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AQUARIUM PROBE


ASHES T KULAMACKAL
RENJU CHACKO VARKEY
TOBIN JOHN VARGESE
Under the guidance of
Ms.Laghima
Senior Lecturer in Electronics & Communication Engineering
College of Engineering, Chengannur

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ABSTRACT
In Aquariums ,constant monitoring of temperature by humans is a tedious process.Similarly the amount of dissolved solvents in water th. The circuit of aquatic probe described here can monitor the temperature of water and correct the variation in temperature. The circuit also monitors the density of water and controls the density within a certain limit.
INTRODUCTION
A number of environmental factors including light and temperature affect fish culture. The temperature of water has profound effect because fish cannot breed above or below the critical temperature limits. Temperature between 24°C and 33°C is found to be the best to induce spawning in fishes. This particular temperature range is also necessary for the healthy growth of nursery fish fries (young fishes). Rise of water temperature due to sunlight may adversely affect the fish rearing process. Also the excessive impurities that are present in the water may affect the health of the fishes.

A number of environmental factors including light and temperature affect fish culture. The temperature of water has profound effect because fish cannot breed above or below the critical temperature limits. Temperature between 24°C and 33°C is found to be the best to induce spawning in fishes. This particular temperature range is also necessary for the healthy growth of nursery fish fries (young fishes). Rise of water temperature due to sunlight may adversely affect the fish rearing process. The circuit of aquatic probe described here can monitor the temperature of water and indicate the rise in temperature through audiovisual indicators. A readily available signal diode 1N34 is used in the circuit as the temperature sensing probe. The resistance of the diode depends on the temperature in its vicinity. Typically, the diode can generate around 600 mV when a potential difference is applied to its terminals. For each degree centigrade rise in temperature, the diode generates 2mV output voltage. That is, at 5°C, it is 10 mV, which rises to 70 mV when the temperature is 35°C. This property is exploited in the circuit to sense the temperature variation in aquarium water. Fig. 1 shows the circuit diagram of the aquarium probe. Since the output from the diode sensor is too low, a high-gain inverting DC amplifier is used to amplify the voltage. CA3140 (IC1) is the CMOS version op-amp that can operate down to zero-volt output. The highest output available from IC1 is 2.25V less than the input voltage at pin 7. With resistor R4 and VR2, the variation in diode v o l t a g e c a n b e amplified to the required level. Resistor R1 restricts current flow through diode D1 and preset VR1 (1-kilo-ohm) sets the input voltage at pin 3. IC3 (7805) provides regulated 5 volts to the inputs of IC1, so that the input voltage is stable for accurate measurement of temperature. The output from IC1 is fed to display driver LM3915 (IC2) through preset VR3 (50-kilo-ohm). With careful adjustments, the wiper of VR3 can provide 0-400 millivolts to the input of IC2. The highly sensitive input of IC2 accepts as low as 50 mV if the reference voltage at its pin 7 is adjusted using a variable resistor. To increase the sensitivity of IC2, preset VR4 is connected at one end to ‘reference voltage end’ pin 7 and its wiper is connected to ‘high end’ pin 6 of the internal resistor chain. When approximately 70 mV is provided to the input of IC2 by adjusting preset VR3, LED1 (green) lights up to indicate that the temperature is approximately 35°C, which is the crossing point. When the input receives 100 mV, LED2 (red) lights up to indicate approximately 50°C. Finally, the buzzer starts beeping if the input receives 130 mV corresponding to a temperature of 65°C. In short, LEDs and the buzzer remain standby when the temperature of the water is below 35°C (normal). With each step increase of 30 mV in the input (corresponding to 15°C rise in temperature), LEDs and the buzzer become active. Pin 16 of IC2 is used to drive the piezobuzzer through transistor T1. When pin 16 of IC2 becomes low, T1 conducts to beep the piezobuzzer. Resistor R7 keeps the base of transistor T1 high to avoid false alarm. IC4 provides regulated 9V DC to the circuit.


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http://dmohankumar.files.wordpress2010/0...-probe.pdf