QDP itself. This will work only if the QDP will reliably start and enter 4-way mode within a precise time frame each and every time power is applied to the unit.

Thanx for the info, but I think I will go with curiosty's product. Its seems fairly easy. I am worried about how fast the relay will release, because his system is probably fast, but Im scared the relay even after his chip is off, will have hold residual power and stay on for maybe 1.5 seconds, which will be too long causing the DQP to get stuck in another mode. I guess I have to simply try and see!

OK, I received your TMR-3 in the mail today, Curiosity. How do I hook it up?