Wireless proximity project

Wireless & IoT
1

Hi, first time poster here. Hoping for some advice on wireless hardware and control options for a project I’ll be starting soon.

I want to have ~15-20 small, wearable wireless units detect when they’re in the same location (separated by ~ 5 - 15m in an obstacle-rich environment) and automatically trigger RGB-LED programs etc. I.e. when two or more of the wearers come into range in the in the same place, a program would be triggered, preferably in time sync across the devices.

Each device may have a switch or button for cycling through various programs. One person may have a master switch to control the group. Android control would be ideal but not required.

Wondering if setting up a mesh with ZigBee or BT/BTLE radios would be overkill?

What controller/platform would you suggest? I think I need something running at least 8MHz for the LEDs.

Any thoughts much appreciated, I’m pretty new to wireless. Thanks for your time!

I’d love if I could keep the cost of each unit below $30 but if a better functioning system is available for a bit more I’d consider it.

Edit: Regarding the ZB/BT question - I know I could use something relatively cheap like this: https://www.sparkfun.com/products/12770, and just do beaconing to detect local devices. But I wouldn’t mind spending a bit more for the ability to synchronize the light show across each device. As long as the power requirements aren’t much higher. Plus I think the ability to control the transmit power on BT/ZB would be a benefit to avoid triggering devices at long range.

2

Proximity via simple means is super coarse and won’t work at all when there are RF-blockages. To do accurate location and ranging takes time-difference-of-arrival methods and $$$. Or GPS.

mesh and other protocols

http://www.airspayce.com/mikem/arduino/RadioHead/

3

As far as I understand the OP he wants nothing more than a pressence detector over rf. Not some sophisticated distance measuring device. The way I understand it, if units are close enough to receive infrequent broadcasts of others then lilipad/tinyavr/micro/nano arduino can change it’s flashing behavior.

I’m quite weak in regards to rf knowhow. But couldn’t 5-15 meters be achieved by the mentioned 434 MHz device with a shorter than quarter wavelength antenna to reduce emissions. If programmable gain reduction doesn’t suffice.

4

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