LENS ELECTRICAL COMPONENTS and ELIMINATION POSSIBILITIES 1) Shutter solenoid coil: 9 ohms, 1.9 mH
2) Iris 2-winding stepper motor: 20 ohms, 1.2 mH, per coil
3) Focus 2-winding stepper motor: 20 ohms, 3.1 mH, per coil
4) IS: 30 ohms, 0.5 mH, per linear motor
5) Zoom lens motor: 6 ohms, 0.7 mH
These are the five independent electrical subsystems that can generate a shutdown error if interfered with. Camera firmware is quite astute in reporting lens problems. The Canon error is E32 for all that I have tested so far. Typically, after an E32 occurs the camera shuts down within a minute. So far, I found this error to be fully recoverable by reconnecting the component.
Note that you must power cycle to cold by disconnecting the AC adapter or removing battery to clear the error.
SHUTTER. I have not disconnected the shutter solenoid for error tests because that circuit has to be left in-place anyway, or it can be replaced by a passive circuit (resistor at least, or at worst resistor series inductor to simulate the net reactance above), so that its signal can be used to drive your own shutter. If the camera shutter driver has a fault detector, it would be on the main board and can be fooled by the passive network. Hence replacing the shutter solenoid with a passive network will work perfectly.
IRIS and FOCUS. Because motor drive is open loop, stepper motor coils can be replaced by passive reactive circuits. However, both these devices have stowed switches whose first ON pulse after a PUP calibrates the reference position of these two components. Because of the stowed switch, an active circuit would have to be added to mimic switch operation. If firmware sets up expected error time windows for the unstowed/stowed signals, then the fooling circuit can be made of 555 timers and some glue logic. If firmware tracks rotations wrt the unstowed/stowed signal, then a solid-state replacement solution becomes very complicated. Either way, because steppers are constantly AC-driven even when still, just detecting motor motion is non-trivial. I have not explored any of these yet, but these are certainly good possibilities. So my guess is this: powering the motor can easily be detected. So for PUP we detect the first motion signal into a coil, timeout the unstowed signal and deliver that to firmware by injecting it into the switch photodetector circuit. That should turn the camera ON w/o error. However, PDN is different. Because the motor is powered all the time, we have to detect motion and then timeout the stowed signal so firmware is happy. Not easy.
IS. After having understood well the drive and feedback architecture I did a simple error test: before PUP, I wedged a toothpick between the lens and its cavity fixing the lens skewed over to one side. After PUP I got the E32 error and a shutdown within a minute. So this simple test explains fully the intricacy of this component. The IS is a tightly firmware-controlled system that has zero tolerance to any perturbations of the lens. It is unlikely that error expectancy override can be simulated within reason in external hardware. The signalling is very complex. To learn more about how the IS operates refer to this excellent article:
http://www.invensense.com/jp/mems/gyro/documents/whitepapers/ImageStabilizationWhitepaper_051606.pdfFigure 11 shows the analogue interface circuit (located on the main board) to the 4-wire Hall effect sensors located beside the assembly's linear motors.
ZOOM. Eliminating this one (1A+1B+1C+3A) on its own is quite important when you have a space-critical application because you can shrink your entire camera volume by almost two-thirds. Because the zoom motor is a servo type, it can be replaced more easily than the steppers. Armature rotation optoswitches are aligned to a triple blade fan shaft encoder, where one is ON (no blade) while the other is OFF (blade). A trivial up/down counter that simulates rotation counting can be excited by the polarity of the motor terminals, with 555s and some glue logic serving to simulate rotation timing signals, and delivering them to the switches. Here the unstowed/stowed (the assembly's 3rd switch, 1C, 11 o'clock) handling is again trivial because motor motion (and direction) can be easily detected by external hardware. Hence the ZOOM external assembly has the highest chance of being eliminated, and it is by far the bulkiest component. Naturally, because the focus mechanism is part of the backshell 1C, it would also have to be handled, or cut out leaving just the motor, leadscrew, and optoswitch.
Next: an attempt at an external shutter controller.