Reading and fixing Chinese scales

[BillTodd]

the other thought I had was making the PIC do calibration to improve accuracy over the long runs... some form of look up table of offsets per cm

Certainly do-able. Of course, it does require a calibration standard of must higher accuracy than the scales (thinks: I have a magnescale strapped to the side of my lathe that's good to a few microns over its entire length).

Though frankly, for the RF30 type mill I'm using them on, they're probably good enough as they are.

what about compensation for temperature? does the PCB expand enough to warrant it

If, as you suggest the pcb is a set of disconnected copper fingers then I guess it is compliant enough to flex with the SS carrier.

I am debating whether to grind the calipery bits off or try to use them as a mount..

They cut easily with a friction saw but watch the temperature,as you don't want the glue to come undone. I drilled mounting holes with a carbide pcb drill.

Were you thinking of making a stand-alone display device or using a PC?

[irving2008]

Certainly do-able. Of course, it does require a calibration standard of must higher accuracy than the scales (thinks: I have a magnescale strapped to the side of my lathe that's good to a few microns over its entire length).

Though frankly, for the RF30 type mill I'm using them on, they're probably good enough as they are.

Ditto for my MD30, the 12" claims 0.04mm across the full length, 0.01mm 0 - 100mm. Since nothing I make (to date) is bigger than 100mm....

Were you thinking of making a stand-alone display device or using a PC?

I was going to use 15 0.8" led 7-Segment displays and a couple of driver chips and a PIC, the displays are only 50p each and the PCB for it is simple enough. Doesn't warrant the hassle of a PC. Depending on the PIC I might add a USB port so a PC can read them too.

[BillTodd]

You might be able to save yourself some effort (I hate PCB layout) by using a EPOS display like this with serial input and large VFD

Or if you fancy tinkering...

http://cgi.ebay.co.uk/new-2-line-by-...item2c52e20dc2

[irving2008]

Hmmmm.... theres an idea...£4.99 isnt going to break the bank...

No doubt if I made it work somebody'd want to copy it


<edit>
Oh Google is a wonderful tool ... These are manufactured for Fujitsu (ICL as was) and are probably a RS232 serial interface (EPSON emulation) with a 12v 10W supply requirement. Shouldnt be too hard to figure it out. Only 9mm character height tho if these were the customer facing ones, 11mm otherwise..