Transmitter/Receiver Pair Ideas ?

Hello there folks,

I would like to have a transmitter and matching receiver that could transmit from the automobile to the house a distance of less than 100 feet.

I dont think i would be into building this however so it would have to be purchased already working, but it has to be reliable. It will be used to transmit data from the car to the home using additional circuitry to measure parameters in the car and display them in the home.

I had already considered a 2.4 GHz transmitter/receiver but the transmitter operating temperature is only from 0 to 70 C which does not go low enough for this area (0 deg C is only 32 deg F) where we can get 0 deg F or even -10 degrees F temperature in the winter. Top end has to be maybe 150 degrees F for the summer when the interior of the car gets quite warm when it is just sitting there.
So it has to work ideally from -20 to +150 F but i would accept 0 to 150 F perhaps.

I might consider a circuit but it would have to have stable frequency and it would have to be reliable. Ideally though i want to avoid building the T/R circuits as i will have enough to do with the data collecting and displaying part.

Thanks much for any and all suggestions.

Could you put a small heater in with the t/r with a thermistor to keep it from getting too cold? Thats what my son did for a space balloon, so the batteries would not freeze.

but the transmitter operating temperature is only from 0 to 70 C which does not go low enough for this area (0 deg C is only 32 deg F)

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That does not mean it will not work. Just that it will not meat specifications or that it has not been tested over that range.
OR
They bought the 0 to 70 parts because the price is better. Which again does not mean they will not work.

Hi again,

Yes i am aware that it may still work, but i feel that the temperature difference will be too much for it to work properly and also i dont feel like experimenting with this.

I also can not use a small heater because it uses too much energy even for a very small heater. As it is i have to limit current to around 20ma at about 33 percent duty cycle.
I could go higher for less time, but i would prefer something 100ma or less.

just a thought, if you only send the data like say hourly, then a few minutes beforehand you could use a small resistor to heat the specified area just enough to enable a "good transfer" and shut it off right before you send the data?

Hi Joe,

Yes that's true, but really i want a more frequent update on the variables. Also, there is quite a bit involved in using that old transmitter/receiver pair so if something doesnt work now or in the future it's a big waste of time. That's why i am asking for a NEW T/R pair. Thanks for the suggestion just the same though.

How much $$$ do you want spend on this project?

If you want a wide environmental temperature range, consider something like this:

But that seems to exceed you power consumption budget.

I guess that you will need to look at fully engineered solutions for professional applications if you don't want to spend time evaluating consumer grade modules.

JimB

I used Linx trm-lt modules and they worked at -37C. Haven't had anything colder yet.

I was looking at the LINX , CC1101 and also the MRF24J40MB awhile ago but never got back to going with either of them as of yet , been too busy for my hobbies

Hi again,

JimB:
That looks interesting, how muchare those systems, the cheapest let's say?

NorthGuy:
Those modules look interesting too. I'll have to read up on them a bit more. Cost might be ok there. I'll check the data sheet for temperature range.

out of the box idea but how about a peltier device powered by a few cheap PV panels on the dash along with smallish deep cycle battery. Basically in cold weather the peltier can warm the circuit board and with the surrounding cold the heatsink will be cold enough then in summer switch it over to cool the board and the sun heating the heatsink should give enough differential to cool the board.
One would think not that much power would be needed and along with a smart charger when the vehicle is started the deep cycle battery would be fully charged.

Like I said out of the box idea but eh to live in a place where brass monkeys are scared aint my idea of home.....

Hi,

Well that's an interesting idea, but after all i am trying to keep this as simple as possible too, so im not sure i want to add all that extra stuff. Maybe in the future though, if the front of the car gets enough sunlight (it's half under a tree when parked).

This turns out to be quite a project after all. Maybe that is why i dont see anything like this for sale (unless i just cant find it). If i could find a small unit for sale i would probably be inclined to just buy it and skip all the building from scratch. I cant be the only person who wants to do these measurements on a daily basis.

I did check the Linx modules and they do in fact have a wide temperature range i think would be suitable. Downside is that they are AM transmitters/receivers not FM, so subject to lots of noise and interference. I'll be looking into them a bit more though anyway.

Hi,

I looked at quite a few modules and chips now. So far they look pretty good.
I wonder how hard the Linx modules are to solder.

MrAl said:

I wonder how hard the Linx modules are to solder.

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Not hard. If I can solder them then anyone can

Hi NorthGuy,

Thanks for the info there.

So then is the way it works is you heat up the side terminal and let the solder wick under the bottom, does that work ok or another way to do it?
Did you have to use a PC board that had the proper clad pattern on it or can you use something else?

I used standard one-sided board with 1Oz copper. I wetted both the board and the bottom of the "pins" with the flux, then I put the tip of the solder wire into the grove and pressed from the top down with the soldering iron (melting the solder on the way), removed wire and waited few seconds which, in my mind, should've been enough for the solder to get drawn under the bottom. I used no-clean flux because it's hard to clean it from underneath the module.

I can't tell if this is the proper way to do it, but it's working so far.