DIGITAL WATER-LEVEL METER full report
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01-04-2010, 11:43 PM
DIGITAL WATER-LEVEL METER
Digital Electronics Unit
In many applications a digital value is desired (for storage, analysis or accuracy). Although the above circuit can be used as an input to an analogue to digital unit, a more elegant and robust solution is to go directly to digital from the probe.
The capacitance probe is connected to an ICM7555 running in astable mode. The 7555 has an advantage as an oscillator for this application because the timing capacitor is grounded. The probe will be the timing capacitor.
The period of oscillation is proportional to the capacitance and therefore to the water level. The period is measured using the capture feature of any Microchip PIC microcontroller that has the CCP (Capture, Compare and PWM) hardware. In this schematic and code example, a 16F88 is used. The output of the ICM7555 is connected to the CCP1 pin.
Timer 1 is setup to count the crystal frequency divided by four, so the count increments every 0.25 microseconds with a crystal frequency of 16MHz. The timer runs freely and rolls over to zero after the maximum count is reached.
CCP1 is setup to capture the timer 1 count after sixteen cycles of the 7555 oscillator, thus giving a larger count for better resolution, and some averaging. The difference in the timer 1 counts between successive captures is the measurement.
The time taken for the measurement is only a few milliseconds maximum, so further averaging can be done by taking multiple measurements without affecting the dynamic response in applications where a wave profile needs to be measured.
Only one resistor is needed on the 7555 in astable mode compared to two with a standard 555. The resistor should be a low temperature coefficient type eg. from the RC55 series from Farnell or equivalent. The value required can be determined by immersing the probe to the maximum level and setting the resistor value so that the 7555 frequency is about 5kHz. This will be the minimum frequency and the maximum period of oscillation. Typically, this is around 1nF.
The 7555 frequency can drift with temperature (see curve in data sheet) and for this reason the air temperature can also be measured so that a correction can be made if required, either in the PIC program or in post-processing of the data. Generally it is better to perform this correction using a computer to convert the values with suitable high precision. Alternatively, record the response of the probe over the desired temperature range and correct for this.
In this example, the ambient temperature near the 7555 is measured using an LM35 analog temperature sensor.
The level measurement can be scaled to water level in the PIC or in the post processing of the data. The measured value is generally more than enough for the probe resolution.
In the code example, the measured value is output without scaling to the RS232 serial port in ASCII format so that the data can be viewed and saved to a file using a terminal program such as gtkterm on Linux, Teraterm or Hyperterminal in Windows. Temperature is also output in degrees Celcius.
Only the 7555, the temperature sensor and a local +5V regulator really need to be near the probe - if the cost can be justified, a MAX485 can be used to transmit the 7555 pulses differentially (RS422 mode) via a twisted pair cable, eg. CAT5 data cable, to the rest of the electronics at some distance. At this end there is another MAX485 to convert the differential signals back to single ended. Other pairs in the cable can be used for the temperature and to send unregulated DC to the remote regulator.
PCB stakes are also known as PCB risers
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19-10-2010, 12:22 PM
ffffffff.doc (Size: 356 KB / Downloads: 261)
WATER TANK LEVEL CONTROLLER USING WATER LEVEL SENSOR
In this project and implimentation, IC and water level sensor are used to control the
water level in a water tank. This project and implimentation switches on the motor pump
when water in the overhead tank falls below the lowest level
and turns it off when the tank is full. It is to replace the
traditional way that use tank ball. The water level is sensed by two
water sensor to operate the switches for controlling the pump motor.
The IC is used to program the water sensor to sense the water and switch the pump motor when needed.
1.1 Project background
A range of level control systems and methods are used in industry. Systems may be based on the use of floats, probes or sensor. Level control is one of continuous process that can be treated as an integrating process. The level controller can be applying on temperature control, pressure control, and water control.
The level controller is used with electrical probes or sensors. The electrical probes are used with power supply and motor. The probes will put inside the tank and the motor will pump as the water goes down. the probes will detect the level of the water and on/off the motor.
The level controller which are using water sensor will sense the low and high level of water in water tank. If the water was low, the motor will pump the water and will stop to pump water after the high level reached.
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09-11-2010, 05:17 PM
i want full project and implimentation report for micro controller based water level indicator
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24-11-2010, 03:43 PM
water level indicator.pptx (Size: 297.71 KB / Downloads: 199)
Presented By:ROSHAN NALE
ELECTRICAL AND ELECTRONICS ENGG. DEPARTMENT
WATER LEVEL INDICATOR
SYSTEM FLOW CHART
WHAT IS WATER LEVEL INDICATOR ?
It’s a system to indicate the level of water in a tank/reservoir using probes which are monitored through a microprocessor.
The water tank is at ground potential and probes are connected to 5 V dc.
The project and implimentation can be used for various application wherever we require water level indication :
domestic water distribution supply system
water supply for power plants viz. Nuclear, thermal
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20-04-2011, 12:11 PM
Automatic water level controller.docx (Size: 73.62 KB / Downloads: 128)
Automatic water level controller using 555 timer IC.
Introduction- The automatic water level controller is used to maintain the water level of the tank automatically. These project and implimentations mainly control the pump through relays which is used to feed the water to the tank.
The main component of this project and implimentation is “555 timer IC”. The output signal which is based on the input signal from the tank is used to control the relay which in turn controls the pump motor circuit.
The 555 timer is a monolithic timing circuit that can produce accurate & highly stable time delays or oscillations. This timer basically operates in one of the three following modes:
• operating range -55o to +125oc
• Operating voltage +5v to +18v
• Adjustable duty cycle
• µs to hours delay in the output
• Source and sink current 200mA (max.)
• Compatible to TTL as well as op-amp & others circuits.
Circuit diagram of 555
Circuit diagram for automatic water level controller
Working:-The working of this project and implimentation is based on utilizing the bistable mode of the 555 timer IC. In the bistable mode the 555 gives both the positive and negative supply continuously until it is not trigged.
The triggered voltage is provided from the tank as shown in the figure when water reach the upper level it established the connection of the control signal to the threshold pin and hence the relay disconnect the circuit of the motor with the supply. In the similar manner when the water level reaches below the lowest level it provides the trigger signal to the 555 and once again the connection is between the motor and supply is re-established through the relay which is controlled by 555.
Working of the RS Flip flop:-
R S Output
0 0 0
0 1 1
0 0 Previous stage
1 0 0
0 0 Previous stage
SENSOR: The sensor used in the project and implimentation uses the bouncy of the water in order to connect the various connections used the timer IC. The sensors are the same that is used now days in the automatic tank connected water filters. Each sensors float is suspended from above using an aluminium rod. This arrangements encased in a PVC pipe and fixed vertically on the inside wall of the water tank. Such sensors are more reliable than induction-type sensors. Sensor1 senses the minimum water level, while sensor 2 senses the maximum water level(see the figure).Leaf switches S1 and S2 (used in taperecorders) are fixed at the top of the sensor units such that when the floats are lifted, the attached 5mm dia. (approx.) aluminium rods push the moving contacts (P1 and P2) of leaf switches S1 and S2 from normally closed (N/C) position to normally open (N/O) position. Similarly, when the water level goes down, the moving contacts revert back to their original positions. Normally, N/C contact of switch S1 is connected to ground and N/C contact of switch S2 is connected to 12V power supply. IC 555 is wired such that when its trigger pin 2 is grounded it gets triggered, and when reset pin 4 is grounded it gets reset. Threshold pin 6 and discharge pin 7 are not used in the circuit. When water in the tank goes below the minimum level, moving contacts (P1 and P2) of both leaf switches will be in N/C position. That means trigger pin 2 and reset pin 4 of IC1 are
connected to ground and 12V, respectively. These triggers IC1 and its output go high to energise relay RL1 through driver transistor SL100 (T1). The pump motor is switched on and it starts pumping water into the overhead tank if switch S3 is ‘on.’ As the water level in the tank rises, the float of sensor 1 goes up. This shift the moving contact of switch S1 to N/O position and trigger pin 2 of IC1 gets connected to 12V. This doesn’t have any impact on IC1 and its output remains high to keep the pump motor running. As the water level rises further to reach the maximum level, the float of sensor 2 pushes the moving contact of switch S2 to N/O position and it gets connected to ground. Now IC1 is reset and its output goes low to switch the pump off. As water is consumed, it level in the overhead tank goes down. Accordingly, the float of sensor 2 also goes down. This causes the moving contact of switch S2 to shift back to NC position and reset pin 4 of IC1 is again connected to 12V. But IC1 doesn’t get triggered because its trigger pin 2 is still clamped to 12V by switch S1. So the pump remains switched off. When water level further goes down to reach the minimum level, the moving contact of switch S1 shifts back to N/C position to connect trigger pin 2 of IC1 to ground. This triggers IC1 and the pump is switched on. The float sensor units can be assembled at home. Both the units are identical, except that their length is different. The depth of the water tank from top to the outlet water pipe can be taken as the length of the minimum-level sensing unit. The depth of the water tank from top to the level you want the tank to be filled up to is taken as the length of the maximum-level sensing unit. The leaf switches are fixed at the top of the tank as shown in the figure. Each pipe is closed at both the ends by\using two caps. A 5mm dia. hole is drilled at the centre of the top cap so that the aluminium rod can pass through it easily to select the contact of leaf switches. Similarly, a hole is to be drilled at the bottom cap of the pipe so that water can enter the pipe to lift the float. When water reaches the maximum level, the floats should not go up more than the required distance for pushing the moving contact of the leaf switch to N/O position. Otherwise, the pressure on the float may break the leaf switch itself. The length of the aluminium rod is to be selected accordingly. It should be affixed on the metal/thermocole float using some glue (such as Araldite).
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25-06-2011, 11:40 AM
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Joined: May 2012
14-05-2012, 01:11 AM
can anyone send me the programming part of this project and implimentation...
i am doing this project and implimentation using pic16f684 microcontroller.
Joined: Apr 2012
14-05-2012, 10:09 AM
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