[racedirector]

My machine is down at the moment due to a weird problem with one of my SLAmstepper controllers and I am hoping someone (James?) can point me in the right direction.

What happened was a motor cable got pulled off while the machine was running. After killing the power as soon as I could and plugging the motor back in, the SLAm attached to the motor didn't work. Well, not "didn't work" at all, the motor wouldn't turn, just like it was stalled (read horrible noise). I double checked the motor was OK and then deduced the SLAm had died.

So I bought another SLAm chip and replaced it but there is something weird going on. What happens is the directions seem to get confused. I mean if I press the right arrow to jog right the motor will go left on one press and right on the other. The same happens pressing the left direction arrow to jog left. The motor will go in either direction if I tell the axis to move to a certain point, for example if it is at 200mm and I tell it to go to 500 there is a 50/50 chance it will go to 500 and a 50/50 chance it will go to -100.

Has anyone any ideas on what components on the board may be causing this? If it is yet another SLAm chip then I will be buying another controller that is not SLAm based. If it is something simple like the bc327 I will replace that but I am not spending more and more fixing the SLAmstepper.

ANy help or pointers would be appreciated.

Cheers
Bruce

[James Newton]

Make sure the step and direction lines aren't reversed.

[racedirector]

Hi James

All that has been checked 1000 times. It is not that it goes in the wrong direction, it that press to go left and it will go right, press to go left again and it will go left. It will even start to go left and then go right by itself. With a new SLA chip on board it shouldn't be doing that........

[john-100]

Hi Bruce ,

I'd check the connection to the IC's direction input pin 9
you could have a high resistance "dry" joint between the pcb and the IC pin
or hidden by old burnt flux you could have a whisker of solder intermittently shorting between pin 9 and an adjacent pin

the two 2K2 resistors thats connected to the BC327 transistors base and emitter should of protected it
but as a quick check ,
a wire link connecting its emitter and collector will set the SLM7062 reference voltage to 0.29V for the full motor current setting instead of the 0.15V when the transistor is not conducting

you could exchange the board with one on another axis to see if the fault goes with the board or stays with the printer port pins
(its possible the damaged SLA7062M has damaged the printer port)



John

[racedirector]

Hi John

Thanks for that. I thought I would discount the pp port first up and attached the board to other pin combos and the problem travels with the board. So I then donned my magnifier and had a real close look at the joints etc and cannot see anything that should be there.

I'll work out the pins on the bc327 and try what you have proposed tomorrow (11:14pm here) and if that doesn't work I might even try and take the SLA chip off the board and build a veroboard version, that is if I can figure out where all the connections should go with wires. In my minds eye I see that as testing if I have buggered the slam board somehow when I took the old chip out. I figure that if I have stuffed yet another chip I have nothing to lose. Pushing my luck but any suggestion on the building a veroboard version bit?

Cheers
Bruce

[James Newton]

The last time I saw this problem, it turned out to be bad input from step and direction signals. I would strongly suggest disconnecting the direction input from the PC, shorting it to ground, and then seeing if it always turns the same way. Then short it to +5 and see if it always turns the other way. The back EMF may have damaged the parallel port.

[RomanLini]

That symptom can occur if the motor wires are not connected right. Please check your motor wires and make sure the common wires are connected to V+ and the phases A,A-,B,B- are all correct.

The SLA chips are extremely rugged and even if one is blown by PSU fault or a motor wire disconnect fault it should not go through the SLA chip to the low voltage terminals (ie to the parallel port terminals). So I really doubt the BC327 transistor or the parallel port or anything int he 5v side is damaged.

The most likely culprits are;
1. motor wires wrongly connected or bad connections
2. shorted pins in your soldering of the SLA chip legs
3. open circuit pins of the SLA chip
4. broken/lifted tracks etc where you resoldered the SLA chip
5. a bad connection on the DIR input pin

[racedirector]

The last time I saw this problem, it turned out to be bad input from step and direction signals. I would strongly suggest disconnecting the direction input from the PC, shorting it to ground, and then seeing if it always turns the same way. Then short it to +5 and see if it always turns the other way. The back EMF may have damaged the parallel port.

Hi James

The p/port is fine - I tested it by moving all my slamsteppers around and they all work everywhere aside from this one board.

That symptom can occur if the motor wires are not connected right. Please check your motor wires and make sure the common wires are connected to V+ and the phases A,A-,B,B- are all correct.

The SLA chips are extremely rugged and even if one is blown by PSU fault or a motor wire disconnect fault it should not go through the SLA chip to the low voltage terminals (ie to the parallel port terminals). So I really doubt the BC327 transistor or the parallel port or anything int he 5v side is damaged.

The most likely culprits are;
1. motor wires wrongly connected or bad connections
2. shorted pins in your soldering of the SLA chip legs
3. open circuit pins of the SLA chip
4. broken/lifted tracks etc where you resoldered the SLA chip
5. a bad connection on the DIR input pin

Hi Roman

1. Can be discounted, the order of connections have been checked and I have 5 pin microphone plugs & sockets for motor connection. As above, all boards aside from this one work in all 4 positions.

2. Have had a good look at my work and while it is not professional I can't see any shorts between legs.

3. Not sure how to check this one or what to look for.

4. A possible candidate. I will double check and run wires from the legs to their proper places to overcome if found.

5. Will check that again also but I think it would go with point #1

Cheers
Bruce