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[on:]

hai

i'm very inspired with usb fuse 500ma at arduino board.
The smd style absolute to me...
Any information about small 500ma fuse?
The ordinary(glass tubular and with metal tube at end of glass) very large also.

Jeckson
makassar

[Reply #1 on:]

Google 'polyfuse' for more info

[Reply #2 on:]

Richard Crowley, thanks for sharing! I have this question too. Now that I have a "decent" pcb design being made, I need a fuse like that to protect against exccessive current on power and I/O lines.
Is a surface mount ressettable fuse a good choice to put on I/O lines or opto-isolator?

[Reply #3 on:]

Is a surface mount ressettable fuse a good choice to put on I/O lines or opto-isolator?

Well a resettable fuse is OK for over current protection they are much too slow for over voltage transients that can also cause damage.

Lefty

[Reply #4 on:]

he fuse on the Duemilanove board is probably something like this...
http://www.bourns.com/ProductLine.aspx?name=polymer_ptc_resettable_fuses_multifu...

The MF-R?? type which are not smd.

Little help info where's MF-R?? types(no smd) to find at cheap price.

Well a resettable fuse is OK for over current protection they are much too slow for over voltage transients that can also cause damage.

The spark gaps at PCB and (voltage regulator+diode) will fix that??

Thank's
Jeckson

[Reply #5 on:]

If you complete your profile and reveal WHERE you are, we might be able to make some useful suggestions. Telling us what "cheap price" means to you would also be helpful.

I'm from Makassar...Indonesia.No one name Jeckson at This town except me.  8-)

Means competitives prices.Seems that Chinese product...??

Thank you
Jeckson
Makassar

[Reply #6 on:]

Is a surface mount ressettable fuse a good choice to put on I/O lines or opto-isolator?

You can't get a fuse of any type that will protect against the 40mA limit of an I/O pin, anything greater is not worth putting on the outputs.

My motto has always been that a semiconductor is a device that protected a fuse. That is it will blow before the fuse blows. If you blow a fuse you normally blow a semiconductor.

The only useful application is where you have a large current capability output and you can afford to limit this to at least a quarter of the output with a fuse - this is especially true of resettable poly fuses which take an age to go (up to three seconds).

[Reply #7 on:]

WHY do you think you want to use a poly resettable "fuse"?  "Inspiration" is not sufficient reason to use one in a design. What exactly are you trying to protect with the fuse?

I think all my USB experiment used that kind of fuse.my usb dev. board didn't used that fuse.
Have old module which the schematic and info no longer available...tha t I planned power from USB port.

Thank you
Jeckson