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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.  ***
"You gotta fight - for your right - to party!"
Don't react - Read.
"Who is like unto the beast? who is able to make war with him?"
It's "bipolar transistor" or "junction transistor" - "BJT" is stupid.
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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