This wearable is part of a research into energy harvesting, which can be found here:
http://126.96.36.199/wordpress/wordpress/ (Slow Raspberry pi server!)
The purpose of this wearable is to compare two sources of energy, not just showing a charging wearable.
The title of this project has changed a few times:
- 1. Not another solar dress
- 2. Energy battle dress
- 3. Victory over the Sun
The first title is indicating that this project is not another mobile phone charging wearable. There is a solar panel, but also a hand crank device in the dress. But it is not about charging anything, because charging from a wearable is anyhow not very efficient.
The second title is indicating that the purpose of this wearable is comparing two sources of energy together in a game. The two source compete against each other. Which one will win? The solar energy or the muscular energy?
The third title is a reference to the oper of the Russian avant garde in the Bauhaus time:
Malevich and El Lissitzky made this oper famous, contributing to the stage design and the graphical displays.
There is some sarcasm in this third title, because it is rather impossible to win from the Sun in this game, only at night you have a chance, the solar panel is even charging slowly in normal daylight without direct sunlight.
Appropriately for the material old discarded jeans are chosen. Thus the material is recycled. The wearable is a simple dress with possibilities to add panels and the hacked Ljusa hand crank.
From the parts of jeans which were not totally worn out pieces were cut and these pieces were sewn together. An interesting folding problem popped up which will be described in another post.
Picture of the wearable in progress: (The hacked Ljusa, with the white card board and the red crank will be redesigned and more properly inserted into the wearable of course)
Wearable made of recycled jeans material.
For the hand crank I have chosen the Ljusa of IKEA, which is a toy generating some power. It stores the power too in a 1.5F supercap. The second source of energy is a solar panel. Added to this is also a 1.5F supercap. With a ATtiny85 and 8 big LED’s – 4 LED’s for each energy source – the winning source can be made visible.
The electronics idea was to show the current Voltage for the two sources in two rows of 4 LED’s. The microcontroller which can just be used is a ATtiny85. Two analog PIN’s and two PIN’s for a multiplexer chip. One PIN is left for one other purpose.
Although the sources are generating energy, there has to be another energy source for the microcontroller at the moment. It would be an nice idea to have the sources (solar and muscle) first generate enough energy for the game to start, but this has to be figured out yet.
The third energy source is a rechargeable lipo battery.
Then there has to be a discharge for the game to restart. This is done using a FRT5 DC5 relay.
The number of difficulties in the electronics were plenty: besides the usual stupid mistakes like connected the LED’s the wrong way there were a few real “Zen master” problems (which means you have to learn something besides correcting stupid mistakes).
The ATtiny85 uses USI instead of SPI, code for this was found at:
Then the implementation of the use of the analog PIN’s proved time consuming. In the end the soution was found in connecting the PIN’s to the GND using a 1M Ohm resistor.
Then the coding of the LED’s, in two groups of 4 inside the bigger group of 8 was proving not straightforward. Apparently the number read using the ADC code is not a “normal” INT number and you cannot use all math available, like subtracting 512 from the value read between 0 and 1024.
The final code can be found here:
Testing pictures of the electronics:
Testing is better down as much as possible outside the wearable. In the end the electronics is on the board and the ATtiny85 had to be removed and placed in the programmer breadboard way too often again, I could have better soldered programming the wires to the board right away…
- testing first the ATtiny85 and multiplexer on a breadboard
- testing the LED’s on a piece of jeans
- the PCB with the supercap, multiplexer, relais and ATtiny85
Remarks about the PCB:
- One relais too much!
- At the left side the two energy sources can be connected.
- The Ljusa has it’s own supercap (storing energy), the solar panel uses the supercap (green thing) on the board.
- The PCB can be redesigned ore efficiently!