Hi there. I am trying to switch a bluetooth module using a P-channel mosfet(AO3401). i set up the following circuit on a breadboard and it seemed to switch fine but irritatingly when i got a PCB made the switch seems to be temperamental in that occasionally it isnt fully 'off' and so leaks current. i am aware that to stop current flowing, Vgs must be 0v. to switch the mosfet i have been setting the arduino pin to LOW to turn the module on and HIGH to turn it off. I would have thought that since the arduno is connected to the same voltage as the S pin then the mosfet would be fine.....Am i missing something here or could anyone recommend how i could make my circuit more reliable? thanks very much.
....it may be that i had just destroyed my mosfet, replaced it and seems to be working so far....
After a quick search the BT-04 module seems to use the BK3231 chip. It does come with a deep sleep option which would be the smartest way to go 
If you really want to go with the mosfet option, be sure to power down all signals (including Rx/Tx) to the module before powering it down. Otherwise you might damage it.
septillion:
After a quick search the BT-04 module seems to use the BK3231 chip. It does come with a deep sleep option which would be the smartest way to goIf you really want to go with the mosfet option, be sure to power down all signals (including Rx/Tx) to the module before powering it down. Otherwise you might damage it.
Thanks for the reply, deep sleep would be by far the best option. do you know whether its enabled by a pin toggle or by software? i seem to remember searching for this in the past and its software enabled and not possible using the arduino IDE, could be wrong though...
No, I have no idea. I would suspect you do it with software (command?) but I have no experience with the chip. I would have to Google it more.
septillion:
No, I have no idea. I would suspect you do it with software (command?) but I have no experience with the chip. I would have to Google it more.
ok no prob. thanks.