I have hooked LEDs up to my variable power supply before. No resistor.
Eurddrue have a wee bit of common sense and look up what actually happens when you use a LED and Resistor in series. You know good ole ohms law.
I has another question...
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Rekarp
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Re: I has another question...
The wood master
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eurddrue
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Re: I has another question...
An LED that is used without a resistor will burn out somewhere around twice as fast. I have been told this by a wise old man who sends me free electronic goodies.
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wallydawg wrote:I think we should check to see if you can withstand 220 voltschainfire95 wrote:220V I believe
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Rekarp
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Re: I has another question...
Old wives tale. I hooked up a 3.3V led and it drew the exact amount of amps as said in the spec document.eurddrue wrote:An LED that is used without a resistor will burn out somewhere around twice as fast. I have been told this by a wise old man who sends me free electronic goodies.
A lesson in Ohms Law.
V=I*R that is Voltage = Amperage times Resistance
Lets say you have a 5V source and have a LED that has a forward voltage of 3.3V and a draw of 200mA.
5V-3.3V=1.7V
By Ohms law : 1.7V/.2A = 8.5 Ohms
You need a 8.5 Ohm resistor. They don't make these so a 10 ohm shall suffice.
The wood master
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eurddrue
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Re: I has another question...
supply voltage-2=x/.015~.02= rating of resistor you should use.<--formula
E.G 5v-2v=3v/.015=200
Don't ask me where Dave pulled this from, but that's all he told me about LEDs. And that if they're in series you can use 1 resistor, but if they are in parallel, then you need to use a resistor in front of each one.
E.G 5v-2v=3v/.015=200
Don't ask me where Dave pulled this from, but that's all he told me about LEDs. And that if they're in series you can use 1 resistor, but if they are in parallel, then you need to use a resistor in front of each one.
Banned indefinitely if you desperately need to contact me STOPPHONESPAMPLOX Please dont be a dick and call for something random like "HEY YURDRUE DOO U HAZ SPAM?"
wallydawg wrote:I think we should check to see if you can withstand 220 voltschainfire95 wrote:220V I believe
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Rekarp
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Re: I has another question...
eurddrue wrote:supply voltage-2=x/.015~.02= rating of resistor you should use.<--formula
E.G 5v-2v=3v/.015=200
Don't ask me where Dave pulled this from, but that's all he told me about LEDs. And that if they're in series you can use 1 resistor, but if they are in parallel, then you need to use a resistor in front of each one.
Well that formula is wrong. It is only correct for LEDs that have a forward voltage of 2V and a current draw of 20mAh. (its based on Ohms law)
eurddrue Dave is wrong I am sorry. But it is really hard to argue with against physics. If your supply voltage matches your forward voltage you do not need a resistor.
The wood master
"I was under the impression Mac owners don't actually USE their machines, they just parade them around trying to evangelize the masses."
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eurddrue
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Re: I has another question...
Rekarp wrote:eurddrue wrote:supply voltage-2=x/.015~.02= rating of resistor you should use.<--formula
E.G 5v-2v=3v/.015=200
Don't ask me where Dave pulled this from, but that's all he told me about LEDs. And that if they're in series you can use 1 resistor, but if they are in parallel, then you need to use a resistor in front of each one.
Well that formula is wrong. It is only correct for LEDs that have a forward voltage of 2V and a current draw of 20mAh. (its based on Ohms law)
eurddrue Dave is wrong I am sorry. But it is really hard to argue with against physics. If your supply voltage matches your forward voltage you do not need a resistor.
ok, I take your word. 
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wallydawg wrote:I think we should check to see if you can withstand 220 voltschainfire95 wrote:220V I believe