-14-
Variable resistor
Besides the normal resistors we also have the variable resistor which is also called
potentiometer (potmeter).
The variable resistor is available in many types and shapes. One of the most familiar
variable resistors is the volume regulator in a radio. The type which is used in our robot
is directly placed on the PCB. The maximum value of a potmeter is always given. The
potmeter in our robot is used to change the amplification of the sound and light sensor.
Capacitor
Capacitors can store electronic energy and when you require it they can offer it back
without great lost. An other characteristic is that they can block a DC current and let an
AC current pass. They will have a certain resistance for AC currents. The symbol for
a capacitor is C. The value of a capacitor is named capacitance and the unit is Farad
(F). Normally the value of a capacitor is very small and is expressed in Nano-, Micro- or
Picofarad:
Abreviation
Meaning
Value
1µf
1 micro Farad
0,000001 Farad
1nf
1 nano Farad
0,000000001 Farad
1pf
1 pico Farad
0,000000000001 Farad
There are many coding systems for capacitors. Ceramic and mylar capacitors which we
normally use, have value numbers printed on it.
Electrolytic capacytor (ELCO)
The Elco is a polarized (meaning; direction-depending) capacitor. The manufacturers
put several markings on this capacitor to recognize the Plus and Minus pin of this
capacitor. Normally one pin is longer (plus) than the other. The minus pin shows a
white marking on it.
Diode
The diode allows the current to flow only in one way (from Anode to Cathode). When
the current wants to flow in the other direction, it will be blocked.
