Auto-reversing headlights

[jimrice4449]

I'l try to make this as simple in explanation as it is in practice. I run my diesls in dedicated sets, that is a permanently coupled 3 unit set or a permanently coupled two unit set with the units connect with a metal drawbar. This requires that some of the trucks be reversed so that all negatve wheels are one one side and all positive on the other. I then run a power buss between units and disconnect the motor from the trucks on one side and connect it to the power buss. I then run a power pick up buss between the units and connect the trucks to it. This assumes that one side of the truck grounds on the frame and the orher is connected to the motor ( now to the power pick up buss). At this point you have no power to the motor. You now connect the two busses with a pair of diodes wired in series (both pointing in the same direction) at one end of your power consist and connect another pair of diodes at the other end of the power consist but aligned in the opposite orientaion of the first pair. If your engine at this point runs in only one direction, you need to reverse on set of diodes. When your eng runs forward and backwards. solder the leads from a 1.5 volt bulb to each end of the pair of diodes on both ends of the power consist. If your luck runs like mine at this point when you run your engine east the west light will go on and vise versa. All you need to do then is reverse both pairs of diodes and you're off. The drawback to this system is if you gang two sets of power consists , the lead engine in each set's headlight will go on.

[SP4449]

Yes, and if you lay them end to end on a flat surface with the polarity bands facing the same direction, that will happen. Do that, then solder the touching wires together, and that junction is where one of the motor leads will connect.

[lonewoof]

Ah, SP...don't you need to have the diodes connected OPPOSITE each other? tie + of one to - of the other?
/lone

[SP4449]

Yeh, George. You need two half-wave rectifier circuits. You can build them from components from the "Shack". Also get a copy of Engineers Mini Notebook, "Electronic Formulas, Symbols and Circuits" by Forrest Mims from the "Shack" and look at the top page 40 or 112.

The lamps and diodes have to have a voltage rating equal to the output of the power pack track voltage.

Connect a lead from each diode together with the polarity marks facing the same direction.

Connect a lead from each of the headlights to an unused lead of each of the diodes.

Connect the free ends of the headlight leads together. This hookup makes a sort of a rectangle.

Connect a lead from one of the motor connections to the joint between the diodes.

Connect a lead from the other motor connection to the joint between the lamps.

Set this up as a test in case you get the connection backwards. If the loco is going forward and the backup lamp comes on, reverse the two leads from the motor to the diode and lamp connections.

Once you have the correct connection, make it permanent by insulating the diode and lamp leads from each other and the metal parts of the loco.

Good luck.

[rogerhensley]

Ok, this'll draw static from someone, but here goes. I have converted three older Athearn locos to reversing headlights with two diodes and two 6 volt GOW (Grain Of Wheat) bulbs. I replaced the 12 or 16 volt original bulb with the 6 volt bulbs and diodes. No, I don't burn out bulbs. I did my first conversion in 1997 and the locos are still lighting their way quite well.

This does have the effect of slowing the loco down which wasn't a bad thing in the case of the Athearns.

[Anonymous]

I'm sticking with DC for my shelf layout (not sure whether I'm chicken or just cheap). How can I wire my locomotives so that the back up headlight goes on when I reverse the engine? I know there are kits out here, but I'd like to do it with components to save money. I remember doing something with Radio Shack do-hickies back in the Stone Age, but I've long forgotten how to do that. Can anyone help?
Thanks, and have a Happy New Year!
George