'Soft' On/Off Power Switch

[Melanie]

The 'load' is connected between the Collector of Q1 and 0v.

[AMay]

My final circuit, sort of like Melanie's, works perfectly as far as I can tell. I have no quick button problem, perhaps because I put a decoupling cap., .1uf, in the circuit.

AMay

[Leonardo]

Hello,

Do I want to connect a load with a battery of 9V, like I make to connect the pic with 5V and that it doesn't consummate a lot?.

Thank you

[Leonardo]

Can this work this way?

[Melanie]

That will work to turn your PIC ON, and have the PIC switch OFF... D2 and R4 are then not required.

However, if you require a Button-OFF function, then you need to tell the PIC that the Button has been pressed. In that case D2 and R4 are required and in your circuit you will then have omitted to take a line from the D2/R4 junction back to an available PIC pin.

[Leonardo]

Melanie,

Thank you very much by its aid.

[flotulopex]

I do have difficulties to make this circuit switch-ON.

Problem description: if I switch-off my power-supply for about 2 to 3 minutes and switch it on back again, the soft-switch won't function and power the PIC. But once the PIC has been "successfully" powered, it works any time (as long as I don't switch-off the supply again).

For Q1, I implemented a 2N3906, then aBC307, then BC557; no way to make it work. Finally an old (metal case) 2n2905.

By "chance", I got it to work by making a false-contact between the 2n2905's (Collector is connected to case) and R1 (any pole) on the breadboard.

Once the contact has shortly happened and as long as the power-supply is not disconnected, the soft-switch will work perfectly (!?).

What shall I do to correct this?
<img src="http://www.picbasic.co.uk/forum/attachment.php?attachmentid=2705&stc=1&d=121475975 5">
NB: I didn't implement D2 + R3 since the program shuts-off the circuit by program (RA1 = 0).