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Old 08-30-2010, 10:44 AM   #1
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Default Scales to suit Shumatech DRO

If you're thinking of building a Shumatech 350 based DRO, this is a cautionary tale of the relevant scale.

I purchased a pre-built 350 board via eBay, and wired it into an enclosure bought separately. As with all things electronic where I have even an ever-so-small role in the assembly, I held my breath, blocked my ears, crossed pretty much everything and plugged it in.

The board fired up perfectly with the welcome message, and I was able to scroll through the setup process with the function keys. I started breathing again.

Next, I made up some cables to connect to the cheap callipers I also purchased via eBay through a vendor in Hong Kong. The measuring unit on the callipers is identical to the pictures shown on the Shumatech website (which is why I ordered them), so what could possibly go wrong?

Well, er - nothing. That is, nothing was showing on the 350's Display. Nothing, notwithstanding that the DRO was providing power to the callipers and successfully switched them to fast mode. I tried all 3 callipers and all 3 inputs sockets. I checked the cables. I reversed the clock and data wires, and tried that. Nada.

The very helpful guys in the Shumatech Yahoo group let me know that the callipers or scales I need for the 350 with Revision 4 software must be 24 bit protocol, and that those that look like mine but with the 24 bit protocol can only be identified by the small crystal on the PCB (disassembly required to check) rather than just by similarity to the pictures I had found.

Going forward, how does someone contemplating a 350 DRO build proceed with confidence in their scales? One of the guys in the Group said that the very cheap scales sold in Hong Kong and by one large US business are not 24 bit. He said that the scales he had purchased in the past through Wildhorse, Neiko and Virtual Village were all 24 bit, and he had purchased some from Virtual Village 3 months ago that worked fine.

I cannot vouch for what he says (yet) but I have no reason for doubt. I have now ordered some from Wildhorse as I have purchased from it before, and its website refers to the scales as 350 compatible. I have no affiliation with any of the above.

The Fignoggle mini-mill DRO plans also mention Shars as a supplier of scales that work with the 350.

In any event, a confirming email to the vendor about compatiblity and a refund may a good idea (note how I ignore my own advice).

I hope this helps someone not waste money on non-24 bit scales. The bright side is that I have more than enough cheap digital callipers for the workshop so I don't lose them all amid the mess.

Mods, please edit if you aren't happy with me naming names based on heresay.

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T70MkIII is offline  
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Old 08-30-2010, 12:15 PM   #2
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Default Re: Scales to suit Shumatech DRO

Hi Richard,
I have just finished fitting a DRO350 + Chinese scales to the X and Y axes on my mill (an Amadeal LV25) and will confirm for the benefit of UK based readers that the scales sold by ARCtrade Euro are compatible with the Shumatec 350.
The only major problem I experienced was with making a good connection to said scales. the user group archives suggest soldering a fly-lead to the lands within the scale socket but of course this negates the warranty on the scale. (the X axis scale costs 75). A suitable plug seems unobtainable here in the UK. I therefore have solved the problem by the simple expedient of making my own plug! which on the X axis scale appears to be working OK only time will tell how successful. If anyone out there needs details shout up and I will post it up.
kindest regards
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Old 09-06-2010, 11:32 AM   #3
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Default Re: Scales to suit Shumatech DRO

Hi All,

This sounds only too familiar - I bought the same kit out of the UK (Lester Caine) back around 2005 and sourced the 2 scales (one already fitted to my BF20 mill) from my local supplier HBM in the Netherlands. I had exactly the same problem but only with one of the scales - and of course, the longest one at that.
Once I had pinned the problem down to the scale, I borrowed a storage scope and looked at the signals - primarily because I assumed I had a levels or odd frequency problem and that was when I discovered the 24 bit issue.
I had a brief conversation on email with Scott who designed the unit although I suspect he had dealt with too many people who told him that his unit didn't work for some reason...eventually I dropped the issue and bought a 'new' second hand scale from another local supplier which worked perfectly. I had thoughts of building a converter but I gave up electronics years ago.
I believe that I must have been right at the start of the deliveries of the newer scales.

I understood that the 'new' version of the DRO350 with a daughter board was conceived to get around the mixed scale problem and I contemplated buying one but no longer need to - and I think it removes the ability to do centering (might be wrong here) which I use very frequently - however it might be worth your while investigating.

Stick with it, the DRO350 is worth every effort you make - you will not know how you lived without it once it is working.

PS, I still have a 500mm long scale, 24 bit doing nothing in particular if anyone wants to make an offer!
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