011_seasonalrotatinglight_2

• Solar cells
• Function: Produce a current through coiled COPPER WIRE, to spin a shaft with MAGNETS on it to wind up a SPRING.
• Constraints
• Need to pick a cell which either independently, or wired together, puts out proper voltage for arduino and minimal switching. Also charge battery(s) to operate through night.
• mA: sufficient to charge battery to ideal capacity for night operation (mA * 6 hours?)
• Possibilities (http://www.futurlec.com/Solar_Cell.shtml):
• 1V 415mA 60mm x 60mm x 2.8mm $3.90 25+ $3.60
• 2V 80mA 58mm diameter circle $1.90 25+ $1.70
• 9V 70mA 85mm x 69mm x 2.5mm $6.90 25+ $6.40
• Batteries:
• Function: large enough capacity/voltage to run arduino from sunset to sunrise.
• Constraints:
• Voltage: needs to power arduino (9v? do smaller arduinos like this: http://www.sparkfun.com/products/9219, spec sheet: http://www.sparkfun.com/datasheets/DevTools/Arduino/Arduino-Pro_328-v13.pdf) run at lower voltage? that spec sheet lists max input but not minimum
• Capacity: needs to make it through the night
• Possibilities:
• 10000 mAh D cell rechargeable batteries x8, $56.99
• Cool, but big, and requires a lot (4 tor 6v? See earlier arduino voltage questions) to get up to operating voltage of an arduino http://www.amazon.com/pieces-250mAh-capacity-rechargeable-Battery/dp/B001CON7PS/ref=sr_1_4?ie=UTF8&qid=1316303503&sr=8-4
• 250 mAh 9v 250mAH $18.99 + 5.49
• runs at 9v (nice!) but small capacity, may be alright as our arduino is just keeping track of time and flipping 2 H switches?
• 2000mAh AA x16 (Sanyo Eneloop), $38.95
• same as D cells, but when wired together to get proper voltage wouldn't take up as much space
• Magnets:
• Function
• Day: respond to current in coil to rotate shaft, winding up spring
• Night: produce current in coil, winding
• Constraints
• size, power (n48? n52?) volume of magnet * strength would presumably affect how much charge is created, or how much the shaft spins in response to the current.
• Possibilities
• just a source for now, wide range of neodymium magnets for consideration as above questions are answered http://www.amazon.com/gp/browse.html?ie=UTF8&marketplaceID=ATVPDKIKX0DER&me=A1T24Q2YX26SWS
• Spiral Torsion Spring
• Function
• Store mechanical energy produced by the winding of the shaft
• Constraints: Optimization problem between the 2 (opposing?) requirements:
• winding force not excessive in relation to force generated by shaft/magnet/coil assembly
• capacity to store sufficient energy for Y pulses of Z duration.
• Possibilities: something topologically similar to this, but probably much less beefy: http://www.ebay.com/itm/STEEL-SPIRAL-TORSION-SPRING-6297411-/310269805275#vi-content also see http://www.springsandthings.com/pdf/spiral-torsion-springs.pdf (may require gearing for our puny widget to wind?) edit: more like this http://upload.wikimedia.org/wikipedia/commons/2/2e/Alarm_Clock_Balance_Wheel.jpg
• Arduino
• Function
• Night: sense body/movement/heat(pick 1) below widget
• IF true, THEN close switch, completing circuit, providing power to actuate pawl to release so that ratcheted spring can unwind X seconds, spinning shaft, producing current in coil
• Day: sense voltage from solar cell
• IF V < min. operating voltage + 1, THEN flip (H-switch?) switching power circuit from solar cell to battery