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Wireless Thermometers

I was wondering if anyone ever tinkered with these low-end wireless indoor/outdoor thermometers made by like LaCrosse and Oregon Scientific.

Overall they seem like outright junk but are close to the mark of being reliable to me. I have one made by LaCrosse I picked up from Fry's a couple years ago, although I can't say it ever worked 100%, it seems to have a stability problem with summer temps, more or less when it goes over 75F or so.

Basically what happens is, the display on the inside unit for the outdoor temp reads "- - -" all day until it cools off outside. Like this morning, last temp I noted was around 81F, now it's just ---.

What is interesting is, if you put fresh batteries in both units, it does seem to work around the clock for several days. But then it starts to peter out, slowly. Like readings above 90F blank, then in a couple days, readings above 85F, then 80F and finally in a couple weeks, around 70-75F is tops.

Odd thing, fall and winter doesn't seem to have a problem. Installing a fresh set of batteries last October keep it running fine until a month or so ago. Even got down to below zero, never missed a beat.

I'm not losing any sleep over it but the thing stumps me on what the fault or design problem is. Last night while looking at Radio Shacks website for a replacement (figured it was a good place to start at), now that they allow customer comments for their products, it doesn't take much reading to see that nearly all of them have basically the same problem. Doesn't matter if it's the $20 model or the $120 one, various comments include "junk", "trash", "returned it" and "disappointed with reliablity".

What I was wondering about is if anyone knows about the mating ritual these things need to initialize the operation. According to the instructions you need to place both the indoor unit and outside sensor near each other, put the batteries in the outdoor unit, then batteries in the indoor unit. After the indoor unit gets a reading (changes from --- to actual temp), you set the time on the indoor unit and place the outdoor unit where you want it to go.

So it seems like when the batteries are placed in the outdoor unit, it may be transmitting some kind of id signal the indoor unit starts listening for when batteries are installed in it. Either that or that ritual just starts a timing sequence.

What I do know is, even with the two units in close range of each other (couple of feet), pulling and replacing the batts in the indoor unit only will never get a reading from the outside sensor anymore. So you do have to follow that proceedure they outline in the manual and back of both units.

Now I already thought of some kneejerk opinions like there may be a thermal problem with the outside unit or it's simply a range problem, but I don't think either is correct.

When I first noted the problem I brought the outside sensor back in, did the batt replacement ritual then stuck a hair dryer aimed at it for quite some time (over an hour). It was constantly above 120F, even using the same batteries as it was outside which seemed to have dropped down to the "can't read anything above 75F point". Putting the unit back (same batts again) gave another couple days of use until it started to fade out again with warmer temps.

The range doesn't seem to be it either, I originally bought the thing to keep an eye on the attic temp, the indoor unit was on a wall and only about

5 feet (or less) directly under the sensor which I placed above it, basically right above the ceiling on the attic floor. The numbers were different but the behavior was exactly the same, it initially got readings peaking out in the 128-135F range, then after a few days would "blank" out at readings above 125F, then around 110F then within a week wouldn't provide a reading unless it was around 80F or below.

Not really any different from the 30 or so feet where I relocated the outside unit to read outside air temps (I went to a wired thermistor type for the attic).

Long winded story but the question remains, does anyone know how these units communicate with each other?

It appears that the inside unit does something every 10 minutes, there is an undocumented icon on the display of like a satellite dish that turns on at

10 minute intervals for about 90 seconds. A shorter one occurs at the 7 minute mark, but only for about 30 seconds.

My guess is the inside unit doesn't transmit anything to the outdoor unit but when that icon is on, it's listening for something from the outdoor unit. Another words when it's working normally, there isn't any temp updates for 10 minute intervals.

It's just that by not changing batts in either unit (but getting the two close to each other, either inside to out or outside to in) then doing that restart initialization makes things work again, but only for a while.

So could there really be an id tag that is getting munged somehow after the battery gets low or something and the indoor unit is ignoring the output from the external sensor even though it's "hearing" it?

I haven't ran across much data on these types of units, guess they are all cranked out from China and generally aren't worth bothering with but the fault seems to be common with most of the models. Is there like a known protocol for them? They all seem to work on 433.92mHz.

If anyone has ever spotted any technical info, would love to get pointed in the right direction. It's not really a matter of repairing it but would like to know how it's supposed to work in the first place.

-bruce snipped-for-privacy@ripco.com

Reply to
Bruce Esquibel
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I like to think I was the one responsible for getting these things on the market after my requests that such a device be made.

Most units do not communicate with each other. Its a one way signal. I have had problems. The first unit I have had for at least 8 years still works, but it never had much range. This unit would not transmit unless a change in temperature occurs. You can usually do that by holding. And, this unit had a perfectly seald transmitter like all good ones should have for outdoors. It also could monitor 3 locations. I have bought two of the recent cheapies from Wal-Mart and both failed after a short time. I have another by the same company except it the delux model, and works well, but I have not tested its range. That first unit I have was always hard to understant the sequence of battery insertion to get it working. Whatever works seems to be OK. I have also taped a 1/4 wave 420 mHz capacitively couple antenna to the case where the internal loop is on th etransmitter. Seems to help range.

greg

Reply to
GregS

I have one LaCrosse unit, one Radio Shack which I'm pretty sure is not made by LaCrosse, and one Taylor unit. They all work fine at all times IF the receiving unit is within ten feet of the sending unit. When battery change time comes around, they can be *very* finicky about whether the sender or receiver is powered up first; I don't remember well but I think it likes sender powered up before receiver.

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Reply to
clifto

Hi!

I have a few different brands of these units...most are Radio Shack, one is an "EnviraStation" and the last one is a simplistic promotional freebie from DeKalb seed corn (!!!) that doesn't have an outdoor sensor.

I've been pretty happy with all of the units and haven't had the problems that you've reported. I have noticed that the outdoor modules with displays tend to have the display damaged by the sun or extreme cold very quickly. The displays usually end up turning very dark or appear to have all the elements on at once.

As far as the outdoor units go, extreme heat and cold are tough on the average alkaline battery. The same is probably true for rechargeables and carbon-zinc types as well. I have found that high quality, name brand alkaline batteries last much longer than cheaper ones. In most cases the outdoor sensors will run for several months before I have to replace the batteries. I try to place the sensors in trees, so they are not in the path of direct sunlight. I suppose this might affect the temperature reading by a few degrees, but the figures should still be in the ballpark.

Interestingly enough, the "freebie" DeKalb unit has both the highest and lowest operating ranges, as it has a button to shift the scale of the thermometer portion around. It is not otherwise very fancy, as it has only a manually set clock and measures indoor temperature/humidity only, but it will reliably run up to 140 and down to at least -10 on the Fahrenheit scale. It also uses the least amount of electrical power, as it has only two AAA batteries wired in parallel.

As far as operation principles go, I think these devices all pretty much communicate somewhere in the 300MHz band. The synchronization process is needed because there may be many of these in a given neighborhood. Even if they aren't all from the same maker, the frequencies used are similar. When the pairing process happens, both units agree upon a (hopefully unique) code between the two. If one piece loses power, the code is forgotten by that piece and re-pairing of the units is necessary.

As for the purpose of the "satellite dish" icon, my guess would be that it is used to indicate the onboard clock is synchronizing itself...that is, if these units have a clock.

William

Reply to
William R. Walsh

: Some of your comments concerning problems with high temps indicate a : possible battery/circuit problem...change the brand of batteries and : if the problem continues return the unit.

: More often one will see problems with low temperatures with the : accompanying diminished battery performance. In this case one should : use lithium batteries.

I have tried different brands of batteries, anything over-the-shelf, Duracell, Energizer and even the Costco housebrand, Kirkland.

None of these seem to make any difference, they all allow the units to work flawlessly for about a week, then it develops the --- problem with readings over 75F or so from the outside unit.

And it just doesn't seem to be a battery problem anyway, if you haul in the outside sensor, pull the batteries out then put the same ones back in on both units, they'll work again for some period of time, at least 2 or 3 days.

As someone else mentioned, it does look like other models can have multiple remote sensors. So it still comes down to the question if there is like a digital preamble sent that is unique to each remote sensor which is learned by the base unit during that initialization process.

Thats about the only thing that makes sense to me where the fault could be. Maybe that satellite icon on the display activates when it hears one of the remotes but isn't matching the id tag it learned.

formatting link

That link seems to be the same unit, although the manual is missing on the website, the undocumented satellite icon is just under the number 6 on the display along the bottom. I think mine is a 7010 or 11, it's single channel.

Anyway, it's not anything to lose sleep over, just seems like a curious operation and widespread fault which is an inch away from being solved.

-bruce snipped-for-privacy@ripco.com

Reply to
Bruce Esquibel

It continues to sound like a battery sag problem to me. If you don't mind a little risk, how about wiring an extra AAA battery in series with the two that are in there? This would raise the nominal voltage from 3.0 volts to 4.5 volts. I suppose this might damage the unit, but I doubt it. In any event, if "something" is marginal at the nominal operating voltage of fresh batteries, and dies when the battery sags a bit, this might demonstrate the hypothesis.

Bill

Reply to
Bill Jeffrey

Is the unit in the sun or the shade? If it's in the sun, the internal temperature may rise high enough to affect the operation of the hardware.

I've had a GE (option of 3 remotes) that worked well until ants invaded the remote unit.

I currently have an Oregon Scientific unit (with VLF time receiver and option of 3 remotes) that has been working well for a couple of years. The remote is hung from a tree limb (for shade) and has a rain shield made from the bottom of a 2 liter soda bottle.

And we do have temperatures above 90F in Atlanta during the summer...

John

Reply to
John

"William R. Walsh" wrote in news:ApAki.6735$Xa3.3719@attbi_s22:

Around there. Mine (a UPM WS410L) operates at 433 Mhz. A particular "set" will operate on only one frequency.

It just needs to discern from units from other manufacturers on the same frequency first (the RF frequency is hard built into the trasnmitter and receiver), then from the house and unit codes (at least mine does).

It is only one way. You set a hous code on the trasnmitter and receiver, and a separate unit code for each trasnmitter.

Not if you set HC to 1, and UC to 1.

That is possible, if equipped.

Reply to
Gary Tait

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