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Author Topic: Why does my dc motor spin with 9v 80mA power, but with 9v1A it does not?  (Read 1283 times)

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Offline jonothonTopic starter

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Hi. I am frustrated a bit because I don't know how I can get my motor to spin under a 9v 1 amp power supply... all it does it vibrate, but does not spin... when i put a diode in between, it does spin, but slowly, and the motor and diode get hot, so that doesn't seem like a solution... when i run the motor under lower amps, like a 9v 80mA, then it spins fine...

but, the thing is i have to use this 9v 1amp power supply... so, what can i do or make in order to convert 1amp to 80mA for my motor to work properly?

Thanks

Offline newInRobotics

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Re: Why does my dc motor spin with 9v 80mA power, but with 9v1A it does not?
« Reply #1 on: November 14, 2011, 01:29:30 AM »
Are You using Lab PSU in constant current mode? Or is it a PSU in regulated voltage and limited current mode? Tell us more about Your setup.
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Offline Soeren

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Re: Why does my dc motor spin with 9v 80mA power, but with 9v1A it does not?
« Reply #2 on: November 14, 2011, 05:31:43 AM »
Hi,

Hi. I am frustrated a bit because I don't know how I can get my motor to spin under a 9v 1 amp power supply... all it does it vibrate, but does not spin... when i put a diode in between, it does spin, but slowly, and the motor and diode get hot, so that doesn't seem like a solution... when i run the motor under lower amps, like a 9v 80mA, then it spins fine...

but, the thing is i have to use this 9v 1amp power supply... so, what can i do or make in order to convert 1amp to 80mA for my motor to work properly?
Sounds like...
Your motor could be for a much lower voltage.
The 1A supply is AC or more likely have a defect diode bridge.
Your 80mA source is either a PP3 battery, or a supply with a high(-ish) internal resistance, allowing the voltage to drop to a level your motor can tolerate.


Measure the voltage over the motor when it's spinning on the 80mA supply - what voltage do you see?
If you have access to an oscilloscope, take a look at the 1A supply - is it a steady DC?

If it turns out that you have a motor running at eg. 3V (at the 80mA) and the 1A supply works correctly giving DC, a resistor of 68 Ohm (1W) should help.

Using an LM317 (variable voltage regulator), you can dial in the exact voltage you need for better control over the speed.


Better problem description => better solutions.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

 


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