Simulating Neon Lamp Relaxation Oscillator in Simulink

User question

I need to simulate a relaxation oscillator problem in Simulink. The relaxation oscillator is represented by a neon light that turns on when its voltage is 75V, and turns off at 30V, and the light has a resistance of 1.2 megohms when it is on. With Simulink, I represent the neon light with two switches so that when the left switch is on and the right switch is off, the light is off, and when the right switch is on and the left switch is off, the light is on. I have a 120 volt voltage source on the circuit, the left resistor has a resistance of 4 megohms, and the right one represents the neon light and has a resistance of 1.2 megohms. The capacitor has a capacity of 6 microfarads and I have a voltmeter connected in parallel to it, and the output signal from the voltmeter is connected to a PS-Simulink converter. My idea was to compare the capacitor charge using the logic blocks compare to constant when the capacitor is 75 volts, the bulb should light up, and when the capacitor is discharged to 30 volts, the bulb should not light up. I don't know how to capture this regulation through the PS switches. I have set the threshold on both switches to 0.5 to automatically determine the command 1 for the switch on or 0 for the switch off depending on the charging and discharging of the capacitor. The two switches are then placed on the Simulink-PS Converter but there is nowhere to connect them in the circuit because when I start the simulation and check the oscilloscope, it gives me the right voltage. My problem is that the schematic in the attached image does not work to solve the problem I described.

Artificial Intelligence Response

Direct answer to the question

To simulate a relaxation oscillator with a neon lamp in Simulink, you need to:

• Use a capacitor voltage threshold-based control logic to manage the neon lamp's ON/OFF states.
• Implement an SR flip-flop to maintain the lamp's state between the ON (≥75V) and OFF (≤30V) thresholds.
• Use Simulink-PS converters to control the switches representing the neon lamp in the Simscape circuit.

Detailed problem analysis

Theoretical Foundations

A relaxation oscillator operates by charging a capacitor through a resistor until a threshold voltage is reached, at which point a discharge mechanism (neon lamp) activates, rapidly discharging the capacitor. The cycle then repeats. In this case:

• Neon lamp ON: When the capacitor voltage reaches 75V, the lamp turns ON, discharging the capacitor through a 1.2MΩ resistance.
• Neon lamp OFF: When the capacitor voltage drops to 30V, the lamp turns OFF, allowing the capacitor to recharge through a 4MΩ resistor.

Practical Applications

This type of oscillator is used in timing circuits, waveform generation, and simple blinking light circuits. Simulating it in Simulink allows for precise control and analysis of its behavior.

Current information and trends

Latest Data from Online Answers

• Online answers emphasize the importance of using an SR flip-flop to manage the hysteresis between the ON and OFF states of the neon lamp. This ensures stable operation and prevents erratic switching near the threshold voltages.
• Simscape Electrical is recommended for a more realistic simulation of physical components, as it provides pre-built blocks for switches and voltage-controlled elements.

Industry Trends

• Simulink and Simscape are increasingly used for modeling and simulating complex electronic circuits due to their ability to integrate physical and control systems.
• Relaxation oscillators are being adapted for low-power applications in IoT devices and energy-efficient systems.

Supporting explanations and details

Implementation Steps

1. Circuit Setup in Simscape:

   • Connect a 120V DC voltage source in series with a 4MΩ resistor and a 6μF capacitor.
   • Place a 1.2MΩ resistor in parallel with the capacitor to represent the neon lamp's ON state.
   • Use two PS-Switches to control the lamp's ON/OFF states:
     • Switch 1 (ON state): Closed when the lamp is ON, connecting the 1.2MΩ resistor.
     • Switch 2 (OFF state): Closed when the lamp is OFF, representing an open circuit.

2. Voltage Measurement:

   • Use a voltage sensor across the capacitor to measure its voltage.
   • Convert the measured voltage to the Simulink domain using a PS-Simulink Converter.

3. Control Logic:

   • Use two "Compare to Constant" blocks:
     • One for the 75V threshold (turn ON condition).
     • One for the 30V threshold (turn OFF condition).
   • Implement an SR flip-flop:
     • Connect the 75V comparator output to the Set (S) input.
     • Connect the 30V comparator output to the Reset (R) input.
   • The flip-flop output (Q) determines the lamp's state:
     • Q = 1: Lamp ON.
     • Q = 0: Lamp OFF.

4. Switch Control:

   • Use Simulink-PS Converters to send the flip-flop output to the PS-Switches.
   • Connect the flip-flop output directly to Switch 1 and through a NOT gate to Switch 2.

5. Simulation Settings:

   • Use a variable-step solver (e.g., ode23tb) for better accuracy.
   • Set the maximum step size to a small value (e.g., 1e-4 seconds) to capture the switching dynamics.

6. Output Monitoring:

   • Use an oscilloscope to monitor the capacitor voltage and verify the sawtooth waveform.
   • Add another scope to observe the lamp's ON/OFF state.

Debugging Tips

• Ensure proper grounding in the Simscape circuit.
• Verify the initial conditions of the capacitor (e.g., 0V).
• Use scopes to visualize intermediate signals (e.g., comparator outputs, flip-flop state).

Ethical and legal aspects

• Ensure the simulation adheres to safety standards for electrical circuits.
• Use licensed software for Simulink and Simscape.

Practical guidelines

Best Practices

• Use hysteresis in the control logic to prevent rapid switching near the threshold voltages.
• Test individual components (e.g., comparators, flip-flop) before integrating them into the full circuit.

Potential Challenges

• Oscillators may require an initial "kick" to start oscillating. This can be simulated by setting an initial voltage on the capacitor.

Possible disclaimers or additional notes

• Simulink simulations use ideal components, which may not fully capture real-world behavior (e.g., parasitic effects, component tolerances).

Suggestions for further research

• Explore the use of Simscape Electrical for more realistic modeling.
• Investigate the impact of component tolerances on the oscillator's performance.
• Study alternative oscillator designs (e.g., Wien bridge, Colpitts).

Brief summary

To simulate the relaxation oscillator in Simulink:

• Use a capacitor voltage sensor and comparators to detect the ON (75V) and OFF (30V) thresholds.
• Implement an SR flip-flop to manage the neon lamp's state.
• Control two PS-Switches to represent the lamp's ON/OFF behavior.
• Verify the simulation using scopes and adjust solver settings for accuracy.

This approach ensures a stable and accurate simulation of the relaxation oscillator.

Disclaimer: The responses provided by artificial intelligence (language model) may be inaccurate and misleading. Elektroda is not responsible for the accuracy, reliability, or completeness of the presented information. All responses should be verified by the user.