Touchdro Now Supports Igaging Absolute Scales

ycroosh

ycroosh

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

IMG_5731.jpg

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

Sent from my SAMSUNG-SM-G900A using Tapatalk
 
Congrats.

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

IMG_5747.jpg

IMG_5751.jpg

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
 
+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?
 
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.
 
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
 
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.
 
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.
Click to expand...
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.
 
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.
 
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