Looking for perfect LogicLevel Mosfet

Hi Guys,
I think i'm looking for the perfect LogicLevel n-Channel mosfet for my project.
Now i'm controlling 12VDC locks that take about 1,7A to open from a 12VDC battery.

Unfortunatly if i use a IRFZ44N, not all the locks open every time i trigger the mosfet. (i trigger the mosfet with +5VDC for about 750ms)
If i connect the 12VDC battery directly to the Lock that wont open, the lock opens all the time.
Also when powering the 12VDC locks with my desk power supply 12VDC the locks open consistently when controlling with the mosfet.

By controlling the IRFZ44N with +5VDC from arduino Uno it theoretically should always open.
Is the battery just strong enough to open the lock and are the losses over the mosfet too mutch ?
What could be my problem, a too high Rds(on) ? Do i need better / realy logic level mosfet ?
Please advise me for a suitable TO-220 mosfet.

Can you work with surface mounted components ?

That is NOT a logic-level MOSFET. You can tell because RDS(ON) is measured at 10V, not 4.5 or 5V.

I´m using IRF520.


RDS(on) max. at VGS = 4.5 V 0.068
RDS(on) max. at VGS = 2.5 V 0.085
Qg typ. (nC) 3
ID 3.6A
VGS(th) 0.6 .. 1.5V

Hi john,
Yeah i know, thats why i ask "do i need a real logic level mosfet".
Do you have some suggestions for me, i find it very hard to find a suitable mosfet.
So controlling the mosfet with 5V and almost untouched (without voltage loss) +12VDC to Lock.

Hi flashko,
I forgot to mention i have a already build PCB, ready for TO-220 package mosfet.
You suggestion sounds like a good option, is it also available in TO-220 ?


Every Arduino related electronics seller should have them:




It's too bad that the parametric selector on DigiKey doesn't let you easily pick the min-RDS(ON) gate voltage. They lump the gate voltage in with both the RDS(ON) value and the combined max/min-RDS(ON) gate voltages

I like the AOD508, AOD514, AOD442G, parts from Alpha Omega Semiconductor.
All have logic level gates, very low Rds, rated for high currents, and with their low Rds they dissipate very little power, so little heatsinking is needed.

Unfortunately, they're all SMD parts.


Didn't you breadboard your project first and prove the functions?

Can you please post a schematic of your project?
Can you please post a jpg EXPORT of your PCB so we can see your component layout.

Thanks.. Tom... :smiley: :+1: :coffee: :australia:

Yes i did some breadboard testing, only to find out after live testing that some of the (low cost) 12V locks are harder to open then others. Probably the +12VDC from the battery, trought the mosfet i am using now, is most of the time JUST enough to open them.
Because it's usually the same lock(s) that won't open, i am wondering if i can give the locks some more punch voltage by replacing my current mosfet for a perfect choice for the job.

Below a export of my pcb:

Arduino controls the base of mosfet with a current limiting resistor of 10K.
Battery +12VDC connected to lock + and gnd wire is connected to collector of mosfet.
Mosfet Emitter goes to gnd = gnd of battery.

Where is there a MOSFET? I see Darlington bipolar transistors. 10K would be much too high for a MOSFET gate.

Started with 1k and tip120. Then tried IRFZ44N with 1k and 10k resistor. Result is better but not perfect yet.

Now looking for best logic level mosfet for the job. As mutch of the +12vdc must go to locks do they always open.

On a MOSFET you want the lowest possible resistance between the gate and the Arduino output. Some say that the resistor is not even necessary. I use a 180Ω resistor (5V Arduino). Also, for a solenoid driver, a freewheel diode is necessary to prevent damage to the MOSFET by high voltage kickback when the solenoids are de-energized. Cap is optional. The 10K pulls the gate down so that the solenoids will not energize during processor reset.

1 Like

Try this one.
0.18ohm on resistance with 6A load, 5V on the gate.

This one looks even better, much, much lower on resistance at high current with 4V and 5V on the gate.

If that didn't work, then there must be something wrong with your battery/wiring/solenoids.
A TIP120+1k (with about 1volt loss) should have worked.
Show us pictures of the setup.

I assume you have tried longer times.