Motor Encoder Output Voltage Division

Support Motor controllers/drivers and motors
1

I am using this motor with the Hall Effect Encoder included.

I am using a STM32 uC that requires (or at least recommends) 3.3V-level input for GPIO/External IRQ. I tried to take the 5V output of the motor encoder and use a 400Ohm/600Ohm voltage divider circuit to make the input effectively 6/10*5V=3V (which is close enough to 3.3V according to the STM32 datasheet.

circuit_diagram
circuit_diagram931×608 4.94 KB

What I’m seeing on my oscilloscope is a square wave of the correct frequency, but only .5Vpp. I was treating the square output pin of the Hall Effect encoder as a 5V voltage source. I am guessing this cannot be done, so I’m wondering if I could get some info as to what circuitry is in the encoder and how you would best recommend changing the voltage level to something lower?

2

Hello.

I moved your post to the “Motor controllers/drivers and motors” section of the forum since it seemed more appropriate.

That is a very low resistance divider; you might try increasing the values of your resistors by around 100 times (e.g. 40kΩ and 60kΩ).

Brandon

3

Good call. First I tried 4MOhm/6MOhm, saw Vpp of like 0.8V.
Dropped down to 37.5kOhm/68KOhm and got like 3.05Vpp which should be fine for 3.3V level uC.
Thanks!

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