CO sensor MQ7 heater mod is ... wrong?

I’ve got MQ7 co sensor and i’m trying to convert it according to esphome’s page instructions. But, more i look more i see that half of those pins are … floating? Like “heater enable” pin (D0, third picture) is connected to ex IC pin and nowhere else, then 1k and capacitor combo are soldered to pin 1 and pin2 of ex IC and nowhere else. Then nowhere is stated either those two pins are connected or not (picture doesn’t show clearly)… mosfet is, as it looks, driven from digital output of sensor (is that ok?) etc…

Does anyone knows who made this mod? I mean, some schematic would be nice to have…?

Ok, after detailed exploration my sensor now works.

  • 1k and capacitor are parralel on both ends, i guess that capacitor just eliminates any spikes.
  • Regarding “heater enable”: i found a hidden connection (via) under 5-pole jumper-connector, which goes to mosfet’s input, so that’s solved.
  • there are (at least) two different boards out, although they look pretty much the same. One of differences is that pin 1 of IC is connected to GND on the board from esphome’s site, but left floating on my board. So pin from 1k resistor is needed to be extra connected to GND. That’s why it would be VERY WELCOME if a schematic would be added to THIS page, so people with different boards could do this mod also.
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