We are always looking for new ways to experiement with circuits in the Tinkering Studio, and when you're looking for inspiration, it's hard to beat Forrest M. Mims III's books. He uses simple, familiar materials to build sensors and circuits, with really clear illustrations and explanations to boot. I love his hand-drawn illustrations, too. They are inviting and accessible, which is not something I usually think when I see circuit diagrams.
I was particularly inspired by this rain-sensor, and I had to try it out.
I started by building a simple version of the sensor with copper tape and LEDs. It's tricky prototyping in the rain, so I tested the circuit out in our workshop first, where I used a pipette to simulate the raindrops.
When the drops bridged the gaps between the strips of copper tape, they completed the circuit and the LEDs lit up. I was really surprised how responsive the LEDs were. The amount of water bridging the gaps between the strips of copper tape really affected the brightness of the LEDS. The more water was on the sensor, the more electricity flowed through the LEDs, and the brighter they glowed. As the water evaporated, the LEDs slowly faded. The result was really lovely.
The next step was putting the sensor to some practical use, and trying it out in the real world. I thought it would be neat to have a rain-activated umbrella that would light up when it rained. The greyer and gloomier the day, the brighter the umbrella would glow.
Luckily, the copper tape has a sticky side, so it was easy to attach the circuit to an umbrella. I made the sensor larger on the umbrella, to increase the chances of detecting raindrops. I soldered on a lot of little blue LEDs, and I added some rhinestones for flair. Then I waited for it to rain, and I took it outside . . .
And waited . . .
And it worked! I love that it's possible to make an environment-responsive circuit with something as simple as copper tape, raindrops, and LEDs. It makes you wonder what else is possible . . .