This question is for users of NJI signals. I have a GRS dwarf signal with red and green LEDs. These signals come with resistors attached. The color bands on the resistors as best as I can make out are red; white; black; black; and brown. Looking this up on-line, the bands represent a 290 ohm resistor.
The paperwork with the signals gives no information as to the LED specs, other than they'll work with a voltage between 9 and 12 volts DC. I called NJI, and the gentleman I spoke with did not have any further information. My impression is that so far as NJI is concerned the supplied resistors are proper and that there have not been any issues.
That said, from reading other posts to this forum it seems that everyone thinks that only 1000 ohm resistors are correct for just about every application, at least for white LEDs.
So the question becomes, for users of the NJI signals, have you had any problems using the provided resistors or are you replacing them with higher values?
Thanks
maxman:
For what its worth (in other words I don't have any specific experience with NJI signals), I have installed a fair number of LEDs. The 290 ohm resistor will work with the LEDs but they will be pretty close to maximum brightness. That has two drawbacks:
First, the LEDs will be so bright that they will leave spots on your eyes when you look at them. I have seen several modular displays where the LEDs were so bright that they were painful to look at for any length of time.
Second, they will be drawing a lot more power than they really need to. If you use a higher value resistor you can tone them down to a reasonable light level and draw less power at the same time.
The 1000 ohm value has been a well established standard for some time, but IMHO 1000 ohms still leaves the LEDs too bright for many applications. For locomotive headlights 1000 ohms is fine. For a lot of structure lighting situations 3300 ohms or higher (up to 10000 ohms) is a better bet where you want the lighting to be less intense.
For your signals I would do some experimenting. Start out with the 290 ohm resistors and see if the LEDs burn your eyes as I have suggested they might. Then try a 1000 ohm resistor, and perhaps a few higher values.
To do this you will need a selection of resistors with different values. I buy mine from Digi-Key in the US. They have great prices and their shipping is cheap and very fast.
http://www.digikey.com/us/en/digihome.html
For a few bucks you can get yourself a near lifetime supply of various resistors. I would suggest that you obtain several values i.e. 1000, 2200, 3300, 4700 and 10000 ohms to start. Buy at least 1/4 watt. I use 1/2 watt because they run a bit cooler.
Here are some specific resistor options:
http://www.digikey.com/product-search/en?pv2=4&pv174=18&FV=fff40001%2Cfff80482&k=resistors&mnonly=0&newproducts=0&ColumnSort=0&page=1&quantity=0&ptm=0&fid=0&pageSize=25
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
I use NJ International N scale three color signals. Each LED has a resistor with a value of 210 ohms. Each of the aspects have a different level of brightness, but they are not blinding. I use them on modules that are displayed at shows so I like the level of brightness as they can be seen in the bright lights in the shows room. I also use Atlas G type signals on my home layout and they have different values for each aspect that are much higher than the NJ-I signals. I supply the resistors as I don't use the Atlas circuitry. Values are 500, 3,400 and 4,700. Because of the differences in manufacturing the LEDs they require different resistors to keep them all around the same brightness.
Add resistance in series with the existing resistors until you get to the level of brightness that you are comfortable with.
maxman That said, from reading other posts to this forum it seems that everyone thinks that only 1000 ohm resistors are correct for just about every application, at least for white LEDs.
That said, I don't agree with the statement that everyone thinks that only 1000 ohm resistors are correct for just about every application.
What I notice on the forum is that, in the absence of the OP stating the LED specs, a 1K ohms resistor is often cited as the go to resistor of choice as a starting point. Then, upon observation, a higher or lower value resistor can replace the 1K ohms resistor to increase or decrease the brightness of the LED. This can be particularly important with brighter colors such as red or white.
Tomar Industries suggests three different values for its resistors, 390 ohms, 560 ohms, and 1500 ohms. I use 560 ohms for green and 1500 ohms for red to balance the two colors.
A higher value resistor will limit the current reaching the LED, thereby prolonging its life. A higher value resistor will dim the brightness of the LED whereas a lower value resistor will increase the brightness of the LED. A higher value resistor will decrease the load on the power supply.
Rich
Alton Junction