Circuit characteristics
The fully automated process of preheating, beating, boiling, etc. of the soymilk machine is completed by the MCU related foot control, the corresponding triode drive, and then the relay group consisting of multiple relays. As long as you master this basic law, you can perform circuit inspection on all models of soya-bean milk machine to eliminate various types of failures. However, some models of the circuit board are a bit problematic. It is to press the component number under the component. Therefore, only the component can be seen on the circuit board, and the component number cannot be seen. This is extremely inconvenient for the detection of the circuit. .
work process
Add appropriate amount of water, warm water or cold water can be, after the power on, start the "pulping" function, the electric heating tube starts to heat, after 25 minutes, the water temperature reaches the set stability, the pre-beating function, when the water temperature reaches the set temperature, the motor starts Work, carry out the first pre-beating, and then continue to heat the anti-overflow motor to reach the beating temperature, beaten/heat, at this stage, the beating and heating are repeated, so that the beans are completely crushed, the soy milk is initially boiled, boiled, After the soy milk is boiled, it enters the cooking stage, and the heating tube is repeatedly heated to make the soy milk fully cooked and completely emulsified.
Component detection
Basic test methods for power transformers, resistors, capacitors and diodes, and triodes: Most of these components can be measured on the road. If necessary, they can be taken separately and tested. The method is very simple.
A. Observe the obvious appearance of the transformer by observing the appearance of the transformer: if the coil lead is broken, whether it is de-soldered, whether the insulating material has burnt marks, whether the iron-tightening screw is loose, whether the silicon steel sheet is rusted, and whether the winding coil is There are exposed and so on. B. Insulation test: measure the resistance between the core and the primary, the primary and each secondary, the core and each secondary, the electrostatic shielding layer and the secondary and secondary windings with a multimeter R×10k block, and the multimeter pointers are Should be referred to in the infinity position does not move. Otherwise, the transformer insulation performance is poor. C. Detection of coil on/off: Place the multimeter in R×1 gear. During the test, if the resistance value of a certain winding is infinite, it indicates that the winding has a faulty fault. D. Discriminate between the primary and secondary coils: the primary and secondary pins of the power transformer are generally led out from both sides, and the primary winding is marked with 220V, and the secondary winding is labeled with the rated voltage, such as 9V. Wait. Then identify them based on these markers. E. Detection of no-load current: (a) Direct measurement method: Open all the secondary windings, place the multimeter in the AC current block (500 mA, string into the primary winding. When the plug of the primary winding is inserted into 220V AC mains, The value indicated by the multimeter is the no-load current. This value should not be greater than 10%-20% of the full load current of the transformer. Generally, the normal no-load current of the power transformer of common electronic equipment should be below 25 mA. If it exceeds too much, the transformer There is a short-circuit fault. (b) Indirect measurement method: a 10?/5W resistor is connected in series in the primary winding of the transformer, and the secondary is still completely empty. Turn the multimeter to the AC voltage block. After power-on, measure with two meters The voltage drop U across the resistor R is then calculated by Ohm's law to calculate the no-load current I, ie, I null = U/R. F. Detection of no-load voltage: connect the primary of the power transformer to 220V mains, and use the multimeter AC voltage. Connected sequentially to measure the no-load voltage value of each winding (generally between 10.5V-11V) should meet the required value, the allowable error range is generally: low-voltage winding ≤ ± 5%, G, general low-power power transformer allows temperature rise 40 ° C ~ 50 °C, if the quality of the insulating material used is good, the temperature rise can be increased. H. Comprehensive detection and identification of the short-circuit fault of the power transformer: The main symptoms after the short-circuit fault of the power transformer are severe heat generation and abnormal output voltage of the secondary winding. Generally, the more short-circuit points between turns in the coil, the larger the short-circuit current, and the more severe the heat of the transformer. The simple way to detect whether the power transformer has a short-circuit fault is to measure the no-load current (test method has been introduced earlier). For short-circuit faulty transformers, the no-load current value will be much greater than 10% of the full-load current. When the short-circuit is severe, the transformer will heat up quickly within tens of seconds after no-load power-on, and the iron core will be hot when touched by hand. Feeling. At this time, it is not necessary to measure the no-load current to conclude that the transformer has a short-circuit point. The test alone is simple. The method is simple.
The basic detection of the MCU chip, because the circuit board is installed in the machine head, the detection is very inconvenient, even if the idea can be detected, but the risk of the live test in the machine head is relatively large, for this purpose by using the detection of the MCU feet to the ground resistance value to judge. It can be seen from the MCU pin-to-ground resistance value that the MCU pin has a significant regularity on the ground resistance value, four control pins and two detection pins, and the red pen measurement is 4.5 kΩ, and the black pen test control pin Both are 8.2kΩ and the detection feet are 8.6 kΩ. If the measured resistance deviates from the data in the table, it indicates that the measured pin is not internally broken or open, or there is a problem with the external components.
The basic detection method of the relay, because the soymilk machine can not be separated from water and steam, the machine head enters the water, the parts are damp and mildewed, and the user will not pay attention to it, which will pose a threat to the relay. Moreover, the relay itself has a large current load and frequent switching, so it is easy to burn out the contacts and the soymilk machine cannot work. Similarly, under the condition of the whole machine under the power, it is very difficult to detect the relay. For this reason, the relay is separately tested. Add a DC12V power supply, note that the positive pole of the power supply is connected to the negative pole of the freewheeling diode, the negative pole is connected to the positive pole of the freewheeling diode, and the external power supply is turned on or off. The sound of the relay pull-in and release action should be heard, and the measurement is performed. Normally open or normally closed contacts should have a corresponding response to turn on or off. If the relay has no action, it indicates that there is a problem with the relay solenoid. In normal conditions, the K1.K3 solenoid resistance is 380Ω and K2 is 190 Ω. If there is no corresponding on or off reflection, it means that the contact has been burned out.
The relay used in the soymilk machine has a working voltage of DC12 V and a contact load rated current of 10 A (28 VDC). Due to the special needs of the working conditions of the soybean milk machine, the substitution of the relay should be selected from high-quality relays of well-known brands.
The basic detection method of the beater motor, a considerable part of the soymilk motor power margin is too small, due to insufficient power, the temperature rise is too high, coupled with the objective factors such as water, moisture and other burning factors, almost a type of each model Common disease. The motor should be visually inspected first to see if there are scorch, short circuit and open circuit in the windings of the motor. Whether the commutator and the carbon brush are damaged, whether there is black powder on and around the motor, and whether the motor is flexible by hand. If the motor is not working properly or does not turn, and the visual inspection does not see any abnormality, then the motor windings should be tested.
A variety of means are available for motor winding detection. Here is a simple and convenient way to detect. Disconnect the motor from the outside, clip the test leads to the leads behind the carbon brushes, turn the motor shaft by hand, and measure the resistance between each pair of commutators one by one. The normal resistance is about 540 Ω. The resistance drops below 50 Ω, indicating that the winding connected between the pair of commutator segments has been burned or has been broken down, resulting in a turn-to-turn short circuit. By using this method, it is possible to quickly determine whether the motor is damaged without disassembling the motor.
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