Assuming an LED resistor can be placed on ether the positive common wire or the negative function wire, where is the best place to wire in resistors. Near the LED, at the midpoint of the lead between the board and LED, or close to (or at) the board itself? I need to install 5 resistors for front end LEDs and 4 resistors for the rear end, for a total of 9 LEDs spread across 5 separate functions (front/rear headlight pairs, front/rear numberboard pairs, and a roof beacon light). I've decided against series wiring of the pairs and will be running parallel lines for 4 of the functions instead.
LED Resistor location
- Thread starter Toolbelt
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Do I need to take heat into consideration? Ie if I place them all in the cab area will it overheat the plastic, or do resistors in this scale even warm up at all?
the common is positive(?) so they will all tie in to the common wire/side, but I will be hooking the negatives to their corresponding function outputs. In the case of the pairs (headlights/numberboards), I will likely solder them to a single wire which will then be soldered to the appropriate function output. So they will be paralleled. Each LED in the pair will have its own resistor (either on the positive or negative side). Also, based on an online calculator, it's suggesting 1/8 watt resistors are more than enough? Other than the amber beacon light(2.2v/20 ma LED), they are all 3v/20 ma rated LEDs, although my plan is to run them at around 9 ma. 1000-1100 ohm resistors is what I came up with. I'm trying to avoid any "Oh shit" moments, so if any of that sounds off base, please sound off. LOL
Iron Horseman
Well-Known Member
I have never had a heat issue from an LED circuit. I've had many incandescent bulbs melt through, and a couple of resistors in an incandescent bulb circuit have heat issues, but never either involving LEDs.
Stock AHM incandescent light bulb run on DCC
I didn't think there would be much heat, let alone even warmth, driving small milliamp leds but wanted to be sure. Testing with my 3v battery with various resistors produced no warmth at all in the leds or resistors, but I wanted to be sure the same could be said when driving them with a 12v function output which would put more load on the resistors. I even tried a 1k resistor on the 3v supply, which worked out to only 3 ma, and the light produced might actually be sufficient. My math equates that to using a 2.7k resistor (or nearest value) on a 12v source. I heard the decoder can also control brightness so I should maybe pick a resistor that puts out slightly more light than might be needed and then dim it down a step it two with the decoder. I would imagine the greater the resistance, the warmer a resistor might get.I have never had a heat issue from an LED circuit. I've had many incandescent bulbs melt through, and a couple of resistors in an incandescent bulb circuit have heat issues, but never either involving LEDs.
Stock AHM incandescent light bulb run on DCC
Dub
Lionel 3 Rail
I just saw a picture on Facebook. One guy in the pipe was Amperage. The guy pushing was Voltage. One guy on top had a rope around Amperage and was pulling it. The circuit is a close system. Increased resistance will lower amperage because you are still at the same voltage.
Power is different. It is measured in watts. A 1/4 Watt resistor is enough for one LED but start adding LEDs in series, the Wattage will increase. In this case it is not a higher resistance but a higher wattage/
The only good article about LEDs and Wattage, I have ever seen was by Bob Nelson in the September 2008 Issue of Classic Toy Trains.
Power is different. It is measured in watts. A 1/4 Watt resistor is enough for one LED but start adding LEDs in series, the Wattage will increase. In this case it is not a higher resistance but a higher wattage/
The only good article about LEDs and Wattage, I have ever seen was by Bob Nelson in the September 2008 Issue of Classic Toy Trains.
