'Soft' On/Off Power Switch

[flotulopex]

Yup, R1 is actually connected du Q1's base. Thanks for noticing, skimask.

My drawing only is incorrect, in fact, I built this circuit according to Melanie's plan in a previous post.

The values of the components are those stated in the same previous post.

Q1 BC327B (most any PNP transistor)
Q2 BC547B (most any NPN transistor)
D1, D2 1N4148 (or equivallent low-power signal Diode)
R1 22K
R2, R3, and R4 12K

There is no delay in the program. In fact, I set RA1 high at the very beginning of the code.

At startup, the circuit draws 4,5 mA. A few milliseconds later, the current peaks up to 600mA (I drive an IR led - it's a remote control).

I'm going to add another Tr to provide the "power" to the IR-led instead of using only Q1. This should solve the problem.

[SteveB]

Simple, but need to ask. Are you sure RA1 is set to digital?

[flotulopex]

I checked an re-checked all over again; I even changed my breaboard.

Finally, I tested all components and surprise: R2 has infinite resistance (should be 12k!).

Everything is fine and the circuit works well now.

Thank you to All for your help.

I add the corrected shema - hope I didn't made a mistake this time.
<img src="http://www.picbasic.co.uk/forum/attachment.php?attachmentid=2707&stc=1&d=121484865 4">

[tekart]

If all you need is a push button to turn on the circuit and the PIC to turn it off then I have tested a simplified circuit that uses a MOSFET. Low part count = lower cost! I didn't have a P-MOSFET laying around, but I *think* that you could replace my Q1 with one and that would eliminate R2 in my circuit too.

Guy

[Leonardo]

If all you need is a push button to turn on the circuit and the PIC to turn it off then I have tested a simplified circuit that uses a MOSFET. Low part count = lower cost! I didn't have a P-MOSFET laying around, but I *think* that you could replace my Q1 with one and that would eliminate R2 in my circuit too.

Guy

Hello,

¿You can replace the transistor by a canal N?.

Thank you