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LTspice Control & Instrumentation Projects

Explore the LTspice and control-system workflow from the control and instrumentation coursework: Wheatstone bridge sensing, signal conditioning, current-loop transmission, first-order and second-order dynamics, and PID tuning.

Sensor Signal Chain

LTspice Sensor Chain

Bridge, amplifier and voltage-to-current loop simulation.

First-Order RC

RC Step Response

Open-loop and feedback transient response analysis.

RLC Second-Order

RLC Oscillatory Dynamics

Step response, damping and feedback comparison.

PID Controller

Tuned PID Response

Kp, Ki, Kd comparison and final controller metrics.

Control and Instrumentation Case Study

Wheatstone Bridge & 4–20 mA Instrumentation LTspice & Control Workflow

A sensor-instrumentation workflow built around a strain-gauge Wheatstone bridge, LTspice validation, signal conditioning and current-loop transmission.

Step 01

Wheatstone Bridge Principle

The sensing stage represents applied force as a resistance change in the strain-gauge arm of a Wheatstone bridge, converting mechanical loading into a measurable differential voltage.

Step 02

LTspice Bridge Validation

The bridge was rebuilt in LTspice with a 12 V supply and simulated at representative force values. The validation table compares theoretical and LTspice output voltage.

Step 03

Signal Conditioning Amplifier

A non-inverting amplifier with gain and offset translates the low bridge output into a practical 1–5 V instrumentation signal.

Step 04

4–20 mA Current Loop

The conditioned voltage is converted into an industrial 4–20 mA signal for more reliable transmission over long cable lengths.

Step 05

End-to-End Output Verification

The full LTspice signal chain verifies the conversion from bridge voltage to amplified voltage and output current against the expected measurement range.

Control and Instrumentation Case Study

First-Order RC System Analysis LTspice & Control Workflow

A control-system study of first-order RC behaviour, comparing open-loop response, unity-feedback closed-loop behaviour and non-unity feedback.

Step 01

Open-Loop Step Response

The first-order RC model is verified from its step response, showing exponential settling and steady-state gain behaviour.

Step 02

Unity Feedback Response

A unity-feedback closed-loop configuration reduces the time constant and reaches a lower steady-state output, demonstrating faster controlled response.

Step 03

Non-Unity Feedback H(s)=0.5

The non-unity feedback case modifies the final value and settling time, supporting comparison of how feedback strength changes system response.

Step 04

Configuration Comparison

Tables summarise transfer functions, time constants, final values, gain and settling-time differences across open-loop and feedback models.

Control and Instrumentation Case Study

Second-Order RLC Dynamic Response LTspice & Control Workflow

A second-order RLC model is analysed through damping, oscillation, feedback effects and performance metrics for open-loop and closed-loop cases.

Step 01

Dynamic Parameter Extraction

The RLC system is characterised through steady-state output, peak value, percent overshoot, peak time and settling time.

Step 02

Open-Loop RLC Response

The estimated RLC model produces an underdamped step response with visible oscillation before settling.

Step 03

Unity Feedback Response

Closed-loop unity feedback changes the damping and final output, providing a direct basis for evaluating controlled second-order behaviour.

Step 04

Non-Unity Feedback Response

The H(s)=0.5 case shows a different amplitude and transient profile, highlighting the effect of feedback scaling on oscillatory systems.

Step 05

Performance Comparison

The comparison table summarises steady-state gain, damping ratio, natural frequency, final voltage, steady-state error, overshoot and settling behaviour.

Control and Instrumentation Case Study

PID Controller Tuning & Stability Evaluation LTspice & Control Workflow

A PID-control workflow evaluates proportional, integral and derivative effects before tuning a final controller to improve settling, overshoot and steady-state error.

Step 01

Proportional Gain Sweep

The proportional-only study compares Kp values to show how gain reduces steady-state error while potentially increasing overshoot and oscillation.

Step 02

Integral Gain Sweep

The PI-control study varies Ki while Kp is fixed, showing the integral action effect on steady-state error and transient behaviour.

Step 03

Derivative Gain Sweep

The PD-control study evaluates Kd values to show how derivative action can improve damping and reduce oscillatory behaviour.

Step 04

Final PID Tuning

The tuned controller uses Kp=350, Ki=300 and Kd=70, producing a fast response with low overshoot and very small steady-state error.

Step 05

Performance Metrics

The MATLAB command-window output reports the final tuned gains and key performance values such as overshoot, settling time and steady-state error.