# LED Headlight TE Revoulution



## chrisb (Jan 3, 2008)

Hooking as new LED Head Light to the HD leads on the Revolution, I getting a less than bright light.
Using a 5mm High Brightness 7000mcd
25 mA, 3.3v
RS number 276-0017

On the LED + leg I have a 1K ohm 1/2 watt resistor

All new wires

It appears that I'm only getting about 1.5 volts on the head no 2 light leads on the revolution
and it does not change with speed, HD nor or rev or HD off on the remote. 
Any ideas?


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## Greg Elmassian (Jan 3, 2008)

First, what voltage are you running, track or battery too. 

An LED will have a constant voltage drop, if you are measuring the voltage at the LED. 

Also, the Revolution has a common positive, and the headlight "output" actually connects to ground when active. 

Sounds like your other leg of the LED circuit is not connected to the positive common. 

Regards, Greg


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## izzy0855 (Sep 30, 2008)

Chris, 

There's an easier way to control the voltage output for all your LED's on your engine, then a resistor. Dallee Electronics makes a voltage power regulator that will handle up to 7 volts output for around $24.00ea. You can regulate the voltage output to all your LED's by adjusting the voltage output on the circuit board with a small flat blad screw driver...here's the link: http://www.dallee.com/AR power supply.htm I use Dallas's power regulators to control the voltage output for all 20 plus LED's on my E8, here's a link: http://cordlessrenovations.com/store/product_info.php?products_id=342 

Rick Isard 
Cordless Renovations, LLC 

P.S. If your going to be at the 2010 NGRC in Tacoma, WA., I will have this E8 on display at my booths...


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## Dan Pierce (Jan 2, 2008)

For voltage drop, a 20 ma led needs 50 ohms per volt dropped. Therefore a 1 k resistor at 50 ma will drop 20 volts. 

Now you have 25ma and we do not know the battery voltage so I will assume 18 volts. 

Now doing the math, you need to drop approx. 15 volts at 25ma which gives us a 600 ohm resistor needed of it is a perfect world. 
Since the voltage dropped would be less than 15 volts and an electronic component groiunda the led, the resistor I would choose in the standard values would be 560 ohm., next size up is 620 ohm. Again the assumption is 18 volts. 

An easier way is you need to use 40 ohms for every volt dropped at 25ma. 

So 10 volts is 400 ohms, 15 volts is 600 ohms, 20 volts is 800 ohms etc..


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## Greg Elmassian (Jan 3, 2008)

A constant voltage power supply for leds is not the way to do things. 

LEDs need constant current. 

I also fail to understand how a voltage regulator circuit is applied to the revolution socket. 

The question was to connect a headlight, not just run a bunch of leds from track or battery power. 

Listen to Dan's numbers. 

By the way, I still suspect the problem is not using the right connections to power the LED, or lower battery voltage than we are assuming. 

Regards, Greg


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## Paul Burch (Jan 2, 2008)

You should need nothing more than the led and a resistor in series. Its just a matter of knowing the voltage supply and then calculating the resistor value.
The following link should help.
http://metku.net/index.html?sect=vi...eng#single


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## chrisb (Jan 3, 2008)

I'm running battery power. I have a switch that connects the battery to to the track leads on the TE REV reciever or to the charging receptical. So I turn on the Reciever, then the TE Remote, Link says OK. I set the direction and then turn up the throttle, wheels turn and the Dallee sound works, horn and bell also work. At this point using a multi meter I set the probes 
on red to the HD common wire and Black on the HD2 wire. The meter needle indicates 1 to 1.5 volts. Throttle does not affect this voltage. Maybe my battery is low but it seems the trucks would not work if it was low. The remote Functions HD NOR and REV as well HD OFF do not affect the HD voltage. I'm lost at this point.


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## Greg Elmassian (Jan 3, 2008)

What reading do you get if you take the LED out of the circuit? Just disconnect any part of the resistor, etc. 

What locomotive is this in? 

Greg


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## Stan Cedarleaf (Jan 2, 2008)

Chris..... for all my Airwire, REVOLUTION and QSI installations, I leave the headlights wired to the main board of the locomotive and let the board control direction. Where that's not possible, I wire LED head and rear lights separatey using 1K resistors wired directly to the motor output on the receiver/decoders and install diodes for direction control. 

I find it to be very simple and works all the time. Yes, it might be nice to be able to turn the lights on and off at will, but for the way I run trains, I turn the trains on and let them run. When they go forward, the headlights are on and rear lights off. When in reverse the headlights are off and the rear lights are on. 

Just another thought.


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## Greg Elmassian (Jan 3, 2008)

Hmm... you ARE using the built in wiring right? Or did you plug this into a socket AND add more wiring? 

We need to know what you are doing... 

Regards, Greg


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## Stan Cedarleaf (Jan 2, 2008)

Deleted...


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## Greg Elmassian (Jan 3, 2008)

Nope, questions for Chris:


What locomotive?
using socket? 
was there a led there before?
are you using the existing headlight wiring?
If 2-4 are true, how does the LED look and work with the shorting plug back in?
There's not enough information to answer the question.


Without more information this is just an exercise in speculation. 


Regards, Greg


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## chrisb (Jan 3, 2008)

I have removed and discarded the orignal wiring in the Bachmann Shay. 
So I have LED and resistor on new wires. Have not wired the rear head light yet. 
Right or wrong , I wired the stuff up out side the locomotive shell Truck, reciever board and sound card now working on the lights. 
The 1 volt is checking the HD2 lead and HD common without the LED and Resistor installed. Oringal wiring is beyond the point of no return.


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## Greg Elmassian (Jan 3, 2008)

1. Bachmann Shay 
2. No 
3. does not matter 
4. no 

good, helps a lot... the situation does not sound good. Do you get any better "voltage" with HD1 and HD common? 

I assume you tried to turn the lights on and off, and tried both directions.. 

What voltage are you running? 

Regards, Greg


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## chrisb (Jan 3, 2008)

1 battery pack
21.5v 2 amp

HD1 and HD common the LED is real bright, 24V on the meter, HD off kills it and reverse/ direction works properly.
HD2 and HD common appear to give a constant 1V regarless of HD on/off and direction. I wonder if the HD 2 part of the circuit is bad?
If the lithium pack is 21,5v is that nominal or is my inexpensive meter wrong when it says 24v?


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## Greg Elmassian (Jan 3, 2008)

sure sounds like bad hd2... you know the led and resistor are ok... your testing and writing show you know what you are doing. 

I'd return the board. 

lithium is a nominal 3.7 volts per cell... 6 times 3.7 is 22.2, so rating it at 21.5 allows the voltage to drop a bit and be in spec. 

at full charge, they are usually around 4.2 volts each, times 6 = 25.2... 

So neither you or your meter are wrong. 

This is also an interesting thing, the Revolution can be sensitive when it gets to 24 volts, it's touchy with overvoltage. 

Many people run with that battery pack voltage you are using (often an Aristo) and have no problem. 

Some people do have a problem. But, the problems encountered are problems with erratic operation. 

No worries, the pack will come off that 24 volts pretty quickly under load. 

Regards, Greg


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## izzy0855 (Sep 30, 2008)

Lithium-ion batteries range from 2.95V - 3.77V each, and if you purchased the Aristo 21.6V 2amp battery-pack, each cell is 3.6Vea. + / _ .03 volts ea. It will take 5 - 6 cycles (charge/discharge) to get your 6 cell llithium battery-pack to reach 24.6V. Each cell is 3.6V at nominal voltage and 4.1V ea. or 24.6V at full charge. Your maximum voltage on the Aristo 6 cell lithium-ion battery-pack is 24.6V, so voltage is not the problem. Question, do you have a inline fuse and does not blow when you put the revolution in reverse? I may have missed this in the previous threads, is your LED's 3mm or 5mm, because most 3mm LED's can't handle more the 18V's for a long period of time. 

Rick Isard 
Cordless Renovations, LLC


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## krs (Feb 29, 2008)

Posted By izzy0855 on 04 Aug 2010 01:15 AM 
.........is your LED's 3mm or 5mm, because most 3mm LED's can't handle more the 18V's for a long period of time. 


Where does that come from????
As Greg mentioned earlier, an LED is a current operated device ( as opposed to an incandescent bulb which is voltage operated), so for an LED it doesn't matter what voltage is applied

as long as the current is limited to a value below the maximum allowed and the voltage is higher than the forward voltage of the LED.
3mm LEDs can handle any voltage as long as the current is in the proper range.

Knut


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## Del Tapparo (Jan 4, 2008)

Posted By izzy0855 on 04 Aug 2010 01:15 AM 
... is your LED's 3mm or 5mm, because most 3mm LED's can't handle more the 18V's for a long period of time. 

Rick Isard 
Cordless Renovations, LLC Most LEDs are rated for a maximum of 3.6V per mm. Thus a 3mm LED at 18V would be a whopping 6.0V per mm.









This would surely convert it from being a *current operated device*







*,* into a one-shot smoke device.


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## Greg Elmassian (Jan 3, 2008)

Uhh... Izzy, you might want to read the thread from the beginning..... or at LEAST the two before your post: 

*HD1 and HD common the LED is real bright, 24V on the meter, HD off kills it and reverse/ direction works properly. 
HD2 and HD common appear to give a constant 1V regarless of HD on/off and direction. I wonder if the HD 2 part of the circuit is bad? *

His LED works on the OTHER Revo output. so the LED is fine and it's the Revo output that is bad. 

The situation is a bad "output" on the Revo. 

Greg


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## izzy0855 (Sep 30, 2008)

Oh yeh, just forget my last two post. 

Rick Isard 
Cordless Renovations, LLC


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