SOLAR XYLOPHONE -> LEGO DRAGON

Fellow ITPer Rory Nugent and I had the idea to create a solar powered xylophone in an effort to explore and learn about possible uses for solar energy. The idea starts with harvesting from an array of solar cells to turn a small motor that will subsequently turn several axled gears - each equipped with small spinning hammers that would each play a note on a xylophone. The really enjoyable part of this idea is that if each gear is a different size, it will spin at a different rate meaning the hammers would hit each note at a different time, so the pattern that emerged would take a long time to unfold, sequential, but not obviously repetitive.



We momentarily abandoned the idea of the xylophone in exchange for a toy piano, with the hope of using a Lego motor and some linkages instead of gears. After realizing that the two solar cells we could get to work in accordance with one another were enough to power a motor, but not enough for the motor to carry an additional load, we gave up on music altogether and decided to make a wiggling Lego dragon.


we are using a slightly modified version of

this circuit from solarbotics:

(a link to the full document below)


while at first we spent a lot of time trying to set the voltage trigger to several different configurations, in the end we settled for what was shown on the site. in place of R4 we are using just a wire and for the rest of the resistors staying with the 100kOhm baseline

things that have raised the biggest questions thus far:

1.) Parallel Vs. Series

that when the solar cells were in parallel, the amperage increased & voltage stayed the same (to be expected), but when placed in series, the voltage increased but the amperage seemed to drop(!?)

2.) Varying Cells

when different types/sizes of cells were combined (in parallel or series) the circuit wouldn't work.
-is this a "phasing" issue?

3.) Voltage Trigger/Moniter

the diagram shown in the solarbotics PDF on how to use the Maxim 8212 voltage regulator in a circuit did not seem to be very accurate in terms of what level of resistance to use to achieve the desired voltage trigger.

4.) Capacitance

if we add capacitance, the time it takes to reach the trigger is longer, and vice versa but what is the relationship between the capacitance and the resistance?