Let's Make Robots!

letsmakerobots - motor is not spinning

i have created the simple circuit using breadboard to blink led every 5 sec using microcontroller.

it works well and the led flashes out for 5 sec.

i want to use motor in the circuit.

but if i place the motor in place of led,the motor does not spin.

is the enough current not passing from microcontroller to motor or i have to use additional components like transistor/mosfets etc.

however if i connect the motor to 1.5 v cell battery separately,it spins well.

Can you help me what could be the reason the motor is not spinning ?

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They suggest this transistor because of the high collector current. your motor can easily draw 600mA under load. An alternative transistor would be a PN100 or a BC337.

This is the transistor the tutorial suggests:


... I'm just wondering what it is in the datasheet that says it is appropriate to boost the current to an acceptable level (is it the 600mA Collector Current)?

See this: http://www.oomlout.com/oom.php/products/ardx/circ-03

It contains a set-up tutorial to run a motor from an Arduino for beginners. I think there's one problem in the schematic though - you don't need the resistor that goes to Pin 9.

You do need the resistor from pin 9 to the trasistor base to limit the current as the base/emitter junction is effectively a short circuit to ground.

I just couldn't get it to work so I did a search and found this video by the guys who put it together: http://www.youtube.com/watch?v=K3GtbPcOT50

"Correction from SparkFun web site:

Note: There is an error with CIRC-03. Omit the 10K resistor and hook pin 9 directly to the base of the transistor."

I, for one, would love to know why it doesn't work by following the schematic.

If you are lucky, you have not damaged your chip. You will need at a bare minimum a transistor circuit capable of handling your motor's current demand. For example, a smallish dc motor will require say a minimum of 50mA. Your microcontroller pins can, at best, offer 40mA.

If you could/would, please put the LED back in the circuit on the same pin and let us know if it still blinks.