Easy To Build Stepper Controller from Recycled Materials

Step 3 Remove Chip from Control Board

The next step is to locate the uln2003 chip on your stepper driver. If your board does not have one, you can order one online for about 50 cents. If your board has a uln2003, you must desolder the chip from the board. This step can be a bit tricky, but is not that hard. First, try to remove as much solder as you can using your desoldering pump. Once you have removed the solder, use gentle, prying force with the tip of a screwdriver. Carefully touch the tip of your iron to each pin, still applying force with your screwdriver.

Comments

[edgukated]

I removed the circuits from 5 different models of HP scanners. They all have different chip sets and none have a ULN2003 chip. Does anybody have any suggestions how I can find an equivalent chip on these boards? ...timmy

[Computothought]

Both the uln2003 and the nte2013 are easy to get on-line. most local (real) electronic stores should have the nte2013.

[14341045]

TE RESPONDO EN ESPAÑOL PERO PUEDES TRADUCIR CON GOOGLE
ES MAS FACIL BUSCARLOS EN IMPRESORAS DE PUNTO, ESTAN CERCA DE DONDE ESTA EL CONECTOR DEL MOTOR PAP, SON 2 CHIP FACILES DE RECONOCER YA QUE ANBOS TIENEN LOS MISMOS NUMEROS EN LA CARA VISIBLE.
EN SCANNER NO HE BUSCADO PERO DEBERIA ESTAR CERCA DEL CONECTOR QUE VA HACIA EL MOTOR, PUEDES BUSCAR LA EQUIBALENCIA EN INTERNET, GOOGLE, ESCRIBES EL DATO DEL CHIP QUE SACASTE Y AÑADES DATASHEET Y TE MUESTRA LA PAGINA CON DATOS DEL CHIP. ESPERO QUE TE SIRVA

[-shtoink-]

I have managed to find quite a few of the ULN2003 or equivalent chips. Different manufacturers of these chips had slightly different schemes for naming them. Double check the chips with a search on line for data sheets to see if they are what you need. It did help to look specifically for the really old scanners. Every UMAX Astra I found as well as the really old Mustek had uni-polar steppers and at least one 2003 chip.

I recommend looking for the ones that have parallel or centronix ports on them. Possibly SCSI, too. The older ones were not small and you can easily see the "guts" and make you decision about its usefulness to you. Anything that has USB is probably going to have very little you want. They tend to have very small stepper motors and might be bi-polar. The exception being some of the UMAX Astra scanners that have parallel and USB. I also noticed the older ones tend to have really thick hardened steel rails. An added bonus for linear motion.

[lenny25]

I've got the same issue, I've been ripping apart scanners, printers, photocopiers. Got lots of unipolar and bi polar motors and plenty of cool steel rods, but no uln chips. Are there any alternatives? I mean something must be controlling the stepper motors.

[murray484]

You can buy the chips for $0.50 at most electronics stores. I noticed that most scanners from big companies did not have the chip.

[-shtoink-]

I think that it is worth it to source some ULN2803A chips since they cost about the same but allow you to run the arrays in pairs so you can push up to 1A. The 2803A has an array of 8 instead of the 7 that the 2003A has. You could get away by using 4 2003A chips, but it could get a little kludgey.

You can see a simple 1 axis version implemented like that here.

[zoot686]

There's no way without using resistors on the input to assure that the pairs in the array share the current load

[-shtoink-]

Would you mind elaborating on this one, please. I am far from an expert and a little bit more info on this whole thing might prove most helpful.

[zoot686]

It's called manufacturing tolerances, and each darlington transistor in that array will be "slightly" different.
And thus the transistor that turns "on" first will take the full current load unless some sort of regulation is supplied to assure that each transistor in the array is "exactly the same"....
And to be truthful, I don't think there's any way to do that as the base leads to each transistor in the array are internal.

This circuit is good for 500ma per phase and there's a lot of small surplus nema 17 and nema 23 stepper that can be used with this circuit, but a lot that can't.
For those that can't, instead of using the ULN2003/ULN2803 just use a set of 4 TIP120's or TIP142's instead of the ULN chips.

look at these links for an idea of how this works and what your ratings will be:
http://www.luberth.com/plotter/TIP120schematic.png
http://www.luberth.com/plotter/tip120pcb.htm

[Reonarudo]

the stepper motors can be easily controlled with 4 transistors so there is no obligation to use a specific IC

[pro2xy]

How do I do that?? I've been trying to do that for a while with very little luck... The best I could get was to make my motor run one step CW and one CCW..... :/

[alex-sharetskiy]

the IC is much easier to use

[james10101]

what about uln2004?

[-shtoink-]

I got two scanners and ended up with three 2003A chips. How's that for lucky? The scanners were UMAX Astra USB scanners that I got a a second hand shop for real cheap. I think the trick is to look for older scanners and not the newer ones. The newer ones seem to have a lot more custom ICs to cut down on manufacturing costs. The exact models I got were the UMAX Astra 1220U and UMAX Astra 2100U. I hope this help on your search.