RF transmission and FSK modules

[Chris Barron]

I have been using Telegesis ETRX2 modules with the latest R3xx firmware and they're great !

I forgot to add, that as well as all the other benefits, the ETRX2 come with 16 digital I/O and 2 A/D inputs. The device can be set to wake up at a preset interval (measuring anything from seconds to hours) and transmit the state of the I/O pins as well as the A/D inut reading ( in the 0-1.2V range)

I use this feature in one of my designs to measure the output from a thermistor via a voltage divider and the unit therefor transmits a value relating to the temperature. The unit can be made to sit in a low power mode in between transmissions, and that means that a couple of AA batteries could last for a couple of years.

You can leave the remote unit powered up all the time of course, and then you send it a simple command to return the contents of the 'S-register' which carries all the information about the I/O pins. You are also able to SET and CLEAR the I/O pins remotely. This sort of functionality means that if your application is very simple, such as a remote control device, you are not required to use a host processor as yoiu are with conventional 433MHz modules


I bought a batch of older AM/FM/ASK/FSK 433MHz transmitters and receivers a long while ago and don't imagine ever using them, now that devices like the ETRX2 are available

[Ioannis]

Very interesting devices. Looks like the Digi's modules.

Have you made any range tests?

Which are you using the low pwer or the PA ones?

Ioannis

[Chris Barron]

Very interesting devices. Looks like the Digi's modules.

Have you made any range tests?

Which are you using the low pwer or the PA ones?

Ioannis

Yes they share some similarities with Digi's modules, and they're cheaper too. Telegesis offer plenty of support because these modules are in widespread use, one Swedish city has installed them in all electric meters for remote live billing applications, so I guessed they were reliable because of that !

Range depnds very much on the transmission path, the same as it does for any radio signal.
Being microwave devices (2.4GHz) they don't penetrate some materials as well as others but on the whole I think they compare favourably with the previous 433MHz modules I used (and they drew less power too)

My lab is in an upstairs room to the rear of the building. I put the main unit in there and walked down the street to the front of the house, about 35m before I started getting dropped packets. in the second test I put a third unit on the front lawn which immediately joined the network and acted as a relay station and then range went over 80m, line of sight.

These tests were all with the low power version. For the extra small cost the high power version would presumably give dramatically greater range, at the expense of power consumption.

[Ioannis]

OK. Thank. Digi has new devices for over 40Km range although these do not support the Zigbee stack.

Hope they will update the firmware.

I tried them and seems that this is true. Also powe can be adjusted for lower consumption.

Modules are small enough.

Ioannis

[Chris Barron]

OK. Thank. Digi has new devices for over 40Km range although these do not support the Zigbee stack.

Hope they will update the firmware.

I tried them and seems that this is true. Also powe can be adjusted for lower consumption.

Modules are small enough.

Ioannis

I know.

The project which got me into all this stuff was a remote machine monitoring project.
The ultimate hardware, for me, is the 6LowPAN protocol. Here, each node gets an IPV6 IP address and messages can therefore be routed to them directly via the internet without any translation.

Unfortunately, 6LowPAN implementations are thin on the ground, and I didin't get a large enough grant to buy the units from Sensinode which are the best application of 6LowPAN I've seen so far.

AVR (boo hiss) make a development board called a 'Raven' and there is a free RTOS and 6LowPAN implementation for use with those boards but then each node needs a Raven board.

[Ioannis]

IPv6 is very new to me. But having a lookat Sensinode site, made me think all stuff I used so far are ancient technology!

Very interesting devices.

Wish we had independancy from money and do all the things we dream.

I am in talks with a client to develop a network for banks so that they can control from the headquarters every stuff connected to the net. Many nodes may need wireless connections and zigbee seems a good idea.

If you feel like in discussing these projects I would be happy on private e-mails exchange.

Ioannis

[Chris Barron]

IPv6 is very new to me. But having a lookat Sensinode site, made me think all stuff I used so far are ancient technology!

Very interesting devices.

Wish we had independancy from money and do all the things we dream.

I am in talks with a client to develop a network for banks so that they can control from the headquarters every stuff connected to the net. Many nodes may need wireless connections and zigbee seems a good idea.

If you feel like in discussing these projects I would be happy on private e-mails exchange.

Ioannis

Ioannis, I might get in touch with you soon but other work is backing me up at the moment.

There are _a lot_ of private protocols, all designed with different uses in mind, and Zigbee is just one, and from what I hear is as much a money making system as it is a desire to build the best networking system.

For full industry standards compliance you should look at Dust Networks
http://www.dustnetworks.com/products/
Mesh wioreless networking with HART standards

They were recommended to me by an engineer who had implemented the wireless mesh system on oil rigs to provide roller bearing wear and vibration information. (The sensor is powered by a coil and magnet revolving within the bearing itself !)

Arch Rock seem to have started shipping their 6LowPAN solution, called Phynet
http://www.archrock.com/products/phynet_router.php
I would have tried to use it if it had of been released 6 months earlier, but not to worry !

Chris