In 2006 Target had a sale on Oregon Scientific indoor/outdoor thermometers and I found out that they supported up to three different wireless temperature probes although they only came with one each. So I solved that by buying three thermometers and sharing the gauges. Two of the gauges read all three probes, while a third is only designed to read one probe, so I made sure that probe is the one outside (the other two are in my crawlspace and attic). Then in 2007 I got a wireless rainfall gauge which reads a tipping bucket gauge that is on my roof. It also came with a fourth temperature probe which runs at the same frequency as one of the other probes, but will be ignored by the other gauges as long as it is on a staggered 43-second reporting cycle. So I have the fourth probe in one of my closed off bedrooms to see how cold they get. Only the rainfall gauge reports that temperature.
Anyway, each of these items is powered by two batteries. That’s 3 temperature stations, 3 temperature probes, plus the the three components of the rainfall system for a total of 18 batteries. They seem to last about a year (maybe a little longer) on a fresh set of alkalines. It is a lot of trouble setting up the network correctly and if you take the batteries out of any probe, then that messes up its reporting cycle and the stations won’t read it anymore. So you have to take the batteries out of the station so that it will re-read the probes, but you have to make sure the rainfall gauge’s temperature probe isn’t detected and that the station that only reads one probe is reading the outdoor probe instead of one of the others. So there’s a whole procedure and it works best if you take all of the stations down at once to change the batteries. However, the batteries fail at all different times and you don’t want to throw out a battery that is still working. But you don’t want to take the chance of it failing in another month and taking everything back down again (and losing the cumulative rainfall).
So I thought I would try out rechargeable batteries. I know what you are thinking: Due to the self-discharge rate of NiMH batteries, won’t they all be dead in a couple of months? Not if I use low-self-discharge batteries. But low-drain applications aren’t economically viable due to the high up-front cost of the batteries, right? Well, not if you can get them on a really good sale, which I have been able to do recently. Target had 4-packs of Duracell precharged batteries for $6.45 last September and in December Rite-Aid had them for $7.09 after one rebate and down to $5.18 after another. These will retain 80% of their initial charge after a year and, because they have about twice the capacity of alkaline cells, they should be able to make it the whole year. If it works, it will still take 5 years to break even on this system (based on the cheapest price I ever got alkalines, which was 16 AA and 16 AAA batteries for $9.99).
The only problem is the voltage of NiMH batteries is only 1.2V instead of 1.5V for alkalines. Even fully charged, a NiMH is only 1.45V. So some devices think the battery is low even though it is just fine. And after installing 12 NiMH batteries yesterday (I had just installed alkalines a couple of months ago in the other two devices, so I am hoping they will make it for 12 more months), some are already reading LOW BATT. On alkalines, the probes and everything would work for months on low, so I am hoping it won’t be a problem and they can last all year on low.
The other potential problem is the batteries that are outside may not perform very well in cold weather. They will really be tested the next couple of days as temperatures drop into the teens, but they are also fully charged. Then the other question is how well they will do in the summer when temperatures in the attic go up to 120 degrees.
Another way to approach this is that you probably only care about attic and spare room temperatures at certain times… very hot days or very cold days. Why not just have one sensor and one thermometer being dedicated to infrequent sampling and not keep so many batteries working year round?
I need to see that tipping bucket thing. Send a helicopter up there to take a video.
The tipping bucket thing isn’t as complicated as it sounds. It is a two-chambered teeter-totter where when one side fills up, it totters, the water spills out of the open end, and the other side starts filling up. I’ve included a diagram that may help (the helicopter is grounded during rainstorms). The little circle is the pivot point. The down arrow is the water coming in from the funnel.
The thing with the probes is I don’t want to go up in the attic on really hot days, plus the stations keep track of the high and low temperature (though not the time that occurs which seems like that would be easy to do since all of the stations include clocks).
Right now it is 64.6° inside, 28.9° outside, 40.3° in the crawlspace, 45.5° in the attic, and 56.1° in the guest bedroom.
I like the idea of being able to track the temperatures. I’d love to see those figures for the morning when you first get up (it’s Sunday, so maybe you’re not up yet) compared to the end of the day after the sun has been out all day.
I imagine the attic most show the most extremes on really cold days (like today) and really hot days.
Can you post this mornings temps?
The temps for today . . .
Low 1015 215P 815P High
Inside 60.1 63.9 64.6 63.9 66.2
Outside 18.7 25.3 32.2 25.5 34.3
Crawlspace 32.4 35.8 41.7 38.1 41.9
Attic 34.0 39.4 55.0 40.5 55.0
Guest BR 53.1 54.1 54.3
Oh, brothers!
I got a free digital thermometer and alarm clock when I resubscribed to a magazine once and took it to work. People kind of obsess about the temperature at work, so it has been nice to have it so people can see how hot (in the winter) or cold (in the summer) they really are. But it is hard to find batteries for it and seems to go through them pretty quickly, so I think I will take my mini-station and the probe I put in the bedroom to work (can’t put the probe outside since our windows don’t open). I re-trained the rain gauge to look for the outside probe instead of the guest bedroom (and didn’t lose any data since it hasn’t rained yet this year). Before I had the rain gauge station and another station in the kitchen and the mini-station next to my computer, so I moved the kitchen station to the computer. I still have 3 probes and two stations in the house, plus the rain gauge which can only read the outdoor probe and the rain gauge itself.
It has been a year since I installed my green weather network. All of the batteries made it through the entire year without needing to be recharged even though the probes were indicating low battery from the first day. I didn’t have rechargeable batteries in all of the indoor stations at the beginning of the year because I had recently replaced the alkaline batteries in those and didn’t want to throw the batteries out (those batteries died during the course of the year and were replaced with rechargeables). Also I think the weather station may not have made it because the batteries came out once when it fell off the computer and then I replaced the batteries in December after the readout got very light and it stopped detecting the outdoor temperature probe. I swapped out batteries I had been using all year and will now use the ones from the weather network in flashlights, calculators, and MP3 players to even out the usage of the batteries.
I made it through another year (54.65 inches of rain measured). All the probes did fine for the whole year, but the indoor stations didn’t do as well. I had to replace the batteries in the rain gauge station and one of the others in December. I think it would be better if I started the cycle in September so the batteries would be fully charged for the whole winter and warm when they were at their lowest, instead of cold like they are now. But since the probes are okay and they are exposed to the weather more, then maybe it wouldn’t make a difference.
This year the indoor weather stations faded again in November or so and I replaced the batteries before the year was up. This year I will replace some of the Eneloop batteries which have a capacity around 1950 mAh with some Turnigy ones that have a capacity of about 2300 mAh. The Turnigy cells don’t hold their charge as well as Eneloops, but they start out with more capacity, so we’ll see if they make it.
I didn’t get a good rainfall total this year because the gauge seemed to be overcounting. I think this could be because of dripping water from the antenna above it or splashes coming up from the roof (the top of the gauge is about 10 inches above the roof). I removed the antenna temporarily, so maybe that will help. I got the batteries changed out this morning before most of the rain hit and have tallied 0.91 inches so far.
The higher capacity Turnigy batteries allowed both of the indoor weather stations to go the entire year without changing the batteries. I didn’t have Turnigy batteries in the rain station and had to replace those batteries in December, so now all of the stations are using Turnigy batteries. All of the probes made it the whole year with regular Duracell or Eneloop 800mAh rechargeables. I moved one probe from the crawlspace to the house when I was making beer to keep an eye on the temperature of the closet where the beer was. But after I got the new furnace and air conditioner, I think I moved the probe to the guest bedroom and now I can’t find it. It is somewhere inside the house because the weather stations are still reading it, and it is around 66 degrees.
This year the Turnigy batteries did not make it the whole year in the weather stations (the temperature and rain gauges outdoors use less power and easily last all year). I replaced the batteries around November. It could be that because they are only charged once a year that they are either not taking a charge as well or not lasting as long. Even rechargeable batteries wear out eventually.
I’m still using my temperature probes, so the investment in rechargeable batteries has certainly paid off. The batteries in the monitors fade before the end of the year and I replace them, but the probes always last all year. Some of the AAA batteries have failed over time, but the AA batteries are generally good. I stopped using the rain gauge, which I had attached to an antenna stand on the roof that I don’t use anymore. I need to find a good spot the rain gauge so I can use it again because that was always good information to have. But you need to be careful with the placement so you don’t get splashes from the ground or drips from trees. And I lost one of the temperature probes. I think maybe I put it somewhere obscure where I wanted a temperature measurement and then I forgot where that was.