12 seconds with a dead short, or 12 seconds when slightly over current?
That might be two different answers.
On 3/21/2016 4:17 PM, Chuck McCown wrote:
Yeah, it does sound a bit pointless.
*From:* Josh Luthman <mailto:[email protected]>
*Sent:* Monday, March 21, 2016 2:16 PM
*To:* [email protected] <mailto:[email protected]>
*Subject:* Re: [AFMUG] Fuse question
12 seconds for a fuse to pop??? How is that event a fuse. That
sounds pointless.
Josh Luthman
Office: 937-552-2340
Direct: 937-552-2343
1100 Wayne St
Suite 1337
Troy, OH 45373
On Mon, Mar 21, 2016 at 4:14 PM, Chuck McCown <[email protected]
<mailto:[email protected]>> wrote:
The poe card would not be the cause, it would be the victim. The
AP or wiring would be the cause.
The polyfuse I am looking at takes 12 seconds to blow. Trying to
protect the power supply and other loads in parallel.
Not sure if that is fast enough to be of great value.
If one AP shorts out, you don’t want it taking down others that
are off the same power supply.
*From:* Josh Luthman <mailto:[email protected]>
*Sent:* Monday, March 21, 2016 2:07 PM
*To:* [email protected] <mailto:[email protected]>
*Subject:* Re: [AFMUG] Fuse question
Meh just replace the card if it's being troublesome.
Josh Luthman
Office: 937-552-2340 <tel:937-552-2340>
Direct: 937-552-2343 <tel:937-552-2343>
1100 Wayne St
Suite 1337
Troy, OH 45373
On Mar 21, 2016 4:05 PM, "Chuck McCown" <[email protected]
<mailto:[email protected]>> wrote:
Well, they have their downside.
A real fuse will be easier to notice when it is blown.
A poly fuse just cuts the current way down.
More of a troubleshooting issue than anything else.
But, if a fuse is blown, then you have to fix the circuit and
find a replacement fuse.
I do have LEDs and by unplugging the short circuit cable the
LED should come back to full brightness.
Just thinking out loud here. Want to make the right choice.
*From:* Josh Luthman <mailto:[email protected]>
*Sent:* Monday, March 21, 2016 2:02 PM
*To:* [email protected] <mailto:[email protected]>
*Subject:* Re: [AFMUG] Fuse question
Cheaper to run a polyfuse...why bother asking???
Josh Luthman
Office: 937-552-2340 <tel:937-552-2340>
Direct: 937-552-2343 <tel:937-552-2343>
1100 Wayne St
Suite 1337
Troy, OH 45373
On Mon, Mar 21, 2016 at 4:01 PM, Chuck McCown <[email protected]
<mailto:[email protected]>> wrote:
Still leaning toward the polyfuse. Not a lot of room,
fuses and fuse holders are more money.
*From:* Bill Prince <mailto:[email protected]>
*Sent:* Monday, March 21, 2016 1:51 PM
*To:* [email protected] <mailto:[email protected]>
*Subject:* Re: [AFMUG] Fuse question
Most of ours are now the DIN-mounted double feed that uses
the 5x20mm glass fuses. However, we also have a few legacy
sites that use the automotive blade fuses.
If something new came along, we would use what it uses.
bp
<part15sbs{at}gmail{dot}com>
On 3/21/2016 12:47 PM, Josh Luthman wrote:
We already stock 5x20mm fuses so keeping with the same
form factor would be nice. Anyone else using those same
DIN clip fuse holders have the same.
Josh Luthman
Office: 937-552-2340 <tel:937-552-2340>
Direct: 937-552-2343 <tel:937-552-2343>
1100 Wayne St
Suite 1337
Troy, OH 45373
On Mon, Mar 21, 2016 at 3:40 PM, Adam Moffett
<[email protected] <mailto:[email protected]>> wrote:
I have no strong opinions sir, but if it's a
replaceable fuse I do like the automotive blades
because every gas station has them.
On 3/21/2016 2:42 PM, Chuck McCown wrote:
I am considering adding a fuse to a new version of
my rack mount POE surge suppressors.
I know many of you like PTC resettable solid state
fuses. I don’t recall ever designing one in to
anything.
Maybe I did on a phone device years ago, but that
would have been to satisfy a regulatory agency only.
Studying up on them I learn that if you have a 1 amp
“hold current” the “always trip” current is 2 amps.
Not like a fuse, which is pretty well guaranteed to
trip at any current over the rating if you wait long
enough.
For a polyfuse, if your load is one amp, you have to
have a design value of greater than 1 amp hold current.
But then it takes double that to actually trip..
And then there is leakage current required to keep
it in the tripped condition.
It does not totally break the circuit.
They are fairly inexpensive compared to glass fuses
and fuse holders.
Could do auto blade fuses too.
Not sure I have the room for anything but a polyfuse
though.
Anyone have strong opinions about this?
