LPG Gas Sensor

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Here is sensor of liquefied petroleum gas, also called LPG, GPL, LP Gas, liquid petroleum gas or simply propane. The SEN-1327 LPG Gas Sensor Module is designed to enable LPG detection interface to Microcontroller without ADC Channels. It allows to determine when a preset LPG gas level has been reached or exceeded. Interfacing with the sensor module is done through a 4-pin SIP header and requires One I/O pin from the host microcontroller.

The onboard microcontroller provide initial heating interval after powerup and then starts to meassure LPG sensor output.If it found the LPG contents above setted value, it will inform the Host controller by pulling the Output Pin to High and Starts to blink a onboard status LED. The sensor module is mainly intended to provide a means of comparing LPG sources and being able to set an alarm limit when the source becomes excessive.

You can use other manufacture LPG sensor like MQ-5 sensor

Optical flex sensors circuits

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This worked, but if I recall correctly the resistance response wasn’t linear but the EZIO ADC, so this meant that I lost resolution and couldn’t reliably tell the difference between a lightly closed hand and a fist.

In the end, I made my own flex sensors. In a nutshell, each flex sensor was an IR LED, an IR sensitive diode (I think), clear aquarium tubing, scrap wires (black), and heatshrink.
Basically, this was a ghetto fibre optic cable (dategloves back then had fibreoptic sensors that detected finger flex). This worked surprisingly well.