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Short Circuit Protection Using Fuse

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wuchy143

Member
Hello All,

I"m a novice hardware engineer trying to think of a way to keep a keyboard up and running even when the trackball which is connected to it(they share the same power rails) shorts out.

Currently there is a filter which I could populate with a fuse but am unsure if this is a viable option. Respinning the PCB seems like over kill and I think there has got to be a more cost effective solution. Does anyone think a fuse is a good idea? So when the trackball shorts out the fuse pops and basically creates an open between the trackball +5V and the keyboard +5v.

If a fuse is an ok solution what should I be concerned about when picking the component?


Thanks for any replies!!:)

-mike
 

wuchy143

Member
It is only a requirement in the spec. They just wanted to be sure that if for whatever reason the trackball shorts out(I would assume they want to protect against someone spilling water on the T.B) the keyboard will be unaffected. The keyboards provide control of very critical things and having the T.B short out could potentially cause the Keyboard to do bad things.

Does this answer your Q?

-mike
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Then use a fuse to feed it, a soldered in one would meet the requirements as it's VERY unlikely to ever fail.

For a start measure the current the track ball takes.
 

wuchy143

Member
Ok. How much margin should be used for something like this? Say for example the T.B uses up 60mA.(some do) Would a 120mA fuse be a good choice? Or is there another more scientific approach used?

I already have a 300mA fuse in stock so I may measure the current like you said and then see if the 300mA is a good one to try. Meaning solder it in and short out the T.B. It's a resettable fuse so if I remember correctly it should come back after it's cooled down.

-mike
 

MikeMl

Well-Known Member
Most Helpful Member
If there are any big bypass capacitors in the TrackBall, there may be a large current inrush when the power is first applied. I would measure the inrush transient as well as the steady state operating current...
 
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