Day 2 starts with some circuit diagram exercises. Every task starts with a sketch of a circuit diagram and has to be translated to a real implementation on a bread board. The following diagrams were made with the fritzing software that can be found at

For the first implementation we use a red LED, a resistor, a button, a transistor and a power source. The transistor has three inlets: gate source and drain. The drain and source are connected to the first circuit that also contains the resistor and the LED, the gate inlet is connected to the button. If the button is pressed, the second circuit is closed and the gate inlet of the transistor gets a signal: the LED lights up.


With the previous setup the LED stays on as the electric charge can not drain. To avoid that the LED stays on after pressing the button we therefore have to add a pull-down-resistor from the button to the ground.

The second setup uses a IC timer, a LED, a resistor, two capacitors and a potentiometer (containing two variable resistors). The aim of the implementation is to let the LED blink in a frequency that can be regulated with the potentiometer. For the realization we use the LMC 555 SNC IC timer and description of the related datasheet (see “How to read a data sheet” post).