iGaging scale to quadrature converter, is there a design available?

I have iGaging type scales and readouts on my mill but would like to use a DRO

(My DRO) **LINK**

Which expects to see TTL level signals from glass scales etc.

I know the Yuriy Android interface reads igaging scales but although I am an Android fan I dont really want to use it for this DRO setup.

I have done a few searches but have not found the circuits of any interfaces although I am sure I saw one a few months ago,

Ian P

Edited By Ian Phillips on 27/03/2014 16:55:29

I looked at the iGauging website and they had all sorts of different encoders.

I don't know which ones you have, but there's no data there anyway.

If I had your scale in my hand I could stick a scope on it and work out what is being issued. As it is I have no idea.

At least there is some information on the DRO. It talks about TTL quadrature, which is enough to know. I've always used high end kit like SICK, Heidenhain, Renishaw. If you pay proper money, you get a proper datasheet.

It sounds like Yuri's Android wotsit is reading ASCII strings and blatting it out to a graphical display. Converting ASCII to Quadrature TTL is what you need, and it is not an ideal thing to do.

Quadrature TTL is fast, it's like the slide giving your DRO an update for every micron of movement.

The ASCII scheme will update you periodically in time. If the slide moves an inch between updates, then first you'll think it in one place then another. It's like the slide dwells at A for ages, then suddenly moved between A and B in zero time.  The TTL quadrature scheme tells you about all the points in between, with infinite time resolution.

It's not ideal to convert between a high level scheme like the ASCII one and a low level one like the quadrature one. Normally you'd go the other way.

iGuaging have loads of different scales, so some might work.

Broadly though it looks like Yuri's Android software is only a display, and possibly an interpreter. Your DRO is smart enough to read a barebones (proper) encoder. The encoders that Yuri reads are smart in their own right so he has to do less in his software.

I'd say you need to inject the signals from your scales into the middle of the electronics of the DRO somewhere. Either that or pull signals from the middle of the scale electronics. Neither is very practical.

My recommendation would be to get some proper encoders;

http://www.industrialencodersdirect.co.uk/

You still would need to think about scaling and calibration. I didn't read the manual of your DRO enough to establish if it could be calibrated to different quadrature encoders. Obviously on some a pulse might represent a micron, others it might represent a meter.

Broadly you will want an "Incremental Encoder" to get the Quadrature TTL signals that your DRO datasheet requests. I think all those encoders are rotary rather than linear. You will find linear incremental scales if you look, but you might end up with Mitutoyo, Renishaw or some other expensive alternative.

Try some of the more generic Chinese scales. You might come up lucky!!

Edited By Andy Ash on 27/03/2014 19:13:04

Hi Ian,
It would be difficult to make a converter to do this. Quadrature scales do not send out position information which iGaging, 2 x 24 bit, BIN6 and 7BCD scales do. They send out two square waves (Some output sine waves that are converted to square waves in the DRO) which are 90 degrees out of phase when the position is changing. When there is no movement there is no output from quadrature scales. To make a converter you would have to calculate the difference between the last and current reading and generate the pattern of square waves that would correspond to that amount of movement. You will find a converter that works in the other direction which converts quadrature input to 2 x 24 bit protocol. This is the QCC100 designed by Scott Shumate to be used with the DRO350.

I've just seen Andy's post.     Here is a link to details of the iGaging protocol . The interface for Yuriy's Android DRO converts the different protocols from the scales to ASCII strings of numbers

Les.

Edited By Les Jones 1 on 27/03/2014 19:22:30

Aha!

New information....

Working. Standby for analysis.

Les, Andy

I am familiar with the operating principles of the various types of scales and displays but admit I must have misunderstood what was involved when I said I had seen a capacitive scale to quadrature converter. As you say it not such a simple task to do.

Shumatech and Yuriy have options to accept inputs from several types of encoders but the display unit I have is not so flexible. I have several rotary encoders with various counts per rev which I have connected to the display, unfortunately whilst there is some small adjustment (for calibration) the display does not let me say, use a rotary (8000CPR) encoder and display the output as an angle, which is something I think I would find useful (if I could find a way to incorporate the encoder into a rotary table.)

Maybe I will just to buy two new glass scales.

Ian P

Iv'e had my tea now too!

The new data on the scales, shows that they are kind of "SSI" esque.

It might be possible to develop an interface, but as I said before it would never be ideal.

How good or otherwise an interface would be depends strongly on more data that would be needed about the scale, and on the demands of the application.

One would need to know the maximum traverse rate of the slide. Also the maximum data rate from the scale.

The DRO expects infinite time resolution, and much respect goes to its designer for that decision. A home hobby lathe probably isn't that demanding. The thing one learns about these systems is that once the time information is gone it can't be got back. Never to throw it away is a good thing.

Absolute encoders can be more precise than incremental ones, for a stationary axis.

Sometimes there is no substitute for absolute information. One may not have the scope to "zero" an axis.

The exquisite acceleration information given by an infinite time incremental signal, means that an end effector can follow a precise path no matter how fast it travels. With the absolute system, the faster the rate of travel, the poorer the quality of the path.

High end encoders are usually available with all the different systems in a single unit, but the price is physical size and usually money too. If you're building a really good robot you need all the information anyhow.

It is clear now that Yuri is doing more than he apparently claims, but not that much more. He's got quite a nice idea though. The technical difficulty isn't high, but it would be great to have on a massive milling machine. I can just imagine standing on the table of a vertical borer or something. You'd be able to reach into your pocket and your mobile phone would tell you where the tool point is. You might even be able to jog the machine through the user interface.

Hi to all,

this seems to be the only thread on iGaging scales.

I hope someone in the know can answer my question.

I have a set of 35-706 7 35-712 of the aforementioned scales on my X2 mill and would like to power them from an external source. I forget to switch them off.....

What voltage should I give these 3 units (power I think will not be so much) - they have two 2032's in each, so either 3V or 6V stabilized?

Thanks in advance

Peter

Peter,

The scales need a power source not exceeding 3v. The two CR2032 cells are in parallel.....

Peter

As John said the cells are in parallel its 3 Volts.

I'm not sure you will benefit much from using an external supply though. I have iGaging scales on my mill and I never switch them off, Battery life is measured in months minimum, years probably. I have not changed the cells in mine for nearly two years now so the effort involved in making a suitable 3V supply and making reliable leads and connections to survive the workshop environment is out of all proportion to any theoretical saving.

Ian P

For those who come after:

Yuri's DRO is a bit more sophisticated than suggested above - he has various interfaces that read the native data output by various types of scale and 'translate' this into a consistent format sent to an android tablet for display.

The typical 'cheap capacitative scales' have a 'fast mode' that update vastly faster than the eye can follow and Yuri's (and many other displays) can keep up with this.

Neil

I have a caliper2pc unit and it works great (no connection to company). I note that they have data about connecting all types and protocols of scales and also do converters which look to be a single PIC and a capacitor for the igaging ones. Might be some useful info at least.

.

Good Morning, Mr Happens ... or may I call you 'Shed' ?

The caliper2pc pages look interesting

Thanks for confirmation that the unit works.

MichaelG.

Hi Michael, yes it's been fine. Also really handy as it has 6 inputs so I have 3 scales on the mill and 3 on the lathe with a touch screen monitor on an arm between them. Then I can just swivel to the machine I'm using load the configuration file and all the settings are there ready. You can install the software and have a play as it has a simulator to provide inputs.

John

Thanks for that, John

MichaelG.

Hi Neil,
Just a small correction. Yuriy's interfaces do not support the fast mode on 'cheap capacitative scales'. This mode was only on the original 2 x 24 bit protocol type scales which no longer seem to easily available. My version of interface does support this fast mode but is more complex than Yuriy's interfaces as extra hardware in needed to send the signals to the scales to set them to fast mode.

Les.

@all

Thanks for the information.

I'm using my machines not so often nowadays, so leaving the scales 'on' might mean a month or two until I come back... So, doing this twice or more times may result in empty batteries when I need them.

Going the PSU-way is a better solution for me. I have ordered the stabilizers already and will report.

Peter

Hello,

I'm looking for people who purchased the original iGaging Absolute DRO scales.

Some friends and I have recently decoded the algorithm these scale use and wrote a sketch for the Arduino platform to make them compatible with the Touch DRO App.

I'm trying to get an idea of how many people still own and use these scales (no longer in production) to decide on the best platform to release the sketch and shield build instructions.

If any members here are interested, send me an email to j*** with "Igaging Absolute" in the subject line. Once a platform is decided on and info posted, I'll make notifications.

Yuriy of Yuriy's Toys website and creator of the Touch DRO App has recently joined our group and has agreed to post a link on his site as well. This should be happing within the next few weeks.

It's our policy to remove email addresses to protect against spamming, please use personal messages to exchange email addresses.

Edited By Neil Wyatt on 16/10/2020 09:57:22

Great stuff, Jimmy

MichaelG.