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Need help with something

Posted: Thu Oct 24, 2013 2:35 pm
by scarabcoder
Yesterday was my birthday :P , and I got:
1 full sized breadboard
1 wireless USB module
1 Mini speaker
1 Usb hub
100 560k resistors
25 5mm red super-bright LEDs

Everything worked, except the resistors. I had a few from my original Adafruit RPi starter kit (http://www.adafruit.com/products/955), and I replaced those with my new ones to test them out. It didn't work with the new resistors. I tried flipping them around, moving the LED, and when I put the original resistor back it worked. So for some reason, my new resistors don't work. Here is a link to where I bought them:
http://www.amazon.com/KOA-Speer-Through ... +resistors
Can someone tell me where I can get some that work for LED lights on the breadboard? I want something on Amazon or Adafruit, maybe eBay too. Thanks!!
--Nicholas

Re: Need help with something

Posted: Thu Oct 24, 2013 2:45 pm
by ShiftPlusOne
560k

The original ones you linked to were just 560, not 560000ohm. They're working fine, but the current you're getting isn't enough to light up and LED. Also, 100 of a single resistor value is a bit much. You would've been better off buying a kit of assorted resistors.

Edit: Also, keep in mind the pi should not provide more than 16mA per pin, so having high brightness LEDs makes no sense without having some sort of buffer for them.

Re: Need help with something

Posted: Thu Oct 24, 2013 3:01 pm
by scarabcoder
Thanks Shift!
I see why it didn't work now :)
But could you possibly link to somewhere where I can buy some that work for LEDs?

Re: Need help with something

Posted: Thu Oct 24, 2013 3:15 pm
by pluggy
Practically anywhere will sell suitable resistors, where you call home would govern where to buy them, I'd favour Ebay.

Anywhere between 200 ohms and 1k ohm would work for an LED. Be aware that if you're using the Pi's GPIO at 3.3 volts, the voltage may be insufficient for blue or white LEDs.

Re: Need help with something

Posted: Thu Oct 24, 2013 3:44 pm
by scarabcoder
Would these work:
http://www.ebay.com/itm/100-x-Resistors ... 4ac73b54d7
(Sorry, I just want to confirm :D)

Re: Need help with something

Posted: Thu Oct 24, 2013 3:50 pm
by ShiftPlusOne
I would strongly recommend that you don't buy 100 resistors of one value.

Re: Need help with something

Posted: Thu Oct 24, 2013 6:20 pm
by scarabcoder
Okay, thanks!
I went and ordered a 560 ohm resistors from eBay, hopefully these will work. Gotta tell the difference between 560 and 560k... :P

Re: Need help with something

Posted: Fri Oct 25, 2013 9:12 am
by Burngate
http://en.wikipedia.org/wiki/Resistor_color_code
It used to be far more useful, but surface-mount stuff doesn't use it.
Ribbon cable can use it, though the 26-way one I've just got from Maplin's has the connectors mounted the wrong way round, so
1 = Blue, 2 = Green, 3 = Yellow, 4 = Orange ...

Re: Need help with something

Posted: Fri Oct 25, 2013 10:29 am
by ShiftPlusOne
Not much help if you're even slightly colour blind =(. I never could read resistors as a result.

Re: Need help with something

Posted: Fri Oct 25, 2013 10:55 am
by toxibunny
I would actually recommend buying 100 resistors of one value, or rather of a few common values - say 330ohm, 1k and 10k. 330 ohm are handy for LEDs, and the 1k and 10k are handy for pullup/pulldown resistors, and also for lots of safety type current limiting.

This way, you've got a nice little collection for use with all sorts of switches and buttons and LEds, and you've got enough to combine them for different values (2 330ohm in series makes 660 ohm, 3 10k in parallel makes 3.3k, for example).

Why not? they're cheap enough...

Re: Need help with something

Posted: Fri Oct 25, 2013 10:59 am
by ShiftPlusOne
A few common values, I understand. But only 100 1k seems a bit like buying 100 of the same shirt when you don't have any clothing. (I am sorry, I am bad with analogies)

Re: Need help with something

Posted: Fri Oct 25, 2013 11:14 am
by toxibunny
Those packs of 100 seem to be a nice compromise between bulk discount and buying too much, at least from ebay. Fair point though..

Re: Need help with something

Posted: Fri Oct 25, 2013 5:49 pm
by pjc123
Rather then guessing what resistor is going to work or not, you should calculate it, or even easier use one of the very simple calculators that are available online like this one:

http://www.hebeiltd.com.cn/?p=zz.led.re ... calculator

Re: Need help with something

Posted: Fri Oct 25, 2013 6:13 pm
by pluggy
LEDs will light up if the current is within an order of magnitude, If you're absolutely fanatical and need it absolutely as bright as possible without cooking something you calculate it, otherwise a 1K will work. A superbright one will probably show signs of life with a 10k resistor. (But not 560k). I'd buy 100 1k, and 100 10k. You can do almost anything with digital electronics with 1k and 10k. The purists won't agree, but hell, life is too short to worry about resistor values......