Development of SPE61A microcontroller non-contact high voltage detector
Design idea and general scheme
1 Non-contact detector design ideas
The development of the detector is mainly used for the monitoring of high-voltage transmission lines in railroads, and its design requirements are to monitor the operation of high-voltage lines in railroads, requiring a correct judgment of whether the high-voltage line is charged, and will be powered, non-powered signal through the light-emitting diode display, but also to issue the corresponding state of voice prompt information.
In addition, the detector is usually installed outdoors, so the device must also meet the requirements of outdoor work.
2 Overall design plan and block diagram
The detector to SPE61A microcontroller as the detection and control core. The device uses a copper sheet sensor to monitor the electric field near the high-voltage line, the electric field signal is converted into a voltage signal and sent to the signal processing circuit, the signal processing circuit will convert the analog signal into a DC powered, non-powered state signal sent to the microcontroller. The microcontroller compares the received signal with the last signal, and if the collected signal is the same as the last collected signal, it continues to collect the next signal, and if it is different, it sends a new signal to the voice module, the instruction module and the signal transmission module, and at the same time, it latches the collected signal for comparison with the next collected signal. After receiving the signal, the voice module sends out a voice prompt with or without power; after receiving the signal, the indication module sends out a power or no power indication; after receiving the signal, the signal transmission module sends out a power or no power status signal to the indoor monitoring computer.
Hardware design of the system
1 Microcontroller
The system adopts Sunplus SPE61A microcontroller as the core of detection and control, SPCE061A is another 16-bit structure microcontroller launched by Sunplus Technology after μ’nSP series products such as SPCE500A. It is designed with two 16-bit IO ports. The controller can operate in a wide supply voltage range (2.6~5.5V) and system clock frequency range (0.375~24.576 MHz). In addition to increasing the data bus to 16 bits and thus increasing the operating speed, the SPE61A 16-bit microcontroller integrates more system peripheral resources. Among them are high-capacity ROM and static RAM, infrared communication interface, RS-232 general-purpose asynchronous full-duplex serial interface, 10-bit A/D and D/A conversion, built-in amplifier input channel with automatic gain control, 32768 Hz real-time clock, and low-voltage reset/low-voltage monitoring system. In addition, the SPE61A has embedded LCD control driver and dual-tone multi-frequency signaling (DTMF) generator function.
The most important feature of SPE61A is the built-in 7-channel 10-bit voltage analog/digital converter (ADC) and single-channel sound analog/digital converter, in which the sound analog/digital converter input channel has built-in microphone amplifier and automatic gain control (AGC) function. This makes the SPE61A equipped with preliminary voice playback and recognition functions.
In this system, the SPE61A microcontroller mainly monitors and processes the input signal. After receiving the signal from the signal processing module the microcontroller will judge accordingly and send the processing result to the subsequent circuit.
2 Sensor
The sensor is used to read the electric field signal and is the signal source of the whole device. The sensor is installed at a distance of 0.8m directly below the high voltage line, and is used to read and convert the electric field signal near the high voltage line. The sensor in this device is designed with a copper sheet capacitor, and two wires are led from each end of the capacitor, one of which is used as the positive pole of the signal output and the other is grounded and used as the ground wire.
In addition, for safety purposes, an extra ground wire (called detection ground) is led from the ground end of the sensor as the ground wire of the indication module, voice prompt module and signal transmission module in the circuit, which is used to determine whether the sensor transmission line is intact. At this time, if the signal transmission line is disconnected, this line is also disconnected, then the indication module, voice prompt module and signal transmission module can not work, the signal indicator can not light, the voice module is able to send voice information, the transmission computer with and without power signal is also disconnected, will not send the wrong signal, improve the reliability of the system, to avoid the signal line is disconnected to send the wrong signal without power, resulting in accidents.
The sensor adopts closed hemispherical smooth shell design, which can be thoroughly waterproof and meet the outdoor working requirements.
3 Signal processing module
Signal processing consists of signal following circuit, filter circuit, voltage doubling rectifier circuit, subtraction circuit, amplification circuit, Schmitt trigger circuit, signal indication and monitoring signal sending circuit, the schematic diagram of which is shown in Figure 2. The input signal comes from the sensor’s AC voltage signal, which is filtered after being followed and forward biased by the signal following circuit, then the AC signal is multiplied and rectified into DC signal, the subtractor subtracts the interference signal between adjacent lines, and the amplifier amplifies the signal as necessary and then sends it to the Schmitt trigger, which sends two kinds of signals to the microcontroller according to the size of the input signal, powered and unpowered.
4 Voice Module
Voice prompt information processing is done by the SPE61A’s own voice module. In this system, the external amplifier circuit and speaker are directly connected to the module, and the voice prompt message is sent through the external speaker.
5 Indication module
The indicator module is composed of two light-emitting diodes, red and green, red means power and green means no power. As the SPE61A port has sufficient driving capacity, so the system directly connected to the light-emitting diodes in the microcontroller port.
6 Signal transmitting module
The detector should not only show whether the high-voltage line is charged in the indication module, but also send the signal to the indoor monitoring computer for monitoring. If the signal is sent to the computer through the detector device encounters a common ground problem, to allow the computer to correctly identify the signal transmitted by the detector must make the computer and the detector a common ground, otherwise, the transmission line is too long not a common ground and lead to computer recognition signal errors. The signal transmission method of this device as shown in Figure 3, the computer sends the signal, the internal test apparatus through the relay switch to control the electric or non-electric line on or off, the computer receives the two signals sent by itself through the relay switch, if the electric line to send a high level signal, the non-electric line to send a low level, when the high voltage line has electricity; if the non-electric line to send a high level signal, the electric line If both lines send high level signal or low level signal, the circuit is wrong.
The amplifier circuit in the voice module, the light-emitting diode in the indication module and the control circuit in the signal transmission module all use the detection ground as the ground, so that the judgment of the sensor transmission line can be completed and the wrong indication message can be sent by the disconnection of the sensor line.
In addition, since the hardware must work outdoors, the entire hardware is mounted in a specially designed waterproof metal housing.
Software design of the system
The system software design is shown in Figure 4. When the system is first powered up and running, it first initializes to the powered state and displays the result in the indication module in this signal port, and calls the voice subroutine to output the voice prompt message. After a delay of 1s, the state is latched. The system first scans the input port, then compares the scan result with the data in the latch, if it is the same, it directly clears the watchdog and returns to the port scan to enter the next cycle, if it is not the same, it outputs the scan result (powered or unpowered) to the indication module in the port to display the result, then calls the voice subroutine to output the voice prompt message, then clears the watchdog and returns to the state latch to store the collected The status signal is latched for comparison in the next signal acquisition, and then goes to the next cycle. In order to ensure the normal operation of the system, a watchdog clearing procedure is provided in both branch cycles.
The entire workflow of the system is as follows: the first time the power is applied or restarted, the work display is powered, and a voice prompt is issued, and after a delay of 1 second, if the indication state does not change, it indicates that the line is powered, otherwise the delay ends and the indication state is changed, and there is no power voice prompt, indicating that the line is not powered.
In addition, in the voice output voice prompts for “line power, please pay attention to safety” and “line power off” and other two sentences of voice.
