Controller

[cjgaus]

Hey there guys. I have come across a cnc pcb router on a site. http://cq.cx/pcb-router.pl

I see it uses a microchip PIC and max232 ic and some 5 watt 13ohm resistors. Im having trouble trying to work out what the other components like the transistors and the diodes and caps. I emailed the guy who made it and he said that it has been years since he did this machine and has no parts list.

What i was hoping is that someone on here has built something similar to this and could reccomend the parts that i can not work out what he has used.

I hope someone can help.

Thankyou

[nanopile]

I have used Allegros A3955 (i think).
It's a chip that control a single coil, usually you need two for a simple steppermotor.
It's a regular H-bridge inside and it makes it's own pwm signal with some capacitors and resistors.
But it's really a crappy circuit since it give diffrent signals with diffrent loads.
I'd prefer a timebased switching rather than sensing the coils powerconsumption.

[leoncrowther]

That looks like a very interesting machine to construct. I am in the process of a construction, but from another plan myself.
The electronics to drive them is basically up to you, what that constructor made in that regard is of little significance. There are many suggestions on the web and I have collected a few with the idea of rehashing one or two to suit my needs. OTOH there is a very promising cct., you might consider at the following site :-
http://www.pminmo.com/3axisPIC/3axisPIC.htm
See what you think of that.
Leon.

[cjgaus]

Thanks for that last post. I like that circuit. I would use it but i spent some money and got a pcb board made up for the circuit in the link i posted. Ill keep doing my research and trying to work out the components

[leoncrowther]

Well if you have to go with that cct., I would suggest the following components will do.
C3,4,5,6 are 1.0uf non polarised or tantalum. c1 & c2 are just filtering, maybe 100uf for c1 or bigger and for c2 10uf. C9 make that 0.1uf ceramic. Q1 can be a resonator intended for that job, in which case c7 & c8 are in the resonator. IC1 would be a 7805. R25 is a pull-up so 1k or 4k7 would do. R26 you can calculate to set the led current to whatever you want, probably about 25mA. R2 & R14 through to R24 will depend on what voltage you are supplying to this whole circuit, so calculate them to give the desired current in the stepper winding that is recommended and calculate the wattage required. I fail to see the need for R1 to R13 as FETs are being used to drive the steppers, so to fill the hole and for peace of mind 1k..10k or whatever. For the FETs almost any power N-type FET should do, try IRF510. Futurlec have them for US$0.55 each (although they are in Australia they quote in US$) http://www.futurlec.com/cgi-bin/search/search.cgi
D1 to D12 although zeners are shown, unless I am missing something, straight diodes would be appropriate here, any 1amp diode should do.
If I were doing what you are doing, I would only complete it for one stepper and get that working first, if all is well then complete the project.
What are you doing about software to run it?
As this answer is getting away from machines, if you need further comment, you may prefer to email me or phone, we are both in Australia...well I am anyway.
Leon.