Was this Schrödinger’s Fuse ?

[Michael GilliganParticipant @michaelgilligan61133]

[Michael GilliganParticipant @michaelgilligan61133]

After 15 years, we finally had a fuse blow in the car

This was attributed to co-pilot error, because a USB plug, for the GPS, was inserted into the ‘cigarette lighter’ socket … without the adapter

The protective fuse blew, as it should.

Where it gets interesting is that the fuses are Littelfuse 357 series ‘Smart Glow’

**LINK**

https://www.littelfuse.com/industries/passenger-car/blade-fuses.aspx

The concept being that there is an LED indicator within the fuse which lights-up when the actual fuse blows. **LINK**

https://ripitapart.com/tag/smart-glow-fuse-review/

I was unaware of this until after I had removed the fuse [there is no mention in the driver’s handbook] but, on, subsequent testing I could produce no ‘Smart Glowing’

.

Referring back to my first link … we see that, although they are still available, the 357 is obsolete, and has been replaced by the 387 [which appears not to be ‘Smart Glow’]

Can anyone advise ?

… Did these things ever work, and if so … under what circumstances ?

MichaelG.

[SteviegtrParticipant @steviegtr]

I guess for the light to glow the short circuit would have to be still present, giving a circuit/ path. If the circuit was clear then there would be no path to complete the led glow circuit.

Just a thought.

Steve.

[Michael GilliganParticipant @michaelgilligan61133]

Thanks for the thought, Steve

I suppose that’s what really made me think of Schrödinger

The ripitapart page that I linked says :

Simply put, this acts like any other automotive fuse would. The only difference is that the LED will illuminate if the fuse is blown, and sufficient load is still present in the circuit to provide enough current for the LED to act as a fault indicator.

But I struggle to understand that state of affairs ^^^

MichaelG.

Edited By Michael Gilligan on 09/09/2020 13:41:50

[SteviegtrParticipant @steviegtr]

Well i guess it is assuming that you had say a wiring short somewhere on the vehicle. Or maybe a rusty lampholder that was shorting to earth. Blowing the fuse, then there being still a fault circuit present the fuse would glow. Showing which fuse had blown without checking all. scenario you had. Item inserted, fuse blown, item retracted. So your circuit was now fault free. Giving no earth return path for the led. Or have i miss read what you meant.

Steve.

[Neil WyattModerator @neilwyatt]

It's only going to work if you haven't cleared the fault to earth.

If it's blown by a transient or you unplug the cause, it won't work.

Neil

Me: "Do you have a book on Schrödinger and Pavlov?"

Librarian: "I'm, not sure, but it rings a bell."

[Michael GilliganParticipant @michaelgilligan61133]

Thanks, both

The original short-circuit was obviously cleared by rather promptly removing the USB plug from the lighter socket.

I pulled the fuse with everything switched off, so never observed it in glowing [or probably not] in-situ.

After removal, I tried testing it with a resistance meter, and also simply connected to 12V, and it appears dead.

My best guess, so far, is that the Smart Glow burned out when the fuse blew … which would make the whole concept questionable … which is why I asked whether they ever worked usefully, and why I mentioned that they were obsolete.

There may [or may not] have been a blinding flash of light deep inside the glovebox at the instant of failure.

MichaelG.

[GeorgineerParticipant @georgineer]

Posted by Neil Wyatt on 09/09/2020 14:10:29:

It's only going to work if you haven't cleared the fault to earth.

If it's blown by a transient or you unplug the cause, it won't work.

Neil

Me: "Do you have a book on Schrödinger and Pavlov?"

Librarian: "I'm, not sure, but it rings a bell."

Neil, I'm sure you could have worked Heisenberg in there somewhere…

I had one of those LED fuses blow from a momentary fault, and the LED then passed enough current to make a plug-in dashcam indicate that it was powered up, but not to actually function. That made it appear that the dashcam was faulty. Once I found out the real cause, I threw away all my LED fuses.

George B.

[Neil WyattModerator @neilwyatt]

Posted by Michael Gilligan on 09/09/2020 14:30:44:

After removal, I tried testing it with a resistance meter, and also simply connected to 12V, and it appears dead.

Did you try both polarities?

If it's an LED, it would only pass current with the test probes one way round.

Neil

[Mick B1Participant @mickb1]

The uncertainty principle ringing my bell is how anybody managed to stuff a USB connector into a cigar lighter socket and have anything happen at all… ?

[Mike PooleParticipant @mikepoole82104]

I think most indicators should be taken with a pinch of salt, many things have been tried but testing is the only way. I had a fault on a programmable controller input rack, the indicators said all the correct inputs were on but the pc was not seeing them, it turned out there was a short on the machine dragging the 24v down to about 17v which was below the input threshold for the pc to see the input on but the indicator was near full brightness.

Mike

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Mick B1 on 09/09/2020 14:57:09:

The uncertainty principle ringing my bell is how anybody managed to stuff a USB connector into a cigar lighter socket and have anything happen at all… ?

.

It’s very simple, Mick … The GPS has a USB connector which plugs into an adapter:

One somehow got detached from t’other, and co-pilot [on autopilot ?] simply popped the USB into the socket … it drops in comfortably, and shorts the terminals.

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 09/09/2020 14:32:50:

Posted by Michael Gilligan on 09/09/2020 14:30:44:

After removal, I tried testing it with a resistance meter, and also simply connected to 12V, and it appears dead.

Did you try both polarities?

If it's an LED, it would only pass current with the test probes one way round.

Neil

.

Yes both polarities … and no, you are wrong [it’s not an LED, it’s two] : have a look at the ripitapart link that I posted.

MichaelG.

[SillyOldDufferModerator @sillyoldduffer]

Posted by Michael Gilligan on 09/09/2020 14:30:44:.

…

There may [or may not] have been a blinding flash of light deep inside the glovebox at the instant of failure.

MichaelG.

The answer to the paradox is obvious. The LED in the glove box represents the convential cat but there are two observers, Michael and his wife. Michael's better half acted as Wigner's Friend so it's her fault the super-position collapsed. This fits in with another of my scientific theories which is: a woman's place is in the wrong. Convinced this view had nothing to do with my divorce, even though the judge made a silly fuss about it.

Altenatively, the universe split into two dimesions and the LED is OK in one and blown in the other…

In the real world, I like Michael's suggestion that fuse blowing takes out the LED &/ or resistor. The blurb says connections are made by loading an epoxy layer with metal powder. It doesn't strike me as reliable when the fuse goes bang. Could be a good idea that didn't quite work out.

Dave

[BazyleParticipant @bazyle]

I was once caught out by the fuses in the boarding house at school. We would daisy chain lots of individual desk lights off the one ceiling light until the fuse blew. I couldn't understand why the lights weren't working when the fuse wasn't blown. It turned out the old victorian hose was wired with fuses in both live and return and it was the return one that had blown as the live had been replaced by a substantial bit of 15A wire by the previous schoolboy electrician.

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