Help needed - stepper motor

[alband]

' Stepper Y129-5
' If you use the wires in the 6 pin connector
' order the following program will cause rotation

' Black +12V
' White + 12V
' Yellow output7
' Red output6
' Brown output5
' Orange output4


main: let pins = %11000000
pause 10
let pins = %01010000
pause 10
let pins = %00110000
pause 10
let pins = %10100000
pause 10
goto main

This was a conclusion to a thread a while back (so old I can't reply on that): http://www.picaxeforum.co.uk/showthread.php?t=5077&highlight=help+needed+stepper
A friend of mine is using the same stepper motor with an 08M. Haven't got the circuit with me so this tread my not move fast.

Anyway, the computer he's using won't download in basic only flowchart from PICLogicator. Eventually I hacked the code into a 08M worthy flowchart and got it turning. The weird thing is the wiring.
The motor was wired up as said by Tech but it didn't work. I disconnected the black and white wires (both +12v) and it worked -slowly. The wait time was 0.1 seconds. As soon as I plugged the black and white in it didn't work again and the 08M heats up (thus I haven't had the black and white connected for very long each time). The 12v supply is from a big mains transformer and could use PWM, a simple transformer, not sure at all. The chip is powered and working fine from 3 x AA's.
Can anyone explain why:
1. the motor can turn when it only has the power from the PICAXe output pins (I thought it would need more)
2. Why the motor doesn't work when the black and white are connected to +12v?

 

[hippy]

It sounds like your hardware is not configured correctly if the 08M is heating up. The way you describe it is that the 08M is connected directly to the stepper which is connected to +12V. Check manual 3 for how to interface stepper motors.

 

[alband]

The second last post in the previous thread was by technical and said otherwise for this motor.

 

[westaust55]

08M heats up . . .

Do you have the stepper motor connected direct to the PICAXE?
If so two problems;
1. The current will very likely exceed the PICAXE IO rating
2. when the 12V is conencted the IO are being pushed above the PICAXE rating.

Either will lead to an early demise of the PICAXE

With 6 leads, it will be a unipolar stepper motor.
In removing the 12V supply you are trying to use it as a bi-polar stepper motor.

Suggest you look at the current (rev 4.3) PICAXE manual 3 from page 14 onwards.

 

[alband]

So technical was wrong?

 

[manuka]

You can only connect loads directly to a PICAXE source pin if they are less than ~25mA! In fact I ran across a tiny bipolar stepper that just allows this, BUT normally extra driving hardware is needed, with the L293D IC best known.

See => www.picaxe.orcon.net.nz/stepdemo.jpg for stepper insights.

 

[alband]

So tech is wrong?

Also, It work with it directly connected - as long as I don't connect the 12V.

 

[manuka]

????????????? I'm confused! Exactly WHAT are your stepper ratings & coil resistances (measured with a DMM)?

 

[westaust55]

I would not say that Techncial was wrong.

He just flagged which PICAXE outputs drive which windings.
Likely he assumed you might read the manuals and thus did not mention the L293D IC which is shown in the manuals and also on some of the Rev Ed starter pack boards.

I did a scan earlier today but cannot find a datasheet for the Y129-5 from Astrosyn’s website. http://www.astrosyn.co.uk

So as Manuaka says, take some readings.

Past posts suggest the Y129-5 is a 12V uni-polar stepper motor.
Lets just suggest it has 100 Ohm windings (and that is quite high).
At 12V the current would be 120 milli-Amps.
But run as a bi-polar stepper motor two winding segments in series so 5 / 200 gives 25 milli-Amps which would be right on the border of causing PICAXE failure.

 

[alband]

Well, don't have it with me.
My friend asked me for help and so I googled for a datasheet the code on the bottom - "Y129-5" and of course, as soon as I saw the forum come up I though "right, this has been coved and should be easy".

My understanding was that the motor had power-ups of some kind in it. I saw it had those two 12V pins and thought that each PICAXE signal must drive a high power FET's or something that is powered by the 12V's.

So, it does need the driver. What are the 12V pins for? I haven't "done" stepper motors before. My understanding of one is that they consist of a number of coils around the outside and the shaft has a magnet. Therefore if you pulse the coils in a circle, the shaft will follow (Probably should have mentioned the knowledge base earlier - sorry).