Fledgling tinkerer here so be kind. I’ve got an idea for a project that would involve creating a simple hot/cold game for my daughter. The idea is two components, one the beacon to be hidden, and the other the kid interface. The interface would get progressively brighter red as one got closer to the beacon and conversely blue.
What I’ve been researching is what sort of RF to use. The range that I’m envisioning is in the neighborhood of 20’. Cannot be LOS as the beacon may be hidden behind a sofa cushion etc. My thought is to trigger hot/cold by using latency/signal strength to the beacon.
What seems most suitable is bluetooth but the modules are pretty expensive. I’m open to any suggestions, any ideas?
A lot of the 433, 915 and 2200 MHz transmit/receive modules have an RSSI output. This is receive signal strength indicator. The easiest to use would be an analog output where the voltage varies proportionately with the signal. The down side is it will respond to any in band signal, the up side is you don’t need a uProcessor to interpret the signal. I did this to keep my dogs in the yard with a transceiver IC from Chipcon which took about two weeks to set all the registers properly and is decidedly not for a novice. I don’t know if any of the modules that Sparkfun sells have RSSI , but if they do, it would be a great place to start your experimentation.
Using received signal strengh level (RSSI) is probably your best bet and would be easy to implement. You might want to put a simple squelch (level detector) so the LED doesn’t flash at random due to atmospheric noise. The only other thing that came to mind (considering that the device could be hidden from sight - ruling out IR or ultrasonic technologies) is to build an inductive proximity sensor. The transmitter sends out a signal through a coil of wire and the receiver (tuned to the same frequency as the transmitter) will control the LED. Basically the same approach as the RX/TX pair, but more complicated. It does have the advantage of using different frequencies than the RX/TX modules which may improve the range. RFID systems use this principal.
Have fun experimenting and be sure to let us know how it turns out.