We need to make sure whatever battery we get can handle the amount of current we need to draw at any given time without bad consequences

Power Source

Possible lithium ion batteries from digikey:

Type Voltage mAh cost rechargeable? Digi-Key Part Number manufacturer notes
coin 30mm 3 100 $9.00 yes P087-ND Panasonic - BSG
coin 30mm 3 100 $9.00 yes P088-ND Panasonic - BSG
coin 23mm 3 50 $7.38 yes P085-ND Panasonic - BSG
coin 23mm 3 50 $7.38 yes P086-ND Panasonic - BSG
coin 20mm 3 45 $2.68 yes P046-ND Panasonic - BSG There is also a P045-ND and P047-ND

Lithium Ion Batteries:

  • no memory effect
  • slow loss of charge when not in use (about 5% per month compared to 30% per month in Ni-MH and 10% per month in Ni-Cd)
  • its capacity diminishes over time regardless of charge/discharge cycles and regardless of if it was sitting on the shelf charged or not
  • they can go into a state known as deep discharge where the battery takes a very long time to recharge or will possibly never come back to life if the deep discharge state is too severe. Deep discharging can take place if the battery is left unused for an extended period of time or when they are recharged so often they can no longer hold a charge.
  • a stand alone cell must never be discharged below a certain voltage to avoid irreversible damage. li-ion battery systems should include a circuit that shuts down the system when the battery is discharged below a certain threshold.
  • they are not as safe or durable as Ni-MH or Ni-Cd batteries
  • The charging procedure is done at constant voltage with current limiting circuitry
  • They age worse at higher temperatures

Charging Lithium Ion Batteries

Inductive charging

Piezoelectric charging

Consumption per component

Component mA estimated time in use in a 24 hour period total mAh consumption per unit quantity total mAh consumption
Tricolor LED 20mW (convert into mA) 2
AVR processor (active mode) 1
AVR processor (inactive mode) 1


I think this is our prime candidate, it's perfect.

Probably some sort of ATtiny by AVR. However,
currently searching for an already CADed dev
board with appropriate amount of exposed GPIOs.


AVR Butterfly
Quick start user guide
User guide
Problem is that it uses an Atmega168 rather than an ATtiny.
But that might be acceptable.

Freescale Microcontrollers are also good:
Development boards

Boards that would require some assembly but would have builting bluetooth:




Possible ones if bluetooth doesn't work out




Ambient Stock Orb

We could buy an Ambient Stock Orb and dismantle it.

  • Cost: $149.00
  • The manual says it synchs with the "Ambient Information Network" which it says is a nationwide wireless service.
  • Requires it be plugged in to a receiver and that the receiver is plugged into the wall
  • You change brightness of the orb by pressing down on it, so some part of it must be a button or capable of measuring pressure.
  • The orb is made of frosted glass. The manual says it may break if you drop it
  • The manual says replacement glass shells are available at www.myambient.com
  • I found you can buy it for $99 at http://ambientdevices.myshopify.com/products/stock-orb but the link that pointed me to there says it is $150 + S/H which agrees with the original website Priya sent us so I don't know whats going on about the price. Unfortuantely, at the time of me visiting this website, it says it is sold out.
  • Amazon.com says it is 4.5 x 4.5 x 3.2 inches ; 5.8 ounces

Weather Beacon

Something similar to the Ambient Stock Orb from the same company is the Weather Beacon
Cost: $99

Illuminated Color LED Morphing Orb


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