Someone help me figure out what size resistor i need
01-27-2007, 02:22 PM
#1
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Someone help me figure out what size resistor i need I am electronically challenged and all the input I need just doesn't make sense to me.
I would like 13000mcd 5mm leds in red to go in my car. To me I would put 12 voltage, but I read somewhere you need to use 13volts???
I don't know, someone just help me out here.
Also, if someone has a good place for me to order them from let me know.
I would like 13000mcd 5mm leds in red to go in my car. To me I would put 12 voltage, but I read somewhere you need to use 13volts???
I don't know, someone just help me out here.
Also, if someone has a good place for me to order them from let me know.
01-27-2007, 05:48 PM
#2
So you want to get 13 volts from 12 volts?
It won't matter to the led if you power it with 12 or 13 volts.
Your title says something about computing resistor value. In what context is this question?
Btw, in order to prevent led burnout, you need to limit the current flowing through. Most leds (depending on material of course) have a .7V drop across them, however they will fry when you send infinite current from your power source thus the need need for a resistor.
In general R=V/I (where V = volts, I = current, R= resistance in ohms). Find out what the nominal (not maximum) current spec is for the resistor of your choice, and plug it in to the equation.
In general, 20-30 mA is current. For example if you have a 5V source, and use a 1KΩ resistor, you'd be supplying 5mA of current to the led. Basic ohm's law.
It won't matter to the led if you power it with 12 or 13 volts.
Your title says something about computing resistor value. In what context is this question?
Btw, in order to prevent led burnout, you need to limit the current flowing through. Most leds (depending on material of course) have a .7V drop across them, however they will fry when you send infinite current from your power source thus the need need for a resistor.
In general R=V/I (where V = volts, I = current, R= resistance in ohms). Find out what the nominal (not maximum) current spec is for the resistor of your choice, and plug it in to the equation.
In general, 20-30 mA is current. For example if you have a 5V source, and use a 1KΩ resistor, you'd be supplying 5mA of current to the led. Basic ohm's law.
