LED headlight for MTH train

DYI circuit here powered off track voltage

http://www.jcstudiosinc.com/BlogShowThread?id=619&categoryId=426

Using the existing CV board all you need is the LED and a 150 ohm or more 1/4 watt resistor in series to one of the leads with the LED placed in proper polarity.

Dale H

I'm a firm believer in Evans Designs LEDs.  I know they can be built for cheaper, but Evans come pre built in a VERY NICE little package ready to put in.  I've put in at least 20 and never had one fail, even when I though I toasted it!  It might be a dollar more to have Evans Designs "put the parts together" for you, but its more than worth it to me to have a ready made two wire solution with MANY choices in colors, blinking, etc....  And they are so much brighter than the standard bulbs that come in engines. 

Warm White would look the best.

Warm white for steam locoa, and cool white in modern dieisels. , they come in 1.8, 3, and 5's. 3's are fine.

Great--thanks for all the help!

I'm a firm believer in Evans Designs LEDs.  I know they can be built for cheaper, but Evans come pre built in a VERY NICE little package ready to put in.  I've put in at least 20 and never had one fail, even when I though I toasted it!  It might be a dollar more to have Evans Designs "put the parts together" for you, but its more than worth it to me to have a ready made two wire solution with MANY choices in colors, blinking, etc....  And they are so much brighter than the standard bulbs that come in engines. 

NOT to mention the Evans Designs LED's Don't Flicker- unlike the Dans Drumheads that do flicker- not too much to the naked eye but try to take a picture!

The Evans design ones are OK for what they are. Run off track voltage 5 to 18 VAC they will vary a bit in brightness since the resistor is sized for maximum voltage. If you run it off the existing 6 volt CV board it may be a bit dim and the pre circuited bridge rectifier is redundant. If you install a single 3mm LED with the resistor sized for 6 volts you will achieve maximum brightness and constant intensity if you run conventional.

Dale H

I run DCS only--make a difference on these LEDs?

I have bought a few of the Evan's Designs LED's, and while they're fine, they are not perfect.  As Dale says, lower voltage is a problem for intensity.  Also, I disagree that they don't flicker.

If you replace it with the Evans design and hook it to the original wiring,it will get 6VDC (some form of PWM I think). The LED is designed as I mentioned for 5 to 18 volts,so it will burn at its low end of intensity spectrum. If you wire it directly to track voltage (in command) it will get maximum voltage and achieve maximum intensity. However to my knowledge, the ED circuit LED does not have a capacitor so it would flicker in case of dirty track. If you add a capacitor to the Evans circuit you also have to add a 22uh choke to prevent the DCS signal from shunting. The capacitor is what eliminates flicker. The capacitor is not needed if you tap directly off the existing CV circuit since it already has some capacitance I think. 

See "caboose lighting circuit" in my blog for a picture of the choke used.

http://www.jcstudiosinc.com/Bl...tegoryMain?catId=426

Dale H

What may be confusing is some responses apply to their AC/DC LED ($3.25) while others to their DC LED ($2.25). 

If connecting directly to the track use AC/DC.  But I don’t believe that’s what you want since you‘d lose DCS control over the headlight – that is, it would be on whenever track power is applied even if the engine is shutdown under DCS.

If connecting to the headlight socket, you can use either. The 2 wires going to the headlight socket carries pulsed-DC. Being DC, one wire is + and the other -.  If you use the DC LED you must hook up with correct polarity (+ to +, - to-) or it won’t light.  The AC/DC LED can be hooked up either way with equal results.  So either will work and you want someone to respond who has successfully installed the AC/DC and/or DC LED into a PS2 headlight.

The dilemma is the AC/DC LED will probably be dimmer than the DC LED.  That is, the AC/DC says it works from 7-19V while the DC from 6-12V.  The PS2 headlight voltage going to the socket actually varies with track voltage (it is NOT constant-voltage as many people think) but using 6V as a proxy is suitable for most applications.

From what I can tell, only their AC/DC LED comes with a capacitor which some claim demotes flickering.  I’d be curious to hear how well the flicker reduction works when attached to a PS2 incandescent signal. So, again, unless someone who has done it chimes in, I suppose you could get some of each and report the results to advance our collective knowledge.  If brightness is an issue, perhaps using a 5mm size (vs. 3mm) might help.  Other things being equal, 5mm LEDs are usually brighter so if it physically fits this might compensate for operating at the low end of voltage.

I’d think you could ask ED about which to use for MTH PS2 headlight replacement and they ought to know?

If you are connecting an AC/DC LED or the DC LED to PS2 headlight wires (as opposed to directly to the track), you don’t need to worry about the choke.  

And yes, it simply boggles the mind how involved it can be to hook up an LED!

The original post wants to replace a light bulb run off a 6VDC board. A direct LED replacement would be a 3mm warm white LED in proper polarity and a 150 ohm 1/4 watt resistor in series to protect it.Circuited this way the LED would achieve its maximum designed brightness without over current damage. We are talking about 35 cents worth of parts here.

All the ED circuits I have seen have a bridge rectifier,and resistor,the value calculated for 18 or whatever volts input in series to the LED used. . Maybe some have a capacitor to reduce flicker. If a capacitor is used in a DCS command environment it could cause signal interference unless a choke is also used in series. These are circuited to run off track power not 6 volts PWM produced from the DCS board.  None of the components are ED adds are usable in the application in the original question,unless it is circuited off track power. There are not AC or DC LEDs,they are all made to run on DC with components added to convert AC to DC and restrict current flow to protect it. Brightness or dimness depends on LED design and assumes they are circuited for their rated current flow,usually 20 ma or 100ma. Forward drop for white is usually about 3 volts,red about 2 volts.  Any can be dimmed by adding more than the maximum resistance required to protect it.

I am not knocking ED LEDs,for those using them the convenience may be worth the expense, Im sure they have fine products. They are not suited for this application unless you just cut out the LED and add your own resistor or run it off track power.. As usual for those willing to do a bit of work DYI is cheaper and can be customized for different applications. Also if the CL2-N3 chip is used instead of a resistor,CV lighting can be had for conventional operators. I guess there are a few of us left.

Dale H

"As usual for those willing to do a bit of work DYI is cheaper..."

And for those who have the requisite electronics knowledge.  It's not simply a matter of laziness.

Dale:

Thanks for all the helpful installation data and diagrams. Plan on using all.

Bob D.

I'll make it simple for you.
Evans Designs 3MM warm white round top LED it'll fit right in the MTH plastic bulb holder.
These come on at about 6-7 volts so you can use the board or track power they're pre-wired and they'll handle up to 20 volts.

David