Author Topic: $50 Robot LED Problems  (Read 3139 times)

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Offline SlotheryTopic starter

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$50 Robot LED Problems
« on: July 30, 2010, 02:32:24 PM »
Ok, so I have just finished my circuit board and I go to plug it in and I realize that the LED doesn't light up. I thought this was strange because a day before I had been probing my board and found that it lit up when I tested for continuity between it's anode and cathode. So is this supposed to happen. If not how can I check to see if my LED is broken/fix this problem?
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Offline Webbot

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Re: $50 Robot LED Problems
« Reply #1 on: July 30, 2010, 05:33:56 PM »
Lots of stuff about this on this forum.

The LED is NOT a power indicator. It will only light up if you tell it to by setting the corresponding pin low.
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Offline SlotheryTopic starter

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Re: $50 Robot LED Problems
« Reply #2 on: July 30, 2010, 07:59:57 PM »
I uploaded the code and it still won't shine leading me to believe the LED may be broken however how can I verify this?
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Offline Razor Concepts

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Re: $50 Robot LED Problems
« Reply #3 on: July 30, 2010, 08:04:24 PM »
remove the atmega8 and put 5v power directly over the led and resistor and see if it lights
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Offline Webbot

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Re: $50 Robot LED Problems
« Reply #4 on: July 30, 2010, 08:16:29 PM »
The usual set up is as follows:-

              
+5v -----
            |
            |
           ---
            \/       LED
            -
            |
            R        Resistor
            |
            |
         Processor Pin


So you have to make the processor pin low (ie 0v) to make current flow through the LED.

Quote
I uploaded the code and it still won't shine leading me to believe the LED may be broken however how can I verify this?
This will depend on what "the code" actually is and where you got it from (sorry but there are lots of versions out there I think). It will need to make the relevant io pin into an output AND set it low in order for the LED to light.

try what Razor Concepts said - but make sure you remove the chip first (with the power off) and make sure you connect the power across the LED+resistor not just the LED as that will blow it.

EDIT: Try using the Search function on this forum for "$50 LED" - theres lots of stuff !
« Last Edit: July 30, 2010, 08:19:18 PM by Webbot »
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Offline SlotheryTopic starter

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Re: $50 Robot LED Problems
« Reply #5 on: July 30, 2010, 09:07:49 PM »
Excuse me gentlemen,
but if my assumptions are correct you are talking to an idiot  ;D I was just probing the Led with a multimeter (probing at 2000 ohms) when I noticed that touching the red probe to the part of the LED which is farthest away from the DIP socket while holding the black probe to the lead closest to the DIP will illuminate the bulb. Therefore, I simply installed the LED backwards correct?
« Last Edit: July 30, 2010, 09:33:36 PM by Slothery »
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Offline Razor Concepts

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Re: $50 Robot LED Problems
« Reply #6 on: July 30, 2010, 09:37:02 PM »
Maybe not  ;D. When i bought the LED as listed in the parts list, the one i received was actually manufactured backwards with the short leg as anode and long leg as cathode. Maybe you received a dud LED also
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Offline SlotheryTopic starter

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Re: $50 Robot LED Problems
« Reply #7 on: July 30, 2010, 09:50:35 PM »
I am simply glad that I solved the problem and I thank you and the others for helping!
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Offline voyager2

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Re: $50 Robot LED Problems
« Reply #8 on: July 30, 2010, 10:19:44 PM »
Quote from: Razor Concepts on July 30, 2010, 09:37:02 PM
Maybe not  ;D. When i bought the LED as listed in the parts list, the one i received was actually manufactured backwards with the short leg as anode and long leg as cathode. Maybe you received a dud LED also
Yeah I've got some like that...

I received some that were meant to be warm white, but they were pink!
 
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