15-01-2013, 04:53 PM
Water level alarm circuit
1Water level.docx (Size: 3.59 MB / Downloads: 58)
Working water tank level alarm
• Water over flow from a tank or reservoir is detected using this simple project circuit. Close switch SW to turn on the device.
• Initially the potential at point A in the circuit is Vcc so the transistor Q1 remains in ON state (Read transistor act as a digital switch), and its collector voltage at Vce sat (0.02V).
• The collector voltage of Q1 is fed to the base terminal of transistor Q2 via100Ω resistor.
• 0.02V is not sufficient to turn on the transistor Q2 hence it remains in OFF state and the Buzzer will not produce any sound.
• A connection from ground is dipped in the water reservoir. When water level rises, the ground comes in contact with the base terminal of transistor Q1. Thus it changes to OFF state and the collector voltage rises to Vcc.
• The high voltage at the collector of Q1 turns ON the transistor Q2 since this high voltage is connected to the base of transistor Q2, then a current flow occur though the Buzzer circuit and it produces beep alarm sound. (Read transistor act as a load switch)
• See the simulation window below, instead of Buzzer circuit we have used an LED for simulation. The switch ON being similar to water touching the point A.
IC NE 555
Design
The IC was designed in 1971 by Hans R. Camenzind under contract to Signetics, which was later acquired by Philips.
Depending on the manufacturer, the standard 555 package includes 25 transistors, 2 diodes and 15 resistors on a silicon chip installed in an 8-pin mini dual-in-line package (DIP-8).[2] Variants available include the 556 (a 14-pin DIP combining two 555s on one chip), and the two 558 & 559s (both a 16-pin DIP combining four slightly modified 555s with DIS & THR connected internally, and TR is falling edge sensitive instead of level sensitive). There is no 557.
The NE555 parts were commercial temperature range, 0 °C to +70 °C, and the SE555 part number designated the military temperature range, −55 °C to +125 °C. These were available in both high-reliability metal can (T package) and inexpensive epoxy plastic (V package) packages. Thus the full part numbers were NE555V, NE555T, SE555V, and SE555T. It has been hypothesized that the 555 got its name from the three 5 kΩ resistors used within,[3] but Hans Camenzind has stated that the number was arbitrary.[1]
Low-power versions of the 555 are also available, such as the 7555 and CMOS TLC555.[4] The 7555 is designed to cause less supply noise than the classic 555 and the manufacturer claims that it usually does not require a "control" capacitor and in many cases does not require a decoupling capacitor on the power supply. Such a practice The IC was designed in 1971 by Hans R. Camenzind under contract to Signetics, which was later acquired by Philips.