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Soft On/Off switch for pic controlled application

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Audette

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Hi Guys,

I have seen the soft on/off switch circuit given by the following link (schematic shown below).
http://www.picbasic.co.uk/forum/showthread.php?t=57

example-switch.jpg
I have been trying to implement the same solution for my application. I have a PCB which is PIC controlled and need a soft on/off switch. The mechanical switch I use is a toggle switch. I have had to change the pnp (Q1) with a P-fet due to the current required from the Vin line. The voltage at the input is 12V and the maximum current drawn can be around 2A.

In the implementation I have, when the toggle switch is turned off, the PIC will detect this and send a '0' to Q2. This initiates the circuit to turn off. However, the P-Fet output voltage reaches around 4V and then suddenly turns back on again. I tried to tie the gate of Q1 to ground using a resistor to make sure that the gate is turned off. But still no joy.

Can anyone tell me what I might be doing wrong please...

Thank you in advance.
 

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