Its Own Sensor: Side Effects

Via boingboing:

The very clever Electron Plumber figured all this out and built an LED “candle” that goes out when you blow on it, using the LED itself as a sensor that detects voltage drops (caused by cool air, caused by blowing)


Realizing a side effect can be exploited is cool. In various incarnations of the Smart Textile class (“wash and wear”, etc.), the instructor showed a very simple circuit that could make a LED blink without any Arduino. Normally, an oscillator that blinks at about 1/second would take several parts, and some fairly large. But, a side effect of the specific manufacturing technique of the common 2N2222 transistor is “negative resistance”. Buying a part specifically designed for negative-resistance would otherwise be difficult (very rare), and expensive.

Instructable and github for the code at the link.

  • It never occurred to me that Arduino can just sample its own voltage.  Duh.
  • He’s calling it “oversampling”, but really its just averaging (with more resolution).

Engineers want to things reliable and predictable: they often focus on staying away from “weird” behavior. Compare with “artists”, “scientists”, etc. See the circuit designs of  Peter Blasser.

What other things have interesting voltage behavior? Motors…

What other measurements have interesting info if we increase the sensitivity? Microphones and …. Incandescent lights and vibration?

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