How would I wire light bulbs inot my KATO units? They come with LED’s and I want to put some light bulbs in them. Do I solder the light bulbs to where the LED is soldered in? I included a photo of the front and rear LED so you can see what I am talking about.
You would have to use a bulb that is the same voltage as the LED (probably 1.5v) or it will be too dim. You just mount it the same way as the LED was soldered in. Watch the heat from the bulb doesn’t melt the shell.
PS-you’d have to use a diode to get directional lighting (I think)
If you use light bulbs in place of the LED’s and still use the light pipes, you will not be happy with the results. You can use one each micro bulbs in the hole for the headlights and one each for each ditch light if you choose. If you are running DC, you would build a bridge rectifier to drop the voltage. If you are running DCC, use a 640 Ohm resistor in series with each bulb.
Cheers
I am going to be running on DCC and am going to be putting bulbe to each headlight. THe bulbs are 12V. Do I still have to put a resister in since they are 12V?
Thanks
I have not used the 12V bulbs, but maybe someone can tell you if this is normal. You can find out by using a voltmeter accross the output or you can try a bulb for test purposes. However, if the bulb is driven from a function, make sure it does not draw more than the function allows or you will cause the function output to cease for good.
I checked a Soundtraxx installation manual and it states you can use the 12 to 16 volt bulbs. Remember, that was for a different unit, but your probably can do the same.
Sorry I cannot help with the 12 volt information any more than I have.
Cheers
Substituting incandescent bulbs for LEDs is likely to create problems with melted plastic from the heat generated by the bulbs. Why don’t you use super-bright LEDs if you’re just trying to make them brighter.
Even if you use 12 Volt bulbs, it would still be advisable to include a small value resistor to prevent overload of the decoder when the bulbs are turned on.
Maybe someone can explain this to me. If that board puts out 1.5v to power a 1.5v LED. (am I correct in assuming this?) Why would you need to add a resistor if your hooking a 12v bulb to a 1.5v output? Isn’t the bulb going to be too dimm anyhow?(without the resistor?) Isn’t he just better off using the same voltage bulb as the boards output?(just confused here)
You are correct sir.
David B
If I use 1.5V LED’s how do I get them in the headlight holes? The smallest LED that I have found is 3 mm. I would need a 1.7 mm LED. How would I get the 3 mm LED’s in the headlights that are only 1.7 mm? Please explain to me how I would go about doing this.
Smoke, try these from Tony’s http://www.tonystrains.com/products/mini_leds-yeloglo.htm
I used them for ditch lights, http://www.youtube.com/watch?v=3mp4Pn1tqy8
and mount them behind the hole and use a clear lens like te details west ones.
Ken.
I don’t know how hot a 1.5v bulb gets. They might work. (check your PM)
I wonder why you can find the 1.5mm led’s in red,yellow and green but not white or clear?
Smoke,
Please forgive my ignorance as I’m not very electronically oriented but why are you replacing LEDs? [%-)]
From what I have seen and understand, LEDs are extremely efficient, don’t get hot, outlast lightbulbs and are available in a wide variety of colors.
A point of clarification for all: Voltage, by itself, wont cause an LED or incadescent bulb to blow, its the current pushed through the LED/Bulb.
If you want to use a 1.5V bulb on a 12V circuit, then you are going to have issues. Quick application of Ohms law:
You have a 1.5V bulb rated for 0.015A (15mA). This means that the bulb has an ideal internal resistence of:
1.5Vdc / 0.015 = 100 Ohms.
If you try to apply 12Vdc to this poor bulb:
12Vdc / 100 Ohms = 0.12 or 120mA !!! (thats about 8x max current for the bulb.)
So what you need to do is add a resistor that will keep the current from exceeding 15mA. To calculate what total circuit resistance we need to keep a 12Vdc source from pushing any more than 15mA:
12Vdc / 0.015 A = 800 Ohms
So thats 800 Ohms total circuit resistance. We know that the bulb has an ideal resistance of 100 already, so we need to add a resistor > 700 Ohms in order to keep the current through the bulb < 15mA.
Now… as for the 12Vdc bulb rated for 15mA on a 1.5V circuit:
Calculate Bulb’s internal resistance:
12Vdc / 0.015A = 800 Ohms
Now calculate how much current this bulb will draw on a 1.5Vdc circuit:
1.5Vdc / 800 Ohms = 1.875 mA (1/8th or 12.5% rated current…very dim)
The same basic calculations can be applied for LED’s also, just to get you into the ballpark for resistor values. My personal preference is a 1K resistor per standard T1 LED. They are rated for 20mA max, so I put a 1K resistor on them when I am using them on a 12Vdc circuit:
12Vdc / 1000 Ohms = .012 or 12mA
12mA is about 60% rated current and the LED glows plenty bright. Plus, 1k Resistors are super common and 1000 is an easy number to do math with 
When in doubt, go with the higher resistance value. Als
Why are you replacing LED’s with bulbs?
If they’re older Katos, I would assume he’s replacing them because they’re either yellow or blue-white. Personally, having changed out a few dozen of these, I would just replace the factory LEDs with some of the newer yellow-white LEDs. Make sure they’re aimed straight into the light tubes or you won’t get full brightness out the other end, which is a very common problem with factory mounted lights.
As much as I remember the decoder delivers about 15 Volt. Your 12 Volt bulb will not have a long life without resistor. Another possibility you can drop the voltage the decoder gives to the lights (white or yellow) by programming.
Wolfgang