A PIC running at 8 megahertz can change pins really fast. Stepper motors won't run more than a few hundred RPMs at best. You might start out at 1 second between steps until you get it running smoothly and then speed it up from there.

 

I usually put a piece of tape on the shaft like a flag to watch how it moves until I get it running smooth.

 

I usually put a piece of tape on the shaft like a flag to watch how it moves until I get it running smooth.

Gear already marked with magic marker.

 

Why??????

Inertia and resonance

 

Not to change anything but while the motor has unipolar wiring, you can ignore the center taps and use it as a bipolar stepper. Then you can use a pololu style driver that is pretty cheap and really easy to use. You can find even cheaper on ebay. It has 3 lines for control - enable, direction and step. (there are others but you can just tie them high or low). You pull enable low (high?), set direction and then pulse step for each step. I'd pair it with a clone arduino nano and couple of buttons for an under $10 solution. You can set it up to have different levels of agitation and time out. You could also add a timer so you know how long you've been etching. Not very much code to write.

I'd bet that is a 7.5 degree angle per step motor which is fine for an agitator. Wouldn't want it for positioning unless geared way down.

By the way, there are lots of really nice parts in a scanner. Gears, motors, power supply, precision rods, glass, springs, encoders/encoder strips, etc. You may also find a stepper driver for the motor though it's probably on the mainboard and not a separate PCB.

 

The logic chart is for a Bi-polar stepper, you have a Uni-polar by the look of it.
Those motors are often fed from a 12v source, a 5amp source should do it.
The phasing sequence consists of 8 steps, not 4.
Max.
View attachment 141851

I don't understand this You say 8 steps but I am just seeing a repeat of 4 steps twice in your table. am I missing something??

I am close. I have the motor moving but in different directions.

Clockwise
Counter clockwise
Counter clockwise
Clockwise



Here are my indexes as measured at the ULN2003 chip.

P3 P5 P4 P6
Index1 1 0 0 0 Input
0 1 1 1 Output

Index 2 0 1 0 0 Input
1 0 1 1 Output

Index 3 0 0 1 0 Input
1 1 0 1 Output


Index4 0 0 0 1 Input
1 1 1 0 Output


I also tried inverting the bits on the input with same results except

Clockwise
Counter clockwise
Counter clockwise
Clockwise

.

 

I am ready to start on my PCB etchant agitator project.

Why are you using a step motor for that? Also, have you looked at this thread? I'm using a fish tank air pump to blow air bubbles from a PVC hose, which in turn agitate the etchant... as we say down here, it's got the three B's = "Bueno, Bonito y Barato" ... which translates into "Good, Nice and Cheap" ...

 

Why are you using a step motor for that? Also, have you looked at this thread? I'm using a fish tank air pump to blow air bubbles from a PVC hose, which in turn agitate the etchant... as we say down here, it's got the three B's = "Bueno, Bonito y Barato" ... which translates into "Good, Nice and Cheap" ...

Because it is my idea and I want to work on this project.

 

Because it is my idea and I want to work on this project.

That's an excellent reason... no argument there...

 

I've very successfully used the MC3479 chip in the past to drive small step motors, but I've just found out it's been discontinued. If I were to try it again, I'd probably go for the A4975.

 

I've very successfully used the MC3479 chip in the past to drive small step motors, but I've just found out it's been discontinued. If I were to try it again, I'd probably go for the A4975.

But I have a bunch of ULN2003 and it is working or at least the problem does not appear to be the chip. I either have a wiring issue or an indexing problem. N offense but I am only interested in solving my latest issue with this stepper right now.

 

But I have a bunch of ULN2003 and it is working or at least the problem does not appear to be the chip. I either have a wiring issue or an indexing problem. N offense but I am only interested in solving my latest issue with this stepper right now.

Ok... will follow up on that