#Tip120 mosfet how to#

Honestly, the TIP120 is Fully On in your setup with 1000 Ohms. 1000K = 1 MegOhms and that would have been problematic. You're good to go!įYI: I know you meant 1000 Ohms. Lastly, the TIP-120 has a built in snubber diode, so you don't even need an external diode. 10.9 milliamps * minimum current gain of 1000 equals 10.9 amperes! Since the fan probably draws an amp or two at most, we are certainly WAY well into saturation of the collector. Now, are we giving the transistor enough drive? Let's see. that makes the pin current 10.9 milliamps. therefore R = 3.6 / 0.01 = 360 ohms which we can slide up or down to standard values (i.e.

We want to put no more than 10 milliamps load on the PWM pin, so our I is defined.

The voltage drop across the resistor is V/R.

The Arduino pin output voltage is 5 volts.

We want the transistor to 'slam' on and off as solidly as possible.

For PWM motor speed control, we are not working in the linear region.

The Arduino output pin should be limited to about 10 milliamps so that when other pins are also used, we don't exceed the specs of the AVR chip.The data sheet says the current gain MINIMUM is 1000.The Darlington has two base-emitter junctions in series, so the turn-on voltage is about 1.4 volts (that is, the usual 0.7 times 2).

#Tip120 mosfet how to#

Here's how to figure out what resistor you need. My question is, how can i calculate what kind of resistors do i need between the fan, arduino and the transistor?