Simple short range wireless network

macrobeak

New Member
I wish to build a robot navigation system using four beacons for ultrasonic triangulation with a wireless network connecting the robot to the four beacons.
The range is very close - less than 10m max.
I am quite confident about the robot control, triangulation and ultrasonics.
However, I am less sure about the wireless communication between the robot and the beacons.
Please could I ask more experienced wireless users for recommendations on inexpensive wireless modules for this application.
Many thanks in advance.
 

BaldwinK

New Member
Hopefully you have not given up on an answer and I am not too late.

I use the nRF24l01+ in the garden for a model tram project. Four trams (fitted with HC-SR04 ultrasonic modules) and two sets of points have the radio chips. One of the points is ‘in charge’ and converses with the other five to sort out a movement pattern. The messages are short but, very importantly, are accurately sent and received using the auto Ack functions.

I started with help from Goeytex (unfortunately now offline) and his two programs for Tx and Rx for the earlier chips. I can’t find them on the forum now but have attached them here. You will have to do a lot of reading – try this tutorial: http://www.diyembedded.com/tutorials/nrf24l01_0/nrf24l01_tutorial_0.pdf and this site sells the modules and has the latest pdf for the Nordic chipset: https://www.coolcomponents.co.uk/wireless/other/nrf24l01-module.html

I paid around a UK pound each for the radio units – shop around now and they are even cheaper.

Believe nothing as there are errors everywhere. The SPI bus is useful for testing radio software as you can hook more than one unit to the same Picaxe chip (different enables of course). Set one to receive, send something from the other, go back and see it in the buffer. Much easier with one connection to your PC for coding and diagnostics.

I found it necessary to add a higher level message sequence to ensure no repeats etc. Also ended up flushing buffers between conversations. Be very sure of the addresses you use, great devices but don’t play at coding them.

I hope to find time to write up the tram project but don’t wait. Sending my whole code will not be helpful without explanation.
 

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MFB

Senior Member
For such a short range, why not consider using IR communications rather than RF? Much cheaper and more predictable.
 

Goeytex

Senior Member
I would say that IR is less "predictable", and then there is the directional thing to overcome.

An omnidirectional RF system should easily outperform an IR system and will be much more expandable if you ever want to increase the range. Stick with RF.
 

AllyCat

Senior Member
Hi,

I am less sure about the wireless communication between the robot and the beacons.
It depends on what (data) you want to communicate, the location (indoors or outdoors) and the method of triangulation, etc.. IR might be simpler/cheaper for indoors use, because IMHO you should not attempt to use the cheapest (super-regenerative) type of radio receivers even for 10 m range.

But if you already have an ultrasonic link between the robot and the beacons, why not use that for your "wireless communication" as well?

Cheers, Alan.
 
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