5A Blade Fuse with LED Indicator - Orange

pmflav said:
Thinking about replacing all of my fuses with these. At about $1 ea they aren't overly cheap, but love the indicator. So if the fuse blows the light glows.
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Or with a normal fuse, if the fuse blows the lights go out. ;) :D

But a nice addition for very quick diagnosis without the need to pull the fuse to check
 
just be really careful with this kind of thing.. What happens if the led fuses shut. ( which it coudl ).. Youv'e just repalced your circuit protection with a wire.


This kind of product seems nice, but you open yourself up to a bunch of uninteneded consequences.. You'd nto pass UL8750 with kind of thing.
 
I was just wondering something about these fuses.


1. Are we sure they glow when the fuse is blown? Or, do they glow when the fuse is operational?
2. If they glow when blown, where is it getting its' ground/return from for the LED to glow? Is it leaking voltage into the circuit? There isn't a return as part of a two pronged fuse, so how does it complete the circuit in order to glow?


I have light switches that have a LED light in the paddle. When the circuit is switched off, the LED in the switch glows. (Makes it easy to find the switches in a pitch-black room.) I found that a minute amount of electricity is flowing through the circuit to make this happen. Even here, when a light connected to this switch blows, the LED in the switch no longer glows.
 
algerdes said:
1. Are we sure they glow when the fuse is blown? Or, do they glow when the fuse is operational?
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They glow when the fuse its blown. the led is wired in parrallel with the fuse. If the fuse is good, there is an effective short across the led, so the voltage drop across it zero. It wont' light up.


If the fuse blows, the short is removed.. so you can form a voltage drop across it.

>2. If they glow when blown, where is it getting its' ground/return from for the LED to glow?


It works as long as what ever caused the short is still there. If that happesn to be the hunk of solder you accidently dropped on your device when you where fixing it, or a bad component.
 
multicast said:
If the fuse blows, the short is removed.. so you can form a voltage drop across it.

It works as long as what ever caused the short is still there. If that happesn to be the hunk of solder you accidently dropped on your device when you where fixing it, or a bad component.
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OK, I understand.
One additional question.
If the purpose of blowing a fuse was to remove power from the malfunctioning device to protect it and its associated wire, wouldn't the LED provide a second path for that same (unwanted) electricity to travel through?
 
algerdes said:
OK, I understand.
One additional question.
If the purpose of blowing a fuse was to remove power from the malfunctioning device to protect it and its associated wire, wouldn't the LED provide a second path for that same (unwanted) electricity to travel through?
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Yes, it does. It relys on the fact that there will be a current limiting resistor in series with the LED. Which will set the maxium currnet that shoudl flow.. Of course if that resitor fails...

You can see then why this is not a great idea, and yout cant' get any safety certs if you put such devices in line.
 
multicast said:
You can see then why this is not a great idea, and yout cant' get any safety certs if you put such devices in line.
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That is exactly what I was thinking about. Thank you for clarifying.
 
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