A Good Example~ (WEEK 3)

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This video show comparison between two alarm.One with foolproof alarm,and the other one without foolproof alarm.

How its Work?(WEEK 2)

Fig.1in the form of block diagram.Pressure variations due to changes in the water level are detected  by Sensor 1.Its weak output is amplified and then processed by the PIC microcontroller,which controls the alarms and drive the LEDs status.

It uses a pressure sensor to detect sudden increases in water depth, as happens when an object falls into the pool creating waves.The unit is built in two sections, each in a weatherproof box. One houses the sensor, while a second, which we have dubbed the Pool Alarm box, houses the PIC-controlled alarm circuit. The two are connected via a 4-way cable.The cable can be run underground across to the pool sensor box. Inside the sensor box is a pressure sensor. This measures the water pressure variations in the pool due to waves, and sets off an alarm if these variations reach a preset level. The sensor box has a thin tube emerging from it. The box is placed so that the probe tip is about 60mm to 90mm under water. This sensor box can be secured to a pool ladder or fixed to the side of the pool.

 Fig. 2,this cross section diagram  shows the internal structure  of the MPX-2010dp pressure sensor.The strain gauge varies its resistance according to the applied load.P1 and P2 are the two port openings.



The pool alarm is plugpack-powered, so it needs to be located near to the mains. Complete safety from the mains power is provided first by the isolation given by the plugpack and second, by the fact that there is no electrical contact with the water itself.



Additional features:


Most prominent on the main alarm box is a weatherproof pushbutton ‘Hold’ switch. This is used to set the operating mode of the alarm. When powered up, the alarm is initially set to its normal monitor mode, where it checks for pool wave movement. It takes about 10 seconds after power up to begin monitoring, and during this time, the green ‘Hold’ LED remains lit.After the 10 seconds, the LED flashes briefly every 1.5 seconds, indicating that the alarm is in the monitor mode.If the alarm senses that the pool wavemovement is sufficient, it will sound the alarm. The alarm period can be varied from between zero and five minutes, with typical settings around the 30s to 3-minute range. During the alarm period, an Alarm LED flashes on andoff at five times per second. The alarm siren can be stopped at any time by pressing the Hold switch. This will also stop the Alarm LED flashing. The Hold LED will also stop flashing, but unlike the Alarm LED, it will remain constantly on. The Pool Alarm is now in the Hold mode, where the alarm will not sound. However, the Alarm LED will flash whenever wave movement is above the alarm threshold. The hold mode is used when the pool is in use.

Wave movement:
The degree of wave movement required to set off the alarm can be calibrated to suit your pool. This is done by dropping a weighted bucket into the pool (simulating a small child falling into  water) and pressing the alarm level switch (on the PC board). The Pool Alarm will monitor the wave movement over a 10s period, and set up the level required for the alarm. During this calibration period, a ‘Status’ LED will be lit. A second quiescent level can also be calibrated into the Pool Alarm. This level is the wave movement within the pool when no-one is in it, but with a light breeze blowing and perhaps the filter running (normal filter running should not trigger the alarm). In practice, the level is calibrated under these conditions (when a reasonable wind is blowing) by pressing the Quiescent Level calibration switch. The alarm then monitors wave movement for 10 seconds and stores the level. During this calibration period, the Status LED is lit. Quiescent level calibration allows the Pool Alarm to provide extra features. First, it allows the mode to return from the Hold to the monitor mode automatically. So when the pool is being used, the Hold switch is pressed to set the Pool Alarm to the Hold mode so that the alarm will not sound. However, during this time, the alarm continues to monitor the wave movement.During pool use, the wave movement will continue to be over the quiescent level and the alarm will remain in the Hold mode. When the pool is not in use, wave movement within the pool will settle to below the quiescent level. In this case, the alarm will change from Hold mode to Monitor mode, after a preset period of ‘no pool’ activity. The period of inactivity can be adjusted to allow for the way the pool is used. If the pool is often vacant for a short time before it is used again, the period can be made sufficiently long to prevent the return to Monitor happening in that time period. The adjustment range is from 1.25 to 75 minutes. One setting prevents the monitor return function. The change from Hold to Monitor and from Monitor to Hold can also be toggled with the Hold pushbutton switch. The Hold LED then flashes for Monitor and is continuously lit for the Hold mode. During the monitoring mode, windy conditions may cause wave movement that could exceed the quiescent level but may be below the alarm level. The Pool Alarm has an option that can return it to the Hold mode if the quiescent level is exceeded for 30 seconds without the alarm level being exceeded. This feature is included to prevent false alarms from the siren in windy weather. The Pool Alarm will then return to the monitoring mode after the wave movement has reduced to below the quiescent level. Should the alarm sound and time out before the Hold switch is pressed, the alarm will return to Hold after the alarm period expires. The ‘return to hold’ option can be enabled or disabled with a jumper pin selection. Just which option you select depends on your pool and whether it is subject to windy conditions. Protected pools may not need the ‘return-to-hold’ feature. This is a compromise between preventing false alarms and providing continuous pool protection.


Pressure sensor:

An air-pressure sensor, the MPX2010DP manufactured by Freescale Semiconductor, is used to measure wave movement. Its internal arrangement is shown in Fig.2. The sensor comprises a strain gauge that provides a resistance variation with applied load. In this case,the load is the air pressure exerted on the gauge due to a tube inserted into the pool. The sensor is called a differential type because it measures the difference in pressure between one port and the other. For our application, we use Port 1, which has a silicone gel protective layer to prevent moisture affecting the strain gauge element. Port 2 is left disconnected and is vented to the inside of the enclosure.

Features of Swimming Pool Alarm.(WEEK 1)

Features:

• Monitors wave height caused by any disturbance in the pool.
• Adjustable quiescent and alarm wave levels. 
• adjustable alarm period.
• Pushbutton switch for hold/monitors.
  -Hold modes gives visual but silent alarm(for testing or attended pool use)
  -Monitors modes gives visual and audible alarm(for unoccupied pool)
• Automatic return to monitor modes after pool water settles.
• Adjustable return to monitor period.
• Optional set-to-hold mode with pool turbulence preventing false alarm.
• Wheaterproof housing.
• Can drive two alarm sirens.
• Plugpack powered.
• Suits all pool where the top water level is below pool edge.

Introduction of Swimming Pool Alarm(WEEK 1)

For this Final Year Project,the project that we have choose is SWIMMING POOL ALARM.Chosen from EPE magazine,this project is an alert system for swimming pool.As we all know,swimming pool is a dangerous place for toddlers.Although swimming pools nowadays were guard by fences,there is always a posibility that a toddlers will find a way to get through.So,while fences may appear as a pool secure,they are never foolproof.As a second line defense,one that warns if someone falls into the pool,can literally be the difference between life and death.

A way to add a secondary defense is with swimming pool alarm.The type of pool alarm described here monitors the amount of pool water movement and sounds an  alarm when this exceeds a preset level.There might be in case of wind that create the water disturbance.But,with this alarm,you can set to a level which ignores typical wind movement and sound the alarm when exceed the level(when someone falls into).