I took the solar rave tricycle to the Vancouver mini Maker Faire recently. It was a huge success. Here is some media from the event:
I give a short interview at the start of this CTV segment:
Time for Solar! I got 250 of these 0.5V 3A crystaline solar cells when Evergreen Electric went out of business and had to liquidate their inventory. Twenty five of them in series produces the 12.5 volts ideal for charging a 12v car battery. (batteries need to be charged at a slightly higher voltage than they operate at). I’m using a commercial solar charge controller because I’m too lazy to design and build my own.
I connected up the microcontroller boards and wrote a simple program for them.
Here is the first attempt at scrolling text.
Here is the first attempt at running the audio processing. You will see some bugs occur towards the end. This is because of problems with the logic voltage supply.
This is a better logic voltage supply that fixes all the problems.
These are the microcontroller boards that will be running the WS2803 LED drivers. They’re built around the PIC18F4550. This chip has a USB transceiver, which means I can write an Artnet-USB stack then control the shopping cart lights from a computer running commercial lighting control software like Madrix.
For redundancy I want each board to be able to control it’s LEDs independent of any connection to external software. I want sound responsive visuals, so I’m adding a pair of MSGEQ7 chips. These are analog frequency response chips that will give the PIC18F4550 the amplitude of seven individual audio frequency ranges on both the right and left audio channels.
The WS2803 LED drivers can be used to form long shift register chains. However with a shift register chain one damaged connection means every proceeding shift register doesn’t get data. This project is going to be mobile (lots of shaking) so damaged connects are something I need to anticipate. Each board uses a 74HC4051 multiplexer chip to break up the PIC18F4550’s SPI clock into eight separate channels. With eight short shift register groups a single broken connection won’t take out very many LED control boards.
Shown here are two completed control boards. The project will use three of them. One for the front, right, and left sections of the cart. The processing power of these microcontrollers is somewhat limited, so I don’t want to make one responsible for generating and pushing data to every LED board. Three independent microcontrollers also adds much needed redundancy. Two thirds of the LEDs will still be running if one of them takes damage.
After installing all the diffusers and LED circuit boards on the shopping cart I find myself with a dozen empty caulking gun silicone tubes. These things look really cool if you sand the labeling off and add LEDs. I think I’ll hold on to them and make glowing shoulder spikes. I can’t get too distracted now though, there’s lots more work to do on the shopping cart.
After adding shiny tape to the cart I started working on diffusing the LEDs. The circuit boards I designed don’t scatter the different colors LEDs out very much. It was a sacrifice I had to make in order to keep costs down with single sided copper clad boards. Diffusing will make blue and red produce purple, instead of two discrete spots of each colour.
This is a lighting diffuser panel from Home Depot. It’s the thing you see over the lights in a lot of office buildings. They gave it to me for free because it was broken!
I wanted to get a lot of the circuit boards done before carrying a rusty abandoned shopping cart back to my apartment. The landlord already think I’m a crazy person. I don’t think she would fully understand if I said “It’s for an art project, I just need to finish building circuit boards for it”.
It was a dark blue shopping cart, so before installing the LED boards I decided to cover the cells with reflective aluminium tape. It will make the lights brighter.