80V board

[sdantonio]

Hi,

I have this huge set of motors (425in-oz) that are rated at 4VDC, 2.8A. I have been told that using a 3977 based driver (35VDC max) I will not get the best efficiency out of them. I was originally planning to run them off of a 3977 based driver with a 28VDC, 25A power supply. I am told they should be run at 4 to 20 times rated voltage which would put them somewhere between 16 to 80VDC.

The highest rated board in Phils website is listed at 55VDC (I believe it is LM-279 based if I remember right) and it is suggested that it be run at 35V unless you "add some extra EMF shielding". Gecko makes boards rated between 24 to 80VDC which sound like the right range to me.

Does anyone have a schematic and PCB layout for a board that will run 24 to 80VDC? And what extra EMF shielding would be required?

Thanks
Steven

[pminmo]

Alan's PicStep board would be a pretty good choice for your application, although I wouldn't recommend running it at 55V, becuase your motors will produce some back emf. Enclose the boards and electronics in a metal enclosure and you should be ok.

At 40V you would b 10 times the coil rating and will get pretty decent performance, not Gecko quality, but you wouldn't have Gecko dollars in it either.

[pminmo]

I should have asked, how many wires are the motor? 4,5,6,8?

[sdantonio]

Hi Phil,

Thank you. The motors are 4 wire, which I believe would make them strictly bipolar. Would your BOB still be the thing to inerface the boards and the computer with? And how sensitive are the LM-279 chips to solder? How are you doing with the board I sent you, is it at all workable or were the lines to thin as I was worried about?

Steven

[pminmo]

Steven,
Que me in ot the board. I've worked/working with several? ST l297/298 are easy to solder. 3977's not so easy. 4 wire stricktly bipolar. Cheapest way is a db25 connector and wires. Easiest way for one of the boards on my website is the interface board.

[sdantonio]

Hi Phil,

the board in question is the 12605 optoisolated BOB. You sent me all the PDF files and then you reworked the copper layout because one of the grouping of lines were to close together to resolve with toner transfer etching.

[pminmo]

Steven,
The board is 90percent assembled. Missing a few parts. But so far things look good.

[sdantonio]

Hi Phil,

Great, do you have a build sequence and any test points? or should I just assemble the whole thing and hope for the best? Actually when it's done if I can plug it into the computer and then measure a few voltages off of it generated by a Mach3 test program that would be really cool.

Is it going to be compatable with the Alans PicStep?

The LM-279 have a rating of 3A max. My motors have a rating of 2.8A. So I basically I have a choice of setting up the board at 3A or 2.5A (unless I can find a bunch of 7.1K resistors). In one case I hit the chips with their max current. In the other case I loose about 50 in-oz torque. Any sugestions on which value is best to choose?

Steven

[sdantonio]

The LM-279 have a rating of 3A max. My motors have a rating of 2.8A. So I basically I have a choice of setting up the board at 3A or 2.5A (unless I can find a bunch of 7.1K resistors). In one case I hit the chips with their max current. In the other case I loose about 50 in-oz torque. Any sugestions on which value is best to choose?

Never mind, I found a resistor that will give 2.7A. Best of both worlds I think. Protects the motor and the LM-297 chip, and I only loose about 20 in-oz torque.

Still need to know about the compatability issue between the two boards when you get the chance.

Thanks
Steven

[sdantonio]

Phil,

If you eveer find those resistor networks that we couldn't find in digikey or mouser (I think they were the 4 X 330 ohm or something like that... the files I got from you are at home), please let me know and I'll buy a few off you.

Otherwise I'll just pigtail a few single resistors together.

Steven

[pminmo]

steve,
Hope to give you an update in a few days. Which version of the picstep? I do have the sips, btw.

[sdantonio]

Hi Phil,

I downloaded and bought parts for picstep v4.0. But I haven't made the boards yet, since most of the parts are the same I could go picstep v3.1 if you think that would be a better match for the optoboard.

Steven