Flashing yellow beacon on DCC locos

[Doneldon]

My grandson wants flashing yellow beacons on his Bachmann DCC Diesels.  He has EZ-DCC so there is no way to program/control the decoder.  Consequently, I'm considering using a flashing LED connected "downstrem" from BOTH the forwrd and reverse lights, and then going to the common.  I've been afraid to connect this up because I don't want to fry the decoder or something.

Will this work?  My thinking is that I won't have a short because the non-working light, e.g.,  the reverse light when going forward, will be turned off (and conversely) yet there will still be current to the LED.

Thanks for any help/ideas anyone may have.

[OldTimer]

Somethimes the EZ-est isn't. 
Old Timer

[richg]

Below is a link to what might work. You will not have to mess with the decoder wiring from what I can see. Use the email address to ask the seller what might work. I have corresponded with him.

It would help to include more loco model details.

http://www.richmondcontrols.com/

Rich

[Jim Banner]

On decoders, the blue common wire that goes to both lights is common positive.  The white and yellow are open collector outputs to negative.  What this means is that you can connect the white and yellow wires (front light and rear light) together and that connection will go to the negative side of your flashing diode.  The blue wire, which is connected to both front and rear lights, is the positive and goes to the positive side of you flashing diode.  Usually the negative side of LED's including flashing ones is marked by a flat on the rim around the bottom of the LED and the positive is marked by a longer lead.  The only problem with this scheme is that both the headlight and rear light will now be on independent of locomotive direction.

If you want to keep your headlight and rear light directional, then add a couple of diodes.  These are quite cheap from an electronics supplier (your local Radio Shack may have them too.)  Type 1N4001 are suitable as are others in that family which differ in the last digit of the part number.  One diode goes in between the negative lead of the flasher LED and the white wire.  The other diode goes between the negative lead of the flasher LED and the yellow wire.  In both cases, the ends of the diodes with the rings painted around them go to the wires, and the unmarked ends to the flasher.

With a built in decoder, it is possible that the wires are not blue, white and yellow.  But there will be a common wire that goes to both lights.  Call it blue.  And there will be a separate wire to the front light.  Call it white.  And there will be a separate wire to the rear light.  Call it yellow.

The only problem that you might run into is that the front and rear lights may be LED's rather than incandescent bulbs.  If this is the case, the flasher LED will not work if wired as above.

The easiest solution then would be to install a bridge rectifier, a four legged bug that can change the ac on the rails into the dc that your flashing LED needs to operated.  A bridge rectifier has two terminals marked with tildes ( ~ ).  One goes to the left hand track pickups, the other goes to the right hand track pickups.  Ideally these would be black and red wires, but might not be.  The other two bridge rectifier terminals are marked + and - and they go to the positive and negative leads of your flasher LED.  The only down side of this solution is that the flasher will be on all the time - you will not be able to turn it on and off with the headlight and rear light.

If you really, really need to turn it on and off with the headlight/rear light control, and the headlight and rear light are LED's, then we are into a whole new story.  It can be done, but it means soldering things on the decoder circuit board.  Not a job for the faint of heart.

Jim

[Doneldon]

Thank you for your help.  I was sure that I would get a useful reply if you answered.

Doneldon

[kamerad47]

Can you explain the mod's to the decoder board to turn off beacon ??

[richg]

Can you explain the mod's to the decoder board to turn off beacon ??

If the beacon is tied into the headlight leads, you can turn off the beacon by turning off the headlight.

I doubt the factory installed decoders have a extra connection for other devices.

There are Function only decoders that can be used but they are not plug and play. You have to solder wires and install a resistor for LED's or 1.5 volt bulbs.

Rich