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How to Choose a Dolls House Transformer


A transformer or AC/DC adaptor or power supply is an important part of a dolls house electrical system. The transformer reduces the voltage of your home power supply down to the 12 volt system which runs dolls house lights. If you are not using battery operated dolls house lights, you will need to use a transformer to supply power to your dolls house. You need to plan carefully so that your transformer will power all your dollhouse needs.
Difficulty: Easy
Time Required: One Hour or Less

Here's How:

  1. Know Your Household Power There are two basic world electrical standards for voltage and frequency. The North /Central American and Japanese standard is 110-120 volts at 60 Hz and the European/Rest of World standard is 220-240 volts at 50 Hz. Your transformer must be compatible with your household electric power supply. Some dollhouse transformers will be rated for AC 100-240 V. These can be used in either Europe or North America. Transformers rated for 110 – 120 V AC can only be used on 110-120 V systems, and transformers rated for 220-240 volts can only be used in countries with 220 volt power supplies.
  2. Know What a Transformer Does The transformer takes the household current and reduces it to 12 volts which is a suitably low power to run dolls house light bulbs. The amount of power your transformer puts out, is sometimes listed in watts, or more correctly in Amps or amperes. 1000 milliamps = 1 amp. If your transformer lists its output in watts, you can convert that to amps (the current drawn) by dividing by 12, the number of volts the transformer is rated for. A 20 watt transformer would produce 20 / 12 = 1.67 amps of power.
  3. Read The Transformer Label If you don't know the power output of your transformer, the label should tell you some basic information.


    The information given on top of a typical Cir-Kit Concepts systems transformer Cir-Kit CK1009C for example, lists an input of 120V AC 60hz 30Watts and an Output of 12V AC 20 watts. Circuit Breaker Protected. This means this transformer will output twenty watts of AC power, is rated for North/Central American household 110V current and has a circuit breaker built in.

  4. Buy a Transformer With a Circuit Breaker Built In Always protect your system with a built in circuit breaker. If the system shorts or overheats, the circuit breaker will open, and the transformer will stop working until the unit has cooled down, when the circuit will close and it will start or need to be reset to start again. This reduces the danger of major shorts or fires.
  5. Check the Label or a Website for More Information A more powerful transformer from Small World Products states it is an AC to DC adaptor, rated for AC 100-240 volt with an output of 5 amps at 12 volts. This would be rated in watts as a 12V x 5amp = 60 watt transformer. This transformer converts alternating household current (AC) to Direct Current (DC) and is circuit breaker protected. It also is listed as a regulated electronic power supply with Switch Mode. The power is more likely to be uniform and even in its supply. A Flicker unit on this transformer is unlikely to cause the flicker of every light in the system.
  6. Choose How Much Power You Need for Each Room. The amount of power your dolls house transformer needs to supply is related to the number of bulbs you will have operating. Common screw in dolls house bulbs usually require 50 - 60 milliamps of current to operate. If you have a room with a 12 bulb chandelier and two, two bulb sconces on the wall, you will probably need to have 12 + 4 = 16 x 60 or 960 milliamps of power. Rounding this up to 1amp you will need a 1 amp transformer, or a 1 amp x 12 volt = 12 watt power supply , just to run this one room.
  7. Add the Power You Need For All Your Rooms For a kitchen with a three bulb fixture over an island, three small lights under the cabinets and a fluorette as a source of light behind a picture in a window to create a view outdoors, you need to calculate the draw of the different bulbs. Fluorettes draw more light than regular bulbs. 6 x 60milliamps for the main bulbs = 360 milliamps plus 70 milliamps for the fluorette for a total of 430 milliamps for your kitchen, or almost 1/2 amp. Combined with the first example that needs a 12 watt supply of power, you are up to 18 watts for a dining room and kitchen combination.
  8. How Many Bulbs Can You Run with 1 Amp of Current? Plug in bulbs (with two wires) are more efficient than screw in bulbs. Generally you can run 20 of these bulbs with 1 amp of current (50mA per bulb). For Screw In bulbs the ratio is roughly 14 bulbs per amp of current. Special lights like spotlights have much higher power requirements. You can check the rating of several kids of bulbs in the Small World Products catalogue.

    Your transformer puts out current according to this formula. Current(Amps) = Power (Watts) / Voltage (Volts)

    1,000 milliamps = 1 amp of current.

  9. Use Tables to Get a Rough Guide for Transformer Requirements Several doll house companies have tables listing the number of bulbs you can run with a given amperage or wattage. The actual number of lights will depend on the rating of each bulb, so these tables should be used as a rough guide only. Always work out the number of lights you plan to have in a showcase, roombox, or dollshouse, and allow for about 20 percent extra for expansion - a working train set, or other electrically powered follies!. Large dollhouses may use several transformers with several different circuits to allow for lighting control.
  10. Does AC or DC current make a difference? The only practical difference in a 12 volt system is that DC (direct current) only flows one way, it has polarity. Light Emitting Diode lights (LEDs) must be purchased according to whether they are AC or DC. DC ones will run from a battery source. If you plan on using a lot of lighting built for railway items so that you can adapt it to a quarter scale dolls house, you may want to have a DC transformer, as railroad lights are usually (but not always) powered by DC current, and if they use LED's they will only work on the current they were designed for.

What You Need

  • List of the Rooms In Your Dollhouse
  • Rough Circuit Plan Showing the Number of Lights in Each Room of Your Dollhouse
  • List of the Number and Type of Bulbs in Each Dolls House Light You Will Install
  • Calculator, Pen and Paper

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