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All things pertaining to wireless and RF links
By Patrick23
#135795
I want to send information from about 300 sensors to a computer wirelessly. Each sensor measures from 0 V to 2.5 V. What technologies/chips can I use? I am new with electronics so could you suggest a tutorial or book to help? Additional information:

Cost should be low
Data accuracy does not need to be high
Power consumption should be low
Data rate is low (new measurement every 1-2 hours)
Distance would be about 100-200 meters form sensor to computer

Can I send each measurement with a number to identify the which sensor it came from?

Patrick
By stevech
#135802
100-200m range is the design driver here.
2.4GHz 802.15.4 would work only if you use 50mW or more and have modest antenna gain, and have virtually unobstructed line of sight. The XBee Pro modules with their data acquisition built-in, and with built-in battery conserving sleep/wake/sample capability, eliminates most all communications and firmware work for you.

Failing that, a sub-GHz version of the XBee (900-928MHz in the US, 868MHz in the EU) - would have better range if you cannot get the 2.4GHz to work. There are XBee modules for sub-GHz as well.

Since XBee is an IEEE 802.15.4 compliant product, each radio has a MAC address just like an ethernet NIC, so you know who sent the message.

XBee series 1 is what I recommend. Series 2 is for ZigBee meshing - which is likely n/a for your goal.
By MichaelN
#135803
Due to the range & data rate, I’d say you should be looking at the UHF ISM band (e.g. 315MHz / 433MHz). The lower the frequency the better, as it will have much better range for a given power output.

If you want to keep costs down, there are a few companies that do integrated chips with the RF chip and microcontroller in one package, and you could make your own PCBs. Do you need to absolutely guarantee receipt of the data? If not, you could use a simple transmitter / receiver arrangement instead of full transceivers (e.g. see Atmel’s ATA8741 or ATA8742). Otherwise have a look at TI’s CC430F series.
By anny0498
#139095
Hey Patrick,

Which interface you are using? I am not sure if WiFi direct feature is of any help. May be you can check WiFi modules with from Whiz-Fi module and Saagrad modules they seems to be good.
By coryduce
#139126
Patrick,

We are working on a sub GHz Arduino based wireless module right now that might work for what you are doing.
http://blog.ckdevices.com/?p=119
It would fulfill your range, low power, number of nodes, and data rate requirements.
I've been doing testing with the library from open.com.au, which can be used to send simple adressed packets at a reliable low data rate.
It would be pretty easy to write some code to wake up, read the voltage on an analog pin, send a packet, and then go back to sleep for an hour.
One module could be used to receive packets from all 200 sensors pretty easy if they are only transmitting every few hours.