Author Topic: Touch DRO for Original iGaging Absolute Origin scales  (Read 1227 times)

jpigg55

Re: Touch DRO for Original iGaging Absolute Origin scales
« Reply #15 on: February 08, 2019, 11:01:32 AM »
Oh BTW, it was probably just my perception, but I think the lag was reduced slightly. Been a while since I used these scales.
If it truly was, I can only attribute this to the lag caused by the OEM display. The update frequency is controlled by the code and clock crystal in the readhead, but there well could have been an additional lag for the time the OEM display unit needed to process the data. The Arduino does this much faster, even though it's processing data from more than one scale. From what Brian told me on his timing test, the Arduino processes the data before the last transmitted bit reaches its full high state. Just too bad there isn't an easy way to increase the refresh frequency.
SB 9A, Clausing 8520, Sanford MG 612

Carpenter84

Re: Touch DRO for Original iGaging Absolute Origin scales
« Reply #16 on: February 08, 2019, 11:21:16 AM »
Actually... How do you differentiate between the absolute scales and the normal ones? I'm not sure I have the absolute scales... In fact, I'm sure I don't. But how do I know?
Shawn

First 9x42 column mill,
Enterprise 10x28 lathe,
Ko Lee 6x12 surface grinder,
Airco dip/stick 160 welder,
Fully stocked wood shop.

jpigg55

Re: Touch DRO for Original iGaging Absolute Origin scales
« Reply #17 on: February 08, 2019, 06:07:36 PM »
Do you have the original display with the scales ??? If so, it should be labeled on it.
The original ones were labeled "Absolute Origin' and the newer were labeled "Absolute Origin Plus".
Or you could post a picture, I might be able to tell.
Last option would be to connect the scales up to 3V power and connect an O-scope.
SB 9A, Clausing 8520, Sanford MG 612

Carpenter84

Re: Touch DRO for Original iGaging Absolute Origin scales
« Reply #18 on: February 08, 2019, 07:48:42 PM »
Mine are the ez view dro. But in looking at the igaging website, between the ez view and the absolute, the scales look identical. Is it the scales that differ or the read outs?
Shawn

First 9x42 column mill,
Enterprise 10x28 lathe,
Ko Lee 6x12 surface grinder,
Airco dip/stick 160 welder,
Fully stocked wood shop.

jpigg55

Re: Touch DRO for Original iGaging Absolute Origin scales
« Reply #19 on: February 09, 2019, 09:20:31 AM »
I'm not familiar with the EZ View scales, although I see on Yuriy's Touch DRO site (https://www.yuriystoys.com/) that if they are an Absolute position type scale, the protocol/algorithm is probably similar to the Absolute Origin Plus scales. Yuriy is in the process of updating the firmware for these scales and should be available soon, if not already out in Beta version. These do NOT have the same algorithm as the original iGaging Absolute Origin scales like Terry and I have.
An easy way to test if they are an Absolute vs Incremental type scale is to turn one on, check the position indication, pull the batteries out, move the readhead, replace the batteries, and see if indicates a new position or not.
Better yet would be to put a clamp or two along the scale so you can consistently move the readhead between the two identical positions and perform the above procedure. If they are an Absolute position type scale, the displayed positions will be the same every time.
SB 9A, Clausing 8520, Sanford MG 612

jpigg55

Re: Touch DRO for Original iGaging Absolute Origin scales
« Reply #20 on: February 10, 2019, 11:18:42 AM »
I reworked my board and hope I've gotten rid of all my soldering issues.
I'll be doing test run #3 today and will post my results later on today.
SB 9A, Clausing 8520, Sanford MG 612

jpigg55

Re: Touch DRO for Original iGaging Absolute Origin scales
« Reply #21 on: February 10, 2019, 01:46:25 PM »
Bad news again.
Evidently, I induced a bad short in the Proto-shield while de-soldering it.
Going to have to start from scratch working up a new connection board.
I'll keep at it, but wait until I have a successful test before posting again.
SB 9A, Clausing 8520, Sanford MG 612

Terrywerm

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Re: Touch DRO for Original iGaging Absolute Origin scales
« Reply #22 on: February 10, 2019, 03:38:45 PM »
Sorry to hear of the pitfall, but sometimes that's the way prototype stuff goes. Hang in there my friend, you'll get there!
Terry

Making chips with old machines!

jpigg55

Re: Touch DRO for Original iGaging Absolute Origin scales
« Reply #23 on: February 16, 2019, 06:16:02 PM »
It Lives, Success !!!
I finally sorted out my electrical and soldering issues and now a 3 axes work. Here's the link to the "Test 2" video:
https://drive.google.com/file/d/1c0pbp6ImWBNh6n_-qEJ-gxZcSaTQTdey/view?usp=sharing
Video quality still stinks since I don't have a holder or stand for my phone and no-one to assist.

I still have to remount the scales, perform the calibration procedure, and hook up the O-scope for some testing which will take a day or two.
I also need to put together a supplies list of components and see about drawing up a schematic.
More to come.
JP
SB 9A, Clausing 8520, Sanford MG 612

Carpenter84

Re: Touch DRO for Original iGaging Absolute Origin scales
« Reply #24 on: February 16, 2019, 08:28:07 PM »
Why wouldn't this system work on the non-absolute scales?

Sorry if that's been mentioned already. It's likely buried somewhere on page 1.
Shawn

First 9x42 column mill,
Enterprise 10x28 lathe,
Ko Lee 6x12 surface grinder,
Airco dip/stick 160 welder,
Fully stocked wood shop.

jpigg55

Re: Touch DRO for Original iGaging Absolute Origin scales
« Reply #25 on: February 17, 2019, 08:48:09 AM »
No, it wasnít covered here, sorry about that Shawn. Since these scales are not produced/sold anymore, I assumed anyone still following from before was familiar with this project. Iíll try to explain a bit
These scales are encoded using a pure binary numbering system referred to in Bits. A two-bit number has 4 possibilities, 00, 01, 10, & 11 (0 to 3, the zero counts). For each added bit, the possible amount of individual numbers doubles, i.e. a three-bit number has eight possibilities, 000, 001, 010, 011, 100, 101, 110, 111.
The scale tape on the Absolute Origin scales is coded using a 3 track pure binary numbering system. What we dubbed the Fine track is a 9 bit number with 512 possible numbers (0-511). What we found was this track repeats itself over the length of the scale approximately once every 5.04 mm. The Mid track is an 8 bit number (0-255). This sequence is repeated along the scale length over the distance of 8 Fine track cycles. Last is the Coarse track, another 8 bit number that can only cycle once over the length of the scale encompassing 256 Fine track cycles. This is what sets the maximum possible length the scale can be, based on the track period, and is what makes it an Absolute position system.
So by combining the numbers of each of the 3 tracks, you get a unique number combination (or address) for each and every position along the length of the scale. A simpler way to envision this is think of a combination of three rulers set side by side. The Coarse track is a single ruler numbered from 0 to 9. Next to that is the ten Mid track rulers, each 1/10th the length of the Coarse track ruler and each one also numbered 0 to 9. Next to those are the Fine track rulers with each single ruler being 1/10th the length of a single Mid track ruler and are also numbered 0 to 9. So the final lay-out would be one Coarse track ruler, ten Mid track rules, and 100 Fine track rulers with the total length of each track being equal.
Now, think of the readhead like a straight edge laid perpendicular to the rulers. When you read along the straight edge you see a combination of 3 numbers, say 4, 8, & 7. If you look, this number combination exists only once along the entire length.
So why arenít all scales made this way ? Easy, cost and functionality.
Most non-absolute scales use a simple count logic. When you set it to zero and start moving, it just counts up or down dependent on direction of travel. If it loses power or is moved too fast, it has no idea of where itís at and displays zero again when power is restored or displays a false position because it lost count. On the plus side, these are cheap and easy to manufacture and can be any length you want.
On the absolute scales, they know exactly where they are at since each position has its own unique address, but are more expensive to produce and are limited in length based on the number of tracks used and the resolution of each track. To make an Absolute scale longer you have three choices.
1.   Add more tracks
2.   Decrease the resolution
3.   Combination of 1 & 2 above.

I hope this helps to explain why this system wonít work with non-absolute scales. It even wonít work with other absolute scales unless they used the same algorithm to encode the scales since part of the algorithm is each track is used to correct the others for noise. I wonít go into details, but youíve probably seen scales where the position isnít very stable, it bounces around. These use the different tracks to correct the noise in the others making them very stable. You should be able to see that in the video where he position indications are rock solid, with the possible exception of the least significant digit if itís sitting on the edge between one position address and the next like you will be able to see in the beginning of video (once Google finishes processing it so it can be viewed) where the Z-axis indication is bouncing between 123.22 and 123.23.
SB 9A, Clausing 8520, Sanford MG 612

Terrywerm

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Re: Touch DRO for Original iGaging Absolute Origin scales
« Reply #26 on: February 17, 2019, 09:20:39 AM »
That is a wonderful explanation of how they work!  Thank you!
Terry

Making chips with old machines!

jpigg55

Re: Touch DRO for Original iGaging Absolute Origin scales
« Reply #27 on: February 17, 2019, 05:59:48 PM »
Maybe its because of it being the weekend, but Google is taking their sweet time processing my videos. Here's another I took while data collecting with my O-scope. It gives a bit of a visual to my description on how the position data works.
https://drive.google.com/file/d/1ZnQalwrrVqgctQe9nvLZcSM7xEuFMiDc/view?usp=sharing
Hopefully it/they will be processed soon so you can watch them.
SB 9A, Clausing 8520, Sanford MG 612

Terrywerm

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Re: Touch DRO for Original iGaging Absolute Origin scales
« Reply #28 on: February 17, 2019, 06:23:04 PM »
Google/YouTube might be slow to process, but I just went ahead and downloaded both of the most recent videos, and they worked just fine.  Lookin' good!
Terry

Making chips with old machines!

jpigg55

Re: Touch DRO for Original iGaging Absolute Origin scales
« Reply #29 on: February 19, 2019, 08:45:15 PM »
I got the first scale re-mounted and calibrated to the App today. I decided to redo my scale mounts and make them a bit better this time around.
The resolution turned out quite a bit better than I thought it was going to be, ended up being 7735 CPI.
SB 9A, Clausing 8520, Sanford MG 612