Has anyone tried using acylic white paint on leds to reduce the amount of blue ? I bought some leds about a year ago & can't stand the blue tint these things put out. I ordered some warm white leds on ebay, but I'd like to use these old ones too. Any input would be appreciated..
Two possibilities with the LEDs you have. Increase the series resistor value to lower the current to the LED which will reduce brightness a little.
I am using 1k resistors.
Another idea I have used is a couple thin coats of Polly Scale Rail Box Yellow paint on the LED.
People are realizing, LEDs are not Plug & Play.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
Thanks Rich, I am using an 820 Resister now, If I go anymore it seems the led is gonna' lose too much brightness. These are 18 volt leds. I will try the paint You suggested while I wait on the new leds to come in. I haven't tried the warm white ones yet, hopefully they will suit everyone at the club as well. We have about 20-some locos needing light repairs,so I'm trying to use up what I have. Again thanks, Randy......
I never heard of 18 volt LEDs. LEDs are rated in current since they are current operated devices. Usually, 20 ma maximum. I run my LEDs around 10ma and they look good. We vary resistance to achieve proper current.
Light bulbs are rated in volts.
Someone posted a while ago about using Tamaiya paint, for the lexan R/C car shells, to paint LEDs to make them more of a warm white color - I don't rememebr if hey used yellow or orange paint - I think it was orange given that some of the 'golden white' LEDs I use are orange color when off.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
18v??? I've seen 12v, but they are always 5mm. I might be wrong, but I don't think an 18v would even light up with an 820ohm resistor.If your going to try the paint, I suggest you airbrush it on for a more even coating.
Can't say I ever heard of an 18V LED. But any of them - 5V ones, 12V ones - are just ordinary LEDs with the resistor incorporated into the package so they work at the rated voltage without a problem. The junction voltage of the actual diode part is determined by the semiconductor materials it's made out of. While I haven't heard of an 18V LED, they're probably out there - probably available in just about any commonly used voltage.
richg1998 I never heard of 18 volt LEDs. LEDs are rated in current since they are current operated devices. Usually, 20 ma maximum. I run my LEDs around 10ma and they look good. We vary resistance to achieve proper current. Light bulbs are rated in volts. Rich
Sounds like something packaged by someone trying ot be helpful - if they came with resistors. A typical white LED with a 750 ohm resisto should be fine at 18 volts, but it's going to be running near it's maximum current rating. With 12.5 volts to the track with DCC decoders I use 1K resistors with white LEDs - this runs them at 8-9ma, a bit under half their maximum rating, and they are PLENTY bright. If you want to use them for flashlights, use a smaller resistor and run them closer to the max.
If you look in data books, or at LEDs that are packaged witht he actual data, you will see two numbers, maybe more. One is the forward voltage drop - for white LEDs this is usually in the range of 3.1-3.5 volts. The other is the MAXIMUM current the LED can handle - standard white ones are usually 20ma. Other numbers may indicate the brightness and/or color temperature. It's the volts and current we are interested in.
(someoen remind me to post the following on my web site because I've posted it in various messages here at least a dozen timesnow LOL )
To calculate what resistor you need, you need to know those two numbers from the LED, plus how many volts your power supply is putting out. Ohm's Law states that Voltage is equal to current times resistence: E=IR (E because voltage is also know as 'electromotive force', I because current is the 'intensitive' and the letter C had already been used). Going back to 5th or 6th grade, you solve for what you want to figure out, in this case R, so R=E/I. Since the resistor and the LED will be in series, the voltage across each one will add up to the total voltage applied to the circuit. The LED voltage is fixed at its rating - we'll use 3.5 for this example. Say your function outputs on your decoder put out 12.5 volts. So: Voltage across the resistor + LED voltage = 12.5. Or Voltage across resistor = 12.5 - LED voltage. Vresistor = 12.5 - 3.5 = 9 volts. Now, you need the current - remember the LED rating is the MAXIMUM - you do not want to run things at their maximum ratings, not if you want long life. So pick something more conservative. say 9ma. 9 milliamps is .009 amps. Plug int he numbers: R = E/I, R=9 volts / .009 amps. R = 1000. Or 1K.
You can work it in any combination, usign the LED voltage, the supply voltage, and the resistor to see how much current will flow through the LED. For those '18 volt' LEDs with 750 ohm resistors: Voltage will be 18- the 3.5 volts of the LED, so 14.5 Volts. Solve for I: I=E/R, or 14.5/750, about .019 amps, or 19ma - right near the maximum.
Just remember the voltage ahs to be in volts, the resistance in ohms (a 4.7K resistor is 4700 Ohms), and the current in Amps (1 ma is .001 Amp).
The below photo is a LED with a couple thin coats of yellow. The voltage from the decoder is 12.5 vdc and I used a 1k resistor. The current is about 9ma. Sometimes you have to experiment.