I need to make a small heater. I was looking at this project:
but I need to design the heating element. I was considering taking 120VAC from the wall, running the hot side through a 1 amp fuse, running that into a relay, then running the relay output into a 300 ohm power resistor for a total of 50 watts. Looking at this part currently:
Do I need an AC isolation transformer? If so, why? Isn't the 1 amp fuse enough for safety?
I am not planning on using a fan or heat sink, only ambient air. What is duty cycle of such a power resistor? Generally I would expect that it can dissipate 50 watts 100% of the time (taking into account the ambient temp derating of course), and I've also seen the 1000h component life spec. Any thoughts?
Max voltage = (P*R)^1/2, which in this case comes out to 122V. Obviously this is close to wall voltage, and peak to peak is much higher than 122V. This thing looks like it's built like a high voltage component though, will this really be an issue? (If it is I can adjust the dissipated wattage downwards a bit, while still using a 50 watt rated resistor)