XPON (Passive Optical Network) technology encompasses various types of Optical Network Units (ONUs), each designed to meet specific needs and applications. Here are the different types of XPON ONUs, based on the underlying standards and use cases: The choice of an ONU type depends on various factors such as service requirements, deployment environment, and the specific standards of the optical network. Each type of ONU is designed to optimize performance, reliability, and service delivery according to its intended use case. gepon onu,xpon ont,gpon ont,epon onu,dual band wifi onu Shenzhen Runtop Technology Co.LTD , https://www.runtoptech.com
Robust energy harvesting system solution for wireless sensors
Wireless sensors are gaining significant traction in the market due to their unique advantages. In environments that are hard for humans to access or require a large number of sensors—where connecting each to a data network is impractical—wireless solutions are ideal. However, relying on primary batteries for such systems is often not feasible. For example, a temperature sensor used during meat transportation must be installed in a way that prevents damage, while HVAC sensors spread across different air sources may use batteries because of their wide distribution. In these scenarios, energy harvesting technology offers a sustainable power solution without the need for traditional batteries.
Energy harvesting alone usually doesn’t provide enough power to continuously run a sensor-transmitter. While energy harvesters can generate between 1mW and 10mW, most sensor-transmitter systems require 100mW to 250mW. Therefore, it's crucial to store the harvested energy for later use. The system’s duty cycle must remain within the limits of the stored energy. Additionally, the sensor might need to operate even when no energy is being collected, which makes efficient energy management essential.
When the stored energy runs out and the system is about to shut down, it should perform some housekeeping tasks first, such as sending a shutdown message or saving critical data into non-volatile memory. This highlights the importance of continuously monitoring available energy levels.
A complete energy harvesting system, as shown in Figure 1, includes an LTC3588-1 energy harvester and buck regulator IC, two LTC4071 parallel battery chargers, two GM BATTERY GMB301009 8mAh batteries, and a simulated sensor-transmitter operating at a 1% duty cycle. The LTC3588-1 features a low-leakage bridge rectifier with inputs at PZ1 and PZ2 and outputs at VIN and GND. VIN also powers a buck regulator with very low quiescent current, and the output voltage is set to 3.3V using D1 and D0.
The system uses a piezoelectric sensor from Advanced Cerametrics, the PFCB-W14, which can generate up to 12mW but delivers approximately 2mW in this setup. The LTC4071 manages battery charging with programmable floating voltage and temperature compensation. It sets the floating voltage to 4.1V with ±1% tolerance, ensuring safe operation. It also monitors battery temperature via an NTC signal and adjusts the charging voltage accordingly to extend battery life.
Each LTC4071 can supply up to 50mA of charge current, but when the battery is below the floating voltage, it only draws about 600nA. The GM BATTERY GMB301009 has a capacity of 8mAh and an internal resistance of around 10Ω. The sensor-transmitter was modeled using a PIC18LF14K22 microcontroller and an MRF24J40MA RF transceiver, simulating a 12.4mA load with a 0.98% duty cycle (2ms/204ms).
The system operates in two modes: charge-send and discharge-send. In charge-send mode, the battery is charged while the sensor-transmitter operates at a 0.5% duty cycle. During discharge-send mode, the sensor is active, but no energy is being harvested from the piezoelectric element.
In charge-send mode, the average power from the PFCB-W14 is about 9.2V × 180μA ≈ 1.7mW. This power must charge the battery and drive the buck regulator that powers the sensor-transmitter. The sensor draws 12.4mA for about 1% of the time, consuming approximately 41mW, or 0.41mW on average. With the buck regulator operating at 85% efficiency and a quiescent current of 8μA, the system balances energy consumption and storage effectively.