Dim Bulb Tester Project

Need some input (no pun intended) on this next project. There are as many schematics as there are versions of this out there. But there is a lack of information as to component choice for the build based on what it will be used for.

I plan on doing a 3 bulb variety and have ordered some of the parts but no one really explains or goes into detail on the following:

Protection Fuse/Breaker:
Some folks use 1.5A others use 3A and still others 5A. I have done some power consumption research on audio equipment Tube and SS and I find that some of the larger amps and receivers have fuses that are as high as 8A. What to choose??

Toggle Switches:
Not a real big deal here but I ran across a guy with 40y+ Exp. (radio and TV repair) who built one using miniature switches. I have a bunch of the these which would be nice to save a buck or two. However, these type of switches seem to be rated between 2A - 5A.
Are these actually safe to use in this application?

Schematic is a pencil sketch at the moment so I can't post it right now. But any help would be appreciated.

EdStraker said:

Schematic is a pencil sketch at the moment so I can't post it right now.

Click to expand...

I don't understand that logic at all. Take a picture with your phone and post the pencil sketch.

Initial Schematic

I think that you should have the output lamp in parallel with the output, not in series.

If any of the SPST switches are on, the limit lamp will illuminate when the bypass is on.

If the load isn't very big the bypass lamp will illuminate when the limit is being used.

Breaker: If you want tight protection, you will meed multiple breakers in parallel. Close only the one that matches the load current you need.

Switches: A 2 A switch never should be used to control a 8 A load.

ak

Diver300 said:

I think that you should have the output lamp in parallel with the output, not in series.

If any of the SPST switches are on, the limit lamp will illuminate when the bypass is on.

If the load isn't very big the bypass lamp will illuminate when the limit is being used.

Click to expand...

I want the output lamp lit in bypass or limit. But I see your point.
bypass lamp in series between SPDT and VM?

Dim Bulb tests are useful for limiting the energy of power converters if a fault occurs.

The incandescent bulb conducts 10x more power on startup, often just like like the Cap banks of PA's but then the series bulb when hot acts as current limiter. Keep this in mind and don't use the 2A switch when holding current fuse rating is 5A but the actual surge current can be 10x more.

Ideally use a breaker usually rated for 10kA surges but use the 2A switches as a selector before using the master input switch. It is the act of surge switching C on and L off (motors) that wears out switches the most.

- you do not need to switch Neutral.
- An alternative method to a tungsten bulb which is a PTC device is use ICL's (aka NTC) for soft start and Polyfuses (aka PTC) for power limiting selectable switches to gang parts in parallel.

Tony Stewart said:

- you do not need to switch Neutral.

Click to expand...

Just me being over cautious.

Was going to use 16A toggles originally anyway, was wondering if the 6A mini toggles were still safe was all. I guess....No.
I was also going to go with a 5A Thermal Breaker as well. Until I saw some equipment with 6A and 8A slow-blow fuses so I thought I'd pose the question. Just didn't want the breaker tripping in bypass for that kind of equipment test.