MSefi.com read only forum (Jan.15,2018)

Megasquirt V3.0
MS-2

Hi all.

My Rover has a 4 phase stepper motor arrangement
Each coil has a common +
Each coil is then earthed directly to the cars current ECU
Therefore there are 5 terminals in total,
1 = common supply voltage ------- from supply relay
2-5 = individual coil earths ------- to ECU

I can presume that the ecu has internal switching to open close the respective coil circuits. The thing is, how does it reverse the stepper motor direction??.. and more importantly, how can i implement this stepper motor type into Megasquirt???

Thanls in advance

Scott

I don't know how to control a 4 phase stepper with megasquirt.

But I do know that to reverse the direction of a multiphase motor is simply a matter of firing the phases in reverse order. So to step the motor forward you would fire coil 1, coil 2, coil 3 then coil 4. To step the motor backwards you would fire coil 4, coil 3, coil 2, then coil 1.

Hence switching any two of the phases on a 3 phase motor will cause the motor to spin backwards.

MSII uses a UDN2916LB stepper motor driver that works for bipolar steppers not unipolar so there is no easy way to driver your IAC. It might be easier to adapt the GM or Ford IAC. You might be able to to use a a board like this:
http://store.qkits.com/moreinfo.cfm/QK179
with some MSII software mods and rerouting of the IAC1 and IAC2 pins to the board. The software mods should not be too hard if you find a add on board that uses similar logic. You can't drive it direct because the HCS12 will not sink that much current.