MOSFET power module and optocoupler

I want to drive a 12V DC motor single direction 10A from Arduino PWM pin. I found several power MOSFET modules. Some have optocoupler, some don't. Both are advertised as Arduino compatible. When should one use optocoupler? Also please check if a 10A 400V 600A peak flyback diode NTE5814 across the motor is the right choice. Thank you.

Hi,
Can you post links to the MOSFET modules you have been looking at please.

Thanks... Tom.. :slight_smile:

A simple logic level power MOSFET with a few other components may be sufficient to do what you need.

What current does your motor take?

Allan

paker:
Some have optocoupler, some don't. Both are advertised as Arduino compatible. When should one use optocoupler?

Using an optocoupler helps separate your 5V Arduino from higher-voltage, high current circuits like your DC motor will be. Any failures in the motor drive circuit, like blowing up a MOSFET, are unlikely to affect your Arduino. If you are just 'lashing stuff up', it's handy to have that isolation.

However, since you want to PWM drive the motor, a random opto-isolated driver might be badly designed and not actually offer much isolation or not switch fast enough and could, for example, result in the MOSFET getting a bit toasty.

In this case, personally, I would prefer an opto-isolated driver - maybe not the cheapest one from eBay tho'.

Always try to look for a module from a supplier that gives you decent information... like a proper circuit diagram.
(this example: mosfet switch has a circuit diagram available, but does not give component values - which is a bit poor)

So... as TomGeorge asked, post links to the modules you are looking at and we'll have a look.

Yours,
TonyWilk

P.S. The diode you mention sounds fine.

This has an optocoupler. I can attach a heat sink easily.
https://www.amazon.com/Transistor-channel-optoisolator-control-Raspberry/dp/B072WSKFQN/ref=pd_sbs_328_5?_encoding=UTF8&pd_rd_i=B072WSKFQN&pd_rd_r=ABW7XTN2QNYSQ0F3T4RN&pd_rd_w=tRXxv&pd_rd_wg=N4N8f&psc=1&refRID=ABW7XTN2QNYSQ0F3T4RN

Its circuit diagram from the vendor’s web:

Here is another FET module with optoisolator. I couldn’t find the datasheet for the MOSFET.

This has no optoisolator. MOSFET is AOD4182, 40V 50A <11mohm @4.5V GS. Two MOSFETs for higher current capability? But I need to glue heatsink to MOSFET. The screw-down terminal (I don’t know the correct name) seems to be for a small gauge wire. Not my first choice.
https://www.amazon.com/DROK-Transistor-Driving-Electronic-Controller/dp/B01J78FX9S/ref=pd_sbs_328_3?_encoding=UTF8&pd_rd_i=B01J78FX9S&pd_rd_r=ABW7XTN2QNYSQ0F3T4RN&pd_rd_w=tRXxv&pd_rd_wg=N4N8f&psc=1&refRID=ABW7XTN2QNYSQ0F3T4RN

This is my first choice. Has optoisolator. MOSFET is IRF5305S. -55V 60 mohm @Vgs -10V -31A.
https://www.ebay.com/itm/5PCS-DC-control-MOS-FET-switch-control-panel-electronic-pulse-trigger-Motor-LED/182071159081?hash=item2a64496929:g:7mAAAOSwoudW-m60
I like screw terminals because I will need 12 to 14 gauge wire for 10A. Heat=10x10x0.06=6W. I am not sure if the space is large enough to attach a heatsink to dissipate 6W.

Advice please. Thank you.

Hi,
OPs “Robotdye” circuit.
optocircuit.jpg
Yes it will do the trick.
Tom… :slight_smile:
PS. Sorry can’t hang around, got to go to work, someone has to keep the wheels of commerce turning… :slight_smile: :slight_smile: :slight_smile:

The first one, from "RobotDyn", circuit diagram looks ok, would be happier if it said exactly what components it is using tho. Looks well made, probably worth a shot.

Second one from eBay... looks a bit cheap and tacky, personally would avoid it.

Third one, the 'DROK' dual-MOSFET board... says "Signal input range: 3.3~20V". It uses the AOD4184A N-Channel MOSFET which I would not use at 3V3 but should be ok with a 5V signal. However there is no diagram of the board and looking at the pictures there seems to be some resistors dividing the input signal to the MOSFET gates and an LED, so the MOSFETs might not be getting sufficient voltage to turn on properly. I'd avoid it.

Last one, your first choice... uses an IRF5305 P-Channel MOSFET and PC817 optocoupler, ok MOSFET for high-side switching, opto is not the fastest but should be fine if your PWM is only 1kHz or so.

In any case, even if there is a diode on the module, it is a good idea to fit a diode like the one you mentioned in your original post directly at the motor connections (otherwise the 'flyback' voltages whizz up and down the wires between the MOSFET and the motor, which is best avoided).

Yours,
TonyWilk

Hi,
The Robotdyn, from its picture looks like it uses PC817.

Can't see what the MOSFET is though.

Tom... :slight_smile:

TomGeorge:
Hi,
The Robotdyn, from its picture looks like it uses PC817.

Can't see what the MOSFET is though.

https://robotdyn.com/catalog/modules/transistor-mosfet-dc-switch-relay-5v-logic-dc-24v-30a.html

Tom... :slight_smile:

The seller lists the item at Amazon. There the seller identified the mosfet as IRF540NPbF.

paker:
The seller lists the item at Amazon. There the seller identified the mosfet as IRF540NPbF.

Ok, on that Robotdyn board it looks like the opto will turn the MOSFET on well enough, but the IRF540N has an RDS(on) of 44mOhm at 16A.

With a continuous 10Amps load, there could be 10A * 0.044ohm = 0.44V across the MOSFET
0.44V * 10 Amps = 4.4 Watts of heat dissipated.

It will get quite hot.

It would be Ok with a heatsink.

Yours,
TonyWilk

What about this?:
Aliexpress Mosfet relay AOD4184, with 5 stars, and 3,21€ / 5 unit

Mosfet AOD4184.pdf (293 KB)

TonyWilk:
In any case, even if there is a diode on the module, it is a good idea to fit a diode like the one you mentioned in your original post directly at the motor connections (otherwise the 'flyback' voltages whizz up and down the wires between the MOSFET and the motor, which is best avoided).

A common, but sadly misguided fantasy regarding "kickback" diodes. :astonished:

iunnius:
What about this?:
Aliexpress Mosfet relay AOD4184, with 5 stars, and 3,21€ / 5 unit

It's a MOSFET. What about it?

Steve

slipstick:
It's a MOSFET. What about it?

Steve

Mmm, yes, it seems to be a Mosfet.!!!

I post thinking in IRF540.
Just to have a comparison because IRF seems to be not good enough for the project of Parker.
Sory for your time wasted answering.