For my energy final, I created a free-form circuit sculpture that wakes up as the sun sets. The form factor was inspired by an artist named Peter Vogel, who makes beautiful sound sculptures with exposed circuitry as seen below.
I also knew that after building the the solar engine beam circuits in class that I wanted to explore other solar engines and see how I could repurpose them for what I wanted to create. After some research, I landed on the Easter Solar Engine. It was perfect given I wanted to make a free-form sculpture and the Easter Solar Engine uses only discrete components to create a voltage threshold that needs to be passed to trigger a load. It does so by relying on the the forward voltage requirements of diodes and LEDs to establish the level of the threshold. You can find some great documentation on how the Easter Engine works on Instructables.
I knew that before I could proceed with the free-form circuit sculpture, I needed to make sure that could get these Easter Circuits working for my purposes. Now let me tell you what my purposes are. I wanted to created I sculpture that would live by natural sunlight (i.e. a window sill) that would trigger various light formations based on how light or dark the room was. Therefore, I needed to integrate two different Easter circuits with different voltage thresholds (in my case 3.3v and 5.4v) and a dark switch to run more voltage through the sculpture the darker it gets. It’s important to note that the Easter Engine Circuit is originally a Beam Solar Engine that’s meant to expend a certain charge once it’s accumulated enough energy from the sun. However, since I knew I wanted to power my sculpture with a wall power supply for the first version, I used it for it’s efficacy as a voltage level trigger.
Firstly, here are two Easter circuits that I created sharing the same power and ground. In this test, I used the threshold levels of 3.3v and 4.2v knowing that I would alter this later on.
Here, I’ve highlighted the string of diodes in each respective circuit to show what is establishing the voltage threshold.
While silicon diodes are said to have a forward voltage of .6V to .7V, I measured the ones I was using just at around .4V. The yellow LEDs I was using has a forward voltage of 1.6V. Here are a couple different configurations of diodes that show you how you can create different voltage thresholds.
Here is a video of me demonstrating how these two circuits trigger at the predetermined voltage levels.
With the Easter circuits working, I next focused on getting the dark switch working as the “tap” for controlling how much voltage would be running through the sculpture. Here is the schematic for my dark switch.
Here is a video of the switch working as expected. Following this initial test, I fine-tuned the resistance values of the photocell and the fixed resistors with the help of my professor.
Now I was at a place where I could start working on the actual fabrication of the sculpture. It’s a process that was about 40 percent planning, 40 percent soldering and 20 percent praying that everything would work. To act as a foundation, I adapted the Easter circuit schematic to accommodate my free-form circuit. Here it is below.
And here’s how I free-formed the dark switch.
Now I was ready to proceeded soldering. An important thing to note is at this point I also added a part to the easter engine circuits to control the drop-off voltage for when the circuit turns off. You can view the instructable I linked to for more info but, simply put, it follows the same principle of using the forward voltages of the diodes to determine the threshold. This addition ended up causing an issue with the behavior of the 3.3V Easter circuit which I can explain later. Here are some pictures of the finished sculpture.
As I mentioned, the behavior wasn’t quite as expected. Once I added the drop off diode strings, the 3.3V easter circuit would only trigger if you’d touch the diodes attached to the base of the Q1 or Q2 transistors. However, the 5.4V Easter circuit worked fine which was a little confusing. After meeting with Eric Rosenthal, he suggested that I play with the resistor values related to the base of the Q1 transistor to ultimately amplify the signal going to the base. Apparently, because all my components are open-air and aren’t shielded as they would be with a PCB, my sculpture is acting as an antenna and I’m getting a lot of noise that could be interfering with my lower voltage Easter circuit.
I’m going to continue to play around to see if i can get it to work as I want it to, but for now, here is a video demo of the behavior I’ve described.