120 ultrasonic positioning devices with a wireless communications backbone creating an 'ad-hoc' network. That was one of the achievments of the Relate project at Infolab21. As an extension, I got to design a cut down version of the ultrasonic devices to aid in the Relate gateways project. The circuits utilise an RS232 transceiver chip to enable the transducers to operate with a 12V swing from a 3V power rail. This enables ultrasonic ranging over a 5m distance, ample for covering a room.
This project gets its own page at:
An MSc project being run by the Ubiquitous Computing group at Lancaster University is using a Wii handset for real-time positioning. The intensity of light from two sets of inra-red LEDs is measured using a Wii controller. Some clever data processing leads to real-time positioning. The Hardware Monkey got to build the boards that power the LEDs - one is shown in the picture. Not an advanced circuit perhaps, but it's good to be involved with the project. It is essential that the LEDs have a constant output so a voltage reference and comparator is built into the circuit to indicate when the batteries powering the LEDs need changing. The comparator circuitry is very basic, but quite sufficient for the present application. The Eagle schematic for the circuit is available at WiiLEDs.sch.
The boards were adapted to create a Wii Sensor Bar with three separate groups of two LEDs. Adding extra LEDs is straightforwards - you just need to solder in an extra resistor in parallel with the others for each LED. The photo shows the two boards with one adapted to power two sets of LEDs.