Electronics 10 Reviewer - Third Quarter 2024-2025 PDF

# ELECTRONICS 10 Reviewer ## Third Quarter SY 2024-2025 ### TOOLS AND MATERIALS IN MAINTAINING ELECTRONICALLY-CONTROLLED DOMESTIC APPLIANCE In every electronic work, it is a must to prepare first the necessary tools, materials, and equipment needed as well as the information. The following list...

# ELECTRONICS 10 Reviewer ## Third Quarter SY 2024-2025 ### TOOLS AND MATERIALS IN MAINTAINING ELECTRONICALLY-CONTROLLED DOMESTIC APPLIANCE In every electronic work, it is a must to prepare first the necessary tools, materials, and equipment needed as well as the information. The following list of tools, materials, and equipment are needed in maintaining and repairing electronically-controlled domestic appliance. | Tool | Description | |:---:|:---| | Soldering Iron | | | Long Nose Pliers | | | Diagonal Cutting Pliers | | | Soldering Stand | | | Utility Knife | Blade Cutter | | Multitester/ Volt-Ohm-Milliammeter (VOM) | | | 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 is a kitchen appliance dedicated to cooking rice. Rice is cooked by heating in boiling water and steam, or a combination (boiling until water evaporates, and then continuing in steam generated by continued heating). It absorbs a great deal of water in the process, expanding its volume and using up the cooking water. For the modern home rice cookers, the smallest single-person model cooks 1 rice cup (180 ml) whereas the largest cooks 10 rice cups (1.8 liter). The typical lower price models use electric heaters to heat the inner cooking bowl controlled by thermostat assembly or built-in electronic control, whereas the high-end models feature various ideas of improved and better cooking methods. Electric rice cookers automate the process by mechanically or electronically controlling heat and timing. Although the rice cooker does not necessarily speed up the cooking process, with an electric rice cooker the cook's involvement in cooking rice is reduced to simply measuring the rice, preparing the rice properly and using the correct amount of water. Once the rice cooker is set to cook, the rice will be cooked with no further attention. #### Principle of operation (basic rice cooker models) The bowl in the rice cooker is usually removable, to which rice and water are in place. A heater and thermostat is beneath the bowl. A spring pushes the thermostat against the bottom of the bowl for good thermal contact. During cooking, the rice/water mixture is heated at full power. The water reaches a temperature of 100 °C (212 °F); it cannot get hotter than its boiling point. By the end of cooking there will be no free water left; most will have been absorbed by the rice, and some boiled off. As heating continues, the temperature can now rise above boiling point; this makes the thermostat trip. Some cookers switch to low-power or "warming" mode, keeping the rice at a safe temperature of approximately 65 °C (150 °F); other models simply switch off. #### Basic Parts of Electric Rice Cooker Diagram of an electric rice cooker with each part labeled: 1. Lid Assembly 2. Lid Handle 3. Lid 4. Measuring Cup 5. Aluminum Pan 6. Thermostat Assembly 7. Cast Heater Assembly 8. Handle for the Body 9. Body Complete 10. Name Plate 11. Switch Assembly 12. Switch Panel 13. Decorative Panel 14. Lamp Board Assembly 15. Switch Lever 1 Lid 16. Mica Heater Assembly 17. Wiring Terminal Assembly 18. Bottom Plate Assembly 19. Power Cord 20. Cord Bushing 21. Scoop It is best to acquire Service Manual and Diagrams specific for different models, design might vary from one manufacturer and/or model to another. ### ELECTRONIC CONTROL SYSTEMS USED IN RICE COOKER There are two types of control system: the open loop system and the closed loop system. They can both be represented by block diagrams. A block diagram uses blocks to represent processes, while arrows are used to connect different input, process and output parts. #### Open Loop System In an open loop control, the controller may operate a switch to adjust the input to the process. This is often done by a timer. A timer is set by the operator which operates a switch on the electrical circuit to the electric heating element. Once the oven reaches the pre-set time it will open or close the switch. Controlled Variable is what needs to be controlled such as temperature. A controlled device is the piece of apparatus which adjusts or switches the controlled variable. A system with no feedback i.e. there is no way to monitor the process to find out if the control system is working effectively. This control system can also be described as simple ON/OFF control. #### Closed Loop System Sometimes, we may use the output of the control system to adjust the input signal. This is called feedback. Feedback is a special feature of a closed loop control system. A closed loop control system compares the output with the expected result or status then it takes appropriate actions to adjust the input signal. Therefore, a closed loop system is always equipped with a sensor, which is used to monitor the output and compare it with the expected result. #### Closed Loop System Diagram The comparator or comparison device compares the desired value with the actual measured variable - temperature in the case of the rice cooker or oven. The difference between the desired value and the measured value is known as the error signal. The error signal is fed into the controller which adjusts the actuator or switch depending on the size and polarity of the error. ### LO2. DIAGNOSE FAULTS OF ELECTRONICALLY-CONTROLLED DOMESTIC APPLIANCE (RICE COOKER) * Observe systematic pre-testing procedure in accordance with manufacturer's instructions * Check and isolate circuits using specified testing procedure * Document results of diagnosis and testing accurately and completely within the specified timeframe * Explain identified defects and faults based on the result of diagnosis and testing * Provide data/information regarding the status and serviceability of the units as per procedure. ### PROCEDURE IN PRE-TESTING AND TROUBLESHOOTING AN ELECTRIC RICE COOKER 1. Determine the specific problem by asking the symptom. * Ask the owner/operator of the electric rice cooker of what is the symptom of the unit. * Request for the detail of the symptom (how does the symptom happen) and how long it has been observed. 2. Operate the device. Make sure that you know how to operate an electric rice cooker. If not, review the operating manual as well as service manual (if available) of the unit prior to its testing and operation * If you have worked on the same unit before, test out to see if it operates in the same way. * Determine the last time it has been modified/repaired. * You must recognize the symptom/ complain of the owner to the unit. 3. Perform visual inspection of the unit. * Prepare the tools needed and remove the cover ready for inspection. * Apply careful physical inspection of the parts/components. (Look for burned and broken components; Inspect for loose connections or broken wires) 4. If all looks fine, test the unit for resistance checks. * Get the multitester and set it at range Rx1Connect the test probes to each of the plug terminal, the reading must be very high since you are measuring the resistance of the keep warm heater having the temperature control at zero position. * Then, turn-on the cook switch, make sure that you have properly inserted or placed the pan into the rice cooker with enough weight to depress the center thermostat, decrease in resistance should be observed since the cook heater will be activated. If this happen, the unit might be in good condition. For safety, place one probe across to the plug terminals and the other probe to the body. There should be very high (infinite) resistance. Proceed to checking for consistency of heat. If there's something different, refer to troubleshooting guide or this lesson. 5. Record your findings for future reference. #### Checking for Consistency of Heat (Rice Cooker is Energized) While receiving the cooker to be repaired, do not focus only on the cooker body instead, consider also the pan and the lid, and ask details for the symptom of the trouble. If the rice cooker needs to be connected to power supply for checking of reliability of heat extra care should be observed and use of gloves and other related PPE is a must. #### 1. Bubbling Test Diagram of a rice cooker with the pan in place showcasing the water level. There is a diagram showcasing the sheathed heater and center thermostat. Input the pan in the main body, and lightly rotate the pan clockwise and counter clockwise to set the pan on the heating plate properly. * Fill water until the center area of the pan bottom is dipped, and close the lid. Then turn the cook switch on. * When it is already producing steam, remove the lid and immediately check the bubbling condition on the pan bottom. Two diagrams showcasing a circle that represents the bottom of the pan. Diagram A has a check mark next to it and Diagram B has an X next to it. Bubbling Condition * A. Bubbles generate throughout the circumference of the pan bottom- Good * B. Bubbles generate only on certain part of the pan bottom-Bad This may result from insufficient or misaligned contact between the pan bottom and the sheathed heater. Check the pan bottom and the sheathed heater for foreign material remained. Clean up the foreign materials or replace the parts if necessary. #### 2. Evaporation Test Diagram of a rice cooker with the pan in place. There is a piece of wood on top of the lid. There is a diagram showing a close up view of the pan. After the bubbling test, remove the lid and put a weight on the cooker. * Cover the entire pan bottom with 2 or 3 pieces of tissue paper (or gauze), and turn on the switch subsequently. Make sure you put enough weight on the pan so you can turn on the switch, a 5x5x40cm lumber or piece of wood will be fine. * The cooker is considered acceptable if it turns-off automatically 1 minute before or after the steam generation comes to a stop. If these requirements are not satisfied, check the center thermostat as well as the contacted condition between the pan bottom and the cooking heater, and then repair or replace the parts if necessary. ### LO3: MAINTAIN AND REPAIR ELECTRIC RICE COOKER * Use PPE in accordance with OHS practices * Perform repair activity within the required timeframe * Observe safety precautions in handling the unit/product as per standard operating procedure * Replace defective parts/components with identical parts or recommended parts with equivalent ratings * Solder/mount repaired or replaced parts/components in accordance with industry standards * Clean unit in accordance with standard operating procedure ### TROUBLESHOOTING, MAINTENANCE AND CLEANING TIPS #### Troubleshooting 1. Conduct a quick diagnosis of the trouble symptom and repair the defective set in the shortest possible time. Do not troubleshoot Rice Cooker unless you have determined the fault. 2. Secure a circuit diagram. 3. If the Rice Cooker doesn't heat, make sure there is power on the outlet, check the electrical cord, and check the thermostat thermal fuse. 4. Always suspect a faulty contact on mechanical switch circuit rather than defective electronic/electrical parts. 5. If the Rice Cooker produces too much or too little heat, test the electrical cord for loose wiring and connection. Also test and, if needed, adjust calibration of the thermostat. 6. Use Personal Protective Equipment. #### Maintenance and Cleaning 1. Turn-off and unplug the electric Rice Cooker and make sure it's already cool before cleaning. 2. Check the owner's manual for your Rice Cooker to learn the specified manufacturer's suggestions for cleaning. 3. You may use a sponge and commercial cleaner or baking soda and water to remove dirt buildup on the external parts. Don't submerge a Rice Cooker in water or cleaning liquid.