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I want to make a device that, with a press of a button, will send an ID signal, wirelessly, to some other device. It has to have:

  • 10m range (~30 feet)
  • <2ms response time (from the press of the button to the reader's response)
  • ID size more than 10bits.

There may be one person standing between the transmitter and receiver but, other than that, receiver-transmitter line is unobstructed. If it wasn't for this, I suppose some IRs would do fine.

What are some cheap options?

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    \$\begingroup\$ If you can relax the 2ms IR could be an option (a single person in between is often not a problem because IR reflects a lot). Otherwise a wireless module like the RFM73 Camil mentions (big simle) or the better known but generally higher priced (but apparnetly not on eBay) NRF24L01 would be obvious candidates. \$\endgroup\$ – Wouter van Ooijen Jan 7 '13 at 12:49
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A low-cost option with excellent open-source library support would be a 2.4Ghz nRF24L01+ RF Transceiver Module, sold on eBay for as little as $1.90 with free shipping.

nRF24L01+

This can be controlled by a low-cost basic microcontroller, such as the popular Atmel ATtiny25/45/85, on a board with minimal support components.

Both the module and the microcontroller can be operated at 3.0 Volts using a CR2032 button cell. Component count is thus reduced further by eliminating the need for a voltage regulator. Individual unique IDs of 10 or more bits length can be stored into the microcontroller at programming time.

Add a pushbutton, enable the microcontroller's internal pull-up for the button input, and you have a truly minimal ID transmission wireless device.

This meets the range requirements in the question, and supports the ID length specified.

  • Here is a comprehensive tutorial on using nRF24L01 devices.
  • If you do not want to use a pre-built module, the reference PCB layout provided in Figures 33 through 38 of the datasheet can be extended to incorporate the transceiver, PCB trace antenna, microcontroller and pushbutton on a single board.
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  • \$\begingroup\$ Is the pinout the same as what's listed here, on top of page 3? If not, can you let me know what it is? Also, I'm guessing the pin spacing is 0.1"? \$\endgroup\$ – Garrett Fogerlie Jan 7 '13 at 14:24
  • \$\begingroup\$ @GarrettFogerlie While the document you linked refers to the now obsolete nRF24L01 device, the pin-outs are the same on the nRF24L01+ modules I have bought. The layout, however, is different from the Nordic reference layout. \$\endgroup\$ – Anindo Ghosh Jan 7 '13 at 14:50
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You can use the RFM73, a 2.4GHz module. VOTI sells it (http://www.voti.nl/shop/p/HF-RFM73-D.html) for only €3,30. He also has a C/C++ library available on that page. It is controlled using the SPI protocol.

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