Stepper problem

[JAZZCNC]

It's hard to tell from the pics but the 8 wire motor looks like it's got 2 red wires going to A+.? You should have
A+ = Red & Blue
A - = Black & yellow
B+ = wht & brn
B - = Org & Grn

If correct then I have known some cheapp drives do strange things like this when the pulse is on the wrong side. So try changing the active state in Mach3 and see if it makes a difference.

Also what are you using for a parallel port cable.? It must be a straight thru cable not an old printer cable.!

[eurikain]

I just updated the wiring diagram.

I have the wires plunged as you said. No double red going to A+, that's just my picture that was not taken right :)

When you say change the active state in Mach3, do you mean change to low active to low high ?

I am using a male-female cable I bought three years ago. I think it's the correct cable, as it worked fine three years ago :/

[Clive S]

Have you measured the resistance between each pair of cables ie between red/blue black/yellow etc they should read all the same + or - a very small amount.

Also as Dean has said re the printer cable make sure it is a straight through cable ie pin 1 to pin1, pin 2 to pin2 etc. AS when you say you have used it before was it on a printer? Not all printer cables are straight through.

[JAZZCNC]

When you say change the active state in Mach3, do you mean change to low active to low high ?

Yes and also try setting the Step pulse so it's ahead of the Dir pulse. You'll find this in motor tuning.

I am using a male-female cable I bought three years ago. I think it's the correct cable, as it worked fine three years ago :/

Clive answered this for me.

[nobby]

Yes and also try setting the Step pulse so it's ahead of the Dir pulse. You'll find this in motor tuning.



Clive answered this for me.

bi polar parallel wants more juice,
you need a 15 amp 36 volt psu
why don't you run them at a higher res?

[JAZZCNC]

bi polar parallel wants more juice,
you need a 15 amp 36 volt psu
why don't you run them at a higher res?

No he doesn't need that high a supply. He'll never pull any where near that amount of current in normal use. More volts would help increase speed but it wouldn't cause this problem provided they are wired correctly.

Like wise running with a Higher Res or micro stepping being the correct term would only make the matter worse if he's struggling with pulses or the PP has it would require many times more pulses and work for the parallel port.
If he was running at Full step then yes but 1/8 is fine and just about what I'd recommend.

I'll wire only three motors and see what comes out. i'll post pictures/videos if I can.

Just start with one motor then test and see what happens.
Don't bother with wiring in series as you'll need even more volts to get speed. Keep with parallel and set the current setting to match the drive rating.
You do however have a miss match with the motors because those 4 wire motors are most likely series wound motors so will stall a lot sooner up the speed curve than the parallel wired ones with the same voltage.


To test the cable you need a continuity meter or meter set to Ohm's just like for testing phases. Probe pin1 at one end and at the other check it against the others. You should only get a reading between same pins # at each end with no crossover between pins.

[eurikain]

Alright, I'm back after about an hour and a half of testing. Here is what I did:

1. Test the DB25 cable. All pins are through, no cross wires, and they work fine.
2. Wire only one motor, in parallel, with 1/8mcs and 2.7A (as close as I can get to 2.8).
   same problem. Same problem as before. Note that when not moving, the motors make weird sounds..., like a constant little quiet electrical noise, hard to describe.
3. Tried switching DIR and/or STEP active low setting. No change.

Here is what I haven't tried yet and will try tomorrow if you think it's worth it:

1. pins 4 and 8 in all four possible positions (00, 01, 10, 11).
2. switch one motor for the other (if same problem, it's not the motors, it's higher in the chain)
3. switch one driver for the other (if same problem, it's the board that's broken)
4. try another computer, who knows, the only thing I have changed since 2010 is this old computer. But it works fine, so I doubt it comes from there, but with those old guys, you never know.

So, if it's not the cable, not the PSU (already tested), not the motors, and not the drives, it's definitely the board.

What do you guys think ?

[JAZZCNC]

Try setting the step pulse in motor tuning to 5 set Dir to 0 You want the Step in front of the Dir.

[eurikain]

So sorry for the delay !

Have you measured the resistance between each pair of cables ie between red/blue black/yellow etc they should read all the same + or - a very small amount.

I will try tomorrow. How am I supposed to test this ?

Also as Dean has said re the printer cable make sure it is a straight through cable ie pin 1 to pin1, pin 2 to pin2 etc. AS when you say you have used it before was it on a printer? Not all printer cables are straight through.

I bought this cable brand new three years ago and only used it with my CNC electronics, never on a printer. I will check that all pins are straight through (actually, how do I do that with no juice on them ?) and get back to you tomorrow.

bi polar parallel wants more juice

Could I wire them in series ? Then they'll need 1.4A and I'll be fine (for now).

why don't you run them at a higher res?

What do you mean ? 1/16 or 1/4 ? FMD2740A can't do 1/8 or 1/4, only full, 1/2, 1/16 and lover.

Yes and also try setting the Step pulse so it's ahead of the Dir pulse. You'll find this in motor tuning.

Sounds good, I'll try that tomorrow and let you know. I'll wire only three motors and see what comes out. i'll post pictures/videos if I can.

[eurikain]

Update on my problems :)

Received my new $10 BOB last week and tried it today. I plugged only one motor. Works like a charm. Plug all motors, boom same problem as before. Unplug all motors and plug just one. Doesn't work with one motor anymore. I turned off the PC, unplugged everything from the BOB. Turn on the PSU and the motors, thought not moving, make a weird high pitch noise, that they make when they don't work correctly. On today's first attempt, the motor plugged was quite when still. So, I am assuming it's either the motors or the drivers.