I ordered a few of these (http://www.adafruit.com/products/1439) in various colors and styles for a project. Today, I soldered some leads on them and decided to test them out on my breadboard. I can't get them to light up. I've set up a test circuit with another LED and confirmed that it lights up when inserted, but then when I plug in the buttons, nothing happens. I'm wondering if there is something dumb or obvious that I may be missing...
I know that normally I would be expected to provide a circuit diagram and/or code, but this situation is so simple that I think it's probably not necessary. +5v -> 10k resistor (also tried 1k) -> LED -> ground. Test LED lights when inserted. Button does not.
With my multimeter, I've determined that the large pins on the button are controlled by the switch, so the small pins must be the LED. I have confirmed that I have 5v between the pins. I've also tried my multimeter's diode test function, and get an open condition in both directions.
Have I got bad LEDs here? Is there something I could have accidentally done in my fiddling around to destroy them?
Thanks in advance.
SOLVED: 16mm LED buttons not lighting
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- joshuabardwell
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SOLVED: 16mm LED buttons not lighting
Last edited by joshuabardwell on Mon Aug 19, 2013 3:39 pm, edited 1 time in total.
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Re: 16mm LED buttons not lighting
You are using too high of resistors for it. Read here:joshuabardwell wrote:I ordered a few of these (http://www.adafruit.com/products/1439) in various colors and styles for a project. Today, I soldered some leads on them and decided to test them out on my breadboard. I can't get them to light up. I've set up a test circuit with another LED and confirmed that it lights up when inserted, but then when I plug in the buttons, nothing happens. I'm wondering if there is something dumb or obvious that I may be missing...
I know that normally I would be expected to provide a circuit diagram and/or code, but this situation is so simple that I think it's probably not necessary. +5v -> 10k resistor (also tried 1k) -> LED -> ground. Test LED lights when inserted. Button does not.
With my multimeter, I've determined that the large pins on the button are controlled by the switch, so the small pins must be the LED. I have confirmed that I have 5v between the pins. I've also tried my multimeter's diode test function, and get an open condition in both directions.
Have I got bad LEDs here? Is there something I could have accidentally done in my fiddling around to destroy them?
Thanks in advance.
Source: http://www.adafruit.com/products/1439There are two contacts for the button and two contacts for the LED, one marked + and one -. The forward voltage of the LED is about 2.2V so connect a 220 to 1000 ohm resistor in series just as you would with any other LED to your 3V or higher power supply.
The led in those buttons are 2.2v @ 10mA and your using 5v;
So math time:
R = (V1 - V2) / I
R = (5v - 2.2v) / 0.01A
R = 280ohms
So you need atleast a 280ohm resistor to make that led light up.
Also the led lights up separately from the button, so pushing the button will not turn the led on or off.
- joshuabardwell
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Re: 16mm LED buttons not lighting
Thanks for the response. I've tried resistors with values from 200 ohms to 1k-ohm and even higher (10k, by accident). Just to be really, really sure, I put a 1k pot in circuit and ran it from 200 ohms (measured on my multimeter in real-time) up to 1k. The LED didn't light.
- adafruit_support_bill
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Re: 16mm LED buttons not lighting
1K ohms should still work. It will just not be as bright. Are you sure you have the polarity correct? Have you tried reversing the leads?
Most diode testers don't work well on LEDs.I've also tried my multimeter's diode test function, and get an open condition in both directions.
- joshuabardwell
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Re: 16mm LED buttons not lighting
Yup. Tried the leads both ways. Confirmed 5v at the pins.adafruit_support_bill wrote:1K ohms should still work. It will just not be as bright. Are you sure you have the polarity correct? Have you tried reversing the leads?
Not enough forward voltage in the test current to open the diode?Most diode testers don't work well on LEDs.
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Re: 16mm LED buttons not lighting
Did you hook it up directly to the the 5v line at all without any resistors? Because if so you may have fried it...joshuabardwell wrote:Thanks for the response. I've tried resistors with values from 200 ohms to 1k-ohm and even higher (10k, by accident). Just to be really, really sure, I put a 1k pot in circuit and ran it from 200 ohms (measured on my multimeter in real-time) up to 1k. The LED didn't light.
I recommend getting one of these as I have one and they are wonderful for testing led's: http://www.vellemanusa.com/products/vie ... &id=522875joshuabardwell wrote:Yup. Tried the leads both ways. Confirmed 5v at the pins.adafruit_support_bill wrote:1K ohms should still work. It will just not be as bright. Are you sure you have the polarity correct? Have you tried reversing the leads?
Not enough forward voltage in the test current to open the diode?Most diode testers don't work well on LEDs.
- adafruit_support_bill
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Re: 16mm LED buttons not lighting
Correct. 5v without a resistor would kill it pretty quickly.Did you hook it up directly to the the 5v line at all without any resistors? Because if so you may have fried it...
- joshuabardwell
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Re: 16mm LED buttons not lighting
It's ... possible ... that I did this, yes. When I first got them, I wasn't sure if they had internal resistors or not (I know--read the product page--it's right there!) and I used a 9v battery to try to figure out which set of pins lit them up. Neither set of pins lit them up (because I fried them), so I switched to a multimeter. So... mystery solved, I think.adafruit_support_bill wrote:Correct. 5v without a resistor would kill it pretty quickly.
I realize how dumb this must sound to somebody who already knows this stuff, but I'm a rank beginner, so thanks for bearing with me.
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Re: 16mm LED buttons not lighting
Yep using a 9v battery, without using any Proper resistance, would of definitely fried them soooo fast that there would of not even been a blink........joshuabardwell wrote:It's ... possible ... that I did this, yes. When I first got them, I wasn't sure if they had internal resistors or not (I know--read the product page--it's right there!) and I used a 9v battery to try to figure out which set of pins lit them up. Neither set of pins lit them up (because I fried them), so I switched to a multimeter. So... mystery solved, I think.adafruit_support_bill wrote:Correct. 5v without a resistor would kill it pretty quickly.
I realize how dumb this must sound to somebody who already knows this stuff, but I'm a rank beginner, so thanks for bearing with me.
Well now the only thing you can do is open the switch up and replace the dead leds; because I doubt Adafruit will exchange them for you frying the leds... But it never hurts to ask.
- joshuabardwell
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Re: 16mm LED buttons not lighting
Well, I only fried two of them, so I think for a total cost of $2, I'm just going to call it an object lesson and go on about my life. Thanks for the input everybody!EternalCore wrote:Well now the only thing you can do is open the switch up and replace the dead leds; because I doubt Adafruit will exchange them for you frying the leds... But it never hurts to ask.
Please be positive and constructive with your questions and comments.