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Having problems with chip and DC motor and potentiometer and Arduino....

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roineust

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Hello!

I have tried to build the following circuit:

https://fritzing.org/projects/drive-motor-using-l293d-sn754410

I have used and copied all the same components and wiring - exactly (i think..).

But - the motor seems to be working at the same speed and is not turning slower or faster, as i turn the potentiometer in each direction.

i have thought of several possibilities, for what is going wrong:

1. maybe the guy in the Fritzing site, refers to a stepper motor and not to a regular DC motor and that changes the whole picture, since i am using a regular small DC motor?

2. At the beginning of wiring and connecting the whole circuit together, i made a mistake and at the channels that are supposed to get 5V (red wires), i connected about 11V instead (the power that i need at max for the motor), maybe i have damaged the chip this way?


That's it...i can't think of anything else...

Can anyone with some serious experience, help me understanding, step by step, what is going wrong here?


Thanks a lot!
 

dwcookiemonster

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First of all, have you powered your arduino board properly.?
If yes,
You need to check pwm signal output (orange wire) from arduino board using oscilloscope, is it present pulsed signal on it (pwm signal), or not?
Then,
If the signal not presents, the problem is on your arduino board.
1. measure analog in (yellow wire), the voltage must change simultaneously when you turns left or right the potentiometer.
2. verify the code was downloaded properly into your arduino board.
3. except 2 points above, you have damaged chip.

If the signal presents,
1. check pwm frequency, L293D can support up to 5kHz switching frequency.
2. check pwm duty cycle, pwm duty cycle must change when you turns left or right the potentiometer. if it's not, verify the code.

larger duty cycle = run faster.
PWM_10percent_duty.PNGPWM_50percent_duty.PNG

You can using regular DC motor <1A for that application.
 

roineust

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Hello dwcookiemonster !
Thanks for the suggestions and PWM explanation!

Indeed it was a fried Arduino problem!
As soon as i replaced to a new Arduino, things started working well.
 
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