heating rope for bators - UPDATE: Back to lightbulb :(

[eggonomist]

I think something that is able to produce a lot of heat needs a good thermostat to keep it under control. A 10% swing in a 60 watt bulb is not going to be seen as dramatic as that of 120 watt one, and 10% is a good number for electronic components. I would think about a good thermostat and have another go with the heating rope. I am going to try a 130-watt heater with a fan built in, used in compact electric fire places. The heating element will be on a dimmer and an electronic thermostat to control the heat produced if the swings get to wild.
However I'm on day 3 now with my old incubator and I have yet to see more than .3 degree drift. I have 2 40-watt bulbs, but there the long slim ones (dollar store), if one blows then the other will adequately heat while I change the blown one out, I had 2 25-watt ones but one alone did not work so I swapped for the 40's, so far so good. I would also check your vents, I found a better vented box held temperatures better when I used the dimmer switch and the fan, without the fan I had more stability with less vents.
My personally theory why you had trouble is because the dimmer switch is not very accurate as no one cares if you have the light producing 30% or 40% of it's lighting ability, it's just dim, but when you measure the 'dimness' then the differential is quite apparent.

 

[arlee453]

eggonomist, I believe you are right - if I had the rope on a good thermostat, rather than a dimmer I'm sure it would have worked much better. The dimmer is just too hard to make slight adjustments - sometimes a small tap would make a 1 degree difference and sometimes a small tap would make it drop 10 degrees.

So far the dimmer is working much better with the lightbulb. I'm getting very close to the 99.5 mark after only a couple adjustments so far.

 

[Three Cedars Silkies]

I changed to the old-style round knob dimmer ($4.50 at Lowes). The range of adjustment is far greater and I've gotten the bator rock stable at 99-100 with a 60 watt lightbulb.

 

[eggonomist]

I think Mrs Prissy said it best, it's an art to match the heat with the incubator. I'm to lazy and want instant results so I went with an adequate heat supply, doubled it, then controlled it, however 2 x25 watt bulbs would have worked and been controllable on the dimmer, the heating element I was using was 50 watt so it all adds up.