3.3v PWM to 5v PWM to 12v PWM

In the end, I want a 12v PWM signal to drive a Solid State Relay (SSR) , which will drive a pump motor and or a fan. Giving the pump or fan a variable speed depending on the signal.

But Arduino zero (fast 48MHz and 10bit) only outputs 3.3v PWM signal.

Someone suggested to look at a logic level converter but the way I understood it was that it only deals with HIGH and LOW?

Is there a product that can do what I want?

Do I indeed NEED a 12v PWM signal to operate a 12v device? Will a 3.3v PWM at 100% duty cycle run the 12v motor at full speed???..

1 Like

Hi Geoff,

Assuming the Fan/Pump motor is 12V DC, then you could use a simply MOSFET or a MOSFET module.

If instead, you are driving a 240V load then I can’t really provide advice on that for safety reasons (and in Australia, you need a license to work on gear at that voltage). Though it’s worth noting that PWM would not be used and instead phase angle would be. SSR ought to be fine it turning on/off every X minutes.


Thanks dude!

Re: SparkFun MOSFET Power Control Kit,

So on on the “device” end is 2 terminals having 12v PWM?

And on the “system” end /input side is 3 terminals …1 where I put my Arduino 3.3v pwm signal?

So there’s 2 terminals left here on the system end. I assume that one is for 12v+ and the other is for
12v ground?

Which is which?

Thanks a million

1 Like

Hi Geoff,

That MOSFET power control kit will allow you to use a low voltage, low current signal to switch a higher voltage higher current signal.

On the 3 pin input side you should connect:

  • Ground to terminal -
  • 12V DC to terminal +
  • PWM output of Arduino to terminal C

On the 2 pin output side connect:

  • terminal - to ground of motor/fan
  • terminal + to power of motor/fan

EDIT: Can you give us some more specifications about your motor/fan combo? You could also do this using a motor driver module but we don’t yet know what your motor current draw is so we’re making a lot of assumptions.


Hey Geoff,

I believe it’s setup as a switch (https://www.electrical4u.com/mosfet-as-a-switch/) on the “system” side, you connect 3.3v power to “+”, ground to “-”, and the PWM signal goes to C. The “+” is like a reference voltage for the signal coming in on “C”. on the other side it behaves like a switch in your 12V circuit.

I see that the spark fun item is out of stock. This might be an alternative https://core-electronics.com.au/freetronics-n-mosfet-driver-output-module.html it’s got a good guide here NDRIVE QuickStart Guide | Freetronics

Hope that helps,


Sorry for the confusion. Please see attached diagram.

Also I have clipped this clip here:

##paste this url into your browser ##

I am starting to think that I don’t need the magic box after all…

1 Like

Hi Geoff,

It very much depends on what SSR you have, do you have a link to the one you purchased?
If the operating voltage is >3.3V you’ll be ok.

An SSR might be overkill if you’re only driving a small fan, note: some SSR’s require a zero crossing point (0V) and hence require an AC signal!


Hi Geoff
Please take note of above posts re SSR etc. Although “switch at any time” SSRs are available they are mostly “Zero crossing switch” and are unsuitable for DC as DC never gets to “Zero” they will never switch thus are only suitable for AC. Refer Liam’s reply.

As Graham says PWM is not normal used for AC especially 240V.

Very true,
If your fan is DC This simple circuit or similar is about all you need. This is the sort of thing Graham and Trent are referring to I think.

That is what PWM is. High and LOW. Never goes negative so is not AC.

I very much doubt the PWM signal is anything like 48MHz. More like 1 or 2 kHz. I haven’t looked but I think the 48MHz is more like the board clock signal.

I believe that little switch board as in the above circuit responds OK to 3.3V PWM. I haven’t tried it at that level so I could not be absolutely sure. The documentation says so so you could believe that it does…
Cheers Bob