Fuse project

[Doc_Bob]

I was asked to have a little demonstration on how fuses work. So, I wanted to have some car fuses "melt" as part of the demo. I want to demonstrate how the little metal link melts and the plastic housing stays intact. Now, how do I do it? Safely? Without starting a fire
Bob

 

[Jagmandave]

Just touch it to a car battery for a moment, it'll pop immediately!

 

[slowrev]

A variac transformer or variable power supply that will handle the current the fuse requires to blow, Plus about 30% with a load hooked up that will draw more current than the fuse can handle. A light bulb ? big power resistor, etc.
Hook an ammeter in series with the fuse so people can see how much current is going thru it, slowly crank up the voltage/.current and watch it blow.

 

[slowrev]

Umm, I always wondered how they test fuses to be sure they will blow at the proper amperage

statistical sampling I assume.

 

[jinman]

Use a very small amperage fuse and a 15 amp rated switch in series with the battery or jumper battery like Jagmandave suggested. Use big alligator clips on each end to attach to the battery terminals, and make sure the switch is open before connecting the clips. The switch will keep you from drawing an arc in the open when you short out the terminals. If you want to be super safe, use two fuses with one about 5 amps more than the other. You might also wire all this into a fuse holder, but a bunch of alligator clips always makes things look "dangerous."

 

[Doc_Bob]

A variac transformer or variable power supply that will handle the current the fuse requires to blow, Plus about 30% with a load hooked up that will draw more current than the fuse can handle. A light bulb ? big power resistor, etc.
Hook an ammeter in series with the fuse so people can see how much current is going thru it, slowly crank up the voltage/.current and watch it blow.

Wow! Where would I get a variac transfomer?????? Any brick and mortar shops have them??
Bob

 

[IH3444]

Got three of em, for lab use only......

 

[Doc_Bob]

Got three of em, for lab use only......

3?? Why do you need 3? I only need one
Bob

 

[IH3444]

Collected up over the years from other labs which had been disolved. One is out on loan now, so I guess I need to check on that one. Thanks for the remind. Are you going to post a picture of the poped fuse? Or better how about a mini video?

 

[mwechtal]

I was asked to have a little demonstration on how fuses work. So, I wanted to have some car fuses "melt" as part of the demo. I want to demonstrate how the little metal link melts and the plastic housing stays intact. Now, how do I do it? Safely? Without starting a fire
Bob

Bob,
From some ham radio sources, I've heard that the cheap no-name chinese fuses will sometimes melt and burn the plastic case, and the metal link is still intact. You might want to use Buss or Littlefuse brand fuses to be sure the fuse actually fuses!

Mike

 

[BB_TX]

Sounds like a classroom type demo. Get some fractional (or at least very low) amp fuses, some wire, some alligator clips, and a nine volt lattern battery. Make up two wires with clips on each end. Clip a wire to each side of the fuse. Then clip/touch each wire to the battery posts

 

[slowrev]

Sounds like a classroom type demo. Get some fractional (or at least very low) amp fuses, some wire, some alligator clips, and a nine volt lattern battery. Make up two wires with clips on each end. Clip a wire to each side of the fuse. Then clip/touch each wire to the battery posts

good idea, or maybe a 12v battrery and one lamp that draws less than 1 amp and another one that draws 2 amps. Use a 1 amp fuse. get the idea ?

 

[Doc_Bob]

Are you going to post a picture of the poped fuse? Or better how about a mini video?

I will definitely do a video.
Bob

 

[BB_TX]

Nine volt lattern battery??? I am not sure where my head was. A 6 volt battery or put 2 together to make a 12. Even though they are 12 volt fuses, a 6 volt battery would blow it.
The light bulbs are a good idea. And if you wanted to get fancy, use a variable resistor so you could gradually increase the current, watch the bulb grow brighter, then POP, all goes dark.

 

[KYErik]

How about a small 12 volt battery charger? Use a 10 amp fuse and start the charger up on the "low" ex. 2 amp setting showing that the fuse can handle that much current, then switch the charger up to the high setting and watch the fuse burn in two.

 

[Doc_Bob]

How about a small 12 volt battery charger? Use a 10 amp fuse and start the charger up on the "low" ex. 2 amp setting showing that the fuse can handle that much current, then switch the charger up to the high setting and watch the fuse burn in two.

Would it blow the charger???? I know this is a silly question, but I am good at that?!
Bob

 

[AlanB]

I am thinking you may be doing this in a class with Kids? And I am guessing that you are willing to put at least a little time into it.

How about a small battery etc. then a series of switches that you can add in various size rated light bulbs one at a time

If you had say 5 or 10 individually switched bulbs, of assorted sizes, then you can play a game with the kids of which can work, and they will see the various results, kind of cause and effect, and it will draw them into the demo instead of letting them just observe.

I would do it with 12V stuff as that is plentifull, and you could do something like say, a driving light, a tail light (like an 1157 with 2 filaments) a headlight maybe a dome light or clearance light, or maybe some LED trailer lights.

I guess it is all in how much time and $ you would be willing to put into it. I know several stores have helped considerably, or just flat given me stuff when I have done it for my kids school, and explained to the manager what I was doing. Heck, make it nice and the auto parts store may want it as a demo for the guy that comes in and just does not get it why he cannot run his driving lights, car stereo with Mega amp and 8 cell phone chargers of that 10a fuse tap

 

[KYErik]

Would it blow the charger???? I know this is a silly question, but I am good at that?!
Bob

No- because on the 2 amp setting, the charger should only be making about 2 amps. On the high setting, the fuse will blow. My small charger has an internal thermal circuit breaker that will cut out if it shorts out.