My digital hive weight logging project
I've always hoped to join the NASA HoneyBeeNet program that relies on volunteer submission of daily hive weight to track nectar flow at dozens of sites across the country. http://honeybeenet.gsfc.nasa.gov/ The understanding of nectar flow nicely complements satellite tracking of vegetation coverage for modeling of climate change, the effects of land use changes, or even how invasive plants and animals are likely to spread.
As a hobby beekeeper with two toddlers, I would also find it extremely helpful to know when nectar is flowing so I can add supers when needed without making unnecessary trips to check the hives' progress!
There are a few rough guides to digital hive scales on the internet, and http://hivetool.org/ demonstrates the type of high frequency (every minute or so?) data that can be collected. However they either rely on cheap digital scales that drift significantly with temperature, or they require outlet power and a PC to run. This is great work, but I don't have a wife that allows bee hives within feet of a power outlet.
I've designed the system around the following requirements:
- Record hive weight and temperature as well as ambient temperature every 1-5 minutes.
- Send data to thingspeak.com for backup and graphing of data.
- Log to micro SD card with a timestamp for reliable backup.
- Power with solar panels and lead-acid battery
I'd be interested in feedback on what's important or interesting to monitor. I'm particularly interested in helping others get their own hive logging systems running to add to the NASA dataset. I'll be writing up a guide (probably on instructables.com) with a complete part list, and I could also put together kits or complete systems by next spring if there's interest.
This isn't a sales pitch. I want to support anybody who's interested, but I'm more interested in feedback on what could be improved. Here's more details on the project. I welcome criticism or suggestions!
The Core microSD datalogger:
I've designed the system around the CPWPlus200 scale used at HiveTool.org, and while it's a bit pricey at $160, it's valuable to me to start with a scale I know will work. After some google research, I think I've found a cheaper shipping scale for $80 that might work just as well, but I won't know until I try it, and I'm focusing on finishing the first prototype before trying to reduce cost.
The logging microcontroller is an Arduino Uno that uses a real-time clock to log an accurate timestamp to the SD card. It talks to the scale via simple serial communication (an important feature that seems to add around $20 to the cost of the scale). I'm using 1-wire temperature sensors so I could add as many sensors as I'd like without complicating the wiring.
All the electronics (minus the temp sensors) fit inside the scale, so while I'll be building a cheap wooden frame to hold the scale, as long as it doesn't get submerged, it'll be relatively weather resistant. The scale is only rated down to 32F, so while I think it'll be possible to run through the winter with some extra care and risk, I'm planning to pack it in the honey house for the winter.
With the scale, this basic system that logs to a microSD card cost me around $290 including the $160 scale. That hurts, but I'm hoping future versions can be closer to $200 with a cheaper scale. It could be powered with an extension cord, and maybe even log to a PC like many others have done.
Wireless logging to the internet
To add wireless datalogging to a free internet service at thingspeak.com (there's others out there like cosm.com etc... that would work just as well) I've used XBee radio transmitters. The low power versions I'm using have a max range of 120m (390ft) but realistically, they're going to be limited to a third or a half of that if transmitting through trees or walls. It's relatively simple to add repeaters, and the remote radio (with a repeater) can be upgraded to 1+ mile range (with line of sight) fairly simply by using a more powerful chip.
I've used a ConnectPort X2 to transfer the signals from the hive directly to the internet via an ethernet cable (connected to your home network) for $108. WiFi versions exist, and you could even use another XBee radio with a computer to relay the data if reliability of the connection wasn't a major concern (the SD backup could always fill in gaps in the internet data).
With the ConnectPort, the wireless electronics cost me around $190.
Solar Power is a big question mark at this point. I plan to us a 12V trickle charger with a 12V lead-acid battery sized to the final measured power draw of the system. The voltage regulator built into the scale can easily take 12-18V (rated to 36V) so connecting straight to the battery and charger should be fine even when it's charging (12V lead-acid batteries run at 12.6V when fully charged down to under 12V when discharged, but they charge at up to 17.8V, so it's important to consider the charging voltage if you're going to hook up electronics to a charger and battery!).
The scale draws about 20ma, I'm guessing the microcontroller will draw under 50ma, and the radio will draw 45ma when transmitting (sleeping 95-99% of the time) so I'm hoping I can keep the entire system drawing well under 2ah per day.
Using some conservative numbers in this calculator: http://www.batterystuff.com/kb/tools...alculator.html it looks like I'll need a 20W panel and a 25ah battery to give me 10 days of backup.
I'm penciling in $200 for the solar system (panel with charge control, wiring, and battery) but I think it will be closer to $100 if I can really run it on a 20W panel. Of course power draw may increase if my scope creeps...
Counting Bees (aka: scope creep)
About a month ago, user Hydronics posted the following guide to counting bees going in and out of the hive using a couple of proximity sensors! http://www.instructables.com/id/Honey-Bee-Counter/
Knowing exactly when bees are moving in and out of the hive seems like the sort of thing that could be incredibly useful to a beekeeper (you could set up a text message alarm for when 30k bees suddenly leaves the hive to swarm in the middle of the day). That said, it'd roughly double the power draw of the system and it'd cost around $150.
I'm almost certain to add it to my hive eventually -- I've got plenty of time before the hives wake up next spring to try to reduce power and I can wait on purchasing the solar panels or battery until I have a solid measurement of total power draw.
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