Proposed hardware components
since the Southpaw space is pretty much empty, i figured it would be nice to set up a list where we collect parts which may be used for the device.
for all parts suggested it would be good to have:
-Short describtion (like 3axis digital compas with I²C interface)
-Reason why you think it would be suited (maybe pointing out advantages over previously suggested parts)
-Link to the datasheet
-available packing options (x y z dimensions + pincount , because size matters)
-estimated power-consumtion for operation and idle (because we most likely run on some kind of battery)
-a supplier to buy the part from (maybe one for the bare part, one for the part on a breadboard for easier prototyping)
-anything else that seems relevant, like number of external parts required for operation.
so i'll start with some core components:
-well known microcontroller, good crossplatform toolchain, widely used, low power, ADC and I²C to interface with analog/digital compass, lithium-battery-management buildin, 1.8 - 9 V operation range. plenty IO ports.
-available in tsop 28 (1x8x14mm ) and LGA 36 (0.5x3.5x6.5mm)
-draws 800µA under normal operation @ 1MHz , 270µA idle, 25µA powersave
-listed at digikey but currently not in stock ~6$
-no external parts needed. can provide a 3.3V output (with automatic linear-down or step-up with very few external parts). LGA packing may be hard to solder by hand but first choice when keeping size down.
HMC5843 3-axis Digital compass with I²C interface
- i²c interface so no mesing with analog stuff, connects nicely to the atmega, 2.5-3.3V
- 16 pin LCC (4x4x1.3 mm)
- draws 160µA when sampling at 2 Hz
- breakout boards and chips available at digikey for about ~20$
- requires 2 capacitors: 0.22µF and 4.7µF , 2 pullup resistors required for i²c (may be possible to use atmega's internal but that needs to be checked)
VL-3032 Rechargeable Lithium Battery
- 100mAh capacity , 3V, 4mA charge current , small encapsuled coin-cell, Ø27x3.5mm, easy to solder, integrates well with the atmeg's li-battery management.
- 5 days of operation for 1000µA load, 15 days for 300µA . recommended continous load : 200µA
- using this battery requires agressive power-saving on the controller/compass. only allows "slow" charging.
additions and improvements are highly welcome.
small addition: Attiny 85V would also do great, it can be clocked significanntly slower which means.. a lot less power, has a smaller footprint. it lacks the battery management functions, but those can re-implemented easily. and.. .it's available for purchase and a lot easier to solder.