I have one master which needs to send information to lots of slave device ~1000 which needs to receive same information.

As I need to power all of the slave device, I was thinking of using same wire to send information in order to reduce installation cost.

How do I achieve it cheaply ?

Another idea is to broadcast wirelessly ( since its the same information ). Is it possible to make cheap RF receiver that can receive data ? ( edit: I can handle expensive transmitter but need really cheap receiver. )

Each slave have avr microcontroller to use the data.

Edit: I need to transfer around 20 bytes of data every 2-3 minutes at average distance of ~25 meters. max 100 meters. min. 1 meters.

  • \$\begingroup\$ How much data? How fast? \$\endgroup\$ – Dave Tweed Feb 14 '13 at 3:09
  • \$\begingroup\$ This is usually done by RS485 / RS422, en.wikipedia.org/wiki/RS485 \$\endgroup\$ – John U Feb 14 '13 at 11:12
  • As I need to power all of the slave device, I was thinking of using same wire to send information in order to reduce installation cost

  • ... 20 bytes of data every 2-3 minutes ...**

This is very doable at the low data rate you are using.
20 bytes at say 11 bit times/byte = 220 bits. At 300 bps that's less than 1 second.
Spread over 2 minutes it is about 2 bits/second.

A simple cheap good enough system is to interrupt the power feed for short periods. The data can either be sent as off and on bits during normal operation with diodes at receivers isolating their power storage capacitors from the bus OR data can be sent in a burst on the power wires. At say 9600 bps that would require about 220/9600 =~ 23 mS. Each byte could be sent separately with a pause between so that one 11 bit byte requires a slot of 11/9600 ~= 1.2 mS. Power supply capacitors in the receiver modules can easily hold up for that sort of time.

If signalling occurs at voltage swings below normal power voltage levels then the signalling waveform will be not affected by DC power supply loading.

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  • \$\begingroup\$ I think moderators will say "Na ah" to that signature in the end.. \$\endgroup\$ – abdullah kahraman Feb 14 '13 at 10:28
  • \$\begingroup\$ @abdullahkahraman - nice to know who your friends are :-). Wholly unconscious addition on my part. Comes of writing answers on lists with sensible rules that allow basic identification within the answer. Anyone who wishes may remove it if it offends them. Or colour it purple or whatever. \$\endgroup\$ – Russell McMahon Feb 16 '13 at 7:16
  • \$\begingroup\$ lol. What is wrong with purple? \$\endgroup\$ – abdullah kahraman Feb 16 '13 at 8:15

Over what kind of distance? How much information? How quickly?

There are lots of answers to your question depending on your answer to those questions.

If you're already having them all hooked up to the same power rails and you can tolerate some noise on them, there are a variety or ready-made ICs which can communicate over power. They'll generally be slower the less complex the supporting circuitry (the homeplug system can do 100Mbps in stuff that's commercially available today, though I don't know what the limitation is on the number of listeners/receivers on a single system is).

If you want to you can just have a buffered and repeated UART signal. I.e. hook the TX line up to a bunch of receivers, and then every 10 devices or so hook up a digital buffer. You'll have to hold the speed pretty low depending on the number of buffers, but it should work well enough.

If you want to go the wireless route there are plenty of cheap and fast options: You can grab a transmitter like this and then as many receivers like this as you want (for the even cheaper version see here). The ones I linked to are kind of a pain to work with, and they're limited in terms of speed (around 4800bps), but they'll do they job.

If you want a more reliable system and you're willing to shell out the money you can just grab any number of branded Zigbee devices. I'm pretty sure Zigbee natively supports sending broadcast messages so this shouldn't be an issue. You'll be a bit limited because every device may respond so they'll be a lot of RF every transmit.

All of this being said: you need to provide specifics if you're looking for specific help!

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