This one is a bit longer as I got carried away with some descriptions that would be more useful later on.
Capacitors
Capacitors are another simple device. They store electricity !
Similar to a battery, but their charge and discharge times are much shorter. There is lots of complex maths to describe how they work,
but there are some nice simple descriptions too.
If you want to compare them to water.. If a battery is like a water tank, you charge it by filling it with water and discharge it by draining it. It takes a lot of time.
A capacitor is more like a water balloon, you can fill it quickly and if you let it go, water squirts out quickly. The more you fill it, the harder it becomes until finally you can’t fill it anymore. The pressure inside the balloon equals the pressure in the pipe filling it.
Of course you can use brute force and overfill it with greater pressure (bigger voltage)… BANG ! A capacitor can do the same thing.
Another comparison is a rubber band. The more you pull the rubber band tight the more energy you store. (the bigger the voltage). You can keep raising the voltage in the capacitor until you exceed the threshold. (keep pulling until the rubber band snaps). Or you can let the rubber band discharge. Charging and discharging is ‘expotential’.
The tighter you pull the rubber the hard it is to keep pulling it.
Each number is one second later…
Think of it like 0, 50, 75, 87, 94, 97, 99 …… volts.
discharge …. 100, 50, 25, 13, 6, 3, 1 ….. 0 volts.
Capacitors can only store electricity for short periods of time before
the charge leaks out. Some capacitors can hold their charge for minutes, usually if it is a big dangerous voltage. Ouch !
A really good example is a disposable camera flash. It uses a single 1.5V AAA battery, it steps this voltage up to about 300 Volts and stores it in a big capacitor. When the capacitor is fully charged, the LED comes on. When you press the button the capacitor discharges all its power very quickly into the flashtube, much quicker than a battery could.
The other use for capacitors is that they will let AC pass, but not DC. The AC is usually Audio or Radio. It may sound strange to some people, but you can have AC and DC on the same wire at the same time.
(it is even posible to have lots of AC signals).
Another example. Your TV masthead amplifier. Down at the TV is the plug pack. It connects to the coax in a small box with a capacitor in it that lets the radio signals past, but stops the DC power from getting back into the TV and breaking it. The DC goes up the coax as the radio/tv signals come down.
Capacitors are measured in Farads, though one Farad is VERY big, most capacitors are smaller than microfarads. One millionth of a farad.
The bigger the capacitiy, the more current it can store.
It can also be said that, the bigger the capacitor, the lower the frequency it will let pass.
The final rating on a capacitor is it’s voltage rating.
Exceeding the voltage rating is just asking for trouble !
Most capacitors are bipolar, it doesn’t matter which way you connect them. But, there are some that are polarised. Electrolytics and Tantalums. If you connect these the wrong way, they will blow up.
(usually in your face when you least expect them) :dead:
Yes, they can be dangerous, so avoid doing it. They aren’t that exciting anyway. Blow something else up that won’t shower your carpet with toxic chemicals.
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