Stepper motor wiring info wanted

[Deano]

Hi peeps

Need someone to tell me how this little servo/stepper motor thing works. It is a sec butterfly motor off 1k gix throttle bodies and I need to run it to work the fast idle as the ecu can control it but I need to tell the ecu how to control it.

At this stage I have looked at the wiring diagram and saw that the wires sort of pair off. The black and pink show that they go join together via the windings and the green and white/blue are joined via the windings
I have confirmed this by using my 'beep' function on my multimeter. I have since hooked 12v up to these wires and j get about 1/500th of a rev out of it or call it a step then it doesnt do anything more. If I change the connections to the other pair then it does 1 step in the opposite direction

Any ideas how to keep this little thing running?

This is what it looks like

http://i1186.photobucket.com/albums/z368/deano179/fbc5e4f7.jpg
http://i1186.photobucket.com/albums/z368/deano179/3afd4779.jpg

[bladehunter]

You need a driver circuit that aplies pulses in the right order to each winding in turn.

This link gives you the basics on stepper motors

http://www.geckodrive.com/ark-2/support.html

BTW best not to take the fuckers apart

[latheboy]

Get a gecko controller then you can have fully CNC control:D

[Redmohawk]

Blade is right, you will need to make a dedicated control board for it mate the one you have is a (bipolar motor) series of four coils all linked in series separated by another set of four. The control of it is quite a pain in the ass but you can get a dedicated chip to do it.

This is the sort of thing your looking for http://www.ozitronics.com/docs/k158.pdf cost under $40 will want two 5 v outputs from your ECU one to tell it what direction and the other to make it step. Not being 100% sure on your electronics skills I'd bet a kit like this shouldnt be a big ask for you. If you need it to be controlled by one output it is possable to make another circuit that will take a varable from 0v to 5v and at say 2.5v it will be stationary and if you go below 2.5v it will spin one way if you go above 2.5v it will spin the other.

If this all seems to hard the other option would be to go to a 12 volt permanant magnet motor or solanoid arrangment. Let me know if you need more info.

[Deano]

That's what I thought you would say. I will ask on the autronic forum to see if the ecu can drive the motor now that I no what it is

[Deano]

Just had a look at the sm4 outputs and it has 4 stepper outputs but not sure if the will contol a motor. Will hopefully get a answer in the next few days

[Redmohawk]

Asked around , auto sm4 will drive a 4 wire mate .

[Deano]

Cool thanks

[Deano]

The ecu can control stepper motors but this one measures 6.7 ohm and the ecu has a 15 to 45 odd ohm window for motor control so this one can't Be run directly off the ecu without some sort of driver

[Redmohawk]

Dont need a driver mate you can run resistors in serise with the motor you just need two, most low resistance steppers are run with resistors it decreases the step time (increases possable rpm of motor) Just run a pair of 12 ohm 5 watt resistors put one in line with each coil doesnt matter which way around or which wire on coil , just as long as each coil has its own resistor.

[Deano]

They say the ecu can run the stepper but the 'hold' part of the stepper is were it all goes wrong. The ecu has an output for a 4 wire stepper but this stepper can be run but the holding of the stepper is going to blow things up as the amps it draws is greater than the ecu allows. I think they said each of the 4 wires is good for 1amp peak and .8amp constant. Even if I have a driver in between they say that the output wires can't be configured to run the stepper driver as the ecu has a stepper chip and is ment to be able to run the stepper directly ( I think )

[Redmohawk]

The resistors will limit the current, if your concerned about current limit of ECU current being exceeded. Current is worked out by voltage devided by resistance your motor is 6.7 ohm add a 20 ohm resistor to it to make it 26.7 total devide 14.8v (battery voltage ) gives you 0.55 amp . Then if you square the 0.55 amp current and multiply it by the resistance of the resistor you add (20 ohm) you will get the wattage the resistor will have to disipate (6.05 watts) so use a 10 watt 20 ohm wire wound resistor and all will be fine. Motors are more complex to work out than this simple formula but this will give you the peek current wich is what your more concerned with anyhow , the resting current will accually be a little lower.

[Deano]

They say if I do that the motor probably won't move/run

[Redmohawk]

I'd suck it and see mate , Almost every stepper I've worked on runs serise resistors and I'd bet the factory ecu from the steppers bike prob has them mounted inboard on the ecu. Look at it this way, if a stepper of 45 ohm was used without a resistor as they say can be done its maximum current draw would be 0.328 amp and the motor would provide 4.86 watt of power forgetting motor losses.

If you run a 11.8 ohm resistor in serise with your current motor it will draw 0.8 amp (max continus current) and the motor will provide 4.2 watt of power forgetting motor losses. I'd just use a 12 ohm resistor in 10 watt wire wound as finding a 11.8 will be almost impossable. The total motor power will be close enough to the same for eather way, a stepper motor does not react the same way to a conventinal DC motor.

The resistors will cost you about $2 to find out if it works, I'd be very very supprized if it doesnt with a 12 ohm value. I am a little rusty on stepper motor control and have forgottem far more than I will ever re learn but pritty sure it will be a ok setup like that. I have run simmilar motors of size design and resistance to drive small automomus robots direct driving wheels without gears on units running wheels around 60mm dia with loads of 1 kg and a pair of motors could drive up a 15 deg incline on 7.2 volts, so I think the torque provided by yours with a resistor will drive a TB through a gear train without to much issue. And costing you $2 to find out isn't much of a risk.

As a matter of fact the motor you currently have will prob react quicker than a different one around the resistance they recomend, the reson most stepper motors run serise resistors is to allow higher voltages to be used to drive them reducing inductive losses at higher switching speeds (increasing motor potential max rpm) this is not a big issue in your case but still a valid point.

Go for it.