# Page 2 capacitor basics – How to use in circuits for DIY beginners learning electronics

Capacitors have 2 primary purposes in electronics.

• Store energy for temporary power. Supercapacitors are very large value capacitors that can actually power small loads for a relatively long time.
• Change voltage over time in order to be used as a signal.

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larger value capacitors are almost certainly polarized. That means one side needs to always be the more positively charged side while the other side if always the more negatively charged. Damage will occur if you reverse charge them. Generally speaking, polarized capacitors are black cylinders with a gray stripe and dashes on the negative side. The positive size also usually has a longer metal lead than the negative side.

## Basic capacitor demonstration circuits

It takes time for a certain amount of current to fully charge or fully discharge a capacitor with a certain amount of capacitance. The LEDs in this circuit give you a way to help see current flowing into or out of a capacitor if you only press one button at a time.

Video below is a variation of the circuit above.

### RC time constant

The time it takes a capacitor to charge/discharge through a resistor is called the RC time constant. One time constant (in seconds) is equal to the capacitance of the capacitor in farads (F), times the resistance of the resistor in ohms (Ω). It takes 5 of those time constants to go from fully discharged to fully charge, or from fully charged to fully discharged.

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#### Voltage ramp

A steady current into, or out of, a capacitor leads to a steady voltage change. Since it is a straight line working it’s way up or down when graphed, it is called a ramp.

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Page 3 – 555 timer basic circuits

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• Information on this site is not guaranteed to be accurate. Always consult the manufacturer info/datasheet of parts you use. Research the proper safety precautions for everything you do.