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Rangkaian Sekring|Fuse Otomatis

Rabu, 21 Maret 2012 by skemarangkaian

Simple electronic fuse
Skema Rangkaian Sekring|Fuse Otomatis
To restrict / security, electric current is usually used fuse/sekring or patron is dissolved when going short (konslet) will drop out and must be replaced with a new one. Then, in order not to drop out of each new change means that more money out to buy, then there fuse/sekring automatically work with the reset button. So there are problems with each short, fuse/sekring will automatic decided flow then to return it does not need to buy a new (if not broken) just press the reset the equipment will live again.

This is one of the simplest electronic
fuse circuit one can make. The circuit uses only one transistor, one SCR, one push button switch and two resistors.


The value of R1 can be obtained from the equation; [Imax] X [R1] = 0.7V.
R2 can be obtained from the equation; R2 = [Vs] X [1K Ohms].
Wattage rating of R1 can be obtained from the equation; W = [Imax] X [Imax] X [R1].
For this circuit to work the current consumption of the load must be greater than the holding current of the SCR.

The working of the circuit is very simple. Initially the load current flows through SCR and resistor R1.The value of R1 is so selected that, the maximum load current multiplied by the resistance of R1 is equal to 0.7 volts. When the load current exceeds the maximum value the voltage drop across R1 becomes more than 0.7V and switches transistor Q1 ON. Now the transistor completely bye passes the load current and the current through triac falls below the holding current. This makes the triac OFF. When SCR is OFF there will not be any current flow through R1 and so the voltage across it falls to 0.This makes the transistor OFF, completely isolating the load circuit.The fuse can be resetted by pressing S1.When S1 is pressed the SCR is again triggered and remains latched to conduct the load current.

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Rangkaian Fan Control Suhu Otomatis

by skemarangkaian

Control suhu otomatis
Skema rangkaian fan control suhu otomatis
This circuit of automatic Control suhu is based on two transistors that can be used to control the speed of a 12 V DC fan depending on the temperature (suhu). A thermistor (R1) is used to sense the temperature. When the temperature increases the base current of Q1 (BC 547) increases which in turn decreases the collector voltage of the same transistor. Since the collector of Q1 is coupled to the base of Q2 (BD 140), the decrease in collector voltage of Q1 forward biases the Q2 more and so do the speed of the motor. Also, the brightness of the LED will be proportional to the speed of the motor.
Note:
  • R1 can be a 15K @ 20°C ,N.T.C thermistor.
  • M1: DC Fan 12V,700mA fan motor.
  • Capacitor C1 must be rated 25V.
  • The circuit can be powered from a 12V PP3 battery or 12V DC power supply.

About thermistor

The standard leaded thermistors are calibrated and tested at 20 °C to a tolerance of ± 5 % or ± 10 %; however, tighter tolerance, point matched thermistors are readily available as are special point match temperatures to fit your application. Since these thermistors have only one controlled point of reference (the point match temperature), the resistance at other
temperatures is given by the “Resistance vs. Temperature Conversion Tables” for the appropriate material curve. The resistance value at any temperature is the ratio factor times the resistance at 25 °C. The resistance vs. temperature conversion tables can
be found at: www.vishay.com/doc?33004 and www.vishay.com/doc?33011.

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