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motor's encoder not working

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nuno
Posts: 3
Joined: Sun 1 Jan 2023 18:33

motor's encoder not working

Post by nuno »

Hello,

I ordered two of the following motors from MChobby shop: https://shop.mchobby.be/en/dc-motor/143 ... 14343.html, because of the encoders.

Unfortunately, one of the encoder seems not to work anymore.

I am using a Pi Pico to read the encoder's A and B wires and I am supplying 3.3V (from the pico) to the encoder. Both are wires in the same way and use the same C function to read the square wave of the encoder A and B wires. For a about a week, I could measure both encoders and generate counts. Now, one of the encoders does not generate counts.

With a multimeter, I read the voltage of both A and the B wires of the good encoder. As expected, I see the voltage going from high to low, and vise-versa, as I very slowly rotate the motor. For the bad encoder, the voltage is always high.

Could this be a defected unit? Any suggestion on what could be wrong?

Please advice, your help is much appreciated.
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Dominique
Administrateur du site
Posts: 230
Joined: Sun 17 May 2020 22:43

Re: motor's encoder not working

Post by Dominique »

Hi,
The encoder is rated for a supply voltage higher than 3.3V.
The Hall effect sensors a separate power supply (named Vcc, between 3.5 and 20 V). It draws about 10 mA.
I would suggest to test it with multimeter and voltage at 5V.
Before that, test the running one with that method... the multimeter does "means operation" over the reading... we must be sure that everything should work as expected with the multimeter.

Cheers,
Dominique
Dominique, MC Hobby.
nuno
Posts: 3
Joined: Sun 1 Jan 2023 18:33

Re: motor's encoder not working

Post by nuno »

I have tried your suggestion and the result is the same. The motor with the good encoder outputs pwm and the motor with the bad encoder outputs high only.
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Dominique
Administrateur du site
Posts: 230
Joined: Sun 17 May 2020 22:43

Re: motor's encoder not working

Post by Dominique »

Hi,
The encoder use a Hall Effet sensor component which are quite reliable.
The circuit is also super simple.
There are two ways to have them defective:
1) Having the magnetic wheel demagnetized
2) Having shorted accidentaly the hall output to power pin (GND / VCC) -OR- to a pin accidentaly configured as output. The pico is capable to deliver more than 10mA peak... which is quite enough to kill the Hall effect component before the Pico dies.

The manufacturer (Pololu 2824 www.pololu.com) , does also takes the support in charge for their products.
It may be a good idea to get in touch with them (via their support/forum).

Dominique
Dominique, MC Hobby.
nuno
Posts: 3
Joined: Sun 1 Jan 2023 18:33

Re: motor's encoder not working

Post by nuno »

The wheels are still magnetized.

Based on your options, I guess an accidental short happened.

Do you know what is the P/N of the hall effect component (I do not see it in the package nor in the polulu website)? I will attempt to replace it, otherwise I have a useless motor for my application.

Thanks for the help.
Nuno
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Dominique
Administrateur du site
Posts: 230
Joined: Sun 17 May 2020 22:43

Re: motor's encoder not working

Post by Dominique »

@Nuno,

I query the supplier for replacement part identification.
Will return information as soon as known.

Dominique
Dominique, MC Hobby.
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