Symbol Mini Stepper Motor
@ August 24, 2009
- Component category: Output devices, motors, servos and locomotion
| Attachment | Size |
|---|---|
| G14197.pdf | 193.83 KB |
This mini stepper motor from the Electronic Goldmine was ridiculously cheap. However, it is wired strangely for a stepper motor, so I've collected some more info on the device.
Electronic Goldmine provided this link to someone's site who claimed to be driving it directly from a PICAXE. I haven't tried this yet.
They also provided a printed schematic for a drive circuit that should work the device, but I had limited success with it. I'll post a picture of the schematic once I have scanned it. I also have a video where it seems to be working fine, but later it developed problems, which led me to do some further research.
Here's a good site on understanding the various types of stepper motors: Jones on Steppers
I found some Dutch sites talking about the identical motor, which was almost helpful with Google Language tools translating the page for me. Most useful was their link to this instructable using the exact same motor.
I'll update this when I make some more progress.
Update 2009-08-25
Winding measurements:
This supports the information I found. The red/blue contacts are for one coil, with white as a center tap. The yellow/black contacts are for the other coil, with no center tap.
Update: 2009-08-27 (at waaaaay too early in the morning)
I confirmed the findings of this guy, who has an instructable on driving the exact same stepper with a microcontroller.
Usnig a bench power supply, I was able to drive the motor clockwise (CW) and counter clockwise (CCW) by making the following sequence of connections:
CW
- Blue to +6V: Red to GND
- Black to +6V: Yellow to GND
- Red to +6V: Blue to GND
- Yellow to +6V: Black to GND
- Yellow to +6V: Black to GND
- Red to +6V: Blue to GND
- Black to +6V: Yellow to GND
- Blue to +6V: Red to GND
So yay for me, the motor works. Now I tried to run it from the PICAXE-28x1, with limited results.
I am only able to drive the motor CCW for some reason. Even when I step through the sequence in CW order, the motor turns CCW. Also, it is supposed to have 20 steps/revolution, but I'm only getting 10.
I even tried half stepping the motor, with the identical results. The motor only turns CCW. And the weird thing is, IT STILL ONLY MAKES 10 STEPS/REVOLUTION! Weird.
I've uploaded my code as an attached file. Note that I created subroutines for each mode (CW - Full step; CCW - Full step; CW Half step; CCW - Half step). Then I just call whichever routine I want to test. All four routines seem to turn the motor exactly the same.
Time to get an hour and a half of sleep before getting up for work. Maybe this will make more sense tomorrow.
@ Tue, 2009-08-25 22:05
Polar and Bears
Now, I've never seen this done, so it's pure speculation, but what if this is a unipolar 3 phase motor? I've only ever seen an even number of phases in a stepper, but there's no theoretical reason not to drive it through a sequence:
red/white
white/blue
yellow/black
treating what appears to be the bipolar phase as a single, isolated, unipolar third phase.
Any idea what the steps per revolution is? That might give a clue if it divides evenly by three.
Was the white lead connected to either the yellow or the black? This would also support my theory and it would remove any confusion about the polarity of the isolated coil.
I was hesitant to post this, because I've never heard of a three phase stepper, but you never know.
@ Wed, 2009-08-26 01:18
The white and black wires
The white and black wires were connected together.
The Electronic Goldmine states:
"2 phase bi-polar / Quadrature miniature stepper motor. Small 0.8" diameter x 0.68" thick stepper motor features a knurled 0.3"L x 0.06" diameter shaft. Has 5 leads, however we include a schematic of a simple 3 IC driver circuit {uses one 74HC86 IC (G4792A), one 74HC365 IC(G12548) and one 4013 IC (G49999A) that will drive this stepper motor. The 5VDC circuit schematic features a Run/Stop input and reverse direction input. The stepper motor features 20 steps per revolution and is perfect for miniature robots. The stepper motor is brand new precision made with 4 pin female connector on end of 2.8"L leads. Motor and schematic only (no driver components)."
See the attached file for the schematic.
Now I tried their circuit. I had to substitue a different flip-flop, due to availability, but it should have the same function. Funny thing is, it worked at first, but now it no longer does. I tested/replaced each of the three ICs in the circuit, double-checked all the wiring, checked the function of each IC and also tried on different steppers (I bought 5).
I don't understand how the circuit is supposed to work in the first place, as it ignores the black/white wires entirely. At the moment, it turns the motor, but unreliably, with some fits and starts. This makes sense if only one coil is being charged, but I really don't get how this circuit was supposed to work with this mirror.
The Electronic Goldmine also provides a link to this site, where I guy says he is driving it as a bi-polar motor with a PICAXE and just ignoring the white wire. I plan to try this next.
@ Tue, 2009-08-25 22:38
I do have a lot of steppers around
Salvaged from old printers and floppyes, but I never found one like this ... But hey everything is possible though..
@ Tue, 2009-08-25 21:03
Oh just forget that weird center tap
@ Tue, 2009-08-25 21:40
Ignoring the center tap
@ Mon, 2009-08-24 17:08
It looks like ...
This little guy looks like it is an unipolar/bipolar 6 wire type stepper wired for bipolar control.
See here for more info: http://www.stepperworld.com/Tutorials/pgBipolarTutorial.htm
To drive this guy you need to use a dual H-bridge chip like the well known L293 or l298.
If there is anything written on the motor please post it maybe there is a datasheet available to clear things up.
Think twice about driving this guy directly from the AVR I do not think it is recommendable.
@ Mon, 2009-08-24 17:20
Weird Hybrid
It seems to be a weird hybrid. There are 5 wires. The fellow on Instructables believes that there are two coils with only one of them center-tapped. The connector on the end of the motor only has four contacts, with the center tapped lead connected to the end of one of the coils.
I've disconnected the white (center-tapped) lead, and will experiment with driving it.
I've found no specifications for the motor itself. I'm attaching the schematic the Electronic Goldmine ships with the motor, but I have built this circuit and it does not work reliably for me. I believe the reason is because they are only driving three wires, and ignoring the one end of the coil that is mated to the center-tapped wire.
@ Mon, 2009-08-24 17:28
Then it should be something like this
The one on the left, which means you can leave out the center wire to drive it bipolar or use the center wire to drive it unipolar.
@ Tue, 2009-08-25 03:42
Except the black/white wire
@ Tue, 2009-08-25 07:16
I assume you measured it's windings already