Software And Hardware Design For Swimming Pool Alarming System

Drowning incidents happened in the public swimming pools every now and then.Especially when there is a crowd of people in the swimming pool,once somebody is drowning the lifeguard won't be able to notice him and take out some effective rescuing measures in time,which will result in a tragedy.It has been taken in to concern among the national authorities about how to avoid the above tragedies and reducing casualties.A new warning and positioning system for swimming pool based on Long Base Line is presented in this paper.The system consists of an underwater acoustic beacon(ie the target),hydrophone arrays,a land based signal processor and a display and control terminal.During a drowning incident,the underwater acoustic beacon worn on the wrist of the swimmer can transmit acoustic signal manually or automatically.After receiving the signal,the four hydrophones deployed at the bottom of the four corners of the swimming pool will upload it to the land based signal processor.Then,the land based signal processor will acquire and process the signal and send the results to the remote display and control terminal via a wireless transmitter.Finally,the coordinate position of the swimmer will be depicted on the display and control terminal and the alarm ring will ring at the same time.How the underwater acoustic beacon and the land based signal processor is designed and realized is explained in detail in this paper.An experiment is completed in the reverb pond and the accuracy of the positioning results is within one meter which meets the design requirements well.The MCU of the underwater acoustic beacon is STM8L151 which cost the lowest power consumption compared with the others currently.In the dynamic run mode,it's power consumption can be as low as 90uA/MHz.In order to further reduce the power consumption,the MCU is waked-up from the HALT mode by the RTC according to a certain time interval.The MCU can acquire the depth value from the pressure sensor via the SPI interface,when the depth value is greater than a certain threshold or the external trigger button is pressed,the MCU will transmit the signal through its I/O port and driver the piezoelectric ceramic ring to send corresponding acoustic signal.The land based signal processor includes a 4-channel signal conditioning module,a digital signal processing module and a wireless transceiver module.The evaluation circuit board based on OMAPL138 is used as the digital signal processing module,the output signal of the hydrophones will be filtered and amplified by the 4-channel signal conditioning module,then it will be sampled synchronously and processed in the digital signal processing module.The digital processing of the signal and the calculation is carried out within the DSP core of OMAPL138.At last,the results will be sent to the remote display and control terminal by the wireless transceiver module.