[kmist]

I just finished building my new 4 axis linisteppper with the V2b PCB's all looks good but when I tried to run the first motor test the 5 watt resisters got red hot when the motor clamped on (I mean RED). I guess I'm ask'en what could I be doing wrong? I have noticed when I hook up the BOB PCB all the power transistors show to be grounded also the 5watt resisters are grounded is it me or is this not right.when the BOB is detached all is well. where do I need to start?
Thanks Kevin

[James Newton]

Check the part number on the small transistors... some kits were sent with the wrong ones, but a follow up email "recall" was sent out to everyone asking them to check and offering free replacements and "goodies" if we got it wrong.

If that isn't it, what voltage is your power supply and what are the specs on the motor? Especially the coil resistance.

[kmist]

Thanks James everything looks good with the kit. my problem is with the size of my motors I thank I'm thing to run an old SLO-SYN 1.7v 4.7a. 150 oz I was just reading about how to tune the linistepper and it comes up with a .21237 ohm resister how do I do this. what would the wattage be.
<'m running a 24 volt power supply 400 watt>

[James Newton]

You can't run a 1.7 volt almost 5 amp motor from a 24 volt supply with a Linistepper. Drop to 12 volts at /most/ 9 volts would be better. If you put in smaller resistors (in an attempt to tune for the 4.7amps) they will just fry quicker. The Linstepper is rated for 3 amps at MOST. Recommended current is 1 to 2 amps. The kit comes with one set of two 1 ohm resistors which will supply 1 amp. There are holes to solder in a second set of 1 ohm resistors which will result in a 0.5 ohms and will provide 2 amps.

But again, they are always going to fry if you try to run that motor with that power supply. If you want to run a 24 volt supply, get a motor that is rated at around 12 volts. There are some good motors listed here:

Good Stepper Motors for the Linistepper

which are a better fit. Try for some with higher volts and lower amps.

[kmist]

Thanks for the help !!!

[pedro13]

Hi, sorry for reopening the thread, but I have the exact same problem: on one of my driver boards the sense resistors (0.75ohm, 5W) are getting hot quickly while the motor is not turning.
The same motor (2A) and same set of TIP122s work with the other boards (they're connected with wires/molex). I've checked for visible defects but there's nothing obvious. Do you guys know what should be the next step of troubleshooting?

Thanks a lot,
Peter

[James Newton]

Check the part number of the small transistors.

[pedro13]

Hi James, all transistors are BC337.

[James Newton]

Does the motor ever turn?

[pedro13]

No it doesn't move at all

[James Newton]

Check the PIC. Power, gnd, clock. Etc

[pedro13]

I reprogrammed the PIC. Also GND and power is ok on pin 5 and 14. not sure how to check the clock.. I guess the next step is replacing the small transistors?

[James Newton]

Check the output pins on the PIC, ensure they are driving the transistors first. I doubt the transistors because SOME of them might fail, but all 4? It's more likely that the oscillator isn't working on the PIC.

[RomanLini]

Hi Pedro13, check the resistor values, and the 6 diodes orientations.

Sometimes the cause of a motor "not turning" is that it's wires have been connected wrong, so the motor jitters but won't turn.

Also, you did not state whether this board has worked before? Or did you build 3 boards and one of them has never worked?

[pedro13]

Hi Roman,

This is a new board 1 out of 3. I've checked the diodes, they're the same as in the other boards, I've also replaced the crystal and the PIC already, but it didn't help.

Thanks,
Peter

[James Newton]

Right, so did you build 3 and 2 work but 1 does not, or is this the first of 3 and you haven't built the other 2?

Please check the output of the PIC, to make sure you are seeing a standard stepping pattern feeding into the transistors as you send step pulses.

[pedro13]

The other 2 are working, I'm testing with the same motor and TIPs, so those are out of the equation. I'm not sure how to check the PIC's output, also the resistors go hot very quickly, in about 10 sec I can't touch them any more (so I can't leave the power on and fiddle with it for too long) Maybe I'll just rebuild that board from new parts all together.

[James Newton]

So just put a meter lead on one of the output pins, power up, step, and see that the output goes up and down. Then do the next output pin. Actually even just one pin will tell you if the PIC is running. Then move between the small transistor and the large one. If that is going up and down, then it is ok. And so on.

[pedro13]

Pin 6 is just sitting at 0.17v steady when I'm jogging in emc.

[James Newton]

Yeah. So the PIC, she is not running. You might try the other pins to make sure. Try the measurement from the TOP of the board, right on the actual PIC pin, not on the trace. Also, power down, pop the PIC out of the socket, clean the leads with light sandpaper, and put it back in the socket. Check for solder joints on the socket, etc...