A few years ago, I found a cheap alcohol sensor that worked at +5 Volts, and provided a nice analog voltage output to be measured by a microcontroller. I purchased the requisite parts that I didn't have, and soldered up a circuit.
I programmed a simple PIC microcontroller to measure the analog voltage output from the sensor, and it would light up LEDs depending upon how much alcohol was sensed. I jokingly called it the Tequilaizer (Tequila Breathalyser…)
It sort of worked, but the microcontroller began to reset itself if I blew too hard on the sensor. I didn't think much of it at the time (mostly because field-testing was too fun :D ) and let it sit for a few years.
I recently came back to the circuit, and realized that my power supply design was probably to blame. It didn't take into account the amount of power required by the heater element in the sensor, nor the 6 LED lights. The circuit would start up, the sensor would warm up to operating temperature, but then when it was blown on, it would try to light the LEDs and would go into a ‘brown-out’ condition, where the voltage dropped too far.
I learned my lesson: always test with containers of rubbing alcohol before drinking too much tequila to care :) .
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