Electrical

General Notes

There are many schools of thought on how to wire your layout, and I'm sure that there are many people smarter than I who will disagree.  However I have two standards that I use on my layout that seem to work well.  First, I always power my switches (I use the Atlas snap variety) with DC.  They run quieter this way, and this allows for matrix control (which I don't use yet).  My other standard is that all other devices run off of AC, usually with a diode to cut the power supplied in half.  Diodes are easy to use, and don't generate the heat a resistor does.  Also AC transformers tend to be much cheaper than their DC counterparts.

Computing Resistance

Whenever you add electrical devices that cannot withstand the full power of  your main electrical bus, usually 12 to 16 volts, you must add a resister to keep the device from burning out.  The proper resister to use depends on the amount of power you are feeding it, and the unique characteristics of the device.  here's how to figure it out:

• Use Ohms law to compute resistance for each item on the circuit. The Ohms is the measure of resistance for each device. Ohms law says OHMS = Volts / Amps. For example a 1.8 volt grain of wheat bulb that draws 60 milliamps (.060 amps) would have 30 ohms of resistance.
• Add up resistance values for all devices on the circuit
• Subtract the answer from 200 for a 12-volt power supply, or from 266 for a 16-volt supply. The result is the Ohms rating of the resister needed. Always round this value up when choosing the resister.
• As a rule of thumb, if there are more than five bulbs in the set, use a resister rated at 1 watt. Otherwise a rating of 1/2 watt is acceptable.
• If you can’t find the resistance value needed just string two resistor in series and add their resistance values together.