| Sept. 16th |
|
This week I've been thinking mainly about two things: the VLF/audio input scheme and
the power supply. I have been trying to come up with a way for a VLF antenna and an
electret microphone to share the same amplifier using a digital SPDT switch. I've decided
(at least preliminarily) on the
FSA3157 digital SPDT.
- See schematic. My initial plan for power was to have both 5v and 3.3v supplies. This way I could mix and match 5v and 3.3v components while maximizing power efficiency. The problem lies in the fact that the actual output of a 3.7v lithium-polymer battery, which is what I plan to use, can range from V<2v to V>4v, so to achieve a supply of 3.3v a buck/boost IC would be required, which are generally expensive and in packages that are way to small for me to solder confidently. I will continue to shop around for buck/boost ICs (as 3.3v is a more standard supply for the types of sensors/LCDs I'm looking at), but otherwise I will make it work with a single 5v supply. I also had a great new idea for a fairly simple functionality of, using an IR receiver/decoder and an IR LED, being able to "learn-by-example" and store a few IR remote commands (such as 'tv-channel-up'). See notes from 9/14 for more details. |
