I am using one of these mosfets to control a CPU fan with an ESP32 and a thermocouple.
I am finding that even when gate is set to LOW, and with a 10k resistor between gate and GND it won’t turn off.
I have repeated the experiment using my UNO R3 and a RFP30N06LE mosfet and it works fine. That is what I originally started with but the ESP32 doesn’t have enough gate voltage to turn it on so I was advised to use the one above.
I should mention the CPU fan is 12V, so well within the 55V limit (that’s my understanding of the specifications).
Hi Dion
Measure at the actual Mosfet pin. Like on the pin itself. It is not unknown to have dodgy breadboard connections.
Or exactly how LOW is the ESP32 going.
Cheers Bob
Gate - source is 0.1mV, so pretty low. When I did research on this mosfet I read that ESP32 may not be powerful enough to turn it on whereas this is running full bore.
It may be worth unplugging everything from the breadboard, flipping it around to use the other side and connecting it all up again in case you are off by one pin on any of your connections or have a dodgy breadboard connection there.
That should be off. Have you tried another Mosfet. That one might have failed short circuit. A multimeter check should show this. Short gate to source and measure the resistance drain to source, positive lead to drain.
Shorting gate to source should DEFINATELY switch off.
Cheers Bob
Unfortunately I only got one of these. I do however have a P30N06LE mosfets and they work, but they need 5V from Arduino to work. They wont open at ESP32 3.3V.
Pulling the gate out of the breadboard won’t help. If the gate capacitor is charged it will stay switched on for probably weeks until the gate and source are shorted and the cap discharged.
If the fan still runs with the source and gate shorted I would say you have a dead (shorted) Mosfet.
Cheers Bob
With a piece of wire.
A link directly on the breadboard between the 2 relevant pins will do. Disconnect the ESP32 when you do this or you could damage that because if everything is still connected you would be shorting this pin to ground.
Just re read your query. It is a bit confusing. I assume that you are referring shorting the gate to source in my reply above.
Cheers Bob
Hi Dion
Probably lots of ways to damage it. And it could be a faulty part from new. Is it a recognised brand or a Chinese knock off.
One of the common ways to damage a Mosfet is switching an inductive load without a flywheel diode fitted. Or if this is fitted failure of this device will ripple through and take out the Mosfet.
Usual repair practise (for me anyway) if a Mosfet has failed and has to be replaced you replace any flywheel diode (s) at the same time.
Although I would have thought it would have worked a couple of times before failure but you never know.
Cheers Bob
Hi Dion
Another remote possibility.
I note you seem to have 2 black wires supplying the Mosfet. Is the voltage the correct way around. Please check this.
If the supply voltage is reversed there is a body diode built into the Mosfet which will be forward biased and thus ON. This would appear to be a shorted Mosfet as this is actually what it is with reversed voltage.
Cheers Bob
