Encoder sensor wire diagram!

Thread Starter

haxed

Joined Aug 19, 2020
1
Hello, i have a small problem, i pulled this encoder from old printer/scanner but cant find any information about it on google. I would apreiciate it if someone could help me. I`m trying to make a stearing wheel for computer.

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Irving

Joined Jan 30, 2016
1,006
OK, I can't find any data on that specific encoder, but based on experience and looking at the PCB, what you have is probably a 2 channel quadrature optical encoder. From that you can ascertain speed and direction but not absolute position. The circuit, taken from the PCB, is below and below that the pin numbers on the encoder. I believe they are correct, but buzz them out to be sure.

I can't tell you the voltages, you'll have to look at where it came from, but at a guess probably 6 - 9v. Use a multimeter on the diode test range to confirm which way round the LED is just to be sure the supply rail is +ve though I'd be very surprised if it isn't. It should work OK on 5v. You'll have to buzz out the connections to the 6-pin connector, I guess two will be for the motor. Once you're sure of supply polarity you should be able to wire it up and a 'scope should show the waveforms below as you spin the motor by hand.

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MaxHeadRoom

Joined Jul 18, 2013
21,403
As to resolution, you have the natural quadrature count consisting of A pulses per revolution, or using 2 edges for x2 or all four (A+B) edges for x4 quadrature count.
Direction is detected by referng to the status of A pulse compared to B, IOW A would be the amount of pulses and the 1 or 0 level of B detects direction.
Max.
 

Irving

Joined Jan 30, 2016
1,006
As to resolution, you have the natural quadrature count consisting of A pulses per revolution, or using 2 edges for x2 or all four (A+B) edges for x4 quadrature count.
Direction is detected by referng to the status of A pulse compared to B, IOW A would be the amount of pulses and the 1 or 0 level of B detects direction.
Max.
Yes, I'd guess pulses per rev will be 1024 as that seems to be standard for these motors!
 

Irving

Joined Jan 30, 2016
1,006
True, but even without he'll get 1/3deg resolution,. By the time that's geared down, say from 3000rpm to 180deg traverse in 0.5sec, ie 25:1, that's ~25000 counts resolution, far more than needed!
 

MaxHeadRoom

Joined Jul 18, 2013
21,403
True, but even without he'll get 1/3deg resolution,. By the time that's geared down, say from 3000rpm to 180deg traverse in 0.5sec, ie 25:1, that's ~25000 counts resolution, far more than needed!
If that is a 1024 line encoder disc, it will take more than a simple slot-opto to read the distinction, it will need the addition of the Moiré grating between head and disc.
The maximum for a simple slot opto is approx 100 pulses/rev at that diameter.
Max.
 

Irving

Joined Jan 30, 2016
1,006
@MaxHeadRoom I think you misunderstood me. His goal is to use it for steering. Assuming he uses a steering arm to traverse 180degrees in 0.5sec (by way of example) and the motor would typically be 3000rpm, then it would be geared down 25:1. So in traversing that 180deg swing the motor would turn 25 revs, giving 25000 counts approx. from the encoder assuming 1024ppr. If he had an indexer at 'straight ahead' he could then estimate the angle either side by the number of counts to a fair degree of accuracy subject to backlash and other mechanical niceties...
 

MaxHeadRoom

Joined Jul 18, 2013
21,403
I was not referring to the OP's project but questioning the only possible output of the encoder if just a slot opto was used at that resolution.
Max.
Max.
 

Irving

Joined Jan 30, 2016
1,006
Ah... those encoders use a 15mm disc with two tracks; its a pretty fine photographic process they use to make the disc. I don't know what they do internally for the reading mechanisnm, never stripped one down to look inside, but i have used several from 256ppr to 2048ppr with both quadrature or quadrature/index outputs..
 

MaxHeadRoom

Joined Jul 18, 2013
21,403
As it is virtually imposible to read a grating and distinguish individual 100 lines with a photo cell alone.
The way it is done in a traditional encoder with fine photo etched grating over 100 lines/rev is that on the read head side, a piece of grating the same resolution is placed in front of the read head, but slightly skewed, this creates a Moiré pattern of a much magnified grating, creating a large light/dark grating or shutter effect, but the same resolution when moving.
Max,
 
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