I have HO built up structures with lights included. Two wires. Power pack has one AC connection -how do you wire/connect the lights?
Buy another powersupply and hook it up to that. 
It’s not a good idea to share track power with accessories as the unit shares the same transformer. I personally use a computer power supply. It provides 12, 5 and 3.3 volts at 15+ amps each. The best part is I got it for free.
The general idea is to hook the lights in parallel to the AC output connection. I have often found that in that scenario the lights are too bright. So when I used this scheme, I connected the lights for two buildings in series and then put the sets of two buildings in parallel to the power supply. This reduces both the light and heat coming from the light bulbs. That way the buildings don’t “glow”, the plastic won’t melt, and the bulbs will last much longer.
Often the problem with this standard lighting scheme is that as the train needs more or less power the light bulbs will dim or flicker. As SteelMonsters says it is often better to get a separate power supply. If you do that, get one that is rated 3/4 the voltage of the bulbs and hook all the light bulbs in parallel as first mentioned above. This will keep the brightness down and make the bulbs last longer, and since it is a separate power supply it will not effect or be effected by the running of the train.
I use a cheap trainset power pack to control the lights. I also use 12 volt light bulbs. If you turn the power down, you can dim the lights to a more realistic level. As you add lights, the voltage stays the same, but the current goes down. Being able to control the voltage helps to brighten things back up. Or as stated earlier, a PC power supply hooked up to the 3 or 5 volt connections would work great for grain of rice/wheat bulbs. Don’t wire ALL of the lights into the same circuit. Wire them in blocks (street lights on one circuit, house lighting on another, stores/warehouses on another, etc.
Medina, how do you wire different lights to different circuits?
Larry
You didn’t mention what size lights you are using. 120 volt, 12 volt, something else?
All light bulbs will work on AC or DC, but you can burn them out quick if there is too much power. Best to use a separate power supply for lighting. An old hobby powerpack works well. You can use all terminals, AC or DC, for lighting.
To get the most out of your lighting, you need to know a few things. What voltage the bulbs are rated for, how many watts are the bulbs rated for and how many lights need to be connected will be the basis for determining your power source and how the circuits are wired. For example, the old-style Christmas bulbs (not the mini ones), were rated at 7 watts on 120VAC. If you run them on 12V, their light output is 1/10 of 7 watts, in other words, much dimmer. They will last forever at that voltage and you can connect dozens together and not exceed your powerpack ratings.
Ohm’s Law is V=I x R, where V is voltage, I is current (amperage) and R is resistance (wattage). Using this formula, you can match your lighting requirements to your power source. For our model lighting purposes, a series-wired circuit and a parallel-wired circuit will have the same current draw. In a series-wired circuit, the wiring daisy-chains from one bulb to the next. In a parallel-wired circuit, each bulb draws from a common hot (or + ) wire and a common neutral (or - ) wire. The practical difference is whether you want to search for a burned out bulb in a long series-wired circuit, since in series, if one bulb goes dead, the entire circuit goes dead. In parallel, if one bulb goes out, the rest stay lit, albeit at a higher voltage, since the bulb that went dead is no longer using current. The current is still there, but now it’s divided by fewer bulbs. The bulbs glow brighter because there is less resistance in the circuit. Nice how that works out.
In practice, a mix of series- and parallel-wired circuits is a good compromise. It gives you an easy way to isola
I agree with the above post in all ways except one.
“In parallel, if one bulb goes out, the rest stay lit, albeit at a higher voltage, since the bulb that went dead is no longer using current. The current is still there, but now it’s divided by fewer bulbs. The bulbs glow brighter because there is less resistance in the circuit. Nice how that works out.”
In a mini christmas string of lights this is true. When the bulbs burn out, they also short out. This reduces the resistance since there are less bulbs in series but it also keeps the bulb lit. In a parallel cirucit, this isn’t true. The resistance increases as less load is placed in parallel. The bulbs should light with the same brightness no matter how much load is on it, with the exception of overcurrent of the cirucit.
In real world circuits, all kinds of complicated loading dynamics occur. Unregulated supplies have terrible changes of voltages depending on current used. Regulated supplies vary form 10ths of volts down to micro volts of variation. In any case, it’s not the circuit, it’s the power supplies response to the load that causes the situation.
I use power supplies for many reasons. They are cheap, very efficient, tough/rugged/abusable, reliable, give many voltages with 3 at high current, regulated for very sensitive computers, have overload protection, easily switchable by several means, and did I mention easy to get for free?
There are 5 voltages in most supplies. +12, +5, +3.3, -5, and -12. If you subract any two, you get many more voltage referances.
+12 and +5 gives you 7
+5 and +3.3 gives you 1.7
+12 and +3.3 gives you 8.7
- 5 and -5 gives you 10
+3.3 and -12 gives you 15.3
and so on.
The instant a cold bulb gets power, it gets a rush current 10X the normal current. Every bit you undervolt these bulbs gives it much longer life. 3/4 voltage gives you a very low chance of replacing many bulbs ever. Try to get away with as littl
To wire the lights in different blocks, use 5 or 6 switches. I use 3 or 4 switches for for the interior lights. I even stagger them, so that each switch will light buildings not necessarily next to each other, but light buildings in other sections of town. I use the rest more for exterior lighting. For special purpose circuits, I use momentary contact mini push buttons. I found some neat microcircuits that have saw mill noises, welding flash, etc. You could even activate them with train detector circuits so that they come on as a train approaches that part of the layout, but that’s another forum.
- Connect a wire from one pole of your power supply to one lug on each switch.
- Connect another from each of the other lugs to separate terminals on a terminal strip.
- Connect a wire from the other pole of your power supply and connect it to a terminal strip. This will be your common.
- Run a length of wire from the terminal controlled by each switch the length of your layout. plus one more connected to your common. This last wire will be your common buss.
- Wherever you put a light, solder one lead to the wire controlled by the switch, and solder the other to your common. This will wire your lights in parallel. If one burns out, the others will be unaffected.
- Do whatever you can to make service and repair easy. I am putting mini sockets in my buildings and plugging the lights into them. Since my layout is built on foam, I stick a small straw through the foam, and run the wires from the socket through it and then solder them through the buss wires. That way, when a bulb burns out, I don’t have to rerun the wires through the foam. If you’ve ever tried to get those mini lightbulb wires through 3 or 4 inches of foam, you understand why I made it so that no matter how many bulbs I have to replace, I only have to run wires through it once, and the straws make it even easier.