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Topic: Help me ID this component (MPS3904W81) (Read 1 time) previous topic - next topic

amjx

Hi all

I recently removed a hard drive from an Apple TimeCapsule and on the drive there was attached what I thought was some sort of thermal protection/measurement component that I could used with the arduino.

Picture of the component: http://bayimg.com/FabpiAAFa
Im pretty sure it says MPS3904 W81 on the component, But when i google that it looks like it is a regular transistor.
https://encrypted.google.com/#psj=1&q=mps+3904+w+81+

Then I wonder why solder a connector to the PCB, run two (yes 2) wires to the transistor and then glue it to the drive instead of just soldering it to the PCB directly. And if it is a transistor why is there only 2 and not 3 wires ?
(On the pic the top wire is connected to one leg and the bottom wire is connected to two legs, all though the pic does not show it too well)

Any help is appreciated
Best regards amjx

nickgammon

It looks like the base and collector are connected. I found this reference:

http://www.onsemi.com/pub/Collateral/AND8494-D.PDF

Judging by that you can connect the B and C and use it as a temperature sensor.
Please post technical questions on the forum, not by personal message. Thanks!

More info: http://www.gammon.com.au/electronics

amjx


nickgammon

This page:

http://forums.parallax.com/showthread.php/134352-Diode-transistor-temp-sensor

mentions:

Quote

The industry standard 'diode' seems to be a 2N3904 (diode connected).
Diodes are usually (appx) -2.2mV/°C

http://www.nxp.com/documents/application_note/AN10349.pdf

http://www.maxim-ic.com/datasheet/index.mvp/id/3000


Since that is the part you have, basically, I think that is a good guess.
Please post technical questions on the forum, not by personal message. Thanks!

More info: http://www.gammon.com.au/electronics

amjx


Since that is the part you have, basically, I think that is a good guess.


I think so too. It was glued to the disc and covered with foam and together with all the nice info you found it cant be any other thing.

Once again thanks

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