12 V auto switch (ON /OFF) to load using PIC16F877A

[anroop]

I am currently working on a OLED display. It needs a supply of 12 vdc. the Display works perfectly which i'm manually switching to 12v (using a mechanical switch). It needs to be automatic, because the Display follows a power up sequence (step by step sequence). I followed the below link and tried that circuit, but it only gave out 3.7 v output. My requirement is 12v , 100 mA to OLED. I would welcome your suggestions.


link : http://teachmetomake.wordpress.com/how-to-use-a-transistor-as-a-switch/

 

[Harald Kapp]

I followed the below link and tried that circuit, but it only gave out 3.7 v output.

Then your circuit surely didn't follow the one in the link.

This setup switches ground (0V). This is probably not good for controlling the display. Typically you'd have the display connected to ground by a fixed connection and switch the +12V line. See this example:

Rload is a stand-in for the display. Any low power transistors can be used, e.g. NPN=2N2222, PNP=2N2907.

See also here.