Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: extreme.aly on March 10, 2015, 07:19:28 AM
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Hello people,
I tried googling this but I cannot find the datasheet for the encoder that comes with Pololu's 37dx52l Motor.
I'm trying to use that encoder to get motor speed on a Beaglebone Black which is 3.3V tolerant. So I made a voltage divider circuit with 1K and 2K ohm resistors. But for some reason, it is giving me way less than 3.3V.. Like 1.3V on the output of the voltage divider.
I noticed that the original signal, 5V expected, also changed to 2V. (2V*2/3 = 1.3V)...
Can anyone suggest a solution for properly dropping down the voltage to 3.3V for this Motor Encoder's output?
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Are you powering the encoder with 3.3v (encoder Vcc, blue wire)?
how are you measuring the voltage of the encoder signal?
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I'm powering the encoder using 5V.
I was measuring the voltage between GND and the encoder out pin.
I found a way to fix it. I used 10k and 20k ohm resistors instead of 1k and 2k.
My theory says that the encoder was not able to supply enough current, so the voltage was dropping. I used resistors of higher value so that less current is drawn. Lesser voltage is dropped.
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:) Hello!
Check out this site;
https://www.pololu.com/product/1102 (https://www.pololu.com/product/1102)
Site with integrated encoder;
https://www.pololu.com/product/1442 (https://www.pololu.com/product/1442)
The specs are;
Dimensions
Size: 37D x 64L mm
Weight: 7.5 oz
Shaft diameter: 6 mm
General specifications
Gear ratio: 19:1
Free-run speed @ 6V: 256 rpm1
Free-run current @ 6V: 250 mA1
Stall current @ 6V: 2500 mA1
Stall torque @ 6V: 42 oz·in1
Free-run speed @ 12V: 500 rpm
Free-run current @ 12V: 300 mA
Stall current @ 12V: 5000 mA
Stall torque @ 12V: 84 oz·in
Lead length: 11 in
;D ;D ;D Hope this helps on the parameters of the
motor. ;D ;D ;D
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:) Hello!
Check out this site;
https://www.pololu.com/product/1102 (https://www.pololu.com/product/1102)
Site with integrated encoder;
https://www.pololu.com/product/1442 (https://www.pololu.com/product/1442)
The specs are;
Dimensions
Size: 37D x 64L mm
Weight: 7.5 oz
Shaft diameter: 6 mm
General specifications
Gear ratio: 19:1
Free-run speed @ 6V: 256 rpm1
Free-run current @ 6V: 250 mA1
Stall current @ 6V: 2500 mA1
Stall torque @ 6V: 42 oz·in1
Free-run speed @ 12V: 500 rpm
Free-run current @ 12V: 300 mA
Stall current @ 12V: 5000 mA
Stall torque @ 12V: 84 oz·in
Lead length: 11 in
;D ;D ;D Hope this helps on the parameters of the
motor. ;D ;D ;D
Obviously I have seen this page. I'm talking about the datasheet of it's encoder. This page doesn't mention the part # of the hall sensor encoder it is using.
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I found a way to fix it. I used 10k and 20k ohm resistors instead of 1k and 2k.
My theory says that the encoder was not able to supply enough current, so the voltage was dropping. I used resistors of higher value so that less current is drawn. Lesser voltage is dropped.
sounds like a reasonable explanation to me, glad you figured it out.
I would not be surprised if the encoder is a custom board (as it is soldered directly to the motor). If you still need additional information regarding the encoder i would try contacting Pololu, if this is a custom encoder board they might be able to supply part numbers for the components they used.
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Hello.
Just curious. Were you able to try any higher resistor values, like 50K and 100K?
My favorite resistor divider calculator.
http://www.voltagedivider.ca (http://www.voltagedivider.ca)
Thanks,
Dan