Technical systems – input, processing, output and feedback
Design & TechnologyEngineering Drawing & DesignAges 15–16
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Engineering Drawing & Design
A real-time block diagram of a familiar technical system (water heater, air conditioner, rice cooker, or float-valve water tank): a setpoint block, a control block, the controlled object and its output, plus a feedback path that returns the measured value to the controller. Students set the desired value, turn the feedback loop on or off, press Add disturbance to let in cold water or open the room door, then compare two curves: the closed-loop system tracks the setpoint closely while the open-loop system drifts far away and loses control.
Lesson: Technical systems: input elements, processing–control elements, output elements, and feedback relationships
What it shows
A technical system can be described as blocks: an input element where the desired value is set, a processing–control element that decides what to do, and an output element that acts on the controlled object. With a feedback loop, a sensor measures the output and returns it to the controller, which compares it with the setpoint; this is a closed-loop system. The simulation uses simple on–off control, so the output oscillates in a narrow band around the setpoint. Without feedback, the open-loop system keeps supplying power and drifts far from the target.
How to use
Choose a Technical system, set the Setpoint and press Run with feedback on; watch the curve rise and then oscillate close to the setpoint. Press Add disturbance, for example opening the cold-water tap, and see the controller correct it. Then press Turn off feedback and repeat, asking students to predict the result first. Click each block in the diagram to read its role, and compare the four systems to identify their sensors.
Parameters you can change
- Technical system 20-litre water heater – 2500 W, Room air conditioner – 2500 W, Electric rice cooker – 700 W, Rooftop water tank with float valve
- Setpoint (temperature or water level) 16–110 °C or cm
- Feedback loop enabled (closed-loop system)
- External disturbance level 0–100 %
- Simulation speed 0.2–5 min/s
Questions to explore
- In the water tank with a float valve, which part acts as the sensor in the feedback loop?
- What happens to the water heater's temperature when feedback is turned off, and why?
- Why does the output of the closed-loop system oscillate around the setpoint instead of staying exactly on it?
