4 PHASE STEPPER MOTOR

[yelida2008]

Hi all,
Bit of an odd one.
I have an aftermarket car ecu that has a 4 phase stepper motor(https://www.oyostepper.com/category-68-b0-4-Phase-Stepper-Motor.html) attached to it.
Unfortunately, the ecu is current limiting to 1 amp.
The motor needs 1.85 amps (6.5 ohm motor, 12volts).
It therefore needs a bigger current supply (no position feedback needed as the throttle body and ecu already have that side covered).
It has been suggested that mosfets or BJT transistors be used.
Not sure what components and configuration is needed.
thanks
_________________
as long as you try very hard, you can achieve anything.
https://www.oyostepper.com/

[Ttelmah]

First thing is, whether this is a unipolar or bipolar drive?. If the latter things
get much more complex. Then, are you sure there is a problem?.
A motor that would draw 1.85A, if a pole was connected to a DC source
may well run fine from a 1A driver. Because motor coils are inductive,
the current actually drawn starts at nothing, and rises with time. If the
driver is only being pulsed on for short times, the current may well never
get over the 1A.
You need to do a lot more research. Measure the actual drive being delivered.
My guess would be if this is a simple design, that the drives are simple
'pull down' outputs. If so a simple current amplifier may be all that is needed.
If the drive is bipolar it gets much more complex. If the signals are bipolar,
the problem with MOSFET's will be generating the bias supply for the upper
FET. If it is a simple pull down, a simple PNP emitter follower may be all that
is needed. However there are then the problems of voltage drop and heat.
such a follower will result in more voltage drop, and with this will come
extra heat. If this is going inside an engine compartment, this is a hot
location, and even behind the dash, is very hot in the sun. Your drivers
need to have suitable heatsinks if they are not to overheat.

A lor more research is needed on exactly how the standard drive is wired
and used. The page you point to, has both unipolar and bipolar motors.

[temtronic]

curious, located this site, 1 of 1,000s...

https://www.omc-stepperonline.com/unipolar-stepper-motor-driver

It shows that unipolar motors have 6 wires while bipolar only have 4.

So 1st step (sorry, no pun intended ) is to count the leads on the motor.

[Ttelmah]

Except you get 8wire motors that can be used as both unipolar and bipolar.....



Just have four separate phases, which you can common one end and use
as unipolar, or can wire in pairs for bipolar. You can also wire the pairs in
series or parallel.

Also ir is very common to be unimpressed by the torque from motors
when running then at the 'rated' voltage. High power applications will
use massive overvoltages to allow the current to be generated quickly
in the phases. So my mill here uses 72v drive for 6v coils. While the
peristaltic pump drives here use 24v, with a 3v motor. You have proper
current control in the drives, so when you slow down the voltage being
fed drops.

[temtronic]

sadly I understand it'd be cheaper to make 8 wire motors ( less steps to make them..)
TI has a good 'how-to-use-steppers', though I can't find it on my desktop anymore..it WAS there 11 hours ago.....
then I got sidetracked seeing how to make 3pahase motors from car alternators.....
then Mr. Sun said I should go out and fix the tractor......