P channel mosfet and manual override switch

Other Hardware General Electronics
1

Hello,

I would like to control a 12V led lamp using an arduino pin.

I am planning to use the following schematic:
pmosf

However, I would like to be able to switch the led ON if I want to by a manual switch. The problem in this case is that the drain pin of the Mosfet will also receive 12v. Will this damage the mosfet? If I use the following diagram won't it be safe?
pmosf2

Thank you!!!

2

pmosf2

  • Your Drain and Source are reversed.

  • Why the diode ? :thinking:

  • 10k base resistor might be a bit high.

  • Put the switch between the collector and emitter.

1 Like
3

I took the schematic from another thread, ok I will reverse those.

I put the switch after all the electronic parts because I would like this to act as a backup switch so in case everything fails I can still switch on the load mechanically, hence the diode at this point. Is that correct?

4

try
image

only a MOSFET or power failure would fail this circuit. The switch current is much lower, too.

5

Thank you for the suggestion. The thing is however that the switch is already there and I can't touch the existing wiring, I only can add electronics to automate as well. So the switch must be after the mosfet, at the drain. If the diode is not enough to prevent current going back to the mosfet, what else can I do?

6

Remove the diode, not needed.

7

So no problem with the mosfet even with the manual switch pressed?

8

pmosf

  • Just add the switch across the Source and Drain.

  • As noted already, your Drain and Source are reversed in this image.

9

Hi,
0fc08239a05007ffcc495edit

Tom... :smiley: :+1: :coffee: :australia:

10

I'm used to a world of correct circuits. :slight_smile: Didn't even see that because I take it for granted.

11

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