For my Tardis tissue box cover, I used a mosfet for the first time. Let's see how I used it !
I bought some 2N7000. Their are cheap, and they can handle 200mA, ore than enough for my day-to-day use.
Mosfet: 2N7000 N-Channel
Unlike bipolar transistors, MOSFETs are voltage controlled. It's easier to use them than BJT (current controlled) : you just apply enough voltage to the gate and the switch operates.
With a pin from an Arduino, you can switch on/off a load off 20mA.
By adding the MOSFET in your circuit, you can switch on/off a load of 200mA !
The pin of the Arduino will only be use to control the state of the MOSFET.
In my Tardis tissue box, I used the MOSFET to turn off / on some leds. I even used the PWM capability of the ATMega to pulse the LEDs (the MOSFET is turned on/off with a variable duty cycle).
- Source to GND
- Gate with 10kΩ pulldown
- Gate to PWM with 1kΩ
- Drain to resistor (22Ω) to LEDs to Vcc
Note: I only put one LED in the schematics as an illustration