This information was offered on the SteppIR forum on Yahoo groups in 2006, but was dismissed by the SteppIR representative because it wasn't "approved" by SteppIR.
There's nothing mysterious about the SteppIR use of conventional stepper motors to drive the element tapes. When the motors are required to move, a train of pulses is sent in the proper sequence using 4 wires per stepper motor. Each of the stepper motors is controlled by a driver chip in the SteppIR controller and those chips can and do fail for various reasons, from lightning discharges to shorting of the control lines.
So, if you know or suspect that one or more of your SteppIR elements are not moving, how do you know if it's your controller, a stepper motor or your control cable that's failed? The easy way is to build one of these testers and see if the drivers in the controller are working. The first tester is built into a 25 pin DIN shell, and contains LEDs that are driven by the stepper motor outputs on the controller. You disconnect your control cable, plug the tester into the controller, and change bands on the controller. If the LEDs illuminate as described below, your controller and drivers are probably OK. If the LEDs for one of the elements doesn't illuminate, the driver for that element isn't working.
The second tester is similar, but is connected in-line with your control cable. In the event that the drivers are working but can't supply adequate voltage and current when driving the stepper motors, this tester should show you that.
Figure 1: This is the how the tester for a 3 element SteppIR looks from the outside of the shell.
Figure 2: Inside the shell, you can see the 1K series resistor used with each LED. Note that there are two windings on each stepper motor and so there are two LEDs used for each motor. The LEDs are just glued into the plastic shell. If you have a 4 element SteppIR, there's obviously plenty of room to add two more LEDs.
Figure 3: Another view inside the tester shell
Figure 4: To use the tester, just plug it into the Antenna Connection connector on the controller
What You'll See with the Tester
When there is power to the controller (whether the controller is turned on or off), the controller applies a holding current to the stepper motors so the tapes don't creep. With this tester, some of the LEDs may glow dimly and if you really want to be able to see the presence of the holding current, just reduce the series resistors for the LEDs.
If you do a "calibrate" on the controller, the LEDs will be on solid as long as the controller is telling the elements to move. As they're about to stop, the pulse train sent to the motors is slowed down to provide a deceleration period for the tapes and you will see the LEDs flashing a bit before the elements come to a stop. The LEDs will then come on again as the drivers are extending the tapes at full speed. They'll flash again as the tapes slow down just before stopping.
Again, when stopped you may or may not see some of the LEDs on solid (but dim). Remember that there is no feedback from the stepper motors to the controller, so the controller doesn't know that the antenna isn't connected and that the motors aren't really running. The accurate positioning of the tapes in the elements depends entirely on the controller knowing how many pulses the motors have been sent in the past.
Figure 5: During Calibrate, when the elements are being driven full speed, all the LEDs will be glowing brightly
Figure 6: Here the elements are slowing down just prior to stopping at their new position (end of Calibrate process) and the LEDs are slowing flashing at full brilliance
Figure 7: Here the Calibration process has completed and the stepper motors are at rest. A couple of the LEDs are glowing dimly and decreasing the value of the series resistors would allow you to see the resting current on all of the drive pairs
Another tester and schematics
