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I am really sorry to bump up this message, but I really need some help understanding this sensor.

It is an optical encoder board from an old HP inkjet printer which I intend to connect later to an Arduino board. I am providing front and back pictures of the board, should be detailed enough to understand the circuit.

When I hook up the red wire to +4.74V, and black to ground I am measuring +1.8V on green and +0.9V on blue. I was expecting to have different readings when putting the paper in between the sensor's LEDs, but instead I have the same readings.

Could anybody please tell me what am I doing wrong here? Thanks

Andrea


* 2013-08-29 18.35.37.jpg (1593.48 KB, 3264x2448 - viewed 121 times.)

* 2013-08-29 18.35.53.jpg (1572.7 KB, 3264x2448 - viewed 111 times.)
« Last Edit: August 31, 2013, 04:49:43 pm by acortis » Logged

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I apologize for bumping up this message (probably not good netiquette) but I really need some help here please.

If you think that the question is not clear enough, I will be happy to provide more details.

Thanks

Andrea
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It could be that the green and blue signal lines need to be pulled up to the operating voltage and that the pull-up resistors were provided on the main printer board?

Lefty
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Thanks for your reply,

I am real newbie when it comes to these things ... can you suggest me how should I hook up these resistors on a breadboard? or maybe a link with schematics on how to do this?

Andrea
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Thanks for your reply,

I am real newbie when it comes to these things ... can you suggest me how should I hook up these resistors on a breadboard? or maybe a link with schematics on how to do this?

Andrea

It could be as simple as wiring two 10k ohm resistors between the two signal wires and +5vdc. Then you should see a switch output value of either 0 volts or +5vdc  on the signal wire as you pass or block it's light path.

Lefty
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Like in this picture? I still do not see any switch ...

Andrea


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 Sorry that's about all I have without a datasheet on the opto device.

Lefty
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Thanks anyways Lefty,
Would you know where I can find a similar product, but with a datasheet this time? Maybe I am looking for the wrong keywords but I am finding only rotary linear encoders ...

Andrea
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This is a linear optical encoder for reading a position of the printer line feed or head.
It is not an optical switch.
It uses +,- and the two others are data lines.
This encoder needs to be driven by small black lines on a strip or disc and need to be specific 92,150 or 300 LPI


Paco
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So what I had shown earlier is an optical switch? and can you give me a link please to the one you show?

Andrea
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Your picture shows an optical linear encoder on the HP board.
This is not a optical switch for sensing only on /off state

Question is what are you trying to achieve with this HP sensor?
Why do you want to use it?

Paco
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Very simply, I am trying to accurately measure the distance that the encoder strip has moved, while it being pulled unidirectionally (not back and forth) by a moving object at a non constant speed. I was planning to have one of the encoder strip attached to the moving object, and the sensor in a fixed reference frame. I need to have a precision of the speed of the movement of the encoder strip that is below the 10 microns over 10 millisecs. My understanding is that the strip encoder I have is for 1200 dpi printer, which should give me roughly 2 microns precision. I was planning to use interrupt counting with Arduino Uno R3.

If you can help me achieving this, I would seriously be most grateful,

Andrea
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Andrea,

1200 dpi does not say anything for the sensor you use.
Does the encoder strip you have has any indication?
if it says 150LPI this means the resolution is 150 value per inch.
So 150 values per 25,4 mm = 0,17 mm per step.
I have hacked a Brother inkjet printer that has an encoder strip that clearly states 150 LPI.
Have a look here.....http://forum.arduino.cc/index.php?topic=178902.0

So this means the sensor is 150 LPI too.
They are always a set.

So could you use this set up from the HP for your project?

There are also 300LPI encoder strip or disk and sensors on the market.

Paco

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You may have traced the encoder incorrectly, as was my case. See link below where a guy did the hard work already. Also, I didn't need any pull-up resistors for mine to work. It was an Agilent 51, Q9871, 0013 that I pulled out of a Lexmark Z42 printer.


https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&docid=8RdCwfe_sqT3zM&tbnid=58K6Z4MwgrxdKM:&ved=0CAUQjRw&url=http%3A%2F%2Fmckgyver.pbworks.com%2Fw%2Fpage%2F20654145%2FDRO&ei=eMawU733H8mUyAT_zoHABw&bvm=bv.69837884,d.aWw&psig=AFQjCNFwTFgaxX9vZOYYgQNbQVl8ydrCTQ&ust=1404180425730434
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