Electrical Glossary

Lots of what we do building droids involves electronics and electricity. There are a variety of terms you'll encounter.

THIS IS A WORK IN-PROGRESS, feel free to add (or correct) terms!!!

Terms

A (Amp/Amperes)

An ampere is a measure of the current or rate of flow of electricity along a wire. If wires were highways, this would kind of be like how fast the cars were going. More amps mean more energy (watts) are available and so you can have more powerful engines or brighter lights. More amps also need thicker wires or the wires get too hot and can melt or catch fire. (That's how some fuses work, when the current gets too high, the little wire in the fuse melts, interrupting the circuit).

Ah (Amp Hour)

The number of amps provided in an hour. Often used to measure energy density, like in a battery. Theoretically an 8 Amp-Hour battery could provide a 1 amp current for 8 hours, or an 8 amp current for 1 hour. Of course there are restrictions, like we don't want to overcharge or overdischarge a battery, and different flow rates can be less efficient than others.

CAUTION: Some car battery manufacturers have taken to lying about the amp-hours of a battery to provide a "starter equivalent". Use care to see if the measure is true Ah, or their fake version.

Battery

A storage device for electrical power. Typically measured in Volts and either Amp-hours or Watt-hours. Since watt hours are amp-hours times volts, you can convert between the two.

I (current)

Current in an electrical formula. Eg: V=Ir is "Volts (V) = current (I) times resistance (r)". Typically measured in amps.

IC (Integrated Circuit, aka: chip)

An IC is a bunch of electrical components, most importantly transistors, shrunk to a very small size. Modern electronics use a lot of ICs. ICs have voltage and amperage limits that should be respected. Exceeding those limits can release the Magic Blue Smoke!

LiFePO4 (Lithium Iron Phosphate)

A battery chemistry. Good energy density can be sensitive to charging/discharging, but considered safer that LIPO batteries. Caution should still be used though.

LiPo (Lithium Polymer)

LIPO is a battery chemistry. Known for being able to store a lot of energy, but also very sensitive when charging/discharging and can burn up violently. Special care is needed when using LIPO batteries.

Magical Blue Smoke ;-)

There's a myth that what makes integrated circuits work is the magical blue smoke contained within. If you release that smoke, then you've destroyed the chip.

mW (milliwatt)

a thousandth of a watt. Lots of circuits are measured in milliwatts. A decent LED may consume 20-50mW.

mWh (milliwatt hour)

A thousandth of a watt-hour (Wh). A AA battery might be rated at in mWh.

NiCd (Nickel-Cadmium, aka Nicad)

Older battery chemistry. Cheaper than newer types of batteries they tend to be safer but don't store as much energy. These are usually what you'd see in a basic R/C car set or kid's R/C car. They are often still a good choice.

r (resistance)

Resistance in an electrical formula. Measured in Ohms (Ω). V=Ir is an important formula, if you have 5 volts and 5 ohms of resistance, then I (current) would be 1 (amp). If you have a 5Ah battery, theoretically you could run that for 5 hours before killing the battery.

V (Volts)

Voltage of an electrical system. Common R/C car voltages are 7.4V or 9.6V. V is both the symbol in an electrical formula and the unit of measure. If electrical circuits were like highways, voltage would be similar to the number of cars on the highway. The higher the voltage, the more insulation is needed between circuits, though at R/C voltages that usually isn't very interesting. Trying to power a chip at too high of a voltage though can cause the electrical current to jump where it isn't supposed to in the IC, causing a short circuit and can damage the chip. (releasing the blue smoke).

W (Watts)

This is a measure of the amount of energy an electrical circuit is using. It is the product of the Amps times the Volts. W = VI, where I is the current (Amps), V is the voltage, and W is the watts. Generally we want lower wattage circuits so they can last longer, however higher wattage may be necessary for a powerful enough motor or light or speaker.

Wh (Watt-Hour)

This is probably how you pay for electricity - actually kWh (kilowatt hours or thousands of watt hours). A watt hour is one watt of electrical energy for one hour. So your 100 watt light run for 10 hours is going to cost you 1 kWh of electricity - except that there are other inefficiencies in the system. Watt-hours are Amp-hours times volts, so Wh = IhV. (I is the symbol for current in amps). Sometimes batteries are rated in Watt hours.

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Electrical Glossary

Terms