thanks guy's i didnt think there were any replies as it didnt flag!! so a quick catch up, yes its for an incubator, dad has used bulbs before but a major problem with them is they fail alot so you add back ups with a LDR to switch on when one fails, another problem is at the size of incubator i am building (old under counter fridge and around 450 eggs) you need 1-2 100W bulbs, and 100W bulbs are hard to get around here, plus because its a competition with dad i want smaller because i want more room for eggs
and therefore better chance of hatch rate! so space and failings being major factors i am looking at other ways, temps are normally quoted as 37.7C for chickens and 35.5 for geese etc etc but reading dads papers from uni and his own notes from when he built them for the farm i need 101 F or for chickens 99.5F -101.8 F, working in C is ok and the normal way for most commercial incubators but dad is a expert on bird embryology and his hatch rates prove that working in F is way better but harder,
anyway the hair things are small and get very hot i doubt i need phase angle just kind of from x temp to x temp heater on say 7 seconds off 3 (i will experiment to get the times this is just an example) then from y temp to y temp 4 seconds on 3 off untill Z temp (near correct temp) where i will say do on 2 seconds off 5 seconds, if i do the experiments i should get pretty close to hardly any fluctuation in temp, so i was thinking zerocross triac driver and just on/off in bursts.
also i have a neat idea how to even out the temp in different parts of incubator (other thread). the soldering iron elements that are 24V give good temp but i think would need a heat sink with fan to get a useful amount out slowly. also the kind of heating elements i have mentioned dont fail as much and putting a backup in takes less space. i know for this comp dad is going the bulb route just to get his working quicker! and i want mine to be better
also the other reason is a bulb would ruin one of my other plans