In this project, we will use the SN74150N, a high-speed 16-channel multiplexer IC, to design a practical digital multiplexer system. The SN74150N is an advanced multiplexer, ideal for tasks where multiple input signals need to be routed to a single output, based on a control signal. With its 16 selectable input channels, the SN74150N is a versatile component for both digital and analog signal switching applications.
Objective
The goal of this project is to build a digital multiplexer circuit capable of selecting one of 16 input signals and sending it to an output based on a binary control input. This project will demonstrate how to interface the SN74150N with switches and LEDs, creating a user-friendly way to switch between multiple signals.
Key Features of the SN74150N
The SN74150N is a 16-channel multiplexer with the following key features:
● 16 data input channels (I0 to I15)
● 4-bit binary control inputs (S0, S1, S2, S3) for selecting which of the 16 inputs to route to the output
● Active-low output enable (OE) for controlling the output state
● Low on-resistance for fast switching times
● TTL-compatible logic inputs and outputs
The multiplexer essentially selects one of the 16 inputs and connects it to the output based on the binary control signals. When the enable pin (OE) is active low, the selected input is connected to the output, otherwise, the output is in a high-impedance state.
Project Overview
● Input: 16 switchable input channels
● Output: One output channel connected to an LED to visualize the selected input
● Control: 4-bit binary control to choose which input is routed to the output
● Components:
— SN74150N multiplexer IC
— 16 switches (e.g., push buttons or toggle switches)
— 4 binary control switches (for selecting which input channel to connect)
— 16 LEDs (to represent the different input signals)
— 1 LED (for the output)
— Resistors (for pull-up or pull-down and current limiting)
— Breadboard or PCB
— Power supply (5V)
Step 1: Understanding the SN74150N Multiplexer
Before diving into the circuit design, let’s review the key features of the SN74150N multiplexer IC and how it works:
● Data Inputs (I0 to I15): These are the channels from which one will be selected and routed to the output based on the control inputs.
● Control Inputs (S0 to S3): A 4-bit binary control is used to select one of the 16 inputs. Each combination of the 4 control inputs corresponds to one of the 16 data input channels.
● Output Enable (OE): This pin is used to enable or disable the output. When it is active low (logic 0), the output will show the signal from the selected input channel. When OE is high (logic 1), the output is high-impedance (disabled).
● Output (Y): The selected input channel will be routed to the output pin, and this signal can be connected to an LED or any other display system for visualization.
Step 2: Designing the Circuit
The goal is to design a circuit where the user can select one of 16 input signals using a set of binary control switches and visualize the selected signal using LEDs.
1. Input Section (I0 to I15)
The inputs to the multiplexer will be represented by switches. These could be push-button switches, each corresponding to one of the 16 input channels. For simplicity, you can use a set of switches where each switch will either supply a low or high signal to its corresponding data input.
Each of the 16 switches should be connected to one of the 16 data input pins (I0 through I15) on the SN74150N. When a switch is pressed, it will send a HIGH signal (logic 1) to the corresponding input channel. The switches should also be connected to ground via a resistor to avoid floating signals when a switch is not pressed.
2. Control Section (S0 to S3)
To select which of the 16 inputs is connected to the output, we need four binary control switches (S0 to S3). These switches will provide a 4-bit binary control input that corresponds to the 16 different combinations of control signals (0000 to 1111). Each control switch will either connect the corresponding control line to high (logic 1) or low (logic 0).
Each combination of the 4 control switches will enable one of the 16 data inputs to be connected to the output. The binary values of S0 to S3 will determine which input is selected.
For example:
● If S0 = 0, S1 = 0, S2 = 0, and S3 = 0, input I0 will be routed to the output.
● If S0 = 1, S1 = 0, S2 = 0, and S3 = 0, input I1 will be routed to the output, and so on, until all 16 combinations have been covered.
3. Output Section (Y and LED Display)
The output of the multiplexer (pin Y) will be connected to an LED that will indicate which input is currently selected. The LED will light up when the corresponding input is routed to the output, providing a visual display of the current signal selection.
You can connect a resistor in series with the LED to limit the current and protect the LED from excessive voltage. The value of the resistor should be chosen according to the LED's specifications (e.g., 220Ω to 330Ω).
If you wish, you can also use a 7-segment display or other forms of output visualization, depending on your project’s requirements.
4. Connecting the SN74150N
Now that we have the basic structure, let’s connect the components together:
● Data Inputs (I0 to I15): Connect each of the 16 switches to one of the input channels (I0 to I15).
● Control Inputs (S0 to S3): Connect the 4 binary control switches to the S0 to S3 pins of the SN74150N. These control the selection of the data inputs.
● Output Enable (OE): Connect this pin to ground to enable the output.
● Output (Y): Connect the output pin to an LED to indicate the selected input signal.
Once connected, when the user flips the control switches (S0 to S3), the multiplexer will select one of the 16 input signals based on the binary control code and route it to the output, lighting up the corresponding LED.
Step 3: Testing the Circuit
After assembling the circuit on a breadboard, you can test the system by following these steps:
Power the Circuit: Connect the power supply to the circuit, ensuring that the SN74150N is powered correctly (typically +5V).
Set Control Inputs: Set the binary control switches (S0 to S3) to a particular value (for example, 0000).
Press an Input Switch: Press one of the 16 input switches to send a HIGH signal to one of the data inputs.
Observe the Output: The corresponding LED should light up, indicating that the selected input is routed to the output.
Change Control Inputs: Change the state of the binary control switches (S0 to S3) to select different input channels. Verify that the correct LED lights up for each input selection.
Step 4: Troubleshooting
If the circuit does not work as expected, here are a few common issues to check:
● Incorrect wiring of switches: Ensure that the switches are wired correctly to the input and control pins of the multiplexer.
● Faulty connections: Check for any loose connections or shorts on the breadboard that could cause improper functioning of the circuit.
● Control switches: Verify that the control switches are properly set to select the desired input.
● LED resistor values: Ensure that the current-limiting resistors are correctly sized to protect the LEDs.
Step 5: Enhancements
Once you have successfully built the basic digital multiplexer, you can consider some enhancements:
● Multiple Outputs: Instead of just one output LED, you could use multiple LEDs or a display to visualize all possible input signals.
● Control via Microcontroller: You could interface the control inputs (S0 to S3) with a microcontroller to automate the switching process, enabling more complex functionality.
● Analog Inputs: If you are working with analog signals, you can adapt the circuit to handle analog multiplexing by using a suitable analog multiplexer instead of the digital SN74150N.
Final Thoughts
This project demonstrates how to use the SN74150N multiplexer to build a simple yet effective system for selecting and routing one of 16 input signals to an output. By utilizing binary control switches and visual indicators (LEDs), this project gives a clear and practical example of how multiplexers can be used in everyday electronic systems. The project can be expanded or modified for more advanced applications, such as audio switching, sensor management, or microcontroller-based systems.