Arthroscopy Tools, What's between pins 4 and 9?

[CoffinDodger]

I've had the great fortune to have some interesting dumpsters near me these past couple years and I stumbled across an interesting catch of surgical power tools. Pretty cool stuff. Been trying to dismantle some but the motors are either press fit in or glued in. I'm assuming press fit. Or there's just bodily goop sticky them together. ANYWAY, I got to probing their sockets and came up with the attached diagram.

This one in particular was from a wire driver I was able to pull the motor assembly out of (but not able to dismantle the assembly). U1 and U3 are hall effect sensors for reading the magnet position of the trigger. In one position the magnet interacts with the "forward" sensor and when the trigger is rotated 180 the magnet interacts with the "reverse" hall effect sensor. Pretty neat way to make some reliable, pressure sensitive, and bodily fluid "proof" triggers.

Where I'm hung up is with pins 4 and 9. I'm getting a diode but I'm assuming these two pins is where the control console pulls a device ID. I just don't know how it do what it do. My first thought was there's a chip there since the sensors were labeled U1 and U3. But U2 could just be for the hidden diode. Pins 5 and 6 appear to be Vcc/GND pins. Figured if it were a chip, I'd get some high or mid resistance value between pins 5/6 to 4/9 but they read OL on my 287. So perhaps it is just a diode for some reason. Maybe to tell the console a device is present?

[NiHaoMike]

Could it be a One Wire EEPROM?

[ConKbot]

Diode, or diode connected BJT can be used as a temperature sensor. Not saying that's 100% it, but a temp sensor for the motor isn't beyond reason.

[Terry Bites]

Prions and Hepatitis.

[coromonadalix]

could be a diode if open / high value in backward measurements and around 0.6 volts ??

temp measurements
a continuity device  Ie  the diode is in serial  for some circuitry / detection presence as you may guess ...   but i would push for some temp measurements

do you have some visual confirmation ?

[CoffinDodger]

Temperature sensor makes sense to me and that can easily double for device presence. I think I'm dropping the idea of device identification. The manual for the control console mentions how to add RFID tools but also has a generic procedure for selecting the tool name from a list. The brochure for this series does not mention RFID. Therefore, it's likely just for motor temp and you (your surgical tech) manually sets the profile for each connected device. The device has speed control too, but tossing the O-scope on while running the motor didn't produce a signal. I'm thinking back emf for feedback like most sensor-less BLDC motors? Anyway, attached some more photos of the assembly. At least as far down as I'm willing to try. Still really cool stuff.

Got up to 20 devices out of this. Most of these seem to be in excellent condition which doesn't surprise me based on what I know of the facility. End of the fiscal year and all (at the time), justifying the budget and seeing an opportunity to upgrade the fleet. Thought about trying to sell the batch to a refurbish-er to help fund the lab addiction and getting them back in circulation. Looking around though everything (of course) is geared towards health care professionals. Feel like I'm going to either get ignored or at least get some really concerned/confused responses.

Anyway, thanks for the responses! Here's some pics.