Picked up a pair of 8" and 12" scales for £30 the pair on ebay. I have read all the info on 'reading' the data stream and thats a no brainer, but whats taxing my brain at the moment are two things...
1/ how to connect to them. I know that several places do the remote display for these but no one wants to sell me the connector/cable on its own. I don't really want to solder wires to them (but if I have to I will...). The spacing seems to be 0.05" but where to find a suitable connector?
2/ How to fix to the mill? The 8" one will be used for the Y, the 12" for the X. Since my X travel is more than 12" (although I rarely use more) I will need some sort of release mechanism to allow motion of the table past the endstops of the scale. I was thinking about something magnetic, small button magnet type of idea. But would it be rigid enough to give accurate readiings?
You can get unbelievably powerful button magnets, however you need to be careful they don't affect the readouts.
yes i was looking at 12mm x 3mm with a 3kg pull! 10 for £4
I wouldn't have throught they would affect the readouts as these are capacitive glass on stainless steel and the readings don't seem to be affected by the small magnet I have here.
Can't help with the mounting but the cables are available from Little Machine Shop or Wildhorse Innovations.
there have been some complaints on the Shumatech Yahoo group about the reliability of these connectors.
I'm in the process of adding scales to my X2 mill and will be soldering the wires directly to the scale.
Some pictures of the scale mods can be found here.
Thanks for that, the pics are useful, although the scales are not identical... i have yet to disassemble, but for a first pass I was going to leave the screens attached.
Cables... $27.50 for a cable , they are having a laugh!
I played with some Chinese scales. Didn't trust the 1.2v flea squeak signal to carry so I put pcb's on the back and buffered then to 5v.
I built hardware interface that did 3 scales and interrupted the processor whenever a full report was in and read it as 3 bytes from the shift registers.
They had 3 counts of jitter which was inconvenient if you didn't want to dump the bottom 2 bits altogether. The battery positive connected to the rule which was not exactly convenient, dragging a ground wire across the metal they were connected to sent them haywire so I had to try and insulate them from the machine with Tufnol. Was getting on pretty good then one of them switched to 5 counts of jitter and I rather gave up.
I have made connectors for them, I've soldered 2mm(?) JRC box headed on them, in the end soldering a flying lead worked out best (I also junked the lcd and wrapped the whole case in adhesive backed foil to improve screening). Apparently the Chinese made lead is a poor fit in some scales (falling out at the slightest touch).
I hadn't thought of using magnets to mount the scale to the mill - It would certainly work but might attract too much swarf if not shielded well.
I have read all the info on 'reading' the data stream and thats a no brainer,
My PC & PIC based DRO project is here (if you haven't already seen it)
I had to try and insulate them from the machine with Tufnol.
Last edited by BillTodd; 17-02-2010 at 09:23 PM.
Bill, yes I'd seen your work... it was that that got me thinking...
Well I just dismantled the 6" one (its the same type as the 8 and 12) and its the same inside as Geoff's. I also discovered that you can get an extra 20mm past the marked scale. The reading heads are identical. Has anyone dismantled the actual scale bit to look inside? Similarly, has anyone found a source of the scale elements on their own? I found a firm selling the reading heads on their own.
Bill: I like your idea of grounding the scale and generating a -1.5v supply by offsetting the PIC supply. I think a simple -ve charge pump would do the job as well.
17-02-2010 #9I also discovered that you can get an extra 20mm past the marked scale. .... Has anyone dismantled the actual scale bit to look inside? Similarly, has anyone found a source of the scale elements on their own?
I remember, back in my days as digitizer tech support, the manufacturer accidentally printed a menu overlay for a capacitive tablet using conductive ink. Oops-Splatt :heehee:
I got the impression that the technology wasn't friendly if messed with.
Did you try insulating the scale then sticking a cap to ground to de-jitter it? They don't seem to bother much with decoupling.
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