Tech Corner By Tom Fassett

 The idea behind this feature is to highlight and explain the technologies behind lighting, animation and anything that deals with electricity in the miniatures world. Too many modelers seem to be scared to death of anything that deals with the movement of electrons through a solid medium and I hope to change that feeling. We are not dealing with large voltages or currents here, so the chance of blowing out a wall in the house is remote. Now, that is not to minimize the practice of safe handling of electrical devices, but only to put things in perspective. You still may get a "pop" and a puff of smoke from time to time, but life as we know it will go on (although perhaps not for the bulb that went "poof").

For the immediate future, we will deal with some simple basics. For those who are beyond this, you can check out some of the more specific tutorials in the allthingsmini.com forum. We will be adding to this as time permits.

First off, electricity does not involve the "black arts," no matter what some people may think. Often, a lack of understanding is perpetuated by the belief that one must understand the complete theory of a principle before utilizing it. This may be true for sending spacecraft to other planets but not for lighting the dollhouse. There are a few basic principles that apply to the use of electricity in most instances we are apt to confront.

First, the voltage of the power supply must not exceed the voltage rating of the device it is powering. This is one of the most common mistakes people make when choosing bulbs for a miniature scene. If you use bulbs rated at 3 volts on a 12 volt power supply, they are going to burn up. If you use bulbs rated at 6 volts on a 12 volt power supply, they are going to burn up. In other words, you must use bulbs rated equal to, or more than 12 volts on a 12 volt power supply or they are going to burn up... You get the picture. Now, if you use a bulb rated at more than the output of the power supply, it will not burn up but will be dimmer than normal. Sometimes this is a desired effect. Mostly though, we are concerned with getting the most brightness out of a bulb so it should match the power supply.

Second, the circuit must be a complete loop (but passing through a resistance device). If the electrons cannot get back to the transformer, they will not move through the wires and nothing happens. That is why there are two conductors (separate wires) in each circuit. This does not mean that the two wires have to return to the transformer--it means that both must be connected to the proper terminals on the transformer and there must be at least one device connected at the other end. This is "the loop." If there is a break in the supply wires, the power will stop right there. If half your bulbs are working and you only have one transformer, there is a break in the line between the last working bulb and the first non working bulb. The part about "passing through a resistance device" just means that there needs to be some device (such as a bulb) in the loop that uses power. If you connect the two wires together without anything on the line you get what is called a "short." This translates into a burned up transformer. Rule of thumb--don't cross the wires...

Third, bulbs and other electrical devices need current. This is the amount of power flowing through the line. Current is independent of voltage and needs to be addressed in a similar way. Unlike voltage, the current rating of a power supply can greatly exceed the current rating of the bulb. This is due to the fact that the bulb will only draw as much current as it needs. I will forgo the "higher math" in explaining this but it has to do with resistance and "voltage drop" of the device, among other things. The important thing to remember about current is that you must use a power supply that is rated at higher than all the current requirements of the devices or bulbs (the opposite of voltage). If you do not, the bulbs will not run at their full brightness and the transformer will heat up (and probably burn out). You need to add up the current requirements for all bulbs or devices to figure out how powerful a transformer you need. If you are using 10 bulbs with a current rating of ¼ amp each, you will need a transformer that can provide more than 2.5 amps. I say more as it is best to leave a little "headroom" to keep the transformer from getting too hot. The closer you get to the maximum drain, the hotter it gets. Often, bulbs are listed with their wattage ratings. Wattage is really a concept that gives you an indication of the amount of power a device uses or a transformer puts out. This can be confusing as we are often faced with information that uses different nomenclature. Essentially, watts are the voltage of a device multiplied by the current. If you have a 3 volt bulb designed for 1 amp of current, it uses 3 watts. If you have a 10 volt bulb that needs ½ amp, it uses 5 watts. If you have a 12 volt transformer that puts out 2 amps, it is a 24 watt transformer. The same can be said in reverse (and is called Ohm's Law); a 12 volt 24 watt transformer puts out 2 amps (in this case, wattage divided by voltage gives current). Simple algebra... ;- )

We will explore other specifics in the future but don't forget to check the Electricity, Wiring and Lighting topic in the forum. There you will find more detailed answers to specific issues and if you don't see what you are looking for, just ask. There are a number of knowledgeable people ready to help. So stop wishing you could light that 20 room house and start doing it!