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In this paper, we use MPC82G516A (8-bit microcontroller), nRF24L01 (2.4GHz wireless transceiver module), PIC12F629 (8-bit microcontroller), and TB88-30 (Step up DC to DC converter) to design a basic wireless node, and extend to 3 types of nodes by different firmware coding, such as the Sensor Node, the Repeat Node, and the Main Node. The proposed Wireless Sensor System was composed of these nodes. The ISFET (Ion Sensitive Field Effect Transistor) with a readout circuit, the DS18B20 temperature sensor, and the residual chlorine meter (RC-24P) are allocated to each sensor node to measure the hydrogen ion concentration (pH), chlorine concentration and temperature in a water pool. These water quality parameters acquired from the sensor node will be transmitted to the repeat node via 2.4GHz wireless signal. The repeat node receives data, and transmits to the main node. The main node will also transmit the data to PC by the using of RS-232 interface. In addition, a wireless signal path from the sensor node to repeat node proffers a single direction relaying method, thereby making the sensor node and repeat node to be in sleep mode when idle. In sleep mode, all nodes consume only 27uA.
Chung et al. (Sun,) studied this question.