Help with suggestions on attaching an encoder to a DC gearmotor

Hello – I have a DC gear motor that has a rear-end that looks like this:

Is there an encoder out there that I can attach to it? I just want an incremental encoder (optical or Hall) with A and B phases.

Thanks in advance.

That’s not an easy one - it looks like you have perhaps a millimeter around the rear shaft and perhaps a millimeter deep. You can try to create a press-fit cylindrical piece of plastic (which doesn’t touch the rear of the motor, making it quite small) and see if it can hold up under high speed. Adding glue might help a bit. You really might want to consider adding an encoder to the output shaft of the gearbox instead.

The output shaft is 7 RPM – the resolution will be useless.

But I was thinking along your lines and using Loctite or superglue.

Ah, higher gear ration than I was imagining. You can get optical encoders with pretty good resolution, but likely an order of magnitude more expensive than the motor itself. Loctite, a light press fit and perhaps a micro magnet for added “pressure” to stay on. There’s a very slim chance you can, with research, find an optical encoder ring with metal center which can press just enough into the rear shaft. Given it weights very little, it might be able to stay on.

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It looks pretty similar to the motor I use with encoder.

They need a few mm extra shaft length and the encoder is soldered to the backplate of the motor.
It’s probably easier to buy a new motor with encoder option. ( …and mor reliable, too)

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This motor has 70 kgf-cm torque – there is no motor with this much torque that comes with an encoder … sadly.

However, I have ordered my motors from China and I have figured out a way to make it work. I’ll post some pictures after I am done with it in about 4 weeks. (Takes 3 weeks to get the motors from China!)

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This is how I solved the problem.

The shaft was 3 mm.

So I got a 3mm ID and 4 mm OD stainless steel tube from Amazon and cut it to length with a Dremel.

I then attached it to the motor shaft with a 5500psi steel infused epoxy. I also cured the “bearing bump” with some flat washers - also attached with epoxy.

Now it is ready for an encoder!!

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Well done! Appreciate the update.