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SMD resettable fuse


#1

After just lost my FEZ Domino I am wondering, -is it possible to implement a resettable fuse on future boards?
I really dont know what happened with the Domino but it is obviously fried. The Domino was attached to a USB hub with external power supply so it was probably able to deliver more than the 500mA normally supplied by the USB standard.

Lets face it, many of us are not electrical engineers and devices like the Domino and Panda is aimed at the hobby marked and we work on breadboards with wires going everywhere, so a short is bound to happen.
Ill rather have a board that shuts down so I can check my circuit than having to replace a $75 board.

So is this possible?


#2

I would second that idea, if possible.

FYI, I had the exact same configuration : connexion to powered hub and external power on Domino. Could it be a clue ?

Even though I’m still crying for my lost Domino, I feel “happier” that someone else got the same problem under the (almost) same conditions. I feel less responsible :-[


#3

Well, if connecting the fez to a powered hub and external power supply could be the cause, the crew could maybe do some tests?

I have had my fez connected to a powered hub and external power supply several times (even with 2 DC motors attached which drew a lot of current)

So far (luckily) I did not encounter any problems.


#4

A fuse will not help at all. The problem is not in power but either static or something wrong on the ios

With thousands of these out already and onle 2 bad ones so far, I think the design is rugged :slight_smile: especially that most users have no idea what they are doing


#5

I have to agree with Gus - I literally screwed my Panda (prototype). I shorted it using a metal screw and standoff that shorted between 3v3 and some IOs, and it’s still working fine

(fingers crossed it stays that way :slight_smile: )


#6

From power connector to the processor, there are 2 regulators, a diode and 3 capacitors. I doubt you will ever damage the processor from anything wrong you do on power. If you were to damage something then it will be the regulator not the processor, which is unlikely to happen.


#7

Im not saying that there is something wrong with the power supply. My thought was that if the circuit started drawing more current that the processor could handle it would shut down. Hopefully before the processor got damaged.
You guys knows more about these things than me so I have no problem with saying this probably was a bad idea. :-[


#8

I understand your concern. I was only explaining that adding a fuse will not save the processor from getting damaged :frowning:


#9

interesting my dominoe is fine however at the weekend i did manage to create a spark when plugging in a external power supply when the domino was also connected to a powered hub. i`m not nessasarily saying this has anything todo with the above comments or not just adding my own experiances to say it may be possible if both powers are connected ? on a side note i was being lasy and powering a small board from the 5v pin on the domino and didnt want to draw to much from my usb port, and yes i know i probably sjhould have setup the external board properly.


#10

A fuze would be useful in one case. If you have a 5A power supply and accidentally short an unregulated pin to ground somewhere then you can fry that track.

If you short any other the other power rails then the regulators will limit the current. It’s just the unregulated rail that can be a problem…