I ordered some MOSFET switch modules. Because they were advertised as "for Arduino" and "Voltage: 3.3V, 5V", I assumed they had chosen a decent MOSFET for the job (like the IRLU7843 or at least the IRLZ34N). There is no additional circuitry on the modules.
Now I see that they use the IRF520, which struck me as odd, as I remember them to be a bad fit for a microcontroller project.
Here's a datasheet. Is there a way to guess the RDS(on) at VGS = 3.3 V or 4.5 V from it?