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Topic: Having trouble with MOSFET (Read 799 times) previous topic - next topic

ticklechicken

Thanks for the help everyone.


Firstly, do you know how the relay is wired up?

Are you controlling the circuit between the power + and the relay, or between the relay and - ?

If the former (which is most likely), then you really need a P channel MOSFET, as that is much better at high side switching.

Here is the schematic from the generator.  I highlighted the two wires I'm tapping into for the remote start (red and red/white).  From what I can tell, I'm controlling between the power and the relay, as Chagrin stated.  I did test this with a relay and got everything to work.  I wanted to use a MOSFET due to space constraints and I thought it was a simple swap.

So I need a P channel instead of the N channel that I have?  I'll look into that.  If anyone has any good links for tutorials, I appreciate it.



Do you have 0 volts on the Arduino going to 0 volts on you controlled circuit?

Yes, they are all grounded together.  This is easy since I'm powering the Arduino off the generator battery.


You will need a flyback diode across the relay winding to prevent inductive spikes damaging the MOSFET.

I thought that was only needed if the MOSFET was controlling something with a winding like a motor.  Since I'm controlling a relay, I thought the diode wasn't needed.

majenko

Quote

I thought that was only needed if the MOSFET was controlling something with a winding like a motor.  Since I'm controlling a relay, I thought the diode wasn't needed.

What do you think makes a relay work?  Magic Cheese?
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ticklechicken


Quote

I thought that was only needed if the MOSFET was controlling something with a winding like a motor.  Since I'm controlling a relay, I thought the diode wasn't needed.

What do you think makes a relay work?  Magic Cheese?

Somehow in my mind, I interpreted "something with a winding" as "something with a moving armature".  I didn't count the winding on the solenoid portion of the relay.  But thinking about it now, I see it.

smeezekitty



Quote

I thought that was only needed if the MOSFET was controlling something with a winding like a motor.  Since I'm controlling a relay, I thought the diode wasn't needed.

What do you think makes a relay work?  Magic Cheese?

Somehow in my mind, I interpreted "something with a winding" as "something with a moving armature".  I didn't count the winding on the solenoid portion of the relay.  But thinking about it now, I see it.

LOL Usually I find relays to be much more inductive than motors.
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