Electronics 10 Reviewer Third Quarter 2024-2025

Electronics 10 Reviewer - Third Quarter SY 2024-2025

• This is a reviewer for Electronics 10, Third Quarter of SY 2024-2025.

Tools and Materials for Maintaining Electronic Appliances

• For electronic work, prepare necessary tools, materials, and equipment.
• The following tools, materials, and equipment are needed for maintaining and repairing electronically-controlled domestic appliances: Soldering Iron, Long Nose Pliers, Diagonal Cutting Pliers, Soldering Stand, Utility Knife, Multitester, Soldering Lead, Desoldering Tool, Wire Stripper, Flathead Screwdriver, Philip Screwdriver, Mask, Non-Static Brush, Apron, ESD Wrist Strap.

Operation of an Electric Rice Cooker

• A rice cooker cooks rice by heating with boiling water and steam.
• Modern rice cookers vary in size, from single-serving to larger models. Smaller models cook 1 cup of rice (180 ml), while larger models cook 10 cups (1.8 liters).
• Simple models use a mechanical thermostat to turn off the cooker when the rice is ready.
• More advanced models introduced since the 1980s use microprocessors to control the cooking process. Some have built-in timers for a "ready time" feature, also enabling steaming function.
• During the cooking process, much water is absorbed by the rice, increasing its volume.
• Cooking is completed when all free water is absorbed and some boiled off.

Principle of Operation (Basic Models)

• Rice cooker bowls are removable.
• A heater and thermostat assembly are under the bowl.
• A spring holds the thermostat against the bowl bottom for good thermal contact.
• During cooking, the rice/water mixture is heated at full power.
• The temperature reaches 100°C (212°F) - the boiling point, and cannot rise higher.

Switch-On Preventive System

• Prevents the rice cooker from operating without the pan in place.

• The thermostat is depressed when the pan is properly inserted, compressing the outer spring.

• The auxiliary lever activates the micro-switch button, placing it in the cook position.

• The switch lever engages with the rod which allows a magnetic pull.

• When the optimal temperature (134°C ± 6°C) is reached, the magnetic pull weakens, and the components disengage. This pushes the switch lever to the warming position.

• If the pan is not inserted, the center thermostat will not be depressed, and the outer spring will not be compressed. This prevents the metal from reaching its normal operating position . The auxiliary lever and switch lever cannot engage for the cook position. In this case, pressing the switch button will not activate the micro-switch and put the system in warming position .

Thermal Fuse

• Opens the circuit when the temperature of the cooking heater becomes abnormally high.
• Incomplete contact between the heater and pan, or forcing the switch buttons to stay on, can overheat the cooker. The thermal fuse protects the unit by stopping the circuit.

Electronic Control Systems

• There are open-loop and closed-loop systems.
• An open-loop system uses an operator-set timer with a switch to control heating. The system doesn't monitor or adjust based on the output.
• A closed-loop system compares the output to the expected result (using a sensor), continuously adjusting the input if needed. More sophisticated systems incorporate a feedback component via sensors to adjust input signals based on output.

Closed Loop System Diagram

• The closed-loop system uses a comparator to compare the desired and actual temperature values.
• The difference, known as the error signal, is sent to a controller.
• The controller adjusts the actuator(s) to maintain the desired temperature.

LO2: Diagnose Faults of Electronically Controlled Domestic Appliances (Rice Cooker)

• Follow pre-testing procedures and manufacturer instructions.
• Isolate circuits using specified testing procedures.
• Document diagnosis and testing results accurately.
• Explain identified defects and faults.
• Provide data on the unit's status and serviceability.

Procedure in Pre-Testing and Troubleshooting an Electric Rice Cooker

• Determine the specific problem; ask the owner/operator for details.
• Operate the device; study the service manuals or operating instructions.
• Check if prior repairs or modifications have been made.
• Perform a visual inspection of the unit; look for issues like broken components or loose connections..

Troubleshooting, Maintenance, and Cleaning Tips

• Conduct a quick diagnosis of the problem.
• Secure the proper circuit diagram.
• Check the electrical cord and the thermostat's thermal fuse if the rice cooker does not heat.
• The faulty contact in the mechanical switch circuit is more likely a problem than electronic parts.
• Check the electrical cord and wiring connections if heat is too high or low.
• Calibrate the thermostat if necessary.

Checking for Consistency of Heat (Rice Cooker Energized)

• Focus on the pan, lid, and other details as well.
• Wear personal protective equipment (PPE) when connecting the cooker to the power supply for checking heat reliability.

Bubbling Test

• Place the pan in the main body, and rotate it to properly position on the heating plate.

• Fill the pan with water to a specific level so the bottom is dipped.

• Close the lid and turn on.

• Check the bubbling condition; good: bubbles across circumference, bad: bubbles on isolated parts.

Evaporation Test

• Cover the entire pan bottom with tissue paper or gauze.
• Place a weight on the pan so it won't move.
• Turn on the switch.
• The cooker is considered acceptable if it turns off within one minute before or after the steam stops. Check thermostat and pan/heater contact for problems.

LO3: Maintain and Repair Electric Rice Cooker

• Use PPE according to OHS practices.
• Perform repairs within the required timeframe.
• Observe safety guidelines.
• Replace parts only with identical or equivalent models.
• Solder and mount parts using industry standards.
• Clean the unit according to standard operating procedures.