Monthly Archives: November 2016

More hive sensors

We’ve had a hive on a scale now for 3 seasons, and have learned a LOT from that data. I have many times pondered putting more sensors into and on the hive, just to see what else there is to learn. The only reason it hasn’t been done, I just dont have the time and patience to sit down and wire up a bunch of things onto an arduino in a way that will stand up to the rigors of living in a beehive. The folks at broodminder.com have solved part of that problem for me, they produce a set of gadgets meant to be used in and under hives, and altho on the surface it may look a bit expensive, in reality, when I tally up my raw cost for purchasing the bits needed to make one, then the time and effort required to get it going, my final choice is just order it and get collecting data instead of pondering how to get more sensors into the hive.

I ordered two of the temperature and humidity gadgets, one to put in the scale hive, and one to use intially in the office for getting all of our software running, then later it can go in another hive. While I was at it, I ordered one of the scales. The scale will be sitting in a temperature exposed, but rain protected spot for a few weeks where I can log some data over time and figure out temperature compensation for this one, then stick it under another hive.

In the week since I got the Broodminder gadgets, I whipped up a small program that can run on a raspberry pi to read the bluetooth le advertisements produced by the gadget. With that program up and running, we added a bit more so the data will get stored into a database over the network as the new readings arrive, and we can plot the live graphs for hive temperature the same way we do for hive weights. This is all in place now, and we have almost a full day of measurements. On the scale hive page you will notice a new graph has been added, hive temperature vs outside temperature.

My starting point was to put the Broodminder-TH on top of the frames in the top box of the hive currently on the scale. The hive configuration for winter is a double deep with the top box full of winter feed for the bees, cluster is currently in the bottom box, a fairly large cluster. What was very interesting to note, the day I put it in was a nice warm day, around 14C in the bee yard, bees flying everywhere. When I lifted the lid, lots of bees on top of the frames in that box, temperature was around 30C, what I expect for a probe just above a brood nest. Two days later, after we had a very cold overnight (frost on the car window in the morning), I went out and pulled the data from the broodminder, and to my horror, the broodminder was reading 14C for temperature. Did they die off that quickly ? And this turned into a big ‘aha’ moment for me, very similar to some of the ‘aha’ moments we’ve taken from the scale data.

This colony is in a double deep, with the cluster in the bottom box, and above the cluster is a full box of stored honey. The frames of honey above the cluster are one great big heat sink, so any heat rising off the cluster is being absorbed by the frames of honey before it reaches the temp sensor at the top of the hive. The interesting tidbit I take from this, over the years I’ve heard the debate, do bees heat the whole box, or just the cluster. Some folks say ‘just the cluster’, others point to snow melt on a lid and are adamant they heat the whole box because warm air rises. Well the light bulb turned on when I saw this, and now I better understand the dynamics of heat flow in the hive. Warm air will rise off the cluster, but, any frames of honey will act as a big heat sink as that air rises to the top of the box, and, by the time it reaches the top, it’ll be a lot cooler than when it rose off the cluster.

It will be interesting to watch this as winter progresses, and get a better understanding of what’s happening inside the colony thru the winter. The biggest detail I expect to learn, we will see the temperature at this probe just under the inner cover start to rise dramatically after the bees have moved up into the top box, and start the first round of brood in the winter. I have LONG suspected that our bees raise the first brood a lot earlier than we have been told over the years. Having this probe giving us temperature and humidity measurements from inside the box will answer my questions in this area quite definitively.