White cable function? Reusable as pick and place part detector?

[brainstorm]

Have you found the function of the white cable (or vias/IC legs) in the vape sensor pictured on the left?:

RED = 5V BLACK(s) = GND BLUE = SIGNAL/SWITCH WHITE = ???

On some (most?) vapes the black and white cables near the LED do not seem to be populated (see right sensor)? I suspect that the white cable is some kind of input signal perhaps?

Unfortunately I do not remember how the original assembly for that particular sensor looked like so can't go back to check connections... so it's a mystery so far :/

[MitkoDyakov]

Hey,

The sensors are 5 pin devices right? Two pins are used for power i.e. GND and VDD. Then you have one output for a LED and another output for heater (basically a high side switch). The last pin goes to the can on the back of the assembly. It is used for capacitive sensing.

Unfortunately I can't tell from the picture which is which. There might be different configs for different brands.

For the ones I had Blue was to the heater. Black and red GND and VDD respectively. The white might be LED or cap sense. There is easy way to test with conductivity option on your multimeter. The device must be off. Then put one probe to the white wire and whit the other probe touch one lead of the LED then the other. If it beeps this means it is LED output. Another option and a bit of reckless one is to touch the white wire when the device is on. If it turns on then it is sense. But be careful not to mess up anything. I don't recommend the last option :)

Cheers, Stay safe.

[brainstorm]

Thanks for the comments, here's a better closeup:

The white cable has a 8.8k reading on my multimeter against one of the terminals of the SMD diode. OL against the case/chassis. Here's what the oscilloscope shows on the blue cable (light blue on oscilloscope) vs the white one (yellow line) when applying vacuum:

Nothing happens when I touch it when powered up nor clamping it to 5V or GND. So it's not sense cap thing as you describe in one of your videos... what else could it be? I'm genuinely intrigued :-S

[brainstorm]

For context, @MitkoDyakov, the reason I'm exploring and playing with all this is because I'd like to reuse that sensor to add to a pick and place machine, see this twitter thread: https://twitter.com/braincode/status/1480134237802033156

Since a single sensor shuts down after a few seconds, I was thinking about using TWO of them to circumvent that shut down and the measurement gap it leaves before it's back online. Then, putting together something like this vacuum setup from @markmaker, but without requiring analog pressure sensors, just those two vape sensors and some digital/timing logic.

For now I'm wiring them up on a perfboard connected to an Arduino and making sure I fully characterize/understand the sensors and their limitations: