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Help with 3V DC motor

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nm3105

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Hi,

I have 2 3V DC motors connected back to back through the axle. When i power 1 dc motor through a 3 V battery, the 2 dc motor gives an output of around 3V dc.

I need to power a 3rd dc motor of 3V with the output of the 2nd dc motor but it does not happen.

What am I doing wrong here?
 
What am I doing wrong here?

Likely nothing. The second motor is acting as a generator but likely lacks the current producing ability to drive the third motor. If you place your voltmeter across the output of the second motor (generator) open circuit you measure about 3 volts. What do you measure when connecting the third motor in there? There are losses at work here.

How about you run the first motor off a battery, then take the output of the second motor (generator) and use it to charge the battery. You would think at a glance that the combination should run forever or at least till one or the other wore out. However, that is not going to happen. Why? Because of physical losses you can not overcome. There are rules about this stuff! :)

So when you try this little experiment what exactly happens? Does the first motor slow down? If you can, measure the current draw of the first motor unloaded (no second motor) and loaded (turning second motor).

Ron
 
Hi Ron,

Thanks for the quick reply. I actually am not able to find the current drawn by the first motor as I do not know the resistance offered by the first motor. If I knew the resistance value, I could have used the V=I*R equation (where V = 3V) and calculate the current (I) drawn.

Is there anyway to calculate the resistance (R) value of the motor.
 
Hi Ron,

I managed to download the datasheet of the DC motor off the internet and found that it requires around 0.12A to run thge motor at full effeciency.

Maybe my 2nd motor (generator) is not producing that much amount of current to run the third motor.

Will need to work on the circuit :)
 
Let us know how it goes. I assumed (my bad) that you had a handy meter to measure voltages and currents. What exactly are you trying to do?

Ron
 
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