This instructable describes an RF beacon using WiFi - we call it a 'Pinger'. It is intended to be used as an alternative to, or to complement, GPS in location based applications. The 'WiFi Pinger' has been specifically designed to operate with the mediascape software described here (nb still under development April 2008). An early application using similar non-WiFi technology is described in this press release.
The Pinger uses a WLAN Compact Serial Module to transmit a pre-configured beacon signal as part of the WiFi standard. It can thus be recognised by any WiFi equipped device. It is compact and low powered and has an (approximately) omnidirectional radiation characteristic. We use it to identify (or tag) places, people or objects enabling recognition by mobile receivers such as WiFi equipped PDAs or cellphones.
The range of the Pinger is around 100m outdoors - and it's intended that the mscaper software will be able to be set for short, medium or long range. It can be powered and/or charged from a USB source - its battery life is over 12 hours.
Step 1: Parts List
1 x 0.22 ohm resistor (RS 135-500)
1 x 47uF 6.5v capacitor (RS 547-9732)
2 x 10uF 10v capacitors (RS 547-9776)
3 x MBRA140 Schottky diodes (RS 625-5650)
1 x flashing red LED (RS 228-6032)
1 x FMMT717 pnp transistor (RS 215-6515)
1 x LM3622 LiPoly charger IC ( DigiKey )
1 x USB socket (RS 515-2011)
1 x 4 way Molex 1.25mm socket (RS 279-9285)
1 x 12 way Molex plug case plus leads (RS 319-1042 & 279-9544)
1 x on/off switch (RS 334-268)
S103 WLAN Compact Serial Module ( RF Solutions (UK) or Datahunter (US) )
pcb from expressPCB (or pyxisdesign) (pcb shown below and file attached)
1 x dual PLF423566-S Varta LiPoly battery (RS 457-8282)
Hammond case (RS 613-8319)
... and tools for surface mounting soldering.