Bee Heater Construction

[BlueBee]

For those of you interested in electricity, bees, experimenting, and Frankenstein, this is for you.  Specifically how I make electrical heaters to add heat into a hive.   

Why experiment with heat?  Check out Finski's posts on boosting your bee numbers in the spring:
http://forum.beemaster.com/index.php/topic,31659.0.html

There are many ways to add heat to a hive if you want to experiment with such things.  Hives can collect a good bit of heat naturally due to solar gain, but much is lost at night.  If you want to go an extra step, you can do things like add plumbing heat tape, green house seed starter wire/mats, old water bed heaters, reptile heaters, incandescent lights, and electronics.   

There are pros and cons with each approach, I have decided for my heating experiments to use an electrical approach that can be powered from low voltage and does not risk setting anything on fire in the hive.  Not sure the bees would like a camp fire in there....

I finally got a photobucket account set up and uploaded the photos showing how to build my electronic heaters.  I've annotated each photo with the construction details.  Here is the link:

http://s1082.photobucket.com/albums/j365/MichiganBee/Bee%20Heater%20Construction%202011/

[gaucho10]

OK Blue Bee,

Now for some questions....

Looking at your pics it appears to me that you installed all 4 heaters under one hive.  Also the heaters appear to be somewhat bulky.  Is there any way to make "one" tray for sliding the heaters under the hive?  Can the heaters be made thinner?  What other available material is there to use as a "heat transfer" ?

It would be interesting to see what the temperature difference is in outside, bottom and top of hive temperatures.  Today I have actually posted my results on my other post titled "new screened bottom board design".

Also....What are you using for power?  I know that you mentioned some type of computer part.  Is that something easy to extract from an old computer without getting too technical?  I understand that you are using a 12V system.  Can that be operated with some type of converter (AC to DC) without getting too expensive?

[BlueBee]

Can the heaters be made less bulky?
I'm sure they can, and that's probably a good idea.  The reason I haven't done that yet is so I can have a universal heater part that can be used in any of my equipment from an incubator, to a nuc, to a full sized hive.  The 1.5x1.5x12" units fit all of these things.  If you're just looking for a full sized hive heater, then yes, I think a pancake shaped heater would work fine.

What other material can be used for heat transfer?
Anything that is a good conductor of heat and doesn't conduct electricity.  If something conducts electricity, it could short out the resistors.  Cement is very low cost for this application and conducts heat good enough.

It would be interesting to see the temperature difference:
See the photos in this album.  I just measured these today, March 24th, 2011.
http://s1082.photobucket.com/albums/j365/MichiganBee/Heat%20Measurements%20March24%202011/
I'm still working on my instrumentation system, so for now it's still a manual process.

Can these heaters be run on a low cost power supply?
Absolutely.  I use both landscape light transformers (12VAC) and computer power supplies (12VDC).  You can usually buy a new 500Watt computer power supply for $20 if you wait for a sale.
http://www.newegg.com/Store/Category.aspx?Category=32&name=Power-Supplies
(There's on sale right now for $19.99)  A 500 watts computer power supply will run about 40 bee heaters.

How much does it cost to run these things?
Here in Michigan, electricity runs about 12 cents per kilowatt hour.  That means you can run something that consumes 1000 watts for 1 hour of time and have to pay 12 cents.  These bee heaters are only about 10 watts each.  To run one for 1 hour is 1/100 that cost, or 0.12cents/hour.  Running a bee heater for 24 hours would cost about 2.88 cents in Michigan.  A month of full power heat would cost about 90 cents in Michigan.  Cheaper than sugar (the bees alternative fuel source).

With insulation you trap a lot of the bees heat too, they are also a heat source.  Adding electrical heat can be too much heat.  My nucs are currently controlled by 8 bit micro controllers that use a thermistor as a thermostat.  Once the nucs get to 85F (via bee heat or electrical heat), the heaters turn off.  From 85F, the heaters bees don't have to work too hard (eating less stores) to get the brood up to 94F.  Brood isn't going to get chilled when it never drops below the 80s.

[gaucho10]

BlueBee,

That is cool stuf .....I'll be checking in on your posts.  Keep it up...

gaucho10

[JRH]

Would running a seven resistor string directly off a 12-volt automotive battery flatten the battery in a very short time?  My electrical math isn't up to snuff ... and my hives aren't near a 120V source.

[BlueBee]

Hi JRH, the math to determine how long a battery should last is:

Battery Amp-hour capacity / Amps a load is drawing = hours of life.

I'm not an expert on the load capacity of car batteries, but it looks like many are in the 50 to 70 Amp hour range.  Let's assume 50 amps for this example.

The total resistance of each of my heaters is 12.6 Ohms.  V=IR, so when powered by 12volts, the current flow will be 0.952 amps.  (Actually that would give off 11.42 watts of heat if there were no voltage drops over the feed wires and losses in the connections).

So to find out how long a 50amp-hour battery lasts, we have:

50amp-hour/0.952 amp load = 52 hours.

You should be able to run a single bee heater for just over 2 days.  :( Unfortunately batteries are not a very dense energy source and that is one reason why most of our cars don't run off batteries.  Oil is much more energy dense.

If you have a remote situation without AC power, I think it would be interesting to experiment with some sort of passive solar setup.  

Caution, to any experimenters out there, beware that wax moths love warm temps too!  In my setup I currently have a screened heater box on the bottom of my hives.  My heater box is like a Screened BB but with a heater below.  A strong hive will keep the wax moths out of the hive, but they can scamper down into the heater box and multiply where the bees can't get to them and cause problems.

[JRH]

This sounds promising for a setup where the heaters are only activated by a sensor that "made" on any temperature below, say, 10 degrees.  Even better when charged by a solar system.  Can you recommend a thermostatic switching device?

Thanks.
Jeff Hills

[BlueBee]

Jeff, you've got a good idea, limit the thing to only run under some pretty low temp and you won't run down the battery over night and you could use a solar setup to recharge the battery during the day.  The problem will be how to control when to turn on the heaters (below 10F in your example).

I can think of at least 2 ways to do this.  First I'll tell you how I control the heaters in my nucs.  In the nucs I don't want them getting colder than 85F, so I use a microprocessor and a thermistor to monitor the temperature in the nuc and turn on the bee heaters if the temp inside the nuc drops below 85F.  I use a nFET controlled by the micro to turn them on.  (FET = field effect transistor, just a fancy name for an electronic switch).  The micro I'm using a low cost ($1.50) 8 bit Atmel Mega48 micro with a low cost thermistor.  Sum total parts cost is under $5.  Low cost but you do need to possess the skill set of programming micros.  Again not real hard to do, it just takes a little time to learn.

Using a micro to control stuff gives you a lot of options since you can define exactly what you want it to do and when.  However if you can get by with less refined controls, there is a really easy and cheap way to do what you're asking.  That would be to use a thermistor in a voltage divider circuit attached to the gate of a nFET.  By judicial selection of the resistances, you could set up these 3 parts to get close to what you're asking for.  It would require 1 resistor, 1 thermistor and 1 fet.  You can probably get all that for under $2.

I'll throw a circuit on here to show the setup later.  Gotta go finish some painting now....

[BlueBee]

Here's a photo of the thermostat device I'm currently using for my nucs.  



It's a small 8 bit micro with a thermistor attached for sensing temps, a couple of FETs for driving the heaters, and some LEDs for eye candy.  

You can do a lot of things with small low cost micros once you get over the learning curve of how to program them.  The manufacturers have stuffed a lot of IO peripherals in these things over the years that allow you to easily interface with analog sensors (like thermistors, photocells, etc) and easily drive digital outputs like FETs, PWMs and LEDs.  Almost all have RS-232 and some have USB if you want to interface to a PC.

Jeff, I was going to add a low cost, hardware only, thermostat circuit here too, but I think I'll start up a new thread for that.  I'm going to build one for my Bumble Bee house and test it out to see how well it works before posting that circuit.  I'll post that sometime this week.

[JRH]

Fascinating.  Can you recommend a book or a place to study programming devices like the Atmel chip?
Many thanks.
Jeff

[BlueBee]

Programming little micros is pretty easy after you get over the learning curve of your first one and how to use the development tools to program them.  You don't have to have a degree in EE or CE to build these things.  There is very little math involved in the hardware design either; you don't need to be a math guru.  About the only math you need to know is V=IR.

You can buy the little micros from Digikey or other electronics parts suppliers.  The Mega48 CPU I used is currently going for about $2.50 in quantities of 1.  There are tons of low cost 8 bit micros from other companies too.  What manufacturer you go with depends on your own preferences.  I do my 8 bit stuff with Atmel parts because I find their tools are easier for me to understand.  However a lot of people also use the PIC series of 8 bit micros.  They are very popular too.

I find the most difficult part working with any micro is the development tools.  They can be time consuming to learn.  Today, 32 bit micros are sometimes cheaper than the 8 bit stuff.  They're fairly easy to program as well, but I find the development tools to be more complicated.  Hence for basic stuff, I still stick with 8 bits.  If you're just starting out I would start with 8 bit micros.  You can do a lot with them and they don't have the complicated interrupt configurations needed in most 32 bit micros. 

I program everything in C, but you can program the 8 bit micros in assembler if you want.  C is quicker to code in.  C++ can also be used with some 32 bit micros but the amount of bloat ware you get is not worth the benefits of C++ unless you are making really big programs. 

Some resources:

Atmel website where you can download the datasheet for the Mega48 I used here.  There is also a bunch of app notes about how to use the chip.  You can learn a lot by downloading the data sheet.
http://www.atmel.com/dyn/products/product_docs.asp?category_id=163&family_id=607&subfamily_id=760&part_id=3301

Microchip is the manufacturer of the popular PIC series of micros.  Here is a link to their stuff.
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=2551

If you need a refresher (or a fresh start) on programming in C, this short webpage is about all you really need to know to program a micro.  If you buy a book, I would go with the cheapest easiest looking one you can find.  A lot of the more complex C/C++ things we don't use in the embedded world.
http://einstein.drexel.edu/courses/Comp_Phys/General/C_basics/

If there is some way to post programming text files on this website, I would post the code I used to make my little nuc controller.