The PWM to Stepper controller will work with any ECU running any firmware that puts out a PWM grounding signal to position a stepper idle air valve. Developed in partnership with, this controller uses a single wire from the ECU to receive the control signal to determine the required valve position. The on-board power supply allows the controller to be wired directly to the vehicle’s 12v system, eliminating the need to run a 5v feed wire to the controller.

The processor in the PWM Stepper Controller has been extensively tested, and can accept any signal from 16Hz to over 500Hz. Note that when operating ECUs using a software frequency timer, at higher frequencies the signal increment resolution may be coarser - instead of presenting a situation where a Duty Cycle range of 0-100% represents 255 controller positions (each of 1 or 2 motor steps), it might only allow 100 controller positions of 2 or 3 motor steps. This is not a limitation of the PWM controller, but is a function of the signal generated by that operating method.

The idle motor is operated in the “Always On” mode. “Moving Only” or “Holding Current” modes are not supported.

The current draw for the PWM signal is very low, and the heavy-duty “PWM Idle” modification common on Megasquirt V2.2 or V3.0 boards is not required.

In addition to driving an idle valve, the MS3 can use the generic PWM function to control other stepper motors such as oil pump throttles, supercharger blowoff valves, and variable-pitch turbocharger vanes.

The PWM to Stepper controller sells for $75.