Quick question - Output voltage of mosfet

MrChips

Joined Oct 2, 2009
19,280
There are two ways to use a transistor as a switch.

The way you have described it, the transistor is on the high side, i.e. it is used to switch the voltage source Vin.

You want the transistor on the low side, i.e. to sink current to ground.
 

MrChips

Joined Oct 2, 2009
19,280
From what you describe, it appears that you have wired the MOS MODULE correctly.



It would appear that your 22V power supply does not have sufficient current capacity to power the relay.
Try driving the relay directly from your power supply and measure the current draw from the power supply.
 

Thread Starter

DryDemon

Joined May 14, 2019
6
From what you describe, it appears that you have wired the MOS MODULE correctly.



It would appear that your 22V power supply does not have sufficient current capacity to power the relay.
Try driving the relay directly from your power supply and measure the current draw from the power supply.
Well my power source are lifepo4 batteries, which have a 30amp current output...
 

bertus

Joined Apr 5, 2008
20,061
Hello,

The problem could be the IRF520 mosfet.
The Vgs(th) is between 2 and 4 volts.( the voltage where the mosfet starts conducting).
It could well be that the mosfet is not driven with enough gate voltage.

I would replace it with an IRL520, wich is an logic level mosfet.

Bertus
 
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