Motor Sensor

Other Hardware Sensors
1

Ok, so I found this little DC motor. 18VDC, 3450 RPM 0.075Amp. But it has what I think is an rpm counter mounted to the rear shaft.

It has a small circular plastic disk connected to the shaft. The disk is scribed with black lines and they pass through a bridge kind of thing that I think is a laser or led light/light sensor. I think it senses the interruptions in the light created by the scribed lines on the clear plastic disk.

So if my assumptions are correct, then I need to determine the outputs of this device. It is mounted to the motor with a PCB soldered to the + - pins of the motor. The PCB has 8 outputs. I assume two are for power, the other six must be for counting rpm/controlling the motor speed. I think I can trace the power easily enough with my multimeter.

So here's my question(s):

  1. First, what is a device of this type called? I cannot search for information without a proper name.
  2. How can I determine the function and limits of the remaining six inputs/outputs.
  3. What are the functions of the other outputs.

I know what I am asking is more of a "give me your best guess", but right now that's about all I can ask for until I have more information to do some searches or make some measurements.

Thanks.

2

First, what is a device of this type called?

Quadrature encoder?

3

Ok, Thanks. Actually an Optical Rotary Encoder. Your suggestion of quadature encoder lead me to the correct page.

Now I know what it is, maybe I can determine how to use it.

I have traced the power inputs to the two left most pins. That just leaves the other 6 pins.

Thanks.

4

OK,

Stand corrected. From what I have found it is a quadrature encoder. I have tracked the six pins as follows.

Pins 1, 2, 3, 4 are all connected together through the motor. I used an led to check and 1 and 2 seem to be positive, 3 and 4 negative.

There are three resistors, a 220 ohm and two 1.8K ohm. Pin 5 is connected to the 220, and one of the 1.8K. Pin 6 is connected to one of the 1.8 as is pin 7. Pin 8 is connected to a cap that is so small I can read the specs from the cap.

So I think the data leads are 5,6 and 7, but not sure what pin 8 is.

Any help on figuring this out would be appreciated. Can't find the data sheet for this thing.

5

So you've found the basic working principles of an optical quadrature encoder. You know that you need a light source (maybe two) and a photodiode or other light detector (definitely two.) Those components probably share a ground pin. The light needs power. The outputs will probably interface to a microcontroller pin at 0-5V or 0-3.3V.

Does that help to identify the connections?

6

MorganS:
So you've found the basic working principles of an optical quadrature encoder. You know that you need a light source (maybe two) and a photodiode or other light detector (definitely two.) Those components probably share a ground pin. The light needs power. The outputs will probably interface to a microcontroller pin at 0-5V or 0-3.3V.

Does that help to identify the connections?

I think so. Times like this I wish I had an O-Scope. I use an led to trace the motor connections, but I think one of them is actually the power for the sensor light(s). I just need to figure out which set of +/- actually run the motor and which run the light source. I'm thinking a 5V power supply connected to each set may give me the information I need. Then just a question of determining which of the other 4 leads are connected to the sensors.

Thanks.