User manual

22
The learning package contains resistors in three different values:
Value 1. Ring
(Tenth)
2. Ring
(Ones)
3. Ring
(Multipl.)
4. Ring
(Toleranc
e)
Use
220 Red Red Brown Gold Series resistors for LEDs
1 kOhm Brown Black Red Gold
Protective resistors for
GPIO inputs
10 kOhm Brown Black Orange Gold
Pull-down resistors for
GPIO inputs
Tab. 2.2: Colour codes of resistors in the learning package
Pay attention in particular to the colours of the 1 kOhm and 10 kOhm resistors. These are mixed up easily.
2.2 Connecting the LED
LEDs (LED = Light Emitting Diode) for light signals and lighting effects can be connected to the GPIO ports.
Hereby a 220 ohm series resistor (red-red-brown) will be installed between the appropriated GPIO pin and
the anode of the LED in order to limit the current flow and thus preventing the LED from burning through.
Besides, the series resistor protects the GPIO output of the Raspberry Pi, since the LED offers almost no
resistance in the direction of the current flow, the GPIO port could become overcharged quickly when
connected to ground. The cathode of the LED is connected to the ground wire on Pin 6.
Connecting LED plug but using which direction?
The two connecting wires of an LED differ in length. The longer one of the two is the positive pole, the
anode, the shorter one is the cathode. Easy to remember: The plus sign has one bar more than the minus
sign, thus making the wire a bit longer. Also most LEDs are flat on the minus end, just like a minus sign.
Easy to remember: Cathode = short lead = flat spot
Connect first an LED via a 220-ohm series resistor (red-red-brown) to a +3.3 V connector (Pin 1), as shown in
the image, and connect the negative terminal of the LED to the ground wire (Pin 6).