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I have 3-6 microcontrollers, up to 2m apart. One of them is designated the server and will be fed sensor data from the others, at least at 100 Hz. (Each data point is just a couple of bytes)

Since the microcontrollers move around, I can't connect them with wires. What's a good wireless solution here?

My initial idea was Bluetooth, mainly because that's the one solution I'm familiar with, but Bluetooth consumes much power (my circuits will be battery-powered) and Bluetooth modules are expensive.

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  • \$\begingroup\$ Data at 100Hz, does that mean 100×a couple of bytes / sec? \$\endgroup\$
    – user17592
    May 26, 2013 at 8:47
  • \$\begingroup\$ Related: electronics.stackexchange.com/q/53229/17592 \$\endgroup\$
    – user17592
    May 26, 2013 at 8:48
  • \$\begingroup\$ @CamilStaps: Yes, and that the latency must be lower than 1/(100Hz). \$\endgroup\$
    – Anna
    May 26, 2013 at 8:50
  • \$\begingroup\$ The nRF24L01+ seems to be what I'm looking for. It can both send and receive, right? Can it receive on multiple channels, so that all clients can communicate with the server simultaneously? \$\endgroup\$
    – Anna
    May 26, 2013 at 8:52
  • \$\begingroup\$ (It seems so with its "6 data pipe MultiCeiver") What's the range of the nRF24L01+? I can't seem to find that anywhere in the data sheet. \$\endgroup\$
    – Anna
    May 26, 2013 at 9:04

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For communicating within a couple of meters range, these nRF24L01+ modules, at around $1.42 apiece on eBay, would suit the requirements:

Module

The module has a PCB trace antenna, which does a pretty reasonable job.

The range seems to be stable at around 6-7 meters during the day, and I have occasionally seen as much as 20-25 meters late at night when most other electronic devices in the vicinity are off.

Sparkfun sells a similar module but with an SMA connector for an external antenna, which claims as much as 100 meters range at 250 kbps data rate. Of course, at nearly $20 plus the cost of an antenna, that may be overkill for the required 2 meter range.

Relevant to the specific application:

The key improvement of the nRF24L01+ over the now obsolete nRF24L01 is the implementation of an auto-retransmit feature, which addresses the collision detection complexity concern raised in comments on the question.

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