Monday, August 22, 2016

Higher and Lower Voltage Cut-out Circuit Based on NE555 IC

Electronic Kit School. - Do you want to save your electronic devices and appliance from over and under voltage which can give adverse effect today? Maybe there many electronic circuit that developed to solve this problem and you can choose it or buy ti easily. But if you want to built by your self it may you have special circuit reference for this work.

In this article we will apply this NE555 IC to build one electronic circuit power supply to protect your electronic appliance or devices from under and over voltage with cut-out it that will make your appliance still secure and saving.

The main component in this circuit to built this work is astable multivibrator IC NE555 that very useful for many application. This IC here will use to set upper and lower condition and with supporting by transistor to give drive the relay will n and off automatically.

Read also: Higher and Lower Voltage Cut-out Circuit Based on NE555 IC


Figure 1. Higher and Lower Voltage Cut-out Circuit Based on NE555 IC

Component Parts

  1. Transformer
  2. Resistors
  3. Capacitors
  4. Diodes
  5. NE555 IC
  6. Transistor NPN
  7. Relay
  8. LED
  9. LM7805
  10. All component (see Figure 1 above)

Circuit like in Figure 1 above show you about the Higher and Lower Voltage Cut-out Circuit using Astable Multivibrator NE555 IC that can give you selecting higher and lower voltage condition. With using RV1 to adjust the lower limit of voltage and RV2 to adjust the higher limit of voltage.

Depending Electronic Zone site that also publish this circuit describe that the supply is tapped from different points in this circuit of the power supply circuit for relay and control circuit operation to achieve reliability. The circuit utilities comparator 2 for control while comparator 1 output (connected to reset pin R) is kept low by shorting pins 5 and 6 of 555 IC. The positive input pin of comparator 2 is at 1/3rd of Vcc voltage. 

Thus as long as negative input pin 2 is less positive than 1/3 Vcc, comparator 2 output is high and the internal flip-flop is set, i.e. its Q output (pin 3) is high. At the same time pin 7 is in high impedance state and LED connected to pin 7 is therefore off. The output (at pin 3) reverses (goes low) when pin 2 is taken more positive than 1/3 Vcc. At the same time pin 7 goes low (as Q ouptput* of internal flip- flop is high) and the LED connected to pin 7 is lit. 

Both timers (IC1 and IC2) are configured to function in the same fashion. Preset VR1 is adjusted for under voltage (say 160 volts) cut-out by observing that LED1 just lights up when mains voltage is slightly greater than 160V AC. At this setting the output at pin 3 of IC1 is low and transistor T1 is in cut-off state. As a result RESET* pin 4 of IC2 is held high since it is connected to Vcc via 100 kilo-ohm resistor R4. 

Preset VR2 is adjusted for over voltage (say 270V AC) cut-out by observing that LED2 just extinguishes when the mains voltage is slightly less than 270V AC. With RESET* pin 4 of IC2 high, the output pin 3 is also high. As a result transistor T2 conducts and energises relay RL1, connecting load to power supply via its N/O contacts. This is the situation as long as mains voltage is greater than 160V AC but less than 270V AC. 

When mains voltage goes beyond 270V AC, it causes output pin 3 of IC2 to go low and cut-off transistor T2 and de-energise relay RL1, in spite of RESET* pin 4 still being high. When mains voltage goes below 160V AC, IC1?s pin 3 goes high and LED1 is extinguished. The high output at pin 3 results in conduction of transistor T1. As a result collector of transistor T1 as also RESET* pin 4 of IC2 are pulled low. Thus output of IC2 goes low and transistor T2 does not conduct. As a result relay RL1 is de-energised, which causes load to be disconnected from the supply. When mains voltage again goes beyond 160V AC (but less than 270V AC) the relay again energises to connect the load to power supply.

And now you can try to use this circuit with realize in real condition with prepare all components and before you also can take the simulation firstly using popular software Proteus 8 Professional for Windows system.


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