I want to add latern lights to a ho scale caboose. I want a capacitor wired to the lights so they don't flicker going down the track. I'm using 0402 red LEDs. Does anyone know how to wire this up? What capacitor do I use? And how do I wire it all up? Thanx.
Best and easiest way is to use a small AAA battery holder and wire the LEDS up that way. That way you won't have any flicker and can eliminate the capacitor.
That is correct but most LED's are 3 volts DC. It would require 2 AAA batteries and could add undesirable weight to the car. To use a capacitor for anti-flicker, the input must be DC, so if you operate DCC you will need a bridge rectifier in the circuit. I would urge you to search for similar from our advertisers but here is one solution: http://store.sbs4dcc.com/SBS4DCCCompactLEDConstantLighting-Anti-FlickerModule.aspx You will also need power pickup, usually with steel wheels. They can be found here: http://store.sbs4dcc.com/electricalpickups.aspx Harold
If you used a battery you would not need a capacitor. The OP could also wire in two LEDs in series to create a 1.5V source without the need for a resistor. He could also use a snap in battery, like a hearing aid battery.
The forward voltage of LEDs varies, depends on the color (the physics of the compounds used). Yellow, red, and green LEDs are approximately 1.5V. White and blue LEDs are approximately 3V. So the color will dictate how much voltage will be needed to turn it on. The power supply voltage must be greater than the LED's forward voltage, if only by a small amount. In addition, resistors are REQUIRED to regulate the power supply's current to the operating current of the LED. LEDs are not like incandescent bulbs which are voltage driven devices with their own inherent resistance. LEDs are current driven and the current must be controlled. Without a resistor or other current regulating method, the power supply will pass all available current through the LED once it turns on. Think of it as a pressure valve. Once the pressure opens the valve, it is a wide open valve. The main question will be the power source. If it's DC track voltage and thus variable, then the circuit needs to work over the range of track voltages. If it's DCC track voltage, you design for that voltage. If it's battery powered you design for that voltage, be it 9V, 3V, or whatever. A little more information about how you are going to power your device is going to be needed before anyone can help you. Lyle
I bought an N scale caboose with a red nano LED installed as an end-of-train device at last year's National N Scale Convention. It had a small hearing aid battery in it, along with a reed switch that I can turn on and off with a magnet. No flicker, and it works great!
The Easy Peasy lighting used in passenger cars has 2 LEDs is controlled with a magnetic switch and powered by 2 hearing aid batteries. The batteries have a life of about 20 hours. I have found that replacing the battery becomes a chore, especially if forgotten and left on. I prefer to use track power for mine.
Here is a very good article for cheap and simple flicker free lighting. http://model-railroad-hobbyist.com/node/22380 Harold
Check out this earlier thread here on TB; I have the same circuit mounted on perforated circuit board, and have it on 25+ passenger cars and cabooses on my DC layout and it works great! The car lights stay on at least 2-3 minutes after the power is turned off. http://www.trainboard.com/highball/index.php?threads/caboose-interior-lighting-dc-how.74758/
