I plan to have approximately 50 incandescent street/building lights on my layout in addition to some LEDs. Since each light is about .08A, I will need a 5A transformer. It will also be used to dim the lights. Any suggestions for the make and model of transformers available?
you could always use multiple transformers and have more than one circuit?? no need for one big circuit, you could then turn lights on in sections to be more lifelike??
Might also consider using a standard wall mount dimmer between the outlet and the transformer.
Sounds like you are asking about a variable voltage DC power supply. A transformer is a device that steps AC voltage either up or down. There is no such thing as a DC transformer.
A couple of questions. What is the voltage rating of the incandescent bulbs? Are the LEDs the type with built in ballast resistors? If so, they will have a voltage rating, and it would need to be the same as the incandescents. If the LEDs have a lower rating, series resistors could be added to match the incandescents.
If the LEDs do not have built in ballast resistors, you will have to provide them yourself. The value of the resistors will depend of the current rating of the LEDs, the voltage rating of the incandescents (or maximum voltage of the power supply), and how bright you like your LEDs.
Ordinary lamp dimmers are not suitable for use with inductive loads, such as a transformer. There are multiple problems with doing so, including potential excess heating of the transformer. Don't do it.
Recovering former former model railroader.
Incandescent lights can be run on either AC or DC. I use 16-volt bulbs for all my lighting, and run them at a fixed 12 volts AC out of a small power supply. This gives me the "warm glow" I want, and will greatly extend the bulb life. Most of these are grain-of-wheat bulbs that only draw about 30ma. My guess is that once you settle on the "ideal" voltage for your lights, you will never change it, so the need for a truly variable supply just isn't there.
Most of these power supplies, by the way, do not have circuit breakers built in. Instead, there's a one-time fuse inside, basically there to keep your house from burning down. Once that fuse goes, the supply might as well be discarded. So, I put a lower-rated fuse in the line to protect the supply.
It takes an iron man to play with a toy iron horse.
I have about 15 old HO transformers, each having approximately .9A capacity. That is an alternative but I was trying to avoid using sooooo many and the additional wiring. I do have a lot of strapping wire (28ga maybe). Would this be sufficient for a 50' run???
The incandescent bulbs vary between 6V and 12V. The LEDs between 9V and 12V and have built-in resistors. I tried to use lamp dimmers and got zero light output. Since I have a plethora of .9A HO transformers AND I want to dim the bulbs in different lighting environments, I just may go that route. I was just hoping I could buy a reasonably priced variable power supply with a higher amp rating to control 40 bulbs or more. I may end up with several hundred bulbs before I'm through. I love lights with dimmers! Almost every light in my house is on a dimmer!!!
You need something like this: http://www.alinco.com/Products/DM-340MV/
I have two.
Search eBay for "Alinco Power Supply." Since they make or made several suitable models, you don't want to limit yourself to a single model by including a model number.
You can also find this stuff at local ham fests. Search for ham fests near you here: http://www.arrl.org/hamfests-and-conventions-calendar
If you want to power different types of lamps from the same supply, you may need to construct some sort of balancing network using power resistors or ballast lamps. Studying up on basic DC theory will help, if you don't already have that under your belt.
Thanks guys! I decided to buy three 5A power supplies to handle all my lighting requirements. They are all variable so I dim the lights to my hearts content!
Use the LM138 voltage regulator chip that is good for 5 amps when the chip is bolted to a piece of aluminum heat sink.
A couple capacitors, one 240 ohm 1/2 watt resistor and a 5k, 2 watt potentiometer.
With three of these tied to a 24 volt DC 20 amp power supply and you will have plenty of capability. The input voltage has to be at least 3 volts higher than what the regulator voltage is. Power supplies of 24 volts DC are rather common.
A variable DC supply of 5 amps or more may be more expensive than just a unregulated DC supply.
If you are not sure of the power supply filtering, use a 5000 to 10,000 ufd cap on the output of the unregulated supply.
I have done exactly that using LM317, 1 amp regulators powered by a 16vdc output of an old MRC power pack.
I have seen this done using a battery charger as the basic DC unregulated supply.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.