Hi Guys,
I've begun lighting up buildings and adding streetlights to my layout. For power, I'm using the "accessories" output of a 12 volt power pack. I hooked 1 wire coming from the pack up to an "on/off" switch so when I throw the main power to my whole layout, the lights don't come on. To turn on the lights, I push the "on/off" switch to complete the circuit for my lighting. Obviously, I don't want the building lights and street lights on all the time.
Today, when I added probably the 30th light to the circuit, the lights got so dim I realized I need to add another power pack. As I was thinking about it, it sounded like an overload protection kicked in because all my lights went out and I heard what seemed to be a ciruit breaker in the power pack. Did I actually "overload" the circuit by putting too many bulbs in parallel? My question is this.....can I just hook up the "accessories" output from a 2nd pack to the same circuit, thus feeding 2 pack's worth of power to my lighting circuit or will hooking up the 2nd pack create a doubling of the voltage....12volts plus 12volts equals 24volts....thus burning out my 12 volt bulbs?
The reason I'd like to hook the 2 power packs together is so that I can hook them both up to my "on/off" switch, thus enabling me to turn the lights on the whole layout "on" or "off" with a single switch. It's not that I am lazy, but it looks like considering the size of my layout, I may end up having 4-5 power packs feeding all my lighting and I really don't want to have to turn 4-5 switches on to get the whole layout lit up. Right now, the first pack I used for lighting is doing double-duty, so to speak. The DC output runs my engine turntable and the AC output feeds my lights. I guess one answer would be to have all the "lighting" power packs only do single duty....in other words, have them only be used for lighting and plug them all into a power strip with an "on/off" switch.
Thanks in advance for any help you can provide.
Mondo
Yes, you definitely overloaded that single power pack with that many bulbs.
Whether you can get by using two power packs depends on how you hook them up --
Two 12 Volt (Actually 16 Volts AC on the "Accessory" terminals) power packs connected in parallel will double the amperage output; connected in series will double the voltage.
Thank you for your input! If I understand you correctly, I can hook up a 2nd power pack in parallel....I'll have the positive terminals from both packs hooked to the same red wire and the negative terminals of both packs hooked up to the black wire and then I will have kept the same 12 volts but doubled the amps available. If I do this, then I can have both packs hooked up to the switch I mentioned....the "on/off" switch that turns on my lights, correct?
If I need 4-5 packs to run all the lights on my layout, then I could end up having 4-5 amps running through the "lighting" circuit. Will I have a problem using 18 gauge wire for my "lighting" bus wires feeding around my layout? And, what about those small wires that attach to each bulb and drop down to the bus wire? Are they a problem?
Thanks,
I don't like connecting the secondaries of two different power packs together at all. You're asking for trouble if you do that.
If you need multiple power packs, you would probably be better off getting a single power supply that can handle more power. Alternately, break the load down into several different loops. I have two sets of structure lights, another one for my train yard lighting, and one for street lights.
I would also separate the turntable from the lights. Right now, you're pretty close to maxed out on that power pack, so I wouln't be surprised if running the turntable with the lights on didn't pop the breaker, too.
To maintain the single on-off switch convenience, plug all of your lighting power supplies into a single outlet strip, and use the strip's on-off button to turn them all off at once. That way, you won't be running a bunch of power supplies when you're not running the lights that are connected to them.
It takes an iron man to play with a toy iron horse.
Thank you for your input, MisterBeasley, As always, as I have seen very often on this forum, you come up with some informative and thoughtful answers to questions.
I'm going to follow your direction and have various power supplies plugged into a power strip which when turned off, will prevent me from "running a bunch of power supplies when I'm not running the lights that are connected to them".
When you suggested I get a larger power supply, I wonder if I should get a 5amp supply that could run a whole bunch of lights, rather than a train power pack. I have a "Pyramid" 5 amp power supply that I use to charge my radio control airplane flight batteries. Do you have any idea how many lights a 5amp supply could run. My understanding is that about 14 bulbs could run on 1 amp...so I'm guessing 5 amps would supply power to about 70 lights.
In my current set-up, I thought that by adding more and more lights, all I was doing was "spreading" the voltage over more lights and that's why the lights got dimmer as I added more. I thought the dim lights looked better but didn't realize that I was overloading the circuit. How do I determine that I'm overloading the circuit.....do I just assume that 14 bulbs take 1 amp and calculate from there?
I also will remove my turntable from the pack that is supplying power to my lights, as you suggested.
One last question, I have 5 overhead flourescent light fixtures, each with two 40-watt bulbs in them. That totals to 400 watts. When I ran my flourescent lights last summer, at the same time our wall air conditioner was on, I blew my 15amp circuit breaker linked to this area. Do you know how many amps my light fixtures are drawing? I know amps = watts divided by volts. Does that mean the amps would be my 400 watts divided by 120 volts...or 3.3amps?
Thank you again for your help.
Please do NOT connect the outputs of two or more power supplies in parallel. This is asking for disaster.
While theoretically possible for identical power supplies, in the real world you will always have issues of imbalance, stray currents, heating and a 50/50 chance of phase mismatch. It's far better to divide your lighting into districts. This will also give you more control. You can turn some areas on and others off instead of all or nothing.
Good luck.
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You might want to look into the 12V power supplies sold on e-bay as power sources for "notebook" or monitors. Probably not the most regulated supplies but for lights etc not as critical.
As to the light question, yes you have the formula correct. Some fluorescent fixtures have a ballast which also consumes some additional power so you might be pulling more than 3.3 amps.
Co-owner of the proposed CT River Valley RR (HO scale) http://home.comcast.net/~docinct/CTRiverValleyRR/
Your math is correct. That Pyramid supply would make a first class supply and it probably has its own on/off switch and indicator light.
Amps x volts = watts. A 15 amp circuit will max at 1800 watts. Rule of thumb is 80% of that so figure 1450 watts. 400 watts of lighting plus an AC unit, especially if the compressor is starting will overload the breaker. It's best to put the AC unit on its own circuit. Lighting is usually the largest load in a house or business. It's usually placed on separate circuits. That way when you plug in an appliance and the breaker trips the lights stay on and you can find the electric panel.
Just like everything else on my new layout I've broken lighting up into districts as well. Using simple/cheap wall wart power supplies I run the leads to a terminal block located under a specific area such as an industry or factory complex, town etc. and run the lights form the buildings down to the terminal boards. By breaking them up into smaller groups the demand isn't all that much and the smaller power supply is more then sufficient. I've been playing around with some LED lighting on the work bench so as to draw even less power for a large factory complex I have planned. I don't have a heck of a lot of experience with LED's so it's a learning process.
I have heard that some guys find that a computer power supply is a good power source for things like lighting and switch machines etc. on model railroading.
In calculating the load for your fluorescent lighting we used to add %20 for the ballasts. Not sure if this is the same for the new electronic ballasts or not.
So 400 Watts + 20% = 480 Watts/ 120 Volts = 4 Amps
Your problem is the air conditioner should be on a separate 15 Amp circuit as was advised by another poster.
mondotrains When you suggested I get a larger power supply, I wonder if I should get a 5amp supply that could run a whole bunch of lights, rather than a train power pack. I have a "Pyramid" 5 amp power supply that I use to charge my radio control airplane flight batteries. Do you have any idea how many lights a 5amp supply could run. My understanding is that about 14 bulbs could run on 1 amp...so I'm guessing 5 amps would supply power to about 70 lights.
As the others as have already pointed out, hooking two power supplies in parallel is a bad idea. If they are not truly identical in performance as well as specs, you will not get the full double power, and there will be fault currents between the two which may or may not be protected from by circuit breakers/overload limiters.
I'm also not a big fan of 5 amp plus power supplies unless you understand what you are doing and take precautions. If you don't use big enough wire with high currents, the small wire may present enough resistance that the circuit breaker never trips when the short circuit occurs. The small wire restricts the current to 4.9 amps, the circuit breaker doesn't trip, and the wire gets burning hot - hot enough to melt foam or ignite paper. If you are going to use 5 amp or bigger power supplies, use at least 18 gauge wire and make sure the circuit breaker works when the wiring is complete by intentionally causing a short at the far end.
In my current set-up, I thought that by adding more and more lights, all I was doing was "spreading" the voltage over more lights and that's why the lights got dimmer as I added more. I thought the dim lights looked better but didn't realize that I was overloading the circuit. How do I determine that I'm overloading the circuit.....do I just assume that 14 bulbs take 1 amp and calculate from there? I also will remove my turntable from the pack that is supplying power to my lights, as you suggested. Mondo
The various bulbs we use in model railroading have both a voltage and current rating - but the current rating is not always easy to find. Currents add in parallel circuits. 12 volt and 14 volt bulbs typically range from 90ma to 150ma. The small 1.5 volt bulbs can be as low a current as 30ma with 50ma being more common. A 12V car tail light bulb might draw as much as 2.5 amps. LEDs can substantially reduce the electrical load because of their efficiency.
hope this helps a little
Fred W
I am a big fan of multiple independent power supplies, and I don't like anything that might reduce the power available to run trains.
That means a separate power supply for each cluster of illuminated buildings (including streetlights.) Signals and panel indicators share other power supplies. Switch machines are on separate circuits, because a twin-coil power spike would dim every light in town.
So, what do I have in the way of suitable power supplies?
Note that none of these are parasitic on train propulsion power. All of them are plugged into power bars with 120V switch/breakers. If I notice that I've come close to overloading any circuit, I either provide a more powerful supply or split the load and add a second supply.
Of course, you could use one of those humongous 120 watt transformers designed for outdoor low-voltage lighting... (Not in MY layout room, you can't!)
I also use lower-voltage lamps - specifically those 150 and 300 lamp miniature Christmas tree strings that the stores sold off at pennies per lamp the week after Christmas. Wired in series, those 2.5v lamps can be load-adjusted for bright industrial lighting or softer, yellower residential lighting - and if one dies, it can be replaced in seconds. (I also install the sockets.)
When it comes to layout electricals, sometimes several low-amperage circuits trump one high-amperage circuit.
Chuck (Modeling Central Japan in September, 1964)
I really appreciate all your thoughtful and insightful responses to my questions.
I will probably break up the lighting of my layout into about 6 "districts". My layout is essentially 3 penninsulas, with each one separated by a backdrop, creating 2 entirely different scenes. I will heed advice previously given and use a power pack for each of the 6 districts, which means about 25 lights on each pack. My next question pertains to power packs. I noted that I can get some good deals on Ebay....MRC Tech II 17va pack for around $20.00. Am I correct in assuming that the cheap power packs that come with small trains sets don't have circuit breaker protection? I don't mind spending a little more for packs like the MRC Tech II that have circuit breakers and provide 17va of power. I'm sure those little train packs don't provide as much power as an MRC Tech II, so I'd need a lot more of the small packs.
Nobody answered my question about why I was able to have twenty-five 12volt lights strung on my first "lighting" power pack, with the lights getting dimmer as I added each one and then, when I added another 7 lights, the pack got overloaded. I thought by adding more lights, I was just spreading the power over more lights and could do so until the dimmness was unacceptable. I think if I remove the last 7 lights and go back to the 25, I should be okay. But, I still don't know why those extra lights tripped the breaker. Do I assume that 25 lights will be okay if I buy additional power packs with the same volt/amp power?
Probably. I use a lot of Miniatronics lights, and they run about 30 milliamps per bulb. Twenty five of those would be 750 milliamps. If you added 7 more, you'd be up to 960 milliamps, pretty close to the 1 amp rating. The numbers are all approximate, but given your results with 25 and then 32 bulbs, I'd say the bulbs you're using are pretty close to these.
For my lights, I found a 4.5 amp AC supply (a big wall-wart) for about $20 at an electronics place. But, be warned on these wall-wart supplies. Many have no circuit breakers. My previous "lighting supply" was a 1.5 amp unit, and I overloaded it. There's a built-in fuse in the supply, but it's a one-time thing, and then it's time to toss the supply and get a new one, because the supplies are sealed, and the fuses can't be replaced.
mondotrainsNobody answered my question about why I was able to have twenty-five 12volt lights strung on my first "lighting" power pack, with the lights getting dimmer as I added each one and then, when I added another 7 lights, the pack got overloaded.
Oops. Sorry 'bout that.
It's simple really. (Assuming the lamps were all in parallel). You just kept drawing more and more current from the power supply with each added bulb. Every supply has a small but finite internal resistance. As you drew more current, there was more voltage "drop" across that internal resistance resulting in less for the bulbs and dimming. Eventually, you exceeded the current capability of the supply.
Karl
mondotrainsI thought by adding more lights, I was just spreading the power over more lights and could do so until the dimmness was unacceptable. I think if I remove the last 7 lights and go back to the 25, I should be okay. But, I still don't know why those extra lights tripped the breaker. Do I assume that 25 lights will be okay if I buy additional power packs with the same volt/amp power?
Nope. As you added more lights you drew ever closer to the point where the supply could not handle the load you placed on it. All power supplies have a maximum current rating. You exceeded the maximum load for this one and it shut down.
Don't just assume that going back to 25 lights is OK. Find out how much current each bulb draws and figure out the total load. If the load is more than 75-80% of the Amperage rating of the supply, that's too much load. Never load a power supply to maximum capacity.
It sounds like you need to split up some of your lighting and add some more power supplies. Because you seem to be somewhat of an electrical novice, I would advise against buying a 5 Amp supply for safety reasons.
Mondo,
From your original description, my guess is that you have 30mA incandescent bulbs. If that is the case, the 30th bulb would bring you up to 90% (900mA) of your 1A power pack. Not a surprise that the bulbs started dimming. That's also pushing the total limit draw of the power pack so that it's probably running rather warm, as well.
Some food for thought. If it's not too late, you might want to consider wiring your lighting "in parallel" rather than "in serial" and use the DC output on your power pack instead of the AC. The advantage is that you can then dial down your power (with the power pack's control level or knob) so that your incandescent bulbs:
I typically operate my lighting at 55-60% power. (For example, a 12V bulb would burn at ~7V.) At that setting incandescent bulbs illuminate a very realistic and warm glow to them vs. a harsh bright light when operating them at full voltage. Your bulbs will also last much longer this way.
The disadvantage is that wiring your bulbs "in parallel" is a little more involved than just simply wiring them serially. I also like the ability to be able to turn certain lights off or on so that I can change the mood and appearance of the layout.
Now is also the time to figure out how you will change bulbs when they burn out. I've gotten into a habit of making my structure roofs "removable" so that I can access my interior lighting more easily. It's a little more challenging to do it this way but I know I'll appreciate it when the time comes to change them. If your roofs are already affixed to your buildings and structures, there are other ways to still light the interiors so that bulb changes don't become nightmarish.
Hope that helps...
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Thanks again to everybody for their insight.
I have wired my lights in parallel, but now will move them to the DC output on my pack so that they can be turned down, using the throttle to reduce the power. And, I will be breaking up my layout lighting into more manageable sections that can each be lit up by separate power packs. I will probably end up using 6 packs in total, dedicated to lighting.
Thanks again,