hub fuses

[jeffcoast]

I googled how they work, it is some kind of polymer that expands when heated as more and more current goes through it, once it gets too hot the current stops flowing. Once it cools, it just starts working on its own.

[rimist]

Cool

[Steve Gase]

before I assemble 12 LE units, and repair my active hubs I would love to know if this will work.

is anyone up to investigating?

I am wondering, though... as the part cools, and power is again restored: will safety be a problem if current is reintroduced over and again -- even if the time before the next 'trip' is short?  in the applications that use this part, is the expectation that the short is quickly fixed?

[dowdybrown]

before I assemble 12 LE units, and repair my active hubs I would love to know if this will work.

is anyone up to investigating?

I am wondering, though... as the part cools, and power is again restored: will safety be a problem if current is reintroduced over and again -- even if the time before the next 'trip' is short?  in the applications that use this part, is the expectation that the short is quickly fixed?

The failure mode I experienced with my smart strings was that a node would get wet and spark and burn resulting in a permanent short until the string was repaired. Plugging the failed string into any other socket on the hub would cause another fuse to blow.  The resettable fuse still won't prevent a node from burning, but it should safely prevent having to replace hub fuses after such an event.

Btw, they are commonly used in PCs.

Matt

[TheBanker]

Interesting.....I think I have many blow fuses also.


Sent from my iPhone using Tapatalk

[RJ]

Think about it guys, The resettable fuse does not trip and then stay off until the short is fixed. It cools down and applies power again.
Now go look at the fuse charts for trip times. How long will the fuse keep power applied at say 6 amps? 8 amps? 10 amps?
Ok so lets think it through you have a short for 10amps and it keeps power on while the fuse heats. Then the fuse trips and cools ver quickly as they have little mass. It then applies the power again but leave it on while it heats which takes longer than cooling. It then trips to do this again.
Meanwhile the plastic RJ45 jack and plugs rated at about 5 amps are starting to melt or catch fire, the wire is burning an shorting even more. 

This is not good imagine you are not there and this happens.
Now the fuse will trip after a time (does not mean node will not burn as this is what is doing the fuse in) and then no power is put back on circuit until intervention of the user to rectify the issue. Yes this also means changing the fuse.
 
These are great for certain things but not as safty for this type of setup. When you blow a fuse you should have blown a fuse. Circuit breakers are a different thing and they would work but they are way to costly and most do not like harsh enviroments. 

Safety should always out weight convienance.

RJ