Hardware/Circuit question

Hey all,
I’m relatively new to the whole hardware scene and have a couple of questions on a strobe flasher controller I’m working on. I have the program working for the most part, beyond some final tweaks I have in mind.

Anyways, on to my questions…

First, I need to switch on/off a device (LED Module) that is 12v up to 2A. There’s a need to toggle it on/off in 10 to 20ms intervals. From my limited experience, it seems like a MOSFET is going to be the best method to accomplish that, but I’m not sure how I would connect it up between the +12v source, the Arduino Pin, and the device.

There’s a secondary idea to also step the voltage down to 7 to 8v. That would be a switched/photosensor’d situation though to control the brightness at certain times.

Is there any reference materials that would help me figure this out?

Thanks!
–Pat

Hi Pat,

I think you are on the right track to use an N-Channel Power MOSFET (rated for over 2A and 12V). The max power that this project could draw is 2A*12V = 24W.

First, I need to switch on/off a device (LED Module) that is 12v up to 2A. There’s a need to toggle it on/off in 10 to 20ms intervals. From my limited experience, it seems like a MOSFET is going to be the best method to accomplish that, but I’m not sure how I would connect it up between the +12v source, the Arduino Pin, and the device.

I would wire the Source Pin to ground (of both the 12V supply and Arduino), the Drain pin wired to your circuit powered by +12V, and the Gate pin to the Arduino output pins (to protect your Arduino I would advise putting a 1kohm resistor between (in line) the Arduino output and the Gate of the transistor.
For more protection I would recommend using a 4.7kohm pull down resistor between the arduino output pin and
ground.

The theory is that when you drive the MOSFET it will tie your circuits Ground to the 12V supplies Ground. I attached a picture to help illustrate what is happening here.

Do you need help with the Arduino code?

Good luck with your project,
Mike

There’s a secondary idea to also step the voltage down to 7 to 8v. That would be a switched/photosensor’d situation though to control the brightness at certain times.

This would be an excellent job for PWM and analogWrite. Assuming your FET switches faster than the Arduino’s PWM speed, no extra hardware should be necessary. (You may need to lower the ‘protection’ resistors Severino2020 talked about, depending on your MOSFET’s gate capacitance. Try it unmodified, if the MOSFET gets hot then it’s likely not switching fully and you should lower the capacitance.)