The dress described in former posts was finished finally.
The dress as a result of an artistic research into energy harvesting and design is presenting a game situation. By rotating a dynamo you have to compete with the Sun and a solar panel in generating energy. The game is created in a wearable so that you can change to another location. Playing the game in different locations makes you aware of the power of the Sun’s energy in comparison to your own muscle energy.
The dress is very much a prototype. As can be seen from the electronics a large amount of testing is needed to make some sort of a playable game.
The electronics was fitted inside 4 acrylic casings:
dynamo charger, supercaps/lipo, the brains: 2 ATtiny85’s and bitshifters, and an LTC3105 energy harvesting chip.
then fitted to the side of the dress: (which makes us aware that we should have thought of a better wiring 🙂
Up left: the charging dynamo, up right, the ATtiny85’s, and the bit shifters, down left, the supercaps, and lipo, then bottom right, the LTC3105 for recharging the discharged energy into the lipo.
After fitting the casings will be covered with small pieces of jeans, only the dynamo charger will be visible.
Two out of the three casings covered.
The choice for 2 ATtiny85’s was made from the first version where we had only 4 LED’s for the two sources of energy. But now after making it all we realized that the 2 ATtiny85 with the bit shifters should have been replaced by one ATmega328, with a LED-block script, avoiding the bit shifters. This would have saved one casing. This will be done in the next (third) version of the electronics.
Besides the solar panel a battery pack is installed to make testing in a room without the Sun easier, you can test by switching to battery pack (right side, next to the solar panel). The wiring between all the casings and groups of electronics is done by female – male connectors. This makes testing easier.
The second version of the script discharged the supercaps after winning. Winning is reaching the 5V mark. But what about starting a new game after abandoning a game half way? It was decided to discharge the supercaps at the start, when you switch on. Discharging is not what is seems. Following the voltage of the supercaps to about 0V, you see the voltage rise again without any charging. So discharging is now done in steps, then some delay, then measure the voltage again, if it is above a limit, discharge another round and so on.
This repeated discharging worked…until the dress was put in the full sun. The solar panel is generating so much energy that the discharging is not fully obtained. The discharging time had to be made bigger.
The installed solar panel is doing 0.1V a second so it will win in 50 seconds if the Sun is not hindered by clouds. At the moment it is practically impossible to win this using this hand crank dynamo hacked from the Ljusa.
Besides that, as could have been expected 🙂 the big LED’s are not visibly on or off in the full Sun. Another interface should be added, or these LED’s like this removed and giving it a try with small superbright LED’s.
A movie of the solar panel racing towards the 5V:
After observing the problem of the LED’s not visibly lit in sunlight, we tested bright LED’s in a simple script at 3V:
So the big 10mm LED’s will be replaced by these 3mm bright LED’s.