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Topic: TIP120 and Dc motor control (Read 1 time) previous topic - next topic


Hi i've followed this tutorial http://luckylarry.co.uk/arduino-projects/arduino-control-a-dc-motor-with-potentiometer-and-multiple-power-supplies/ and got it working. now here's the question:

1. If i increase the voltage say 12v 5A do i need to change materials used in the circuit?. the 1k resistor?, the diode? and potentiometer?. because when i tried it with 12v 5A the tip120 quickly becomes hot and suddenly motor stops and after 3-4 secs the motor start again but can't control it anymore with the potentiometer the motor goes on rampage.. i need to turn off the arduino to make it work again.

2. Do i need a higher potentiometer say 50k or change the 1k resistor or the diode?

3. What's better Mosfet IRF510 or Tip120?

thanks in advance


5 A is absolute maximum continuous current for TIP120, symptoms as you described say transistor damaged, if you run it w/o heat think - overheated. MOSFET is better in this manner, as dissipate a lot less power. Look for logic level type, you can't drive IRF510 from arduino, need additional voltage amplifier stage.


What happens if i change the 10 k potentiometer to 50 k pot?


10 k pot regulates voltage at the analog input, you free to change , it doesn't change much as input impedance arduino 100 M.


10 k pot regulates voltage at the analog input, you free to change , it doesn't change much as input impedance arduino 100 M.

ok thanks how abou the 1k resistor and diode should i use a higher wattage for the resistor say 1 watt? and for the diode higher current say 3Amps?.. thanks

Runaway Pancake

Feb 25, 2012, 04:23 pm Last Edit: Feb 25, 2012, 04:28 pm by runaway_pancake Reason: 1
It's unfortunate that "luckylarry" shows his work as pictures, no schematics.
I haven't the patience to read through a verbal account when a schematic conveys the point "instantly".

***  "I'm using the TIP120 because its emitter pin uses no more than 5 Volts which is what you're looking for with the Arduino...", luckylarry notes.  I'm speechless.  ***
"Who is like unto the beast? who is able to make war with him?"
When all else fails, check your wiring!


If you change transistor to MOSFET, resistors would be different. Have a look:
There is no pot, but you can introduce one ( 10 k is optimum value ), connecting middle pin to analog input of arduino, two others
to +5V and Gnd on the arduino board. Reading a voltage value with analogRead, you could vary motor speed by pot.

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