Glass scale pinout question

Tomzo

Tomzo

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For my first touchDRO install I used magnetic scales but for this project I am using glass scales. I am working through the process of identifying the pinouts and getting the scales connected. I followed the instructions on finding the pinout and identified the pins from the IC in the glass scales. When I connect 5V and 0V to the appropriate pins from the scales (the third pin on the IC on either side) to the adapter board, power up, and measure voltage from the other pins I get a reading of ~3.7V that does not change as the scale moves. These scales have five wires so one is a reference and the other two are A and B. All read the same. I noticed that the stranded grounding wire from the scale is soldered to the 9 pin connector housing on the scale side but is not continuous with the ground wire from the scale. I am not sure that makes much difference but I thought I would mention it.

I tested two of the three scales I have with the same result. What am I doing wrong?

Thanks in advance!

Tom
 
Those are not just on/off pins, they send a signal that you need more than a voltmeter to measure. Your meter is probably averaging that signal and giving you a reading based on that. There might be a way to identify the signals, I'm not sure. I would use an oscilloscope, but that doesn't help much unless you have one available.

I would think you could connect A/B and move the reader head to see if you get the expected result. Swap if it reads incorrectly. Don't do that unless you have verification from someone more familiar with these circuits, I'm just guessing.

The shield being connected on only one side to the housing is normal. It's a noise suppression trick. Connecting both ends can create ground loops.
 
I have always been looking for an excuse to get an oscilloscope - perhaps this is the time!
 
Although on Yuriy's instructions he indicates that a regular voltmeter should work so I think I have a different issue going on.
 
I assume your scales are (apparently) not working?
You went through his tutorial? Posting it again here for review:

How to Find Glass DRO Scale Pin Functions

Chinese Glass DRO Scales have become very inexpensive, and can be found on eBay, AliExpress, etc. for under $100/piece. Unfortunately many sellers are unable or unwilling to provide accurate documentation, so it's often up to the buyer to figure out what the pinout of the particular scales is...
www.touchdro.com
 
markba633csi said:
I assume your scales are (apparently) not working?
You went through his tutorial? Posting it again here for review:

How to Find Glass DRO Scale Pin Functions

Chinese Glass DRO Scales have become very inexpensive, and can be found on eBay, AliExpress, etc. for under $100/piece. Unfortunately many sellers are unable or unwilling to provide accurate documentation, so it's often up to the buyer to figure out what the pinout of the particular scales is...
www.touchdro.com
Click to expand...
Yes - that is the tutorial I was following. I sounded out all the pins and connected them accordingly. My scale looks almost exactly like the scale he used in that tutorial.

1670372064856.png
 
Well I found my problem and, as anyone who has seen any of my posts before, the problem was me. I had the 5V going to the wrong side of the IC. The text says positive is on the left but I think the image shown above that is in the guide shows a red tool and my tiny brain made that positive. I saw the connector on the left side and figured it was some sort of ground bus. Needless to say, connecting it properly solves a lot of problems.

Thanks to all who tried to help me help myself!

I still think I will get an oscilloscope....perhaps Santa will bring me one.

Tom
 
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