sjrapid
Posts: 9
Joined: Sun Oct 21, 2012 8:43 pm

Gertboard Kit - Swapping the LEDs for another colour/size

Sun Jan 20, 2013 9:48 pm

I'm (finally) in the process of building my Gertboard Kit, and I want to swap the leds provided (3mm) for something bigger and also 4 each of green, yellow, red.

The Farnell part number on the LEDs in the kit is 158-1113. Farnell's web site says that this led is rated at 2v, 20mA. This suggests a 68R resistor in series when running from 3V3, yet the resistor networks seem to be 1K parts

Am I missing something here? Or do I just find some 2V 20mA leds in different colours and swap them out assuming that it will all work?

Comment welcome!

Best regards

Steve

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bgreat
Posts: 235
Joined: Mon Jan 23, 2012 2:09 pm

Re: Gertboard Kit - Swapping the LEDs for another colour/siz

Sun Jan 20, 2013 11:42 pm

You did not miss anything. The 20 mA is the maximum continuous current rating. It would be used to obtain the maximum rated brightness. It is not the normal operating current for most uses.

Enjoy!
Bill

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Gert van Loo
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Contact: Website

Re: Gertboard Kit - Swapping the LEDs for another colour/siz

Sun Jan 20, 2013 11:44 pm

The 2V, 20ma means that if you pump 20mA through it, you will have a voltage drop of 2V.
It does not always mean those are the recommended working conditions!!
Take a reasonable efficient (10-40mcd @10mA) LED and it will work very well.
You are unlikely to get an exact colour balance even if you take three colours with the same
intensity (expressed in candela ) your eye has different sensitivity for different colours.

sjrapid
Posts: 9
Joined: Sun Oct 21, 2012 8:43 pm

Re: Gertboard Kit - Swapping the LEDs for another colour/siz

Mon Jan 21, 2013 4:02 pm

Thanks for the helpful coments

Steve

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