Lesson 3 Resistors

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jedW
 
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Lesson 3 Resistors

Post by jedW »

Lesson 3, RGB LEDS, uses 250 ohm resistors but the pack I purchased, the Adafruit ARDX - v1.3 Experimentation Kit for Arduino, does not come with those resistors. I have tried using the other supplied but it doe snot work.

Should it work with the other resistors and therefore something else is wrong with my setup? or How can I get the 250's?

Thanks

FYI: My son and I love the starter pack

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adafruit_support_bill
 
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Re: Lesson 3 Resistors

Post by adafruit_support_bill »

Lesson 3 calls for 270 ohm resistors. Most any value between 220 and 1K should work for this lesson.

If it doesn't work with that range of values, post a photo of your setup.

jedW
 
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Re: Lesson 3 Resistors

Post by jedW »

Thanks for the help
Image links below

http://flic.kr/p/envDmC
http://flic.kr/p/envzFm

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adafruit_support_bill
 
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Re: Lesson 3 Resistors

Post by adafruit_support_bill »

Green-blue-red is a 5.6K ohm resistor. That is too high. Something between 220 ohm and 1K ohm should work.
http://www.hobby-hour.com/electronics/r ... ulator.php

jedW
 
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Re: Lesson 3 Resistors

Post by jedW »

But nothing between 220-1K was in the starter kit we purchased from AdaFruit, so we need to purchase new ones?

If so, We live a block from your office on Varick, can we buy from you?

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adafruit_support_bill
 
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Re: Lesson 3 Resistors

Post by adafruit_support_bill »

The ARDX kit should come with a number of 560 ohm resistors (Green, Blue, Brown, Gold). Are these the ones in the photos?

Make sure that you have the LED connected correctly. The led that comes with the ARDX kit is a common anode LED. The tutorial states:
If you are using a common ANODE LED insted of common CATHODE, connect the long pin to +5 instead of ground

jedW
 
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Re: Lesson 3 Resistors

Post by jedW »

Bill
Works great now. Thanks!
But my son and I are confused. We thought you had to go to ground to complete the loop. To go into +5 seems, well, wrong.
Explanation much appreciated

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adafruit_support_bill
 
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Re: Lesson 3 Resistors

Post by adafruit_support_bill »

There are 2 common types of RGB led: Common Anode and Common Cathode. With the Common Cathode, all the cathodes (negative sides) of the leds are tied together. With a Common Anode, it is the Anodes (positive sides) that are common. With a Common Cathode, you wire the cathode to ground and let the digital pins drive the anodes HIGH to turn the leds on. When using a Common Anode led, you wire the common anode to +5v and let the digital pins pull the cathodes to ground. In this way the LED lights when the output is LOW.

Although it may seem counter-intuitive, many LED driver circuits are designed for common anode operation because "low-side" drive circuits are generally simpler.

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