# Touchdro Now Supports Igaging Absolute Scales



## ycroosh (Dec 6, 2015)

Good day,
By popular demand, I finally added support for iGaging Absolute scales to the TouchDRO (using MSP430 "Universal" controller firmware). 




The firmware is still in "BETA" version and can be downloaded from my blog's "Downloads" section (http://www.yuriystoys.com/p/downloads.html). In a few days I will post a detailed how-to guide, but here is the short version.

The USB cable that comes with the Absolute scales has 6 wires:
Brown - Vcc (+3V)
Red - Ground
White - Data
Green - Clock
Black - "Request"

For now you can cut into the cable (mine was not shielded, by the way) and connect Ground, Cock and Data to the corresponding MSP430 pins. (For details on the pinout, see this post: http://www.yuriystoys.com/2014/01/dro-interface-pin-functions-for-msp430.html)
The head needs to be connected for now (otherwise the reading head won't send the position). I will post a circuit that will bypass the reading head in a few days.

The position is read out in 0.01 mm (i.e. reading of 123 means 1.23mm), so the PPI in TouchDRO needs to be set to 2540. 

I will keep posting the progress, but I hope this will be useful for some "brave souls".

Regards
Yuriy


----------



## Navy Chief (Dec 6, 2015)

Anxiously awaiting the updates for this.  Thanks for the hard work on this. 

Sent from my SAMSUNG-SM-G900A using Tapatalk


----------



## kingmt01 (Dec 6, 2015)

Congrats. 

I've been thinking about going to glass scales before long. I'll probably post on g+to get some input about them.


----------



## ycroosh (Dec 7, 2015)

Good day,
Had some more time today to play with the scale. Basically the reading head can detect when the display is there. The way around it is to pull data and clock lines to Vcc using two 100 KOhm resistors; the "Request" line need to be pulled low (tied to the ground). With those two changes the adapter can read the scales without any problems. Below are some picture of how this setup should look:







The little PCB is a regular stripboard with strips running horizontally (in the first picture).
The capacitor is there mostly because I have a habit of slapping bypass capacitors everywhere. The usually make a difference on the regular iGaigng scales, but these seem to be much more stable in the first place.

Hope this helps.
Thank you
Yuriy


----------



## middle.road (Dec 8, 2015)

+1 to what Chief says above. Thanks Yuriy.

I haven't ordered anything yet. Need to get a DRO up and running on the BP. (or perhaps I should learn how to use a vernier dial...  )

So could I, at this stage start the _procurement _cycle?


----------



## kingmt01 (Dec 8, 2015)

When I bought my  iGaging scales the cost wasn't hafe what they are now. If your only using 1 scale I could see where they still make sence but at the price I'm finding them now it seems like it would be better to build the Touch DRO using the glass scales that are about the same cost.


----------



## ycroosh (Dec 9, 2015)

I agree 100%. I use glass and magnetic scales on all three of my machines and they work flawlessly. With glass scales the setup is rock-solid: no noise issues, not jumping and very responsive readout. Apparently a lot of people already bought these scales, so I was getting a dozen emails per week asking to add the support. They seem to be much better than the original iGaging scales, though. The different in price comes from the construction (ground hardened stainless steel vs. extruded aluminum and plastic).
In any case, it wasn't a that big of a deal to add the support. Plus, this way someone might use a mix of Absolute scales with other kinds (the firmware now supports most of the common stuff on the market).

Regards
Yuriy


----------



## kingmt01 (Dec 9, 2015)

I was referring to the price of the old style. I'm actually quite happy with mine. I don't experience the problems others refer to. With your app I get 2/10 resolution & as close as I can measure over 6" it has at least that accuracy & repeat ability. 

My problem is on my machine I didn't have any way to cover them without it getting in the way. That's not the scales fault but I'm concerned it will cause then to fail. The only problems I've had has all been self inflected.

I was already looking into these scales when I learnt of your design. They were cheap back then. If I remember correctly I had an average of $20 a scale & built the whole thing for less then $200. It was worth while for me but the cost savings isn't there anymore.


----------



## Navy Chief (Dec 9, 2015)

kingmt01 said:


> I was referring to the price of the old style. I'm actually quite happy with mine. I don't experience the problems others refer to. With your app I get 2/10 resolution & as close as I can measure over 6" it has at least that accuracy & repeat ability.
> 
> My problem is on my machine I didn't have any way to cover them without it getting in the way. That's not the scales fault but I'm concerned it will cause then to fail. The only problems I've had has all been self inflected.
> 
> I was already looking into these scales when I learnt of your design. They were cheap back then. If I remember correctly I had an average of $20 a scale & built the whole thing for less then $200. It was worth while for me but the cost savings isn't there anymore.


I have to disagree with you regarding the cost savings, there is no way that I could have purchased 3 glass scales for my machine for the same cost as the  3 iGaging absolute scales that I purchased and I can cut them to length easily to fit exactly where I need them to unlike glass scales. I will be well under $300 for a complete 3 axis build for my mill using the iGaging absolute scales.


----------



## RJSakowski (Dec 9, 2015)

The primary reason for my going the iGaging scale route was their size.  There is no way that I could install a glass scale for the x axis or the tailstock on my Grizzly 10x22 without severely compromising the capability of the lathe.  I ended up with 3 axes of scales, with covers on the x and z axes and with resolution down to  .4 thousandths.   The ability to to adjust the x axis gib  was compromised by the requirement to remove the scale to access the screws; a minor inconvenience.  I have full protection on the x and z scales.  

There is some dithering on the readout when setting the readout resolution to .1 thousandths.  Dithering or a jumping around of the least significant digit is a common issue in digital displays.   One way that it is dealt with is the decrease the update frequency which has the undesirable effect of slowing the response time.  Another way is to use an averaging algorithm. This creates a more pleasing display  but introduces a certain lag to the response.  Also an undesirable trait.  If the display resolution is set to  a thousandth, there is very little jumping.  I set mine to a tenth to take advantage of the scale resolution of .0004".

For a better price on iGaging scales, check with davidh on this site.


----------



## kingmt01 (Dec 9, 2015)

The glass scales would be about $300. Not knowing what size you need they may be cheaper. I've yet to use any glass scales but from Yuriy & others that have been messing with both scales they have me believing the glass are far better. The interface might run you around $35 but should be under $50. As far as I know you can't upgrade the non shielded cables. So you will probably want romx to shield them so that is a few more bucks that is already on the glass ones. You have to make covers for the iGuaging that is already in the glass ones.

I'm not against anyone using the iGuaging scales. They just don't seem cost effective to me since the price has more then doubled. I'm still happy with mine but since I can do glass for the same cost I think I'll go that route for my new machine.


----------



## RJSakowski (Dec 9, 2015)

My cost for 3 axes, including TouchDRO, was about $120.  The iGaging Absolute scales would have made it around $200.  The best price that I have seen on a glass scale system was around $350 from China and close to $700 on a USA sold system.  Glass scales alone would be $450 from USA.


----------



## kingmt01 (Dec 9, 2015)

Cheapest glass scales I've seen was $58 that I believe was with free shipping. I don't remember the size but they were small. The size I need is up to around $120. I'll have over $400 in building it & could buy a complete one for $600 but I like Touch DRO & don't want to go to anything else.

I really wish the microcontroller could do 4 scales.


----------



## RJSakowski (Dec 9, 2015)

Glass scales have a 1 or 5 micron resolution.  The iGaging type scales have a 10 micron resolution.  I have installed and used both.  I have not had a problem with either.  I would prefer the higher resolution on the lathe, especially since with the x axis, the diameter is reduced by twice the cross feed advance but I couldn't fit glass scales. Yes, a good installation will have covers to protect the scales. 

On the two glass scale installs that I did (mills), I had to modify or make covers.  Most of the components for the mounting were thrown in the scrap bin so I didn't benefit there.  I had a stockpile of 1/4" stainless steel flexible conduit which I had purchased on eBay for cheap for another project.  The only downside was that I had to splice the scale wires to get them through the conduit. and still use the mini USB connectors.  

The bottom line, the additional cost for the install for all the "extras" was minimal and the amount of effort doing a quality install was about the same.


----------



## mksj (Dec 9, 2015)

Having used both, the glass scales are rock solid, have no reader lag, and have a better absolute accuracy if you need that high a resolution. There are newer smaller glass scales like the M-DRO slim styles that are much smaller than traditional glass scales, 27.8mm wide by 24 mm tall with the protective cover on the scale. The reader/size of my Igaging Absolute scale once mounted is comparable. The Igaging scales are still less expensive (about half of the slim scales) for the same size, easy to trim, and might be more immune to contamination, although never had an issue with glass scales properly installed. Still, when you start looking at all the costs and time, the glass scales would be my preference. Newer magnetic scales are currently far more expensive for what you get, and have there own issues. The magnetic strip tape and a reader can be had for a fraction of the price of a scale.
http://www.allendale-stores.co.uk/docs/mdro/m-dro-gs500-encoders_technical.pdf


----------



## middle.road (Dec 10, 2015)

Are the Ditron (DC10) glass scales any good? I see one vendor up on ebay that has them at a decent price.
I'm not sure which way to go. DavidH has good prices on the 'Absolutes' and that's the direction that
I've been leaning towards.


----------



## ycroosh (Dec 10, 2015)

They are as good as any other Chinese glass scales. I have a set and they work very well.
If cost is not an issue, glass scales beat capacitive scales hands down: they are much more accurate and stable.


----------



## RJSakowski (Dec 10, 2015)

ycroosh said:


> They are as good as any other Chinese glass scales. I have a set and they work very well.
> If cost is not an issue, glass scales beat capacitive scales hands down: they are much more accurate and stable.


Glass scales have better resolution.  I have not had a problem with either regarding stability.  For small machines, size can definitely be an issue.


----------



## middle.road (Dec 10, 2015)

Cost is currently a big factor, unfortunately.  I'm trying to get the Bridgeport going.
I'm no d*mn good at using the vernier dial, I just don't have the touch.
I've passed on two projects that would have brought in some holiday money, so I need to do something.
I didn't realize that the DRO 'standards' were so varied. Just trying to find info on this old Mitutoyo so 
that I might jerry rig another scale is impossible - or so it seems.


----------



## JPigg55 (Dec 15, 2015)

WARNING !!!
Yuriy's MSP set-up works with his Absolute Plus scale, it doesn't work with the original Absolute DRO scales.
The Plus scales seem to use a BCD format, whereas the originals seem to use a Binary format.
Still working on the issue, but wanted to give a heads up for those thinking of using his design with the older type Absolute scales.


----------



## ycroosh (Dec 15, 2015)

That's correct. I think there are two different versions of these scales: one (DRO Plus) uses standard SPC protocol, and an "older" version that isn't listed on their website that uses a different protocol.
This is the supported kind: http://www.igaging.com/page44.html.

JPigg55, if I could entice you to lend me one of your scales for a weekend, I should be able to figure out the protocol.

Thank you
Yuriy


----------



## Navy Chief (Dec 16, 2015)

ycroosh said:


> That's correct. I think there are two different versions of these scales: one (DRO Plus) uses standard SPC protocol, and an "older" version that isn't listed on their website that uses a different protocol.
> This is the supported kind: http://www.igaging.com/page44.html.
> 
> JPigg55, if I could entice you to lend me one of your scales for a weekend, I should be able to figure out the protocol.
> ...


I need to check and see which type I have, off the top of my head I have no idea if they are the older model or the plus model. If they are the older model I will be happy to send one out to you to work on figuring out.


----------



## Navy Chief (Dec 16, 2015)

No dice on helping out with the scales,  all of mine are absolute plus models. 

Sent from my SAMSUNG-SM-G900A using Tapatalk


----------



## JPigg55 (Dec 16, 2015)

I'll be sending one.


----------



## terryw123 (Feb 8, 2017)

I have those cheap dro's and what I did to keep dirt and grit out of the mechanism is I put a tube sock over the scale and use nylon tie wraps to hold it in place.  Works good.


----------

