Issue using the 3.3V pro mini board

Hello,

I’m building a little quadcopter using 4 mini coreless motors, a pro mini 3.3V 8Mhz board and an RF24 module powered by a 3.7V battery, but i’m having a wierd problem, for some reason, i can’t get the mosfets to works with the pro mini board, the circuit works with uno and nano boards but when i try to use the pro mini the motors just don’t spin. I’ve already checked the voltage through the hole circuit and everything but the drain voltage of the fets is right. That only happens when using the pro mini board, i tested the same circuit with an arduino nano and a uno board, using the same code and the thing works just fine.

I have no idea whats happening can anyone help?

Post the schematic and MOSFET part numbers.
Do you have the 3.7V battery powering the Pro Mini via the VCC pin?

I’m copying 4 of the following schematic:

i’m using RFP30N06LE mosfets (https://www.sparkfun.com/datasheets/Components/General/RFP30N06LE.pdf)

Powering the board through the RAW pin

Edit: i tested the circuit with 2 different pro mini boards, same problem with both

Power into RAW goes thru the 3.3V regulator.
Connect to VCC instead so you get the full range of the battery.
That will allow the MOSFET to turn on more fully (and have a lower Rds, or On resistance) to allow more current flow thru the motor.

Won’t this fry my board? I read that the board operates at 3.3V

The 8 MHz Promini will run on 3.3V up to 5V without a problem. It is the same chip as on the 5V promini, the only difference is the regulator and the resonator.

I agree with CrossRoads. In addition you should get a multimeter if you don’t already have one. Put an LED with a resistor in place of the motor and turn the PWM output to 100% on. Measure the gate and the drain voltages.

You should also mention the motor current draw. This is a high power MosFet but in your gate can’t get much above 3V you will drop a lot of voltage across the MosFet

image

I guess it is working now, the only thing is forgot my RF24 module runs with 3.3 V and fried one xD but the rest of the circuit is working fine. Just gotta modify my circuit and test some more like this. Thanks for the help!

CrossRoads solution worked, but thanks for the led thing advice, might use it if i need to trobleshoot anything else!

About the current draw, i don’t really now, they are some cheap motors i bought on aliexpress and i can’t find much information about them. I’m considering the current draw is 0.5 amps, i saw that information on a store page for a motor that looks like mine

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