As the subject says, I need a pulse emitter and receiver, with a range of 100 meters (outdoors) with two or more inputs/outputs. Something like this would be ideal:
http://www.cdt21.com/products/tx_rx/cdttx02m/
The problem is that they are expensive: about 225 euros for a pair of transmitter and receiver.
Any suggestions?
Well ISM band transceiver modules like the RFM12 and RFM22 are a few quid/bucks/euros each, but you'd need to code up some protocols. The libraries for the JeeNode (see jeelabs.org, jeelabs.net, jeelabs.com) can drive the RFM12 for various purposes.
I'm not interested on transmitting data, just ON/OFF states. The product I referenced has 6 switches which would correspond to 6 push buttons: you just need to put the transmitter into a box with 2 AA batteries, add a few wires connecting the buttons to the TX switches, and you have the complete transmitter. For the receiver, just connect the outputs of the receiver to the Arduino inputs, and you are done. The full setup is just a bit more complicated than using straight push buttons on a breadboard.
If I understand correctly, using something like the RFM12 requires a device (such as another Arduino) for driving the transmitter, apart from some sophisticated software, as you mention.
The following sort of cheapo devices have been around for many years, so I assume
they work, although I've never used them. Apparently use simple on-off keying. The
devices like RFM12 and XBees all use a protocol that makes their transmissions more
reliable, but you do need a uC.
http://arduino-direct.com/sunshop/index.php?l=product_detail&p=341
Thanks oric_dan, but that device supports just one "button" and there is no clue about its range. It's interesting nevertheless, it might see application on other projects.
I'm afraid I'll have to resort to an XBee, which in itself is not bad, but using an extra arduino + software for doing what a dumb telecommander would accomplish seems like a waste.
The nRF24L01 requires just a short byte stream to be sent to establish TX mode, then another short byte stream to transmit data. Doesn't take much of an engine to run that.
I'm contemplating an ATtiny25 approach, inspired by How-To: Shrinkify Your Arduino Projects - Make:
and drive a nRF24L01 with it, behaving as wireless switch closures.
I can see doing that for easily under $3 per copy including the nRF24L01 (I just bought several for $1.50 each) - which is pretty cheap and should have plenty of range at 256kb/s - plus a small breakout board and battery.
No hands on yet, but my understanding is I should be able to tell the nRF24L01 I closed a switch and it will deal with making sure the far end receives it in a manner roughly analogous to the UDP datagram.
There is certainly no need to spend 225 euros to go 100m. I guess if you need the switches
to be operable at the same time, then you'll have to go to some kind of extra logic to decode
the signals. The JeeNodes that MarkT mentioned are a lot cheaper than going Arduino board,
XBee shield and Xbee on each end. I imagine they should do 100m.
http://jeelabs.com/products/jeenode
http://jeelabs.com/collections/types?q=Wireless