Use this example to investigate the design of a four-bit binary counter with a 555 timer IC generating the digital clock signal (Figure 1).
Figure 1. Example Circuit
For this exercise, apply a constant voltage source and a DC current source
to the base. By performing a DC analysis simulation, for which you sweep the current source to the base, you can see the relationship of
plotted against
. Observe this relationship with Multisim simulation.
Begin by drawing your schematic in the Multisim environment.
Figure 2. Multisim Environment
There are two fundamental tasks in the design of a circuit: the placement of components and the wiring of these components to create a complete design.
Figure 3. Select a Component Dialog
The component browser organizes the database components into three logical levels. The Master Database contains all shipping components in a read-only format. The Corporate Database is where to save custom components to be shared with colleagues (via a network collection and so on). Finally, the User Database is where custom components are saved that can be used only by the specific designer.
Additional Points
To invoke simulation, you need a power source and a ground somewhere in your circuit to correctly reference voltages and currents in your circuit simulation.
Figure 4. Placing a Ground Symbol
To place a VCC power supply:
Additional Points
Now place the remaining circuit components using the techniques discussed in the previous steps.
Now place the resistors and capacitor in the design.
At this point, your schematic should look something like Figure 5:
Figure 5. Components Placed
Multisim is a modeless wiring environment. This means that Multisim determines the functionality of the mouse tool by the position of the mouse. You do not have to return to the menu to choose between placement, wiring, and editing tools.
Figure 6. Wiring the Circuit
Figure 7. Wire the Components as Seen Above
You are now ready to run an interactive Multisim simulation; however, you need a way to visualize the data. Multisim provides simulation-driven instruments such as oscilloscopes, wattmeters, and more to help you visualize the simulated measurements.
Find instruments on the right menu bar -- they are indicated by the following icons.
Figure 8. Instrument Toolbar
When you are done, the circuit looks like this:
Figure 9. Oscilloscope Connected to the Four-Bit Counter
It is simple to begin running and visualizing an interactive simulation in Multisim.
Figure 10. Simulation Toolbar
Figure 11. Visualizing Simulation in the Oscilloscope
You have just successfully built, simulated, and analyzed a digital circuit using Multisim.
Now that you have explored how a four-bit digital counter works, are you able to design an eight-bit decimal counter with two seven-segment displays using a 555 timer IC to generate the clock signal?
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