aon
Well-Known Member
Here's something I made today. I dedicate it to @eSGEe as nothing was soldered 
The variable transformer is an old Lübcke unit I saved a few years ago from a piece of industrial gear that was going to be scrapped... Knew I'd have some use for it eventually. It feeds into an isolation transformer either directly or via a current limiting resistor. The resistor is 470 ohms, so at full 230V output it will limit the current to ~0.5 amps (at which point the resistor will be dropping the whole voltage and the output will be zero). 230V*0,5A = 115W, the power rating of the resistor is 200W so that should be fine. It will probably heat up the enclosure quite a bit if left running at full limit for extended periods but I have no plans of doing so. Maybe I could add a temperature switch as a failsafe.
The isolation transformer has a 1 Amp fuse which is also what the variable transformer calls for. So with the current limiting engaged the fuse shoudn't blow.
The red bulb indicates power on, the orange bulb is across the resistor so the more current is going through -> the bigger the voltage across the resistor -> the brighter the lamp will glow.
I'll have to get a label maker and add some labels.
The variable transformer is an old Lübcke unit I saved a few years ago from a piece of industrial gear that was going to be scrapped... Knew I'd have some use for it eventually. It feeds into an isolation transformer either directly or via a current limiting resistor. The resistor is 470 ohms, so at full 230V output it will limit the current to ~0.5 amps (at which point the resistor will be dropping the whole voltage and the output will be zero). 230V*0,5A = 115W, the power rating of the resistor is 200W so that should be fine. It will probably heat up the enclosure quite a bit if left running at full limit for extended periods but I have no plans of doing so. Maybe I could add a temperature switch as a failsafe.
The isolation transformer has a 1 Amp fuse which is also what the variable transformer calls for. So with the current limiting engaged the fuse shoudn't blow.
The red bulb indicates power on, the orange bulb is across the resistor so the more current is going through -> the bigger the voltage across the resistor -> the brighter the lamp will glow.
I'll have to get a label maker and add some labels.