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I want to build a Tracy Island style eyes-that-glow-when-that-person-calls project and I'm looking for advice on what components to use.

For those who haven't watched Thunderbirds, my plan is to have photos of my friends and family up on my wall, each with a small battery powered receiver circuit which, being wirelessly individually addressable, would begin flashing LEDs behind the eyes of the person when a "START" signal was sent from the transmitter with the right address, and likewise stop when a "STOP" signal is sent.

My TV is hooked up to Skype on my htpc and I'm happy hooking up an arduino to it and keeping a list of the receiver IDs and corresponding Skype IDs, so that when someone calls me on skype I can trigger the glowing eyes on the right person.

These circuits won't be activated often. Are there Tx/Rx ICs I could use which power off until a signal is received (I could accept that it powers on when any signal is received, even if it's for the wrong person) so that I can run this from a battery?

The LEDs I'll put behind the photos' eyes won't draw much current and will be blinking for < 10 seconds a couple of times a day at most, so if there is a receiver like that, I could put a battery operated circuit in the frame of the pictures and not have to worry about running wires for power or signal.

How would you recommend setting this up?

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  • \$\begingroup\$ I had a look for this sort of thing; as far as I can tell, all of the active reciever ICs consume a few milliamps in recieve standby. Depending on how big a battery you're willing to fit, that might give you a few month's battery life? \$\endgroup\$
    – pjc50
    Feb 11, 2013 at 9:59

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To answer your question:

"Are there Tx/Rx ICs I could use which power off until a signal is received"

No not really: receivers are "high power" devices. Even the lowest power receivers will use mAs as @pjc50 notes.

The current work on low-power radios focuses on duty-ratioing and/or time sync techniques to save power and achieve long run-times with small batteries. The goal is to minimize the time the radio is on as much as possible but still have a responsive network.

Contiki and TinyOS are two embedded operating systems with this focus. They both run on a variety of low-power wireless microcontrollers and implement different low-power control schemes for radios. You could use any of the hardware supported by these OSes to complete your project. Both have sample code that should be easy to modify for your purpose.

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    \$\begingroup\$ Good points - I think I'm asking too much with Tx/Rx functionality. Is there some way I could bastardise mid-range RFID, so that emitting a specific frequency would power an induction loop, hooked up to - say - a transistor, which would close the circuit between my battery and LEDs? \$\endgroup\$
    – JP.
    Feb 15, 2013 at 15:40
  • \$\begingroup\$ for your application, the range you are talking about is tens of feet. To power an RFID tag at tens of feet requires tens of watts; this is not a trivial transmitter. But yes, you could put an induction loop in the wall behind each picture and run the proper transmitter. You might be able to couple enough power to latch a FET and bootstrap to your LED... but I don't know. I could rig up the solution I mentioned in a day or two. Some beamy power thingy is a lot less certain. Power coupling will also require the loops to be oriented and I don't see to implement that cleanly for what you want. \$\endgroup\$
    – Mariano Alvira
    Feb 16, 2013 at 23:18

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