Digital components with electrical signals

The digital components in this library simulate real components. The input and output signals are not purely logical signals, but are in fact voltage levels. The connections are therefore electrical connections, which can be connected to all other electrical components, such as switches, resistors and capacitors.

The symbols' presettings correspond to those of the components used in the training package TP 1012 from Festo Didactic. Transistor-transistor logic modules (TTL modules) of type 74HCxx are used in this component set. These standard TTL-ICs are designed for operation with a supply voltage of 5 V. The supply voltage connections are not shown explicitly in FluidSIM. There must be adequate supply voltage present to generate the required output voltages.

In digital technology, a distinction is made between just two voltage levels: high voltage and low voltage. The presettings in FluidSIM correspond to those of the standard TTL-ICs. Input voltages below 0.8 V are regarded as low, while input voltages above 2.0 V are regarded as high. The low output voltage level is 0 V and the high output voltage level is 5 V. These settings can be changed for each symbol.

In order to designate the voltage levels in abstract terms, the two logical states are usually called simply high and low, true and false, or the abbreviations 1 and 0 are used.

In order to guarantee efficient simulation, the digital components in FluidSIM are not modeled as a circuit consisting of transistors, but as a simplified model that nonetheless takes the essential characteristics of the components into account. Output voltages rise and fall via a voltage ramp up to the required voltage level within around 20 nanoseconds. Output connections are connected to the output voltage with an adjustable internal resistor, i.e. ohmic loads at the output result in a voltage drop. The voltage level at inputs that are not connected is always 0 V.