Telemetry, RF packet network

[Hikeeba]

I am programmer gettin into EE. I need to design a telemetry system that has multiple transceivers all sending info to a main computer/transceiver. They should be identifiable (by address) and the main computer should get digital data bytes from the sensors. What is the best way to go about this? How should I handle the RF communications? Are there systems already that can control packets of data, with many senders/recievers at once that I could use/build?

Thank you,
John

 

[nbucska]

Determine 1.) info speed 2.) max. delay. 3.) Distance
4.) one or bidirectional ?
before starting to design. <nbucska@pcperipherals.com>

 

[Hikeeba]

1) the speed doesn't need to be that fast, i'm sending small messages

2) the delay i'm looking at around 50ms for a 16byte packet, or 320bytes/second

3) distance, the RF only needs to travel around 100yards

4) bi directional communication, the sensors will be doing display output also

so any ideas on how i should start? what books/forums/techniques to use?

 

[Tuti]

The first point is the interface. If you use microcontrollers, you should try the following site:

http://www.parallaxinc.com/html_files/products/RF_Mods/RF_comparison.asp

The second point is the protocol. There are many protocols in the market (CEBus, CAN, TTPA, Ethernet, Ninth bit, etc). You should chose one regarding your specific application.

aarias@bo.ibm.com

 

Easy way: 802.11b (Wireless LAN) cards can be purchased for around $70 on the internet.

Less easy way: Family Radio Service walki-talkies (sold at Target, K-mart, etc.) cost $30/two. A microcontroller circuit could be used as the MODEM (the walkie-talkie is functionally equivalent to a phone line, except that you cannot &quot;talk&quot; and &quot;listen&quot; at the same time). If you are not good at signaling (its not so easy), you can buy MANY different MODEM chips from companies such as MX-COM.

 

Suggest you also look into the Bluetooth technology. There are some solution for longer ranges or you may add PA for longer ranges. You may use a structure of scatternet to help coverage larger then the intended original range. Multipath issues should not be neglected. motib@pacbell.net