Unknown component identification

Jiggy-Ninja

http://www.adafruit.com/blog/2012/05...inout-diagram/

What is the component just below the USB connector, and to the left of the SOT transistor? I've seen something like this on a few other boards, but I can never place exactly what it is.

Kholdstare

Not very sure, as it can be either resistor or capacitor. But my bet is on capacitor.

AlephZero

The label looks like "501K" whcih would not be a standard value capacitor or resistor

I wouder if it's this (quote from http://arduino.cc/en/Main/arduinoBoardUno)
If the labelling convention is the same as for capacitors, the "501" would mean "50 foloowed by one zero", i.e. "500" which matches the stated fuse rating.

There are links to the schematic and board design from that web page, so they should give you the answer.

schip666!

I believe it is a fuse on the USB power in.
The schematic shows an F1 500ma fuse on the XUSB line (lower right corner):
http://arduino.cc/en/uploads/Main/ar...-schematic.pdf
And I think I can make out the F1 label, in magenta between the two components, on the layout picture here:
http://balau82.files.wordpress.com/2...-0-light-1.png

Kholdstare

Hmm. Did not think about fuse.

dlgoff

I was thinking some kind of optocoupler. e.g.

https://docs.google.com/viewer?a=v&q...kb7GUVCoYy-grA

Studiot

Yes it's a fuse.

See here

http://arduino.cc/forum/index.php?topic=107605.0;wap2

jim hardy

Good find Studiot

it's a ptc thermistor...
great idea - a fuse that resets itself after short is removed!


Only way to go when it's soldered in !

http://www.bourns.com/data/global/pd...TC_appnote.pdf
http://www.bourns.com/data/global/pd...short_form.pdf

Jiggy-Ninja

I wasn't referring to an IC.
This makes perfect sense. I had tried to look at the schematics, but all the various undifferentiated boxes of the Eagle (I assume) schematic left me a bit confied about what was what.

I had pulled out my multimeter and did a couple continuity tests, and found that one end is connected to one of the USB pins, and the other goes to the middle pin of the SOT MOSFET, which I had assumed was the gate, and looked around that area in the schematic.

Lesson: Don't assume pinouts! Check the damn datasheet! You know the saying.

The only PTC devices I've seen so far are the through hole ones that look like a large ceramic cap with the leads kinked in a little at the top. I had no idea they looked like this in SMD form. Though it makes sense since it would need a large surface area to dissipate heat from.