Unknown component identification

In summary, the component just below the USB connector, and to the left of the SOT transistor, is most likely a fuse. This fuse protects the computer's USB ports from shorts and overcurrent. If more than 500 mA is applied to the USB port, the fuse will automatically break the connection until the short or overload is removed.
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  • #2
Not very sure, as it can be either resistor or capacitor. But my bet is on capacitor.
 
  • #3
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)
The Arduino Uno has a resettable polyfuse that protects your computer's USB ports from shorts and overcurrent. Although most computers provide their own internal protection, the fuse provides an extra layer of protection. If more than 500 mA is applied to the USB port, the fuse will automatically break the connection until the short or overload is removed.
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.
 
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  • #5
Hmm. Did not think about fuse.
 
  • #8
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/pdfs/Bourns_2010_industrial_PTC_appnote.pdf [Broken]
http://www.bourns.com/data/global/pdfs/bourns_auto_short_form.pdf [Broken]
 
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  • #9
dlgoff said:
I wasn't referring to an IC.
schip666! said:
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/arduino-uno-rev2-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/...-arduino_uno_ref-brd-eagle-5-10-0-light-1.png
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.
 

1. What is "Unknown component identification"?

"Unknown component identification" is the process of identifying an electronic component that is unknown or unmarked. This can be done by analyzing the physical characteristics and properties of the component, as well as conducting tests and using reference materials.

2. Why is "Unknown component identification" important in the field of science?

Identifying unknown components is important in science because it allows researchers and scientists to understand and analyze the functioning of electronic devices and circuits. It also helps in troubleshooting and repairing faulty equipment, as well as in designing and creating new technologies.

3. What are some common methods used for "Unknown component identification"?

Some common methods used for identifying unknown components include visual inspection, measuring electrical properties, using reference materials and datasheets, and conducting tests such as continuity, diode, and transistor tests.

4. Can "Unknown component identification" be done by non-scientists?

While knowledge and experience in electronics and circuitry is helpful, "Unknown component identification" can be done by non-scientists with the help of online resources and tools. However, it is important to exercise caution and safety measures when handling electronic components.

5. Are there any challenges in "Unknown component identification"?

Yes, there can be challenges in identifying unknown components, especially if they are damaged or have no visible markings. In such cases, additional tests and analysis may be required, and it may be difficult to find a definitive answer. It can also be time-consuming and requires a certain level of expertise.

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