What ESP-32 mosfet

himmelberg
Posts: 2
Joined: Sun Jul 03, 2022 7:33 pm

What ESP-32 mosfet

Postby himmelberg » Sun Jul 03, 2022 7:42 pm

Hi,

I need to control a 3W (0.6A) 5V solenoid using ESP32. So far I have tried IRLZ44N and IRL540N without success. These mosfets are able to drive test LED via current limiting resistor but not the solenoid.
Frequency I need is up to 50Hz.
Should ESP32 be able to drive 5V gate to source mosfets?

What would be a good alternative choice? Would AO3416 (https://pdf1.alldatasheet.com/datasheet ... O3416.html) be suitable for that?

Thanks

ESP_Sprite
Posts: 8921
Joined: Thu Nov 26, 2015 4:08 am

Re: What ESP-32 mosfet

Postby ESP_Sprite » Mon Jul 04, 2022 2:16 am

In general, for using a mosfet like that, you mostly need Vgs(th) to be below the voltage the ESP32 outputs on a GPIO (i.e. 3.3V). For both the mosfets you picked, this is the case. Can you show the schematic of how you're trying to drive that coil? It sounds likely that something is going wrong there.

himmelberg
Posts: 2
Joined: Sun Jul 03, 2022 7:33 pm

Re: What ESP-32 mosfet

Postby himmelberg » Mon Jul 04, 2022 2:01 pm

Hi.

Pls see the schematics:
ESP32Mosfet.png
ESP32Mosfet.png (21.27 KiB) Viewed 3114 times
But also after further looking into datasheets
IRLZ44N: https://pdf1.alldatasheet.com/datasheet ... LZ44N.html
IRL540N: https://pdf1.alldatasheet.com/datasheet ... L540N.html

I see that lowest Vgs specified is 4V (in Rds(on) row). So it is above 3.3V. For these two mosfets I was not able to find "On-Resistance vs. Gate-Source voltage" figure like for AO3416:
AO3416.png
AO3416.png (15.92 KiB) Viewed 3114 times

ESP_Sprite
Posts: 8921
Joined: Thu Nov 26, 2015 4:08 am

Re: What ESP-32 mosfet

Postby ESP_Sprite » Tue Jul 05, 2022 7:46 am

For the other two mosfets, you can kinda get an indication from the 'typical output characteristics' figure: assuming that your relay needs less than 10A (which I think is a very likely assumption), you can see that for a Vgs of 3.0V the voltage over the mosfet itself (Vds) would be smaller than 0.1V, meaning the relay would see more than 4.9V over its coil.

Do you have a flyback diode over that coil? If not, the answer could be that it worked at some point but the back-emf from the coil blew up your mosfet.

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