LinX TRM-433-LT anyone?

P

Pfrogs

Member
Hi,

I was wondering if anyone has already used a TRM-433-LT transceiver RF module, from LinX Technologies, with a Picaxe? (http://www.linxtechnologies.com/Documents/TRM-xxx-LT_Data_Guide.pdf)

I am thinking on getting some TRM-433-LT transceivers to communicate between Picaxes, but would like to know if anyone have tried them already and, if so, what is their opinion on these transceivers.

Also, will it be easy to interface this type of transceiver with Picaxe? (it has a direct serial interface through a digital data line...is this any similar to a TTL interface...speaking in terms of "user-friendly" programming?)

Looking forward for a reply :)

PS: Seize the moment to wish you all a Merry Christmas and a Happy New Year...full of succesfull Picaxe projects ;)
 
M

manuka

Senior Member
What cost ? These certainly seem sensitive, & at 10mW quite powerful, but I'd say a few 100 metres may be a more typical range in built up areas. What is your application ? N.B. Noise on this 433 MHz spectrum slice may be a major issue is some locations

In general I suggest starting simply with 433 Mhz data modules, & winding the data rate downwards (1200 or even 300 bps). There are numerous offerings in the US$5-10 range that suit no brainer PICAXE connection, but IMHO it's worth considering transceivers (such as HopeRF & Yishi) for versatility. I've assorted 433 MHz insights here. Mmm-these Linx look like some SURE models I've yet to have a play with!
 
Last edited:
P

Pfrogs

Member
They sell for ~12$/ea from Linx website (or distributors) and require only an additional external antenna.

I want to use them to send data from sensors connected to a picaxe, and all the circuits will be inside a hermetic capsule that will be submerged in liquid (around 2 L). So I have limited space and that is why I want to use these Linx transceivers (they are about half the size of other transceivers modules I've seen).
What I really wanted was to use a bluetooth transceiver, but I guess at 2.4GHz the signal will be seriously attenuated with submersion. So I decided to go for 434MHz, which is legal in Europe (and most places) and should be able to pass the signal through the liquid solution (I don't really need distance, as the receptor will be located nearby (máx. 10 meters)).
Another thing that I liked about the TRM-433-LT is their low current specs, which will be important for my case since all will be runing on batteries for some hours/days (with intermitent transmission and data sensing).

Thank you for the link Manuka. Interestingly, I took knowledge about this LT series from your website (thank you!) ;) I have also looked into HopeRf's HM-TRS module, which is also an interesting module with TTL interface, but I still think the TRM-433-LT is a better choice for my application (much smaller and lower power reqs)..even if that will require greater troubleshooting and "brainpower" to make it work :eek:.
I am thinking on producing some software checksum to overcome the most probable noise issues in this freq and application and use the Rx/Tx to check data reception, etc...

In the end, what I've been trying to understand now is how does the digital data signal works and if that is somewhat straightforward to interface with a Picaxe. If I use a "serout" command to the pin connected to the digital data signal of one module, will the other picaxe in the other module read the "serin" straightforward (considering that signal has no interference)?
 
Last edited:
M

manuka

Senior Member
Interfacing is indeed normally dead simple, although associated "wake up - this message is for you" conditioning tweaks may be needed too. Have a look at code samples shown at my resource site. Mmm -guess these Linx are the units I showed here back in 2007 ? If so then that RSSI outlet looks handy, although considerable wrestling with the diverse options may be needed too. What are you intending about sockets etc ?

Now that they are finally available I should order a pair myself- anyone fancy swapping for a spare pair of RS232 fitted HopeRF HM-TR ?!

N.B. Underwater comms at 433 MHz be a major headache, so suggest you do some trials VERY early on. What depth ? Stan.
 
Last edited:
P

Pfrogs

Member
Thank you Stan, that was pretty much what I wanted to hear.
Unfortunatly, the TRM-433-LT seem to be out of stock everywhere, so I will have to wait for mid-January before I can try them.

I wish to use this in an aquarium so it'll not be very deeply submerged, but I'm aware that water is always a problem in RF.
I'm planning in using an embeddable antenna also from Linx (the Splatched...http://www.antennafactor.com/documents/ANT-433-SP_Data_Sheet.pdf). I will also use the RSSI and PDN pin and program the picaxe to control sleep/wake-up functions (I'm thinking on giving an "address" to the slave holding the sensors, so it only "really" wakes up when receiving that address else go back to sleep...this way I may be able to save some power, depending on how much noise will be triggering the RSSI). I'll also use the A REF pin to control the noise threshold with a resistance (may have to play with this).

Can't wait for them to be available to start playing with them. Will keep you updated with my experience. Thank you!
 
M

manuka

Senior Member
OK-just an aquarium! Have you considered simple IR data? The sender & receiver could be then just placed on the inside of the glass tank, or even on top ( with submerged sensors). Consider access by a glass fibre optics too maybe?
 
P

Pfrogs

Member
Thank you for the suggestions.
This will be for a research project that I'm involved in and unfortunatly the liquid that I'll be using absorbs in the IR spectrum, so I ruled out IR comm. The fibre optic comm is a good ideia, but I also require the aquarium to be hermetic and under pressure, so I think that would complicate the design. So I will try the RF communication first, and if that turns out to be complicated, I'll consider your fibre optic suggestion.
Thank you for your help and suggestions so far.
 
M

manuka

Senior Member
OK- if the reaction vessel is glass then IR data will travel thru' the walls of this OK. Just what sort of pressures (& for that matter what sort of liquid!)? Mmm- do you even need a transceiver - is data just one way from within this vessel? What exactly are you measuring & how often ?

I see UK firm Simple Solutions has these at ~£10 each. Browsing specs however shows they're only AM OOK (On Off Keying) devices that may be intereference prone compared with impulse noise resistant FM types.

Given the apparent delivery delay & predictable setup hassles (!) it strikes me you certainly should just grab some cheapier tx/rx initially for trials & to gain experience. Range certainly doesn't seem as if it'll be an issue in this case ! Are such cheapies available in Portugal? Stan.
 
Last edited:
P

Pfrogs

Member
As I mentioned, this is to be used in a research project that I'm involved, and unfortunatly I'm not allowed to reveal much about it. Sorry! Hope you understand.

I actually already ordered 2x TRM-433-LT from Simple Solutions (didn't see them before). I did noticed the AM/OOK issue, but I couldn't find any other modules that would fit the main specs I need (size and low power spec). I'm aware that I don't really need a transceiver, but to compensate for the interference prone I decided to use a transceiver in order to let the transmitter know that data was currectly received, otherwhise, send data again.

Yepp, unfortunatly in Portugal is hard to find some electronics and at a cheap price. It still compensates to order from abroad, although most of the times shipping costs are really high.
 
M

manuka

Senior Member
Yikes- you can SURELY mention if the container is glass or metal. If things are that evil in the enclosed brew (to the point of such non disclosure) then I'd say all manner of electrical problems will arise!
 
P

Pfrogs

Member
manuka said:
Yikes- you can SURELY mention if the container is glass or metal. If things are that evil in the enclosed brew (to the point of such non disclosure) then I'd say all manner of electrical problems will arise!
Click to expand...
I did mentioned it was an aquarium (so glass it is..sorry if that wasnt clear)...what I cannot reveal is what liquid it is (even if I did, you probably wouldn't know what it is) so I mentioned one of the relevant properties for this thread, which hampers using IR comm...ie. high IR absorbance..so no IR signal would reach the receiver, even with a clear glass container)...the use of a fibre optic would probably solve that, but it requires putting "wires" into the container... and in that case, maybe I could just use electrical wire to communicate... but I require wireless comm to avoid other construction problems.
But thanks anyway for your premonition! Wish you better luck...
 
A

Andrew Cowan

Senior Member
Assuming you have already sorted a container for this, then I'd imagine you need to do some tests with *the liquid*. Do you have any RF transmitters you could try? Generally lower frequencies travel further through water.

A
 
P

Pfrogs

Member
I already sorted a container but unfortunatly I don't have any RF transmiters available to test it yet. I'm aware of low frequency travelling further but I cannot predicted how this is going to behave in my liquid. So I'm aware this is going to be a trial/error project...but that's part of the fun :D. Nothing like trying!
 
D

Dippy

Moderator
Absolutely!
Let us know your setup (power and antenna config) and how it performs.
It'll be very useful for others.
 
P

Pfrogs

Member
I surelly do that once I get the TRX and play a bit with them (to bad, the store will only re-open on Jan,4th).
 
You must log in or register to reply here.
Top