What is a current limiter and what’s its purpose?
A lighbulb current limiter is effectively a high-power resistor in series with the load. In this case the resistor is a lightbulb. The wattage of the lightbulb determines the maximum power that can be delivered to the load since they are in series. In my lightbulb current limiter, I also have a variac to vary the input AC voltage so that I can bring equipment up to operating voltage slowly for testing. The purpose of a lightbulb current limiter is for powering up equipment that is in an unknown state, especially valve equipment. For example, if you acquire an old valve psu, it is bd practice to just plug it into the wall and see what happens. If there is a problem on the secondary side of the transformer your brand new psu’s transformer could go up in smoke (ask me how I know).
Required parts:
- Incandescent lightbulbs (whatever wattage you want)
- Sockets for those lightbulbs (screw of bayonet)
- One switch per lightbulb (so that you can vary the amount of available power)
- Power cable of sorts (or a 3 prong plug and some ac cable)
- Wall socket (you will understand the purpose of this in the pictures)
- Some sort of enclosure for all this
- If you want to, also a variac
How to build it:
- Mount the bulb sockets, the wall socket, and the switches to your enclosure
- Mount the variac if you want to (it’s not required for the limiter to work)
- Follow the schematic to wire it up
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