Hi,

newbie here. Just burnt an ESP32. I get a "failed to connect. no serial data received". Tried with another ESP32 and no issue, so the old one is gone I guess.

I burnt the board by driving a 5W lamp on 12v using an FQP30N06L connected direct to pin 15 on the ESP32.

I didn't have a resistor between the pin and the MOSFET gate, would that be the issue? Like MOSFET not turning on and trying to source more current???

Could anybody advise on the right choice of MOSFET to use as a switch driven from an ESP32 pin with a resistor (this time) and able to handle a load of 12v / 3A (will replace the lamp)?

Thanks in advance
Ludo

 

I didn't have a resistor between the pin and the MOSFET gate, would that be the issue?

Should not have been unless the mosfet was defective. A 1K resistor in series with the gate is sufficient.
Is pin 15 a GPIO?

 

Should not have been unless the mosfet was defective. A 1K resistor in series with the gate is sufficient.

yes 15 is a gpio. board is https://wiki.dfrobot.com/FireBeetle_Board_ESP32_E_SKU_DFR0654. Why do you choose 1k? I looked at the curve of the FQP30N06L and it seems that with 3.3 at gate it mght not turn on fully?

 

yes 15 is a gpio. board is https://wiki.dfrobot.com/FireBeetle_Board_ESP32_E_SKU_DFR0654. Why do you choose 1k? I looked at the curve of the FQP30N06L and it seems that with 3.3 at gate it mght not turn on fully?

and the mosfet and circuit worked for a while. Inoticed the problem with the board when trying to upload a new sketch

 

yes 15 is a gpio. board is https://wiki.dfrobot.com/FireBeetle_Board_ESP32_E_SKU_DFR0654. Why do you choose 1k? I looked at the curve of the FQP30N06L and it seems that with 3.3 at gate it mght not turn on fully?

To limit the current through the GPIO. Correct 3.3 volts may not be sufficient for that mosfet. Did you notice if the mosfet was running hot when activated?

 

To limit the current through the GPIO. Correct 3.3 volts may not be sufficient for that mosfet. Did you notice if the mosfet was running hot when activated?

1k at 3.3v give me a current of 3.3mA. Enough for the mosfet? The mosfet wasn't hot. The board must have burn because I drew too much current??? Then would that be a problem with no resistor at gpio or with mosfet not fully on or a combination of both?

 

1k at 3.3v give me a current of 3.3mA. Enough for the mosfet?

Mosfets are voltage activated not current. If the mosfet shorted from gate to drain that would probably damage the GPIO pin and possibly the ESP. Is the mosfet defective?
Another option is an inverter circuit to drive the mosfet as shown below. This will allow the mosfet to fully conduct with a 3.3 volt output from the GPIO.

 

Mosfets are voltage activated not current. If the mosfet shorted from gate to drain that would probably damage the GPIO pin and possibly the ESP. Is the mosfet defective?
Another option is an inverter circuit to drive the mosfet as shown below. This will allow the mosfet to fully conduct with a 3.3 volt output from the GPIO.
View attachment 300596

thanks for taking the time with my newbie questions. MOSFET if ok. Do you know of a mosfet i can drive directly from a gpio with just one resistor. Trying to not have too many components.

 

thanks for taking the time with my newbie questions. MOSFET if ok. Do you know of a mosfet i can drive directly from a gpio with just one resistor. Trying to not have too many components.

I use a FDS6547A. They are obsolete currently but may be still available.

 

MOSFET if ok.

How did you check it? If it's good as you say then I don't know why the ESP would have failed.

 

sorry, just visually and heat. Don't have time tonight. Will check tomorrow and let you know. Thanks again for helping.

 

sorry, just visually and heat. Don't have time tonight. Will check tomorrow and let you know. Thanks again for helping.

Best way to check the mosfet is using this test circuit. The lamp should be OFF until the button is pressed.
When ON the voltage at the drain should measure appx 0.1 volt
The DMN3009SSS-13 should be a suitable substitute if you can't find the FDS6574A.
https://www.digikey.com/en/products/detail/diodes-incorporated/DMN3009SSS-13/18680942