Electronics Gurus....what's this component on opto board?

[BadMouth]

starting to delve into the Logitech G27 steering wheel hack and everything seems more complicated....

The opto board has a resistor going to the IR LED and this other component (the green thing) that has one leg going to a shared ground (assumed based on MOMO opto board components and layout) and the other going to it's own pin on the harness.  I get that the resistor is probably to control the current to the LED, but what is this other thing and what is it's purpose.  The MOMO wheel I hacked had neither of these.  The pinout and wire colors appear to be the same except for the pin that goes to this thing.  I'd like to know more before I put a meter to it or try my other optical encoder.


So far, all the boards on the G27 say Snowball on them.  

[BobA]

Probably an NTC thermister.

Link

[MonMotha]

RT is indeed generically the designator prefix for "thermally sensitive resistor" aka a thermistor.  However, I'd guess it's a PTC rather than an NTC.  PTCs can be used as a crude, auto resetting fuse.  Then again, it may also be used to compensate for thermal effects on the LED, which may mean it's negative or positive, depending on the characteristics of the LED.

If you want to know, you can measure it.  If it measures lowish resistance at room temp, it's a PTC.  If it measures high resistance at room temp, it's an NTC.

[ed12]

yep thats a ntc

it is used to limt current per-say

ed

[BadMouth]

Thanks for the quick responses.  I'll read up on it and try to understand what purpose it's serving here and if it's really needed with the other self contained optical encoder.

[ed12]

green is n type  black is p type

ed

[andres0031]

hello I need to know the reference of black and transparent components. I dont want to buy the entire board is so cost!

[SavannahLion]

hello I need to know the reference of black and transparent components. I dont want to buy the entire board is so cost!

You mean the little doodles at the bottom of that picture?

It's an LED emmiter / reciever pair. Probably in the infrared range. If you're seeking to use the parts directly, I really have no idea what their part number is. I've been using whatever I have lying around. These things are very pervasive and easy to find.

If you're not too electrically inclined, tell us what you're trying to do and we can probably come up with a solution that's a good balance between cost and "ready to use" based on your skillset.