Problem using a DC motor

Thread Starter

Lerior

Joined Jan 18, 2018
28
Hello everyone,

I ran into a problem when I was trying to run a 9V DC motor. I designed a simple n-channel E-MOSFET circuit that can run a motor and control its speed, however, the motor did not work. My circuit is working on breadboard and there's no issue regarding wiring; I replaced the motor with an LED to test it and it worked. So it is just the motor. Any idea as to why is it not working?

I attached my simulation below, I couldn't find a motor symbol in Multisim so I replaced it with an inductor.
 

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MaxHeadRoom

Joined Jul 18, 2013
19,029
You should be able to control it satisfactorily with the 2n7000 in an ON/OFF manner but not analogue control.
Max.
 

Thread Starter

Lerior

Joined Jan 18, 2018
28
You should be able to control it satisfactorily with the 2n7000 in an ON/OFF manner but not analogue control.
Max.
And that's what I want to do, initially turn it off/on using the pot to control the gate. It works well in theory, but when I built it on breadboard, my small dc motor wasn't working.
 

MaxHeadRoom

Joined Jul 18, 2013
19,029
For on/off all you need is a switch, one way you take the gate to common (off) the other to +ve through a 5k resistor for full on.
Or replace the Fet with a switch!
Max.
 

Thread Starter

Lerior

Joined Jan 18, 2018
28
For on/off all you need is a switch, one way you take the gate to common (off) the other to +ve through a 5k resistor for full on.
Or replace the Fet with a switch!
Max.
I did try that. Still, mortor wasn't running.
 

Thread Starter

Lerior

Joined Jan 18, 2018
28
When you say it wasn't working do you mean that the speed control was unsatisfactory or that the motor didn't run at all?
It didn't run at all. As I said, I tried replacing the motor with an led to test my circuit, and the led worked just fine.
 

AlbertHall

Joined Jun 4, 2014
8,358
It didn't run at all. As I said, I tried replacing the motor with an led to test my circuit, and the led worked just fine.
That original circuit should make the motor run up to full speed and be able to make it stop though the speed control in between may not be good. If the motor didn't turn at all then there is something wrong with the connections.
 
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Thread Starter

Lerior

Joined Jan 18, 2018
28
Thank you guys. The motor did work ONLY when I used 9V power supply, instead of a 9V battery. That's rather strange but I'm glad everything works now!
 
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