I'm trying to figure out how to use a mosfet in order to allow me to use a small voltage to switch a larger voltage / current driving a motor. My son wants to write a program to control his small rc car, and controlling the motors via something like this seems like a good way to go.
I read this page, https://oscarliang.com/how-to-use-mosfet-beginner-tutorial/ -- and I got some irf520n mosfets, connecting them up as pictured.
The large battery pack positive output is connected to the source on the mosfet, and the then I have a wire from the drain to the motor, then from the motor to the negative output of the large battery pack.
I have the small battery pack, intended as a switch, connected positive to the source, and negative to the gate.
At least from reading that page, and trying this, I believe that's what I've set up, but it's not working. When I turn on the large battery pack, the motor runs, regardless of whether the small one is turned on or not. Pretty new to all this, so any tips are much appreciated.
I did notice while researching this question that irf520n mosfets are not logic level mosfets, so the 3v I'm applying might not be enough, but the data sheet here: http://www.infineon.com/dgdl/irf520npbf.pdf?fileId=5546d462533600a4015355e340711985 looks to me like it the switch should work with between 2 and 4 volts (it has VGS(th) min of 2 and VGS(th) max of 4 on the data sheet).