User manual

know which order and at what time. If you do it right, the

LED stays off. If you do it wrong, the LED stays on, and the

bomb explodes.

But unlike in real life, you can remove the wire, press the

reset button, and try again. Who will discover the rule? How

exactly does this bomb have to be defused?

LED with built-in resistor

The green LED only needs a voltage of about 2 V, but the mi-

crocontroller works with 4.5 V. A normal LED should not be

connected directly to the controller. The general rule is: LEDs

may only be used with resistors. The special LEDs used in this

package already have a built-in resistor that is visible. The LED

has a shorter wire that is internally moulded into a small cup

in which the LED crystal is inserted. This connection is called

the cathode and is the negative connection. The longer wire

is the anode, i.e. the positive pole. In the LED plastic, you can

see a small block on the tip of this wire. This is the built-in

resistor, which by the way has a kiloohm (1k Ω). The casings of

these special LEDs are shorter than other LEDs. This protects

against confusion.