Wireless audience LED wristband 

it is really amazing that they can make such a quality product for a low price so much that its considered disposable. can you imagine! the plastic molding, the quality of the "silicone" band and the intricate miniaturized circuit board. also incorporating the mounting holes, snapping clips and even the on board battery contacts.

Had one years ago they gave us at a concert with no instructions. It came on at one point during sound checks, then went off. Was going nuts trying to figure out how to make it work. Then, finally, at the end, the place went dark, and they all came on, and started doing all kinds of stuff

I have a number of these :} been distributed to us at an open air concert in Abu Dhabi some 8 years ago. All they did was to lit different colors in a controlled way, or in tune with the music. RF part is transparent, all manipulations are done in the controller. Only a narrow band of radio frequecy is transmitted and all units receive it and respond according to their programming. L & C combination make up a band pass filter tuned roughly to the transmitted radio frequency

The CMT2210 is just an on-off keyed radio chip that sends a data stream into the micro. To independently address these wristbands you'd just have to implement a serial number in the micro controller's eeprom.

The neat thing about the IR ones is the ability to control areas of the audience with the IR spotlight. But you could do something similar here without individually-addressing them by using directional antennas on transmitters with relatively weak signals. Not sure if the RF chip is smart enough to report signal strength, but in cases of signal overlap you could use timeslicing to avoid interference. Then the microcontroller can hear both signals and decide to do something smart like responding to both signals or just the last one heard.

Turning it on myself is exactly what I want to do as a IR/RF hacker.

Button could be part of an addressing process - press button, unit stays awake for a while & listens for a special radio command to set the address. This could easily be done in bulk for speed. As cheapo MCUs don't typically have eeprom it could just be held in RAM

They are a lot more effective than in the old days when bands would ask everyone to hold up a lighter. Because everyone had a lighter.

I wonder if anyone has made an opensource universal transmitter for these (and every other brand out there) so they can be used at other gigs and not just binned after one use

The way you drew that RF antenna was correct, that is a Pi-filter to let through only the relevant frequency

The ones I have seen have a tab that prevents the battery from contacting the circuit. You arrive at the concert, pull the tab out, battery connects, device now has power for the concert and maybe a few hours afterwards

At a local theme park, you can buy color changing hats and the button lets you set the colors or cycling mode. But, if it's on in a show, the signal (I think IR but not sure) takes over and sets the color with the rest of the audience.

The inductor with capacitor to ground at each end is a Pi tuned circuit, tuned to the transmitter frequency. The inductor then in series with the antenna is a loading inductor to compensate for the antenna being to short for the frequency in use - likely 433 MHz.

I like it so much when you look at the actual circuitboard and turn it around trying to wrap your head around it rather than just jump straight into the picture. It's so good, thank you! :)

would be interesting to see the transmitter which sends the signal to the wrist bands.

There is a larger 3V CR2477 which could be what the double CR2032 battery holder could be made for. The voltages and currents work out a bit better for 3.0V than 6.0V Especially as the data sheet for the CMT2210 lists its absolute maximum voltage as 3.6V. Might be worth checking the diameter of the battery holder to see if it's 20mm or 24mm.

I’m glad you have what is presumably a big electrical installation job somewhere, but I still miss the normal workbench…!

RF is what keeps me alive! W8BT

Next step, figure out the presumably simple protocol and create a transmitter. Could be a lot of fun at a concert using them.

I believe some of the (PIXMOBS) have a motion sensor which allows limited use following the concert.