Suggestions please Vol3

Edited By Michael Gilligan on 02/02/2012 09:41:54

Edited By Ian S C on 03/02/2012 10:55:25

Hi Gray

I note from a different post that you have retired now, did you get your counter built?

This looks like a good idea for the cross slide of a minilathe. On big jobs I lose count of where I am upto then go oversize/undersize.

For the Z axis I have fitted a digital caliper and it works great because it's out of the way, to fit the same thing on the cross would get all the debris on it and it would get in the way. I envisage one of the cheap rotary encoders fitting on the end of the lead screw at the back of the cross slide. The one I am thinking of using has 24 pulse output which would give me a resolution of 0.0833333 mm which is close enough for me, I would then use the dial on the handle to finish off.

I am at the moment writing the algorythem because I will be using a PicChip to pull the thing together. My head is hurting working out the how to work out the direction of travel but I suppose that's what keeps they grey matter alive!

Cheers Michael

May I just say, having put a PC mouse to to sleep, removed the encoder bits. Don't forget the steel ball, it's easily drilled and makes a useful knob. You all knew this of course.

Regards Bear..

Hi Michael,
If you want some sample code to get you started with writing code for a PIC I can send you versions for a PIC16F628 and a PIC16F690. If you PM me with an email address I wil send you copies of the code.

Les.

Hi Les

Thanks for the copy of the code, it is well annotated. Just got to find the old rev counter I made so I can recode it for it's new purpose and hope I didn't use all of portb to drive the 7-segment displays!

Cheers Michael

Hi Michael,
I think you will have problems using a PIC16F628 as you have to use some port B pins to drive the segment displays. (I am assuming multiplexed 7 segment LED's) There will be lot of writes to port B for the multiplexing which will probably cause the PIC to miss some interrupts (Hence loosing position.) With the LCD display I used there is only a couple of writes to update the display and these would happen just after an interrupt had occured. I think you would be better off using a PIC with enough I/O pins to only use port B for the quadrature inputs. Another option would be to use an Atmel micro as these do not have the same problem of missing interrupt on change events.

Les.

Gray,

If this is something to just give you a guide as opposed to being a readout working to 18 decimal places.

What about one of the ARC cross slide units with a pulley on it , pulled along by a Bowden cable. Adjustments could be made for travel by the size of the pulleys ?

This way the pitch of the screws doesn't matter.

John S.

These units work well enough, but I'm finding battery life to be abysmal - a couple of months at the most.

Martin.

Good heavens man, 2 months ?

That works out to sixpence a week, you need to take the old pop bottles back and use the refund money to get a new battery.

John S.

MichaelG, I had a look on Google, was quite interested to see that the "mouses without a ball" actually have an 18 x18 camera, and it can be used as a scanner, or a rather crude web cam, and the ones building Robots find uses for them. Ian S C

Excellent! I've been on the lookout for something like that for years!

Neil