EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: cyberfish on February 27, 2012, 08:49:21 pm
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I'm thinking about making an Android app that changes phone settings (silence, etc) based on proximity to some "tokens".
My current plan is to make those "tokens" out of small 9V battery-powered bluetooth devices.
The biggest challenge is battery life. I would like the battery to last half a year at the very least, and with a 9V, 500mAh battery, that means the device must draw less than about 1mW, or ~300uA at 3.3V, in a discoverable (no need for pairing and connection except for configuration) state. This is assuming I can build a buck converter that's efficient at that current level (I never looked into it). If a linear regulator turns out to be more efficient, the power limit would be a lot lower.
So does anyone know of any such bluetooth module? Must be hand-solderable, SMT is fine (I can solder TQFPs by hand).
To recap:
- 1mW max in a discoverable state
- speed doesn't matter
- range doesn't matter (few feet/meters)
- hand-solderable
- ideally less than $15 or so
A module on SparkFun seems like a good fit http://www.sparkfun.com/products/10253 (http://www.sparkfun.com/products/10253) except I can't find any mentioning of the 26uA discoverable mode in the manual...
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http://www.rovingnetworks.com/products/RN_42 (http://www.rovingnetworks.com/products/RN_42)
under specifications it lists power usage in different modes. Ive been looking for a similar item this may fit the bill as well. time to read more datasheets :)
Chris Lee
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9V's suck.
how about CR123? they're cheaper (http://www.batteryjunction.com/tpen-tcr123a-.html), lighter, smaller, long shelf life (10 years), much higher energy density, etc. unless you need 9v...
-sj