Lights on Locos

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Maxitrains

Member
Hi, I was watching some videos ( cause on photos I couldn't realize ) that some locos have their lights on bright even if they are moving slowly or not moving at all ( referring to this clip especially on 1 min 35 secs ). I was wondering how this could be possible if the train was not moving. Unless its a DCC feature, and I don't know much about DCC.

When I run my trains at low speed the lights are very dimm and this upsets me a little, since it doesn't look authentic.
.
Thanks
 

jbaakko

Diesel Detail Freak
DCC usually had constant lighting, some people set the lights to come one when any power is applied, some manually turn them on. DC also has a "constant lighting module" that you can buy and add to DC units, to have the lights on the same brightness all the time.
 

Maxitrains

Member
So even for DC there's a method!!!

From my guessing, this module will have a battery or am I wrong? If it has a battery, will this charge when you run the train.

Well I guess I'm only guessing here

Do you have a link for a similar module for DC locos?

Thanks
 
Another method is using a low voltage bulb or an LED with a fixed voltage regulator. Foir example with a 3.3V regulator and a white bulb, it will reach full brightness at about 3.5V then stay the same brightness after that.

Mark
 

Larry

Long Winded Old Fart
I have an MRC 9500 transformer w/Momentum that I use all the time. When you turn the knob to start the engine the lite comes on 1st before the loco starts moving, then it starts picking up speed just like a real engine. Then when you turn the knob to stop, the engine starts slowing down very slow. After it stops the lights stay on for at least 2 or 3 seconds.
Would this help your situation?

Larry
 

GN.2-6-8-0

Member
For DC operation I've always used a 1.5V bulb with a Radio Shack bridge Rectifier. crack the throttle and though theres no way near power for the loco to move you have a nice bright headlight.
Have to rethink this with DCC as I'm hoping the same arrangment will work using the headlight leads on a DCC decoder.

Anyone tried this yet?:confused:
 

Maxitrains

Member
OK, as for the 1.5V bulb this should work fine since the trains normally start moving at 3.5 to 4 Volts, depending on the type of motor, so then I will be needing this voltage regulator to keep the voltage flowing to teh bulb at 1.5, otherwise I have to change bulbs every 15 secs :)
 

Maxitrains

Member
I went to the components shop, and asked him for a TO-92, but then he told me that the TO-92 only holds up for milli Amps, and that the LED or BULB I would use, might not hold it.

So then he suggested to use the LM317, which is similar but can hold up to about 3 AMPS, and it is also variable voltage ( together with 2 capacitors, a resistor and pre-set pot), which when soldered together I think it will still all fit in locos, now I have to start thinking on how to put these 5 components together :) . I hope this works

I also bought 2 x 3mm LEDs bright white that costed me around US$ 3.00 each :S

This is the small circuit that was advised to use for the light



http://www.national.com/mpf/LM/LM317.html

Is this the corect way to put the components together? cause I always get mixed when I use POTS

 
Last edited by a moderator:

Maxitrains

Member
OK I managed to put everythign together and make it work, but the new problem is how am I going to fit all this into my engines :S. I tried opening my RS-3 and there's not even space for the bulb, imagine to fit all that :S
 
Yes, a TO-92 type regulator has a max current capability of 100mA but most LEDs these days cannot handle anything past 20mA before damage occurs. Bulbs are different.

FYI, I originally did a LM317 circuit because I wanted to manually set the voltage and yes, it works. The only problem is the 317 requires an input voltage approx 2 volts higher than the set out voltage, or in other words 2 volts of loss before regulation. So (for example) if you set 3 volts output to the bulb, it needs to see more than 5 volts on the input before the output gets to 3 volts. I see this as a big limitation as I have a few locos that run a nice speed at around 4-4.5 volts.

Then I tried a fixed regulator (the 3.3 volt one is nearly perfect). Run to an LED with a small resistor inline to protect the LED a bit, it put out the full 3.3 volts with an input of only 3.6 so it doesn't have that inherent loss factor. In the TO92 package it can run 2 or 4 LEDs without and issues.

Then again, go DCC and all your problems are solved. Well, sorta...you'll just have a new set of them to deal with. :)

Mark
 

Maxitrains

Member
Thanks for the advise , I will go get some TO-92 and try to set with it, is there any specific resistor you used, or you places one according to the brightness you wanted?

About DCC, I think its not worth for me to switch to it on a 9' x 5' layout HO scale, with not more then 9 turnouts, and one main line.
 
Thanks for the advise , I will go get some TO-92 and try to set with it, is there any specific resistor you used, or you places one according to the brightness you wanted?

About DCC, I think its not worth for me to switch to it on a 9' x 5' layout HO scale, with not more then 9 turnouts, and one main line.
IF you have trouble finding the part, try Digikey - they are an amazing company to deal with. I order online and get it next day, even here in Canada. They have lots of white LEDs as well including some cool surface mount ones.

I used a 3.3 volt fixed regulator, TO92 chassis. Many white LEDs are actually quite happy with 3.3 volts, definitely check the rated voltage first. If the LED's recommended voltage is lower, then a small resistor is in order to pull the current down a bit (for example, say a 3.1 volt LED, a 33 to 75 ohm resistor should do it).

Also, as you mentioned, you may wish to drop the brightness a bit. One handy tool to have is a "resistor wheel", or even just a 1k to 5k pot then you can put inline to set the brightness then replace with the fixed resistor afterwards. The resistor wheel is the easier tool as it tells you what resistance you are testing with - the pot you'd have to read with a meter afterwards.

Mark
 




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