Hippogriff
Member
Hi all,
I'm new here and I am probably guessing that "LED / Resistor" questions are quite common. Hopefully I'm not going over too much old ground but a view from some folk in the know on here would be very helpful to me.
I have a lovely RGB star LED that I want to control with a PIC. That's all working fine, but I want to make sure I have the LED as bright as possible without it exhibiting its deathwish. The LED has forward voltage figures of Red = 2.5 volts, Green = 3.8 volts, Blue = 3.8 volts and a maximum forward current of 350 mA. The power supply is 5 volts.
I figured, using the equation, that I should be able to use resistors of around 7 Ohms, 3 Ohms and 3 Ohms for red, green and blue respectively. Going up a bit, for safety, I then figured on 10 Ohms, 5 Ohms and 5 Ohms.
Are those the lowest value resistors that I could use to ensure this LED is the brightest it can be from a 5 volt power supply? I only ask because the circuit that I was initially following used 5 Ohm, 10 Ohm and 15 Ohm respectively - I think that was designed to give a "warm" colour when the LED was white!
Anyway... I feel relatively comfortable with that equation. You work it out and then add a little bit for safety - that seems fine. I'm just looking for confirmation there.
However, what I don't understand is the wattage of said resistors and whether it even matters. I have available to me some 0.6 watt resistors and some 1 watt resistors.
If I choose to use the 0.6 watt resistors or the 1 watt resistors, will I affect the brightness of the LED or will it have no bearing whatsoever? I've tried to check with my eyes... but, ummmm
, I can't seem to tell - so I'm wondering if anyone can tell me what the real story here is.
I'd appreciate any advice that anyone on the forum can give - obviously I'm only starting out with this stuff - so assuming I know little would be good.![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
I'm new here and I am probably guessing that "LED / Resistor" questions are quite common. Hopefully I'm not going over too much old ground but a view from some folk in the know on here would be very helpful to me.
I have a lovely RGB star LED that I want to control with a PIC. That's all working fine, but I want to make sure I have the LED as bright as possible without it exhibiting its deathwish. The LED has forward voltage figures of Red = 2.5 volts, Green = 3.8 volts, Blue = 3.8 volts and a maximum forward current of 350 mA. The power supply is 5 volts.
I figured, using the equation, that I should be able to use resistors of around 7 Ohms, 3 Ohms and 3 Ohms for red, green and blue respectively. Going up a bit, for safety, I then figured on 10 Ohms, 5 Ohms and 5 Ohms.
Are those the lowest value resistors that I could use to ensure this LED is the brightest it can be from a 5 volt power supply? I only ask because the circuit that I was initially following used 5 Ohm, 10 Ohm and 15 Ohm respectively - I think that was designed to give a "warm" colour when the LED was white!
Anyway... I feel relatively comfortable with that equation. You work it out and then add a little bit for safety - that seems fine. I'm just looking for confirmation there.
However, what I don't understand is the wattage of said resistors and whether it even matters. I have available to me some 0.6 watt resistors and some 1 watt resistors.
If I choose to use the 0.6 watt resistors or the 1 watt resistors, will I affect the brightness of the LED or will it have no bearing whatsoever? I've tried to check with my eyes... but, ummmm
I'd appreciate any advice that anyone on the forum can give - obviously I'm only starting out with this stuff - so assuming I know little would be good.