feasability please: many small stepper motors..

Projects General Guidance
1

Hi,
Here on tutorial:

I read "...These motors can be found in old floppy drives and are easy to control...".

The motor I got out of floppy was little different. I first setup from another Arduino tutorial I can't find link of it, the L293D circuit. I used diods for back EMF as it is usual, and the included example of Arduino IDE using digi-pins of 8-11. It works, but the chip (brand new for the project) and motor both get hot very fast.

I first decided to go back to the original tutorial with ULN2003, but the motor there has 5 wires with vcc separated, while my stepper has only 4.

I thought to ask here before changing setup that may be I'm doing something wrong with L293D that motor and chip get that hot?

I checked with datasheet of L293D and I've nothing in difference with. I'm not using heat sink / fan, but well, anyway it should not get that much fast so hot (max around 15 seconds and I can't touch the chip).

Also I'm using good isolated wires so no false contact.

Any idea please, where from the heat is coming from?

How I must go with the missing vcc wire of my stepper, if I get back to ULN2003 please?

2

Any idea please, where from the heat is coming from?

From the current you are switching.
What voltage are you using, what ever it is it is too high for the motor.

How I must go with the missing vcc wire of my stepper, if I get back to ULN2003 please?

You can't use a ULN2003 with your motor because you need a h-bridge circuit to drive your sort of motor.

3

I'm not familiar with floppy disk drive stepper motors, but 5 wire stepper motors I've seen have had four coils each with a live terminal and a common terminal. I don't know how this would work with four wires, unless perhaps the motor only has three coils. I suggest you check which pairs of wires are connected to which coil, by measuring the resistance between each combination of wires. Once you have identified the live wire and common wire(s) you should be able to work out the drive algorithm. You will probably need some trial and error to work out the physical order of the coils, unless that's obvious.

4

I don't know how this would work with four wires,

Motors with four wires have two coils, see:-
http://www.thebox.myzen.co.uk/Workshop/Motors_4.html

5

Grumpy_Mike:

I don't know how this would work with four wires,

Motors with four wires have two coils, see:-
http://www.thebox.myzen.co.uk/Workshop/Motors_4.html

That makes it all clear, thanks. I hadn't appreciated there were so many control strategies for a 'simple' stepper motor.

6

Thank you,

I used 12v battery capable for 7Ah.

I thought it is ok to use 12v as floppy has 12v input from power of pc (as long as I know)

Ok, then I have to start changing power from 5 up to see where motor works normal and less heat. Any other suggestion? May be better to use L293B for higher current of it?

7

Yes 12V is way too high.

Any other suggestion?

Use a proper stepping motor driver with a chopping regulator like:- Pololu - A4983 Stepper Motor Driver Carrier

8

Thanks, and a final question...

Generally, for such floppy / cd /dvd stepper motor to use an h-bridge, no spec. difference to use L293B or L293B right?

(I know better designs exist, like coupling 297 and 298, etc. just to understand difference of D and B there which I think is simply about current they can bear?)

9

Yes you can have more current with the B than the D

10

Thank you very much, also, that motor tutorial is simply excellent great!