How to correctly use MQ7 on a FC 22

Other Hardware Sensors
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I have a FC 22 with MQ7 and an esp32. I used this schematic 1.5V and 5V cycle for sensors like MQ7 · Issue #26 · miguel5612/MQSensorsLib · GitHub except I replaced the transistor with a BF 170 which is cheaper and can handle up to 500mA.

Half of the time, I get absurdly high analogRead values for the 1.4V cycle, close to 4096, like at certain points of the pwm. I noticed that the digital output led on the fc22 also blinks very fast with the pwm, which confirms that it intermittently outputs high voltages with the pwm

When I connect it separately to a stable 1.5V power adapter, the digital output led does not glow.

How do I correctly use this sensor?

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