Tools for the project

[Ferenczyg]

I think is necessary to work in a 'controlled environment'. This, for electronics related topics, start with a good schematic-routing tool.

We have a lot of demo proggies with a lot of potential, but I think one is over the others for this work, it's eagle freeware version because is no cost and can be used in wintel an linux boxes. It can be downloaded from:

http://www.cadsoftusa.com/freeware.htm

The version has limitations of course but I think it will be useful to interchange schematics and similars, so this is my bet for the tool.

Opinions?

Fer

[pminmo]

I too use the free version of Eagle, have for over a year now. I have both a simple 5804 single channel stepper design:

http://webpages.charter.net/pminmo/CNC/5804channel.jpg

and a 3977 chopper design captured in it:

http://webpages.charter.net/pminmo/board2.jpg
http://webpages.charter.net/pminmo/proto3977.jpg


Phil

[Ferenczyg]

Well, two are a lot better than one, so if no other opinions appear, by absolute majority eagle wins at least for now

That open new lines of thought:

1) Unipolar, bipolar or both?

-unipolar is practically equal to work in a 5804 basis for me
-bipolar can be 3977 (no info for me) or 297/298 combo based (at least i got the IC's )

2) We go for current chopper or resistor limited? L6505 is easy to add to a 5804 i think, and 297/298 combo has the option. My opinion is that chopper have more future, a low increasing in difficulty and will be cheaper

BTW I think we must work in a schematic basis, then when the schematic work have arrived to a consensus we must:

1) create a one sided PCB artwork (I think one side is a must, to simplify building)
2) create a 'make your one side pcb like a pro ' doc or select some one of the good links out there in the web (preffer second)
3) create a 'how to use your solder like a pro ' doc or select some one of the good links out there in the web (preffer second)

Opinions plz..

Fer

[pminmo]

Personally I don't like ballast resistors. The footprint of the 3977 is no good to somebody that is not a skilled solderer. The 296/297 pair makes the best sense to me. Single sided would be desirable for the DIY'ers, but might be a challenge. The free version of Eagle would probably limit it to a one axis driver, but that does have merit. Interchangeability for troubleshooting, having a spare on hand for quick replacement to be two biggies.
Chopped bipolar makes the most sense to me.

Phil

[Ferenczyg]

Then if we go for the 297/298 Combo (capabilities, ease of build) with current control (no ballast) the proof of concept schematic is at the picture below. The combo is able to provide 2.5A if a heatsink is used.

If we go for a one axis board (I think is a good idea) then We need to add 2 way connectors for step&dir, 4 way connectors for the motor, and 2 ways connectors for logic volts, motor volts and sync signals between boards, and switches to disable the RC sync net because only one of the axis have the control of that.

This, as a secondary effect, limits the soft to step/dir and discards phase signals. This must not be a problem but an advantage but must be notyfied to the SW ppl I suppose.

What do you think? For me 2.5A is a good value, the ICs are below 15$ and the one side PCB for one axis can be a little big but not so big.

Fer

[berin]

And what are your thoughts about printing out schematics and then doing a transfer? Most people wont have a cnc machine to rout out the pcb controller board. Its very easy to do a transfer with a laser printer. Create the design and put it in a PDF file to have a standerd on printing. Print it with any old laser printer on darkest setting. Clean the pcb with soap, asitone, alcohal. then iron on the pcb design (about3-5min). Then take the pcb with paper and drop it into hot water NOT boiling. Leave it in there for about an hour or so, then start cleaning the paper off with a tooth brush lightly. it will come out great, then etch, and clean off the laser printer ink with asitone and drill holes.
When I get home I need to find a program I was using for making PCB's. Its only the demo but its even easyer then eagle to make PCB'S. Down fall is the demo doesnt let you save files but you can print to your hearts content and there are no parts limate. It will open saved files as well.
Are you guys intrested in doing a straight phase driver from the parallel port for the begginer? Or us some logic on the first setup? I do feel a straight phase driver or 5804 would be best for the first timer? My reason's are mainly based on the fact that I use to work at UMO in the computer lab. And teaching is in my blood, so a phase driver circuit would be a good teaching tool on HOW the controllers work.

[pminmo]

Ferenczyg - Yes, but I would also like to see input conditioning on the dir and clk lines, and possibly limit logic. On my boards I used either a 40106 or 74HC14 schmidt trigger. They are pin compatable and depending on what is driving interchangable. A PC output port is not really compatable with the 40106 becuse of it's guaranteed high state put it right on the low to high transition limit, when driving directly from a PC the 74HC14 is plugged in. When using Eagle it's easy to create a graphics file that can be used with a laser printer to make a board, done it many times. This 5804 board was done in eagle and with a laser printer:
http://webpages.charter.net/pminmo/CNC/5804channel.jpg

Another thing is a idc connector for gnd and logic signals comming in see:
http://webpages.charter.net/pminmo/proto3977.jpg

Building a 10pin IDC cable is very inexpensive and quick, and if descrete wiring is wanted they can be ommited.

My last suggestion is to put a 5V regulator on board. Reduces noise coupling in a very electrically noisey enviornment.

I'll post my driver schematics and email you the eagle files if you would like to see what I'm referring to:

Phil

[pminmo]

After thinking about it some, maybe the best solution is to worry more about interface and physical size and compatability. There is no reason we couldn't come up with a set of boards and let the user select which ones. For example here is my 3977 board:
http://webpages.charter.net/pminmo/3977schematic.pdf
http://webpages.charter.net/pminmo/3977board.pdf
Plus Eagle files: http://webpages.charter.net/pminmo/3977.zip

I quickied up a L297/298 board: (not finished but to throw out a point, no diodes, plus not checked, component layout not thought through at all but it does route 100%)
http://webpages.charter.net/pminmo/L297schematic.pdf
http://webpages.charter.net/pminmo/L297board.pdf
Plus Eagle files: http://webpages.charter.net/pminmo/L297.zip

There could be a 5804 board as well or embedded or high current boards, as well as you could mix and match depending on the stepper and application.
My point here is to compare the two board layout files. You'll see they have the same physical layout for the power and stepper connectors, and IDC connector to breakout board or limit logic board. Imagine a 5804 board the same. 5804 could be done single sided, it would be tuff to do the 297/298 single sided. BUT, this board http://webpages.charter.net/pminmo/board2.jpg I bought from www.olimex.com. The board is sized to fit 4 on a single panel. The did it for $38 shipped back to us. (i.e. $9+ per channel) Prototype...includes plated through holes, solder mask and single side silk screen. Dupe orders of the same panel would be about $10 less. I have the setup to make my own boards via laser emulsion. At this price, no way will it ever get used again. The other thought is Olimex sells boards and assembled electronics very reasonable, I wonder if they would offer the boards for sale at a real reasonable price if we contacted them and offered the project info.

My preferred solution is a group of boards, single channel, same physical and electrical I/O. Plus a compatable breakout board, that connects with a simple 10pin IDC connector to each axis driver, plus a board that is takes a PC parallel input, has 3 IDC outputs to the 3 driver boards, has limit logic, kill function, spindle and coolant control. Also a potential embeded remote board to manually control axis, or count for an LCD display of xyz position.

BTW have at the eagle files and use as you see fit, not to be used for and resold for profit and I assume no liability.

Phil

[Ferenczyg]

berin: of course the end is the artwork of the pcb, then the final user decide the transfer method, toner or ligth or others. I assume there is no cnc resources for someone wanting to start in cnc. I got none, for example so a pdf with the artwork when the circuit have been tested is the end. From the *.sch or the *.pcb the ones with cnc resources can generate gerber or similar files, or outlining the mill path of the pcb (eagle have some scripts for that)

pminmo: I totally agree about the need of a breakout board with signal conditioning (out and in)t in order to build a decent solution. The breakout board is where the axis and the limit switches will attach, as in your picture. We need to provide 3xStep/Dir, 1xAxelimits and 3xhomelimit (discuss this please), all optocoupled if possible. The IDC connectors are a must to avoid cable hassle. Then the user could attach 1 to 3 drivers and the switches he think he need.

About your schematic, I understand that the schmidt triggers are related to signal conditioning, this must be in the breakout board, IMHO.

By my side this weekend will try to make a one side 297/298 artwork

Fer

[pminmo]

Ferenczyg
Yes there needs to be signal conditioning on the breakout board, and as long as there is and the wiring is short it shouldn't be a problem. I put it on mine for a couple of reasons, primarily the 3977. It has real fast inputs. Second, since this is a electricall noisy enviornment and periodic glitch's can ruin a part, I felt a slow CMOS input to the board was worth cost which was almost nothing.

Phil

[Ferenczyg]

Ok, I think your schematic is quite good just I thougth that if we have a breakout board we can move all the in and out signals conditioning to the board, and leave the driver boards only for driving. Other thing to discuss is how to provide voltage for the logic of the drivers. I think that we can feed from the breakout board through the IDCs, it will be easier and cheaper, a TO-220 7805 or LM380 is able to feed 3 driver logics easily. Do you think that noise feedback via gnd can be a problem in the case of using a shared voltage source for the logic?

Ofcourse, the motor voltage must be attached to the driver board itself

Fer

[berin]

well as far as a controller of x y z, there are plenty of pic chip's which could handle the task with ease. opto encoders are rather cheap on mouser and digikey. Not to mention using a pic chip like the 16f877 has enuff io lines to drive an LCD and recive input from 3 encoders. plus a few buttons for changing modes. A layout like that could easly handle goto options as well as comunicating with the computer about possion change.

Also as far as building a driver, a chip you guys may want to at least look at and there is a series. Is the SLA7024, which has onboard chopping driver which is adjustable via a POT. It requires phase driving but outputs ? I forget 30v 1.5a something like that. There are different version's which have different power ablites. These are what I'm going to build my controller out of. Also you know you can build a stepping controler out of a flip flop and an X OR chip. I have a good schematic somewhere of a whole step setup. rewire or have jmper settings and you could switch between half and full stepping.