RE: 100:1 Metal Gearmotor 37Dx57L mm with 64 CPR Encoder

I have some questions about the Pololu "100:1 Metal Gearmotor 37Dx57L mm with 64 CPR Encoder"

Are there filter capacitors on the encoder board across the “Motor +” and “Motor -” leads?
I usually place 0.1mFD capacitors across the “Motor +” and “Motor -” leads, looking at my Pololu motors it appears, they might already be located on the encoder boards.

Do the encoder outputs need any conditioning / buffering on their connections to a micro-controller in order to get the nice clean signal outputs shown in the scope plots on the motors web page?



Hello, zappman.

The encoder board does include a 0.1 uF (microfarad, not millifarad) capacitor across the motor terminals, but it should not hurt to add additional capacitors.

The oscilloscope captures on the product page were made with direct connections to the encoder, so you should not need anything between it and a microcontroller.

- Kevin


Thank you for your response.

One more question about the encoders.

On the web page for the motors is says:

Color Function
Black motor power
Red motor power
Blue Hall sensor Vcc (3.5 – 20 V)
Green Hall sensor GND
Yellow Hall sensor A output
White Hall sensor B output

The question is:
For the “Hall sensor Vcc” can I use “3.3V” instead of “3.5V”,
making the encoder compatible with a 3.3v micro-controller,
without using a level shifter or voltage divider?

Looking at the scope plot on the web page, it looks like the voltage of the encoder signal output is only 2.52 Volts with Vcc being 5 Volts, if this is correct, Then maybe I can use a Vcc of 5 Volts with a 3.3 V micro-controller?




You are reading the oscilloscope captures incorrectly. The “2.52 V” you are seeing is the trigger level; the pulse outputs range between 0 and Vcc (the channels are both at 2 V per division and span approximately 2.5 divisions).

The encoders might work at 3.3 V (I have seen ones work at this level), but I can’t guarantee it since this is technically out of spec. A perhaps more reliable option, if you have 5 V available, is to power the encoders at 5 V and run the outputs through voltage dividers before connecting them to your 3.3V microcontroller.

- Ben

Hi Ben,

Thanks for the explanation about the encoder signal levels.

Now, I understand the scope plots much better, and know exactly what I need to do.