I've been a northern beekeeper some years * I'm ashamed to say it took 20 yrs for the light bulb to go on I do have a semi-reasonable excuse A 2A extension cord must reach the yard I hope you can solder and use a meter The rest of you may find it worth a laugh The heat source is a "peanut" bulb (from a tensor lamp?) the size of 2 (shelled) peanuts 12V 50W, this is powered by a small "junk" computer PS, simalar exist in printers I run it at 5 or 6V (12.5 or 16W)(6V is 2 in series from 12) Probably at full power it would overheat & have short life The bees don't like light so enclose it in metal The pins on the bulb don't like to tin, dip them hot into flux several times. Do NOT bend these pins in the slightest. ie when insulating be gentle The leads are (inside)phone wire, all 4 wires used Being lazy I wondered if offset Al (printing plates .010" Al) would do -- it does, only 1 layer seems OK Cut and bend an envelope about 3 x 2.5" with tabs to seal edges. This will fit between 2 boxes if you make sure the frames are clean and wiggled a little bit Wax bits that drop on this do not melt, only soften It does not seem to injure brood It probably should be in contact with the bottom of the cluster or nearly so Now the Mk V design is much more interesting and only a bit more complex It is a "heat pipe" to dip into a divided division board feeder (full depth) Since the pins will electrolyse if into the feed the bulb has to be in a dry well at the top of the pipe. Use a all Cu penny, sanded to size, for the floor of the well & soldered into the .5" Cu pipe (If you never filled more than 85% full you could dispense with the well, just glue the bulb in place with a gob of silicone) If you cross drill the pipe to get some convection (warm feed!!!) don't let the bees into the pipe many would be killed when filling. There should be at least 1 hole to let the air out For wintering (a weak lot) you turn it on at 0f or 5f or for breeding always at 50f(10c), maybe sooner It seems to give about 30f(18c) temp rise to the hive If your are on the ball this will be controlled by a thermostat (I'm not so together) These bulbs can be bought for $2 Depending on the winter it would cost $1-2/bulb for the whole winter. I think this is cost effective However due to global warming I haven't gone nuts with this, I've only made 5, 3 of the mk3 & 2 of the mk5 design * I'm at 95-98 cold percentile. dave -- Visit www.honeybeeworld.com/bee-l for rules, FAQ and other info ---