Abstract: A switching power supply with protection function includes a transistor controlled to be on or off by a PWM signal from a PWM controller to convert a DC voltage into a square wave signal, a filter filtering the square wave signal into an output voltage signal, the output voltage signal being fed back to the PWM controller to be compared with a predetermined voltage, and a switch device having an input terminal for receiving the output voltage signal from the filter, an output terminal for connecting to a load, and a control terminal. If the voltage of the output voltage signal from the filter is not equal to the predetermined output voltage, the PWM controller will not output a signal to the control terminal of the switch device and the switch device will be in an off state.

Abstract: A polarity adjusting apparatus for automatically adjusting polarity of a connection between a power supply and a charging circuit includes first˜fourth diodes, first and second input terminals configured for connecting to positive and negative terminals of the power supply, and first and second output terminals configured for respectively connecting to positive and negative input terminals of the charging circuit. The anode and cathode of the first diode are respectively connected to the first input terminal and the first output terminal. The anode and cathode of the second diode are respectively connected to the second input terminal and the first output terminal. The cathode and anode of the third diode are respectively connected to the first input terminal and the second output terminal. The cathode and anode of the fourth diode are respectively connected to the second input terminal and the second output terminal.

Abstract: An exemplary system for expandably connecting electronic devices includes a master device, a first slave device, and a second slave device. The first and second slave device each has a control chip and an address setting module. The control chip includes a bus interface connected to the master device via a common bus. The address setting module has a counter unit. The master device sets a first address for the control chip and the counter unit of the first slave device, the counter unit of the first slave device calculates the first address and sends a calculated address to the control chip and the counter unit of the second slave device as a second address of the second slave device. The first address and the second address are different from each other, thus a plurality of slave devices can connected to the master device via a common bus.

Abstract: A simple network management protocol (SNMP) management card includes a processor, a network interface card (NIC) chip, a network port connected to the processor via the NIC chip, a power sourcing equipment (PSE) chip, and a power port connected to the network port via the PSE chip. The network port is configured to be connected to a network device. The PSE chip receives power from the power port and transmits the power to the network device via the network port.

Abstract: A serial advanced technology attachment (SATA) interface tester includes a memory, a signal converter, at least one SATA interface, and an indicator. The at least one SATA interface is adapted to connect with SATA interfaces of a motherboard, and is electrically connected to the memory via the signal converter. The signal converter receives serial signals from the motherboard via the at least one SATA interface and converts them to parallel signals and then passes the parallel signals to the memory to perform a writing process. The signal converter receives parallel signals from the memory and converts them to serial signals and passes the serial signals to the motherboard via the at least one SATA interface to perform a reading process. The indicator is electrically connected to the memory for indicating testing result of the SATA interfaces of the motherboard.

Abstract: A fan detecting apparatus for detecting operation of at least two fans includes at least two airflow detecting units with two signal transmitting terminals, a judging unit with at least one judging terminal, and at least two identity indicating units electrically coupled to the corresponding at least two airflow detecting units respectively. The airflow detecting units detect airflow of the fans, and output control signals to corresponding identity indicating units when airflow from corresponding fans is no longer detected. Each of the identity indicating units has an identity code corresponding to a fan which is electrically coupled to the airflow detecting unit, and transmits the identity code to the judging terminal of the judging unit when it receives the control signal. The judging unit indicates which of the fans is no longer producing detectable airflow according to the identity codes received at its judging terminal.

Abstract: A fan detecting apparatus for detecting at least two fans includes a processing unit, at least two airflow switches, and at least two indicating units. The processing unit includes a first terminal configured to output a driving signal, a second terminal configured to receive the driving signal, and a third terminal, the processing unit alarming when the second terminal does not receive the driving signal from the first terminal. The at least two airflow switches are serially coupled between the first and second terminals, monitor airflow from at least two fans in a computer room, and turn on or off according to strength of airflow from the at least two fans. The indicating units are respectively coupled between corresponding airflow switches and the third terminal of the processing unit, and indicate status of corresponding fans according to on or off status of the airflow switches.

Abstract: A power supply circuit includes a power supply input for receiving power from a power supply, a power supply output for supplying power to a load, a voltage reference circuit, and a switch circuit. The voltage reference circuit is connected between the power supply input and the power supply output for regulating voltage of the power supply circuit. The switch circuit is connected to the voltage reference circuit and the power supply output. The voltage reference circuit supplies regulated voltage to the switch circuit. The switch circuit controls current between the power supply input and the power supply output to be changed alternately at a certain frequency, thereby changing power output to the load to save electricity.

Abstract: An airflow detecting apparatus for a fan includes an amplifier circuit (100), a comparator circuit (200), a micro control unit (MCU) (U1), and an indicating circuit (300). The amplifier circuit has an input terminal receiving a voltage signal from a piezoelectric film (H1) disposed at an airflow path of the fan, and outputs an amplified voltage signal at an output terminal. The comparator circuit has an input terminal receiving the amplified voltage signal from the amplifier circuit and compares the amplified voltage signal with a reference voltage signal received at another input terminal of the comparator circuit, and outputs a voltage level signal at an output terminal. The MCU receives the voltage level signal from the comparator circuit and processes it to output an indicating signal. The indicating circuit receives the indicating signal from the MCU and indicates status of airflow.

Abstract: A wireless mouse includes a main body, a cover disposed above the main body, a circuit board mounted in the main body, a power switch disposed on the circuit board configured for controlling power supply from a power source to the circuit board, and a trigger mounted on the cover and movable relative to the cover. When a user depresses the cover, the trigger actuates the power switch to allow the power source providing power to the wireless mouse; when the user releases the cover, the trigger releases the power switch to interrupt power to the wireless mouse.

Abstract: A fixing device for securing a circuit board to a plate member includes a spacer, a nut member, and a fastener. A coupling hole is defined through the spacer. A female thread is formed on a part of an interior surface of the coupling hole at an end thereof. A nut member comprises a pressing portion and a coupling portion extending from the pressing portion. A male thread is formed on a part of an exterior surface of the coupling portion at a free end thereof, corresponding to the female thread of the coupling hole of the spacer such that the coupling portion is capable of being movably retained in the coupling hole. A threaded hole is defined in the nut member. A fastener includes a head and a threaded rod extending from the head for being screwed in the threaded hole of the nut member.

Abstract: An exemplary video signal control circuit includes a central processing unit, a signal bus, an address bus, a data bus, a latch module, and a display module. The central processing unit is connected to a latch-enable terminal of the latch module via the signal bus and connected to an input-enable terminal of the latch module via the address bus for controlling the latch module. The central processing unit transmits video signals to the latch module via the data bus and then to the display module if the latch module is latch-enabled and input-enabled. The video signal control circuit transmits the video signal to the display module via the data bus instead of general port I/O pins, and thus the quantity of display units is not restricted by the quantity of the general port I/O pins.

Abstract: A circuit for testing a power down reset function of an electronic device includes a reference power source (Vref), a first variable resistor (R1) with one end connected to the reference power source, a second variable resistor (R2), and a jumper (10). One end of the second variable resistor is connected to the other end of the first variable resistor, and the other end of the second variable resistor is grounded. The jumper includes four pins, with a first pin (101) connected to a node (B) between the first variable resistor and the second variable resistor, a third pin (103) grounded, and a second pin (102) and a fourth pin (104) commonly connected to a voltage testing pin (20) of an electronic device (2). The circuit is simple, is conveniently operated, and saves costs.

Abstract: An exemplary charger control circuit includes an input port having a positive terminal and a negative terminal, an electrode control circuit, and an output port having a positive terminal and a negative terminal. The input port is connected to a source of power. The output port is connected to a load. The electrode switching circuit detects the electrode polarity of the input port and the output port for selectively coupling the positive terminals and the negative terminals of the two ports, and protecting the electrical equipment.

Abstract: An exemplary electromagnetic induction switch includes a coil, a magnet suspended in the coil, a rectification circuit, and a relay-switch. The coil is connected between two input terminals of the rectification circuit. Two output terminals of the rectification circuit are respectively connected to two relay leads of the relay-switch. One of two switch leads of the relay-switch is connected to a working circuit, and another one of the switch leads of the relay-switch is connected to the working circuit via a power source, thereby controlling the power source supplying power to the working circuit.

Abstract: A PCB assembly includes a motherboard, a daughter board, and an elastic strip. The motherboard is electrically connected to the daughter board via connectors. Each of the motherboard and the daughter board includes an area connected to a power layer or a ground layer. One end of the elastic strip electrically connects to the area of the motherboard. The other end of the elastic strip electrically connects to the area of the daughter board whereby increases electrically connection between the motherboard and the daughter board.

Abstract: An I/O port tester includes a first relay, a second relay, a first resistor, a second resistor, a plurality of serial plugs, a water sensor plug, a direct current (DC) voltage plug, and two data plugs. A half of the serial plugs is correspondingly connected to the other half of the serial plugs. The DC voltage plug is connected to the water sensor plug via a switch of the first relay and the first resistor, and connected to the water sensor plug via a switch of the second relay and the second resistor. The first and second resistors respectively simulate two different working conditions. The data plugs are respectively connected to an inductance coil of the first relay, and an inductance coil of the second relay.

Abstract: A reset device for a computer system is provided. The reset device includes a hardware-reset signal generating circuit for outputting a hardware-reset signal to reset the computer system; a switch connected to the hardware-reset signal generating circuit, the hardware-reset signal generating circuit outputting the hardware-reset signal when the switch is on; a timing circuit set for outputting a controlling signal after a predetermined time that the switch has been on has passed; and a latch circuit communicating with a central processing unit (CPU) of the computer system and the timing circuit, the latch circuit latching the controlling signal and delivering the controlling signal to the CPU, the CPU controlling system settings to resume default values based on the controlling signal.

Abstract: A miniaturized modem system including a modem chip on a board and a DAA chip on another board mounted together so that the boards face one another thereby substantially reducing the size of the system. The arrangement satisfies the requirement of the FCC for maintaining a minimum limit on spacing between the modem section and the DAA section thereby avoiding inadvertently applying voltage surges to the phone line. The modem system is mounted directly on a housing that is a receptacle for a telephone jack thereby further substantially reducing the size of the modem system.

Abstract: A voltage measuring device includes at least two voltage dividing circuits, an analog to digital converter, and a processor. Each voltage dividing circuit is configured for dividing a voltage output by a direct current power supply. The analog to digital converter is configured for converting the divided voltage to a digital signal. The processor is configured for processing the digital signal and selecting one of the at least two voltage dividing circuits, to divide the voltage according to the processed digital signal.