““Smart City”, “Smart Grid”, “Ubiquitous Power Internet of Things”… In recent years, some new concepts have been put forward one after another, and these plans intersect with each other. The frame began to go underground. Taking Qingdao as an example, the main roads and the construction of the old high-tech zone renovation and new areas all require cables to go underground. Every 50m-100m is covered with a smart manhole cover to ensure urban safety and release urban space resources.
Author Ethan Li
“Smart City”, “Smart Grid”, “Ubiquitous Power Internet of Things”… In recent years, some new concepts have been put forward one after another, and these plans intersect with each other. The frame began to go underground. Taking Qingdao as an example, the main roads and the construction of the old high-tech zone renovation and new areas all require cables to go underground. Every 50m-100m is covered with a smart manhole cover to ensure urban safety and release urban space resources.
Product definition and terminal function of electric power intelligent manhole cover
Product Definition: The intelligent manhole cover monitoring system can detect whether the manhole cover is lost. The intelligent manhole cover monitoring system uses the current advanced wireless communication technology and power technology to continuously collect the state of the manhole cover and the underground environment information, including water level, temperature, harmful gas, etc., and then store it. and teleportation. The opening of the manhole cover and the inspection of the manhole cover are incorporated into the unified maintenance management system, and the corresponding alarm processing mechanism is established, and the state of the location of the manhole cover and the alarm content are displayed through the Electronic map. Arrive at the scene in time to deal with it, and quickly solve the safety problem.
Power manhole cover monitoring terminal function:
• Intrusion alarm: real-time monitoring of manhole cover opening and damage
• Environmental monitoring: Downhole O2 concentration toxic gases such as CO, H2S…
• Status management: remote control or key to open and close the manhole cover
• Realize interconnection with other systems through communication protocol interface
• Full lifecycle management of IoT-based devices
Ethan Li, a technical distributor who has cooperated with ADI for more than 30 years, an engineer from Excelpoint Shijian Company, introduced to us the ADI IC from sensing (iSensor MEMS), acquisition (Analog to Digital Converter), to digital isolation communication interface (iCoupler) ), power supply system (ADI Power by Linear), in a typical small and smart application “electric smart manhole cover”.
Product Typical Signal Chain
Figure 1 Typical signal chain of power smart manhole cover
System technical requirements
• System power supply: 24Vdc(Range16V~36V) online power supply system (also requires a backup power supply system or a lithium battery power supply system)
• Manhole cover tilt detection: threshold alarm, 1~2° error
• Gas detection accuracy: ~5%
• Communication method: isolated RS-232/485 bus communication, rate • Static power consumption: • Alarm response time: • Maintenance-free time: more than 1 year
Power Supply System – ADI Power by Linear
The power supply needs to activate the high-power mechanical action switch, and also ensure the manual safety of the power failure of the system after going down the well. Therefore, the power supply method adopts the online 24Vdc power supply Vin=16~36V, and the backup power supply is 6~8 sections of Li-ion (25.2Vfull /29.4Vfull) series charging.
Successful design use case: LTC4020 high-voltage buck-boost compatible MPPT solar charging function + LTC4416 external path management high-reliability design solution.
Figure 2 LTC4020 application diagram and features
• Multi-chemistry support
• VOUT tracks VBAT
• 4 switch topology charges “any battery from any source”
• External power FETs and current sense R allow for high current charging
In addition, there are flyback LT8302 isolated power supply solutions, LT860X multi-channel synchronous rectification DC/DC, and Silent switcher technology LT8609S, LTC8645S, LTC8650S and other complete power supply solutions for reference.
Application of ADI MEMS G-sensor in Inclination Detection
Successful design use case: ADXL362, an ultra-low power 3-axis MEMS accelerometer, to ensure the static power consumption of the whole machine.
• Ultra low power consumption
1.8 μA (100 Hz ODR, supply 2.0 V)
3.0 μA (400 Hz ODR, power supply 2.0 V)
270 nA motion activated wake-up mode
10 nA Standby Current
• Deeply embedded FIFO minimizes host processor load
• On-chip temperature sensor
For the design of the 3-axis G-SENOR inclination angle measurement, please refer to the complete application note AN1057 on the ADI official website.
Downhole gas detection
The system generally requires four kinds of gases: O2, CO, CO2, and H2S plus conventional auxiliary detection. The detection error accuracy is ~5%, which is not high. Now the customer’s design scheme is still electrochemical sensor plus amplifier, such as ADA4528, AD623 TIA signal conditioning After the MCU on-chip ADC acquisition scheme.
Ethan Li recommended to us ADuCM355, a platform-level product for gas detection based on an electrochemical sensor solution released by ADI in 2019.
CO detection base on ADuCM355 complete solution
• Low power consumption
Active current consumption of digital section is 30 μA/MHz
Sleep with External Sensor Bias, 8.5 μA
Shutdown mode without SRAM retention, 2 μA
• 26 MHz ARM Cortex-M3 processor
• 16-bit, 400kSPS ADC
• 2 low power, low noise TIA amplifiers for electrochemical detection
ADuCM355 features high integration, high precision, high safety and reliability, small size, and low power consumption. It has significant advantages in gas detection based on electrochemical sensors. Some customers have begun to import and evaluate the ADuCM355. The specific application design of ADuCM355 is not discussed in this article. For details, please refer to the circuit notes CN0425 and CN0429 on the ADI official website.
Isolated communication interface
Communication method: isolated RS-232/485 bus communication, functional isolation 2500Vdc, communication rate
Magnetic coupling technology polyimide isolation
Single-ended “one-pulse two-pulse” encoding architecture
Differential key control architecture
Ethan said that ADI can provide a complete set of product solutions for iSensor+ Single process+ iCoupler+ ADI power by Linear. In addition, Excelpoint Shijian has cooperated with customers in the Shandong region for design support, has experience in successful design and use, and has already mass-produced. With the development of cities and the vigorous promotion of the pan-power Internet of Things, the functions of power smart manhole cover products will continue to be enriched. It is believed that there will be more comprehensive and in-depth cooperation between ADI products and customer program design in the future.
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