Troubleshooting: Dash Photon Detector for Car Aircon Recirculation Button

[chirhone]

My car aircon recirculation button often turns off by itself. I guess this happens when the aircon is cold enough.

Problem is. When it turns off and the indicator light disappears, the pollution outside gets into my car and my pm2.5 monitor registers 20x higher.

What kind of photon detector can I fit into the almost 2 inches round button so if it detects the light is turns on it will sound a buzzer alerting me to it? I post this here instead of at Computing and Technology because the photon diode may need to be assembled using wires and small dc battery, hence connected to electrical.

 

[mfb]

Commercial photo diodes are cheap, simple and tiny (<1 mm² isn't an issue). Let one activate a transistor that switches an oscillator, hook it up to a small speaker. It will need a bit of tuning to get the light threshold right. Add a switch to disable the system. Battery, speaker and switch will probably be the largest parts. If the sound should stop after a while you need a bit more electronics.

 

[chirhone]

Commercial photo diodes are cheap, simple and tiny (<1 mm² isn't an issue). Let one activate a transistor that switches an oscillator, hook it up to a small speaker. It will need a bit of tuning to get the light threshold right. Add a switch to disable the system. Battery, speaker and switch will probably be the largest parts. If the sound should stop after a while you need a bit more electronics.

Do you know something more accessible like a module? I don't know how to design it from scratch like connecting transistors to the photodiodes. There may be commercial photodiodes with transistors already that I can just use it by connecting to the battery? Anyone?

 

[mfb]

There is a good chance that such a thing exists as a pre-built component, but finding that might need some time. A buzzer that just needs power would take care of the oscillator, that gets rid of most individual components.

 

[pyroartist]

Why not just do a little probing around under the dash and find the wire that turns on the light and connect it directly to a buzzer or a on-off buzzer driving circuit such as a 555 timer?