Help choosing MOSFET

Other Hardware Motors, Mechanics, Power and CNC
1

Hi everyone,

I need to turn on or off the power supply for a 20V-20A-400W motor from an Arduino, and I need help choosing the right MOSFET (or anything, really) for this application.

It won't be "controlling" the motor during use: it'll just be in line with the power supply to prevent the motor from working based on a timer on the Arduino. I've looked around and searched, but I get confused when it comes choosing the model.

Some relevant data:

The 400W is a maximum, and will never last for more than a minute at a time.

The main limitation is the limited space, so shields don't fit.

Operating temperature will be at most 30ºC (air flow is decent).

Thanks for your input

2

Don't count out using a relay, but they are large.

.

3

A Solid State Relay will be the easiest to control and interface. Something like this from Sparkfun would be ideal.

Using a transistor is more complicated. The most common type of MOSFET, N-Channel, would be on the low side of the motor, i.e. between the motor - terminal and the power supply ground. If you put it on the battery side it requires a lot more circuitry.

4

Despondent:
Hi everyone,

I need to turn on or off the power supply for a 20V-20A-400W motor from an Arduino, and I need help choosing the right MOSFET (or anything, really) for this application.

It won't be "controlling" the motor during use: it'll just be in line with the power supply to prevent the motor from working based on a timer on the Arduino. I've looked around and searched, but I get confused when it comes choosing the model.

Some relevant data:

The 400W is a maximum, and will never last for more than a minute at a time.

I very much doubt the maximum power is 400W, since your stall current is likely many times 20A,
and the capacitor inrush current to the motor controller (if there is one) will also be high - unless
there's a soft-start circuit. Expect 100A peak pulses as a rough maximum.

The main limitation is the limited space, so shields don't fit.

Operating temperature will be at most 30ºC (air flow is decent).

Thanks for your input

I presume (its usually the case) that you want high-side switching. This means either p-channel
switch or an n-channel switch driven from a charge-pump driver (the sort with continuously
operating charge pump, not on relying on PWM).

I'd suggest a maximum sensible on-resistance to go for of 10 milliohms, but less is better (smaller
heatsink requirements).