... the gas concentration using a simple circuit.MQ-2 gas sensor for liquefied petroleum gas, propane, high sensitivity of hydrogen, natural ... :1, using high-quality dual-panel design, with a power indicator and TTL signal output instructions;2, with a the ... using the instructions:Explanation: Use Preheat 20SInput voltage: the DC5V power consumption (current): 150mADO output: TTL digital 0 and 1 ( ...