Re: [CAD_CAM_EDM_DRO] Re: tool changer logic- mathematical challenge

Lance Hopper wrote:

>[snip]
> I didn't think about a PIC, but it's basically a build it yourself
>PLC if I'm not mistaken.
>
> Do you have personal experience with PIC's? I wouldn't mind
>hearing more about them.
>

A PIC is a microcontroller (made by microchip: http://www.microchip.com
). You would need to write software (in assembly language, unless you
buy a C or BASIC compiler, or you get one on a free demo) to respond to
a "tool change" input, tell the ratcheting mechanism to move, then tell
the mechanism to stop when the toolchanger is in the correct position
(based on sensor input).

Another worthwhile microcontroller line is the AVR series from Atmel:
http://www.atmel.com .

The hardest part is getting a physical interface to your equipment.
There are several companies that make things like the "BASIC stamp" (
http://www.parallaxinc.com/ ), but most are geared toward hobbyists - no
case on any of them, little to no protection on I/Os, almost never any
I/O isolation, etc. You'll have a hard time finding something that you
can attach a power supply and some wires to and have it ready for
programming.

I recently designed and built a manual pulse generator using an AVR chip
- it definitely takes a lot longer to DIY rather than buying something
built for the purpose. You will get a better solution in the end,
because the end product will only have what you need to put in it, but
the road there is not as easy.


/* programming hints, regardless of whether a PLC or a microcontroller
is used:

You should only need 4 sensor inputs - Just make an array of 8 nibbles
with the proper sensor input bit pattern for each of the 8 positions.
When a command comes to advance, just turn on the motor until the input
pattern matches the next one in the array.

Have a timeout - if there are no state changes for some time period
(like 1.5-2x the expected period), then shut off the motor, and signal a
fault if possible.

*/

- Steve