So I've seen these 8 dollar e-cig vape pens. One model from Exxus has an "autodraw" feature without a power button. You just move air over its transducer and it charges the heating coil.

It also has an LED at the bottom, which fades up when activated, and fades down when the transducer stops producing its signal. It ALSO, though, flashes when the battery is "too weak to power your pen" as the OEM puts it. The LED will also flash once you have drawn too long.

So I'm assuming that the flashing is caused by undervoltage. I also understand the fade up/fade down thing.

I can't seem to find very much information on the pressure transducers themselves, short of the fact that they are for sale all over alibaba/aliexpress.

I don't have one to teardown, so I'm wondering if all of the circuitry is contained in the transducer? Or is there perhaps some external circuitry for either the fading effect, the blinking, or both?

Also, does the battery voltage drop that much when powering the coil, only to "rebound" once the current stops flowing?

I'm just trying to figure out how this thing is working because curiosity.

Anyone?

TIA!