In recent years, with the popularization of fire alarm equipment in various types of buildings, the demand for fire protection equipment power monitoring systems is increasing day by day. In a project, the author needs to design a monitoring device for the fire equipment power supply, which can monitor the operating status of the fire equipment power supply in real time, and determine whether the power supply of the fire equipment has power supply interruption, undervoltage, overvoltage and overcurrent.
working principle
The fire equipment power supply comes from the power grid 220V power frequency AC. Common AC voltage and current transformers are used to realize real-time monitoring and acquisition of single-phase or three-phase AC power in fire-fighting equipment power supply. The principle of detecting the voltage and current of the AC power supply is to convert the high voltage and high current of the AC power source into a low voltage that can be detected by the MCU through the voltage transformer and the current transformer. According to the actual application requirements, the AC voltage detection range is AC200V-AC400V, and the AC current detection range is AC0.5A-AC5A.
As shown in Figure 1, the alternating voltage signal of the power supply is input to the primary winding of the current-type voltage transformer through the series current limiting resistor, and is outputted through the secondary side of the transformer. The output matching resistor converts the output current signal into a voltage signal and sends it. SCM sampling processing. The series circuit uses five 49.9KΩ resistors. When the input voltage is 220V and 380V respectively, the currents are 0.88mA and 1.5mA respectively, which satisfies the linear transformation range of the transformer 2mA.
As shown in FIG. 2, the current signal of the AC power source is directly connected to the primary side winding of the current transformer, the induced current is outputted through the secondary side of the transformer, and the output matching resistor converts the current signal into a voltage signal, after being amplified by the operational amplifier, Send MCU sampling processing.
Device selection
For the three-phase AC power supply, according to the detection principle of the circuit, it is necessary to have three ADCs and three operational amplifiers to realize voltage and current detection respectively on the hardware. For the circuit requirements, the author selected the R5F117BC microcontroller in the Renesas RL78/I1D series as the main control chip. The chip has 12 AD conversion channels and 4 operational amplifiers inside, which are integrated on the pin function (3 pins per op amp, 4 channels of op amps integrate 12 channels of AD), so the author's monitoring circuit is satisfied. Design needs.
In the pin assignment of the circuit, the three AD channels integrated by the operational amplifier amp0 are respectively used for analog-to-digital conversion of the output signals of the three-way voltage transformer corresponding to the three-phase power supply; the operational amplifiers amp1, amp2, amp3 are used for three The amplification and analog-to-digital conversion of the current transformer current signal (the internal output of the op amp has been connected to the corresponding AD conversion channel), and the system connection is shown in Figure 3.
to sum up
The Renesas R5F117BC microcontroller has a wide range of analog-to-digital conversion channels and multiple operational amplifiers, making it ideal for applications that require conversion and amplification of multiple analog signals. The high level of integration of its analog peripherals eliminates the hassle of adding op amps and AD converters. When the system design scheme has high requirements on overall power consumption, circuit board size, BOM cost, etc., the chip is a better choice. In fact, a variety of microcontroller chips in the Renesas RL78/I1D series are designed for multi-channel signal processing, users can choose the cost-effective single-chip according to their needs.
Industrial Strip Lights Led Driver
Industrial Strip Lights Led Driver
12V led driver , 24v led driver, led power driver, Specifically for Industrial strip light, Isolated driver, easy to install, high security, constant Voltage power based. Are generally aluminum materials, long type driver.We have skilled engineers to answer all your questions and enquiries and provide all-round solutions basis on your project(s) and provide technical supporting.
- Standard Linear Lighting, strips lighting
- Cost-effective light-line solution for industry,commercial and other applications
- Good quality of light with high lumen output to meet different requirements
- Easy to order and install,requiring less time,reducing packaging waste and complexity
- Flexible solution
Parameter:
Input voltage: 100-277vac / 100-347V
output voltage: 25-40vdc / 12Vdc / 24vdc
current: 100mA-8000mA.
Power factor: >0.9
Dimming:0-10V / PWM / RX / DALI.
>=50000hours, 5 years warranty.
certificate: UL CE FCC TUV SAA ect.
FAQ:
Question 1:Are you a factory or a trading company?
Answer: We are a factory.
Question 2: Payment term?
Answer: 30% TT deposit + 70% TT before shipment,50% TT deposit + 50% LC balance, Flexible payment
can be negotiated.
Question 3: What's the main business of Fahold?
Answer: Fahold focused on LED controllers and dimmers from 2010. We have 28 engineers who dedicated themselves to researching and developing LED controlling and dimming system.
Question 4: What Fahold will do if we have problems after receiving your products?
Answer: Our products have been strictly inspected before shipping. Once you receive the products you are not satisfied, please feel free to contact us in time, we will do our best to solve any of your problems with our good after-sale service.
12V Led Driver,24V Led Driver,Led Power Driver
ShenZhen Fahold Electronic Limited , https://www.fahold.com