Hardware
|
Table of Contents
|
Power
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
- http://www.powerstream.com/li.htm
- The basic algorithm is to charge at constant current (0.2 C to 0.7C depending on manufacturer) until the battery reaches 4.2 V per cell, and hold the voltage at 4.2 V per cell until the charge current has dropped to 10% of the initial charge rate. The termination condition is the drop in charge current to 10%. The top charging voltage and termination current vary slightly by manufracturer.
- A charge timer should be included for safety.
- Trickle charging is not acceptable for Li-ion batteries. They cannot accept an overcharge without causing damage to the cell.
- Some safety measures in a charging circuit should be to make sure the temperature is in an acceptable range, make sure the current isn't too high, something to prevent damage due to short circuits, something to stop too much voltage from being applied to the terminals, protection from the voltage in the battery raising too high, and protection from the voltage in the battery going too low during use
- http://www.analog.com/library/analogDialogue/archives/31-2/liion.html
- A new battery charging IC, the ADP3810, is designed specifically for controlling the charge of 1 - 4 cell Li-ion batteries.
- Provides some pictures of charging circuits that include the mentioned IC
- Description of a universal charger from atmel that can charge many types of batteries including Li-Ion
- http://ourworld.compuserve.com/homepages/Bill_Bowden/page12.htm has a description of a 2 cell lithium ion charger
- http://www.freescale.com/files/microcontrollers/doc/ref_manual/DRM043.pdf talks about using a freescale microcontroller to build a charging circuit
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 |
uController
I think this is our prime candidate, it's perfect.
ATTiny
Probably some sort of ATtiny by AVR. However,
currently searching for an already CADed dev
board with appropriate amount of exposed GPIOs.
Candidates:
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:
http://www.cse.unsw.edu.au/~pcb/Bluetooth/bluetooth.html#micro
http://www.inf.ethz.ch/personal/kasten/research/bathtub/bluetooth/
Communications
RFID
Bluetooth
Possible ones if bluetooth doesn't work out
Zigbee
802.11
Encasing
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 a replacement at http://ambientdevices.myshopify.com/products/replacement-glass-orb for $23.51 but it says it is sold out
- 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
- Amazon.com says its 3.5 x 3.5 x 5.5 inches
- It has replacement glass at http://ambientdevices.myshopify.com/products/replacement-glass-beacon for $23.51
Illuminated Color LED Morphing Orb
- Amazon.com
- Windy City Novelties
- Cost = $4.50
- Dimensions: 2.75" x 2.75"
