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Simple questions about DC Motor and capacitors  


boggiano
(@boggiano)
Active Member
Joined: 6 months ago
Posts: 5
Topic starter  

Hello,

I'm just playing with a L298D and a little DC motor.
I was checking the acceleration with this code:

for (int i = 130; i <=255 ; i++) {
Serial.println(i);
analogWrite(pinEna, i);
delay(500);
}

What I see is that it starts spinning when i is around 140: OK!

So I added a 100nF capacitor between the legs of the motor and I see this:

first time it starts about 160 then, after,  about 130.
Is it correct to say that the first time the power supply needs to power motor and capacitor, after that the capacitor helps to supply the motor itself ?

Also, I would like to use a 100uF polarized capacitor but not sure how to insert it.
What about if I reverse the rotation of the motor?
I think that, in this case, I can only use ceramic capacitors.

Is this correct?

Sorry if they are silly questions, just starting to learn, here! 🙂

Thank you!


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noweare
(@noweare)
Trusted Member
Joined: 12 months ago
Posts: 98
 

It depends where the rotor is located with respect to the stator. The rotor will be attracted to the stator pole and the motor will need more current to move. I thinks it is called clogging or something like that. You can feel it when you turn the shaft of the motor by hand. It can cause problems in motion control as once you get to a position and release the power the rotor will move into alignment with a stator pole. 

I do not think your cap is doing much as far a helping it start easier. I have seen caps located there but I think it is for decreasing electro-magnetic interference.


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