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Wiring your first physical breadboard is a frustrating experience. One wrong connection and the circuit does not work. Unfortunately without an experienced instructor by your side, it is difficult to find out where is the mistake. Our breadboard simulator acts as a virtual and patient instructor checking on your every connection.

Practice does not make perfect. Only perfect practice makes perfect - Vince Lombardi

Use the following steps to complete the wiring of the breadboard

  • Select your schematic. The 1 to 2 demultiplexer is the easiest to start. When you select your schematic, the ones where you have completed the breadboard will be shown with a green background.
  • Operate the switches in the circuit simulator. Read the description of the circuit for more information.
  • Using the schematic, wire up the circuit in the breadboard simulator. When a wire end is placed in a socket of the breadboard that corresponds to a node on the schematic, the respective node of the schematic will turn red.
  • If a correct connection is made, the wire ends will snap into the socket.
  • When all the nodes are wired up, a red LED will light up near the VCC/GND terminals.
  • You may now operate the breadboard switches and observe the LED results.
  • Sign in with your Google account to save your breadboard connections and earn a digital badge.
  • Note that all the VCC (red wire) and GND (black wire) connections are already done. When you wire up the actual circuit using the under US$10 Home Laboratory Kit, do remember to connect the VCC and GND wires.
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Note that the holes connected by the blue lines are electrically connected in the breadboard.

breadboard internal connections

If you are unfamiliar with the breadboard, there are many resources available online that explains how they work. We recommend this quick Breadboard Infographic from Make Breadboarding Workshop or the longer Breadboard Tutorial from Science Buddies.

Johnson Counter

A Johnson counter is a modified ring counter, where the inverted output from the last flip flop is connected to the input to the first. The register cycles through a sequence of bit-patterns. The MOD of the Johnson counter is 2n if n flip-flops are used. The main advantage of the Johnson counter counter is that it only needs half the number of flip-flops compared to the standard ring counter for the same MOD.

This circuit is implemented using D-type flip-flops.

    Notes:
  • Enable the flips flops by clicking on the RESET switch (SW6).
  • Click on CLK (SW7) switch and observe the changes in the outputs of the flip flops. SW7 is a momentary switch.
  • The D flip flop clock has a rising edge CLK input. For example Q1 behaves as follows:
    • The D input value just before the CLK rising edge is noted (Q0).
    • When CLK rising edge occurs, Q1 is assigned the previously noted D value (Q0).
  • The MOD or number of unique states of this 3 flip flop johnson counter is 6.

7474 Dual D-Type Flip-Flops IC Pin Out

7474 Dual D-Type Flip-Flops IC