User manual

A button has a similar function as a switch. You already know
switches from switching light on and off in the apartment. When
we push the rocker down, the light comes on. When we push it up,
the light goes out again. A switch remains in its position. This
is different for a button. When we push the button, the circuit
is closed. It will only remain closed while we push the button.
When we release it, it will open the circuit again and the light
will go out. The button will automatically return to its original
or resting position with its internal mechanics.
There are buttons that close the circuit when actuated, and such
that open the circuit . Buttons that close a circuit are often
called »N. O.« (normally open) and those that open the circuit
»N. C.« (normally closed). The figure shows a button that is
enclosed with the learning package. It closes the circuit when
pushed and the current can then flow from contact 1 to 2. The
two other contacts each are connected with each other.
3.4 | Resistors
Resistors are needed to limit current and to set working points,
or as voltage dividers in electrical circuits. The unit for
electrical resistance is Ohm (Ω). The prefix Kilo (k, thousand)
or Mega (M, million) shortens the way of writing large re-
sistances.
1 kΩ = 1000 Ω
10 kΩ = 10,000 Ω
100 kΩ = 100,000 Ω
1 MΩ = 1,000,000 Ω
10 MΩ = 10,000,000 Ω
In circuit diagrams, the symbol Ω is usually left out and 1 kΩ
is shortened to 1 k. The value of the resistor is applied to the
resistor in the form of a colour code. Usually, there are three
coloured rings, and an additional fourth ring that indicates the
accuracy of the resistor. Metal film resistors have a tolerance
of only 1 %. This is indicated by a brown tolerance ring that
is a little wider than the other four colour rings. This is to
prevent mistakes for a normal value ring with the meaning »1«.
Resistors with a tolerance of +/--5 % are available at the values
of the E24-series, with each decade containing 24 values at about
equal distance to the adjacent value.