Cheap Idea for a DRO

[BillTodd]

I like the idea of using a PC or laptop for the readout's and controls. I've never really got into VB programming but I'm quite happy with PIC assembler (not C though...that scares me).

You should be able to understand the code easily enough :)

I was told that VB interface to RS232 Com Port is not that well documented and is a bit tricky?

Doesn't seem tricky to me - maybe I've already done all the head-on-wall banging necessary ;)

Have you thought of a USB version seeing that RS232 com ports seem to be disspearing off the modern PC's (especially laptops)?

Yes I had thought about it, but VB has it's own problems with the USB driver interface so if I were to do it I just use a cheap USB-serial adapter.

Did you have any thoughts on producing longer bar's/PCB for the read head to slide on? All the cheap Chinese calipers seem to come with a short 150 mm bar.

It would be nice to be able to make accurate scales of any length, but then would require some way of accurately calibrating them, which is probably the hardest part. Given that long scales (upto 1000mm) are available for not too much money (600mm are about £70), unless you need very long scales, is it worth making one???


Since there seems to be some interest here, I've attached the PC app and PIC files to this post. The VB app has a sort of demo mode that'll allow you to add scales and adjust the value by dragging the mouse over a button. The current version is a fixed 640x480 window to suit my panel-pc, but I have a part finished MDI (multiple document - so I could add hole layout and utility functions) version that I would like to finish ... sometime.

[1113562]

You should be able to understand the code easily enough :)


Doesn't seem tricky to me - maybe I've already done all the head-on-wall banging necessary ;)

Yes I had thought about it, but VB has it's own problems with the USB driver interface so if I were to do it I just use a cheap USB-serial adapter.


It would be nice to be able to make accurate scales of any length, but then would require some way of accurately calibrating them, which is probably the hardest part. Given that long scales (upto 1000mm) are available for not too much money (600mm are about £70), unless you need very long scales, is it worth making one???


Since there seems to be some interest here, I've attached the PC app and PIC files to this post. The VB app has a sort of demo mode that'll allow you to add scales and adjust the value by dragging the mouse over a button. The current version is a fixed 640x480 window to suit my panel-pc, but I have a part finished MDI (multiple document - so I could add hole layout and utility functions) version that I would like to finish ... sometime.

Thanks Bill,

I think I may have managed to grab the demo VB DRO last night. I installed it and had to go and find/install the required inpout32.dll. After that its seemed to open just fine, but of course I have no multiplexed input to test it yet. The version I installed as far as I could work out could only open two scales (X and Y). Is that a limitation or me being stupid?

I will certainly make up the PIC board just to see that it all functions correctly with my Lidl/Aldi 150 mm callipers seeing I have most of the parts.

One question I have is whether there is a practical maximum cable length between the reader and the PIC board. There is some posts that suggest that EMC/noise issues exist at this interface and running single ended clock and data over long wires is not ideal for low pick-up. With all 4 channels on one board there will have to be a compromise about the best location of the board relative to the machine scale positions.

You may have a point about the long T/Comb PCB and bar if you say you can pick up 600 mm callipers for £70. My mill X axis is 18" travel so one of these would be just fine. It just seems wrong to buy the whole thing just for the PCB and maybe the bar when the readers can be purchased complete for <£4 as recent posts suggest.