using the uln2003
15 Feb 2013 08:04 #30078
by castingman
using the uln2003 was created by castingman
Hi everyone new to the forum and to cnc in general so i hope this isn't a stupid question 
i do a lot of metal casting and want to build a lathe and router for making the foam plugs i use. the mechanical side of things is the easy part for me, it's the computer side thats messing with me basically i want to build a lathe i have two matching steppers (.9 degree step) out of a copy machine i want to drive these with the uln2003 chips i have a power supply providing adequate voltage my problem is configuring linuxcnc . I'm not sure which files need to be modified. i have found another post about using this chip but it did not provide the answer i have been searching for i have read the docs followed links searched prayed etc. but i'm as confused as a termite in a yo-yo i'm not asking for anyone to do it for me just give me a guideline i really appreciate any help i can get ,and thanks in advance 
btw i hope i posted in the correct place if not i do apologize and im running the latest cd version installed to the hd of a machine that meet all requirements
i do a lot of metal casting and want to build a lathe and router for making the foam plugs i use. the mechanical side of things is the easy part for me, it's the computer side thats messing with me basically i want to build a lathe i have two matching steppers (.9 degree step) out of a copy machine i want to drive these with the uln2003 chips i have a power supply providing adequate voltage my problem is configuring linuxcnc . I'm not sure which files need to be modified. i have found another post about using this chip but it did not provide the answer i have been searching for i have read the docs followed links searched prayed etc. but i'm as confused as a termite in a yo-yo i'm not asking for anyone to do it for me just give me a guideline i really appreciate any help i can get ,and thanks in advance btw i hope i posted in the correct place if not i do apologize and im running the latest cd version installed to the hd of a machine that meet all requirements
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15 Feb 2013 21:06 #30112
by andypugh
The ULN2003 doesn't have a huge current limit. if the stepper motors have a current-limit to suit then they may be a bit weedy. (Though for cutting foam they might be OK).
The ULN2003 can only be used for driving Unipolar stepper motors. They must have 5, 6 or 8 wires. A 4-wire motor can't be driven Unipolar.
There will be no current-limiting in the drive system, so you will have to rely on the motor resistance to limit the current. This means running at low voltage, so the steppers may not spin very fast.
Having said all this, there is nothing but time to be lost by trying. You can use Stepconf to make a normal stepper configuration. You then need to edit the HAL file to work with the ULN.
The main difference is that rather than using the normal stepgen (step/dir) you need to use one of the 4-signal types:
www.linuxcnc.org/docs/html/hal/rtcomps.h...n_a_id_sec_stepgen_a
You probably want to try Step Type 7.
You can change this by editing the HAL file created by Stepconf.
The assignment between the stepgen virtual "pins" and the parallel port physical pins will also need to be changed. You should be able to figure this out from the HAL file and copying/changing what stepgen has done. You need to change stepgen.N.step and stepgen.N.dir to stepgen.N.phase-A, phase-B and then add phases C and D.
Assuming a 5-wire motor (if it's a 6-wire one then you connect the 2 centre taps to act like 5 wires, if 8-wire then you connect one end of each winding to each other.) then you connect the centre wire to your PSU, and each of the other wires to a ULN pin (as the ULN switches pins to Gnd)
Replied by andypugh on topic using the uln2003
Hi everyone new to the forum and to cnc in general so i hope this isn't a stupid question
The ULN2003 doesn't have a huge current limit. if the stepper motors have a current-limit to suit then they may be a bit weedy. (Though for cutting foam they might be OK).
The ULN2003 can only be used for driving Unipolar stepper motors. They must have 5, 6 or 8 wires. A 4-wire motor can't be driven Unipolar.
There will be no current-limiting in the drive system, so you will have to rely on the motor resistance to limit the current. This means running at low voltage, so the steppers may not spin very fast.
Having said all this, there is nothing but time to be lost by trying. You can use Stepconf to make a normal stepper configuration. You then need to edit the HAL file to work with the ULN.
The main difference is that rather than using the normal stepgen (step/dir) you need to use one of the 4-signal types:
www.linuxcnc.org/docs/html/hal/rtcomps.h...n_a_id_sec_stepgen_a
You probably want to try Step Type 7.
You can change this by editing the HAL file created by Stepconf.
The assignment between the stepgen virtual "pins" and the parallel port physical pins will also need to be changed. You should be able to figure this out from the HAL file and copying/changing what stepgen has done. You need to change stepgen.N.step and stepgen.N.dir to stepgen.N.phase-A, phase-B and then add phases C and D.
Assuming a 5-wire motor (if it's a 6-wire one then you connect the 2 centre taps to act like 5 wires, if 8-wire then you connect one end of each winding to each other.) then you connect the centre wire to your PSU, and each of the other wires to a ULN pin (as the ULN switches pins to Gnd)
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16 Feb 2013 06:59 #30158
by castingman
Replied by castingman on topic using the uln2003
Thanks to both of you for the info thats what i was having a problem with i couldn't find the proper direction to take the steppers i have are made by oriental motor they are a 9 wire 24 volt .9 deg. step there is a local parts house in orlando that has newer 1.8 deg step motors but i'm not sure of the voltage requirements i havn't fabricated the actual lathe yet i want to get a working electronics side first i am having a little trouble finding info on the motors i have but i think i have the wiring figured out but if i'm mistaken about them being unipolar please let me know the model number is A2427-9214 and thanks again for the help
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