1. PRESENTATIONPRESENTATION
ONON
Project GuideProject Guide
Mr. S. K. JhaMr. S. K. Jha
Presented ByPresented By
Ankit Srivastava(0809020019)Ankit Srivastava(0809020019)
Anurag Tiwari(0809020026)Anurag Tiwari(0809020026)
Ashish Verma (0809020031)Ashish Verma (0809020031)
Buddha Prakash (0809020034)Buddha Prakash (0809020034)

2. INTRODUCTION
 Power instability in developing countries creates
the need for automation of phase selection or
alternative sources of power to back-up the utility
supply .
 Most industrial and commercial applications are
dependent on power supply .
 If the process of changeover is manual, not only
considerable time is wasted but also the device
or machine may get damaged from human error
during the changeover connections, incurring
massive losses.

3.  Digital phase selector that can be installed in residential
and office premises where single-phase equipment are
used. When any of the mains phase lines fails, it
automatically selects the available phase line (out of three
phase lines or backup lines).

4. CIRCUIT DESCRIPTION
It comprises phase (or inverter) sensing,
control logic and relay driver sections .
The phase-sensing circuitry has R,Y,B and
inverter sensing sections, which sense the
presence of R,Y,B and inverter supply,
respectively.
The control logic circuitry decides the
phase priority for one out of four lines .

5. BLOCK DIAGRAM

6. The order of phase priority is R-phase
followed by Y-phase , B-phase and then
backup (inverter )as shown in the truth
table given below .
The relay-driver section drives the relay
according to the signal received from the
control logic circuitry .
Power supply provides the power to control
the logic circuit and relay driver sections.

7. TRUTH TABLE

8. Explanation of control logic
The control logic circuit comprises NOT
gate, AND gate, diodes and a few passive
components.
It is basically a priority encoder and works
according to the truth table.
If an input variable is at logic ‘0’ it means
that particular phase (line) is absent in the
phase selector .

9. If an input variable is at logic ‘0’ it means
that particular phase (line) is absent in the
phase selector .
 if an input variable is at logic ‘1’ that
particular phase (line) is present in the
phase selector.

10. Circuit Diagram

11. Circuit Description
 Figure shows the circuit of the digital phase selector. The R-phase
of AC mains supply is rectified by half-wave rectifier IN4007 (D1).
The rectified signal is limited to 9 volts by the zener diode and
filtered by a 10úF capacitor. The 15-kilo-ohm resistor acts as the
current limiter.
 The cathode of the zener diode is connected to pin 1 of optocoupler
4N35 through a 1-kilo-ohm resistor. The 1-kilo-ohm resistor acts as
the current limiter for 4N35. Each optocoupler consists of a gallium-
arsenide infrared LED and a silicon npn phototransistor. When R-
phase is present, the internal infrared LED drives the internal
phototransistor of 4N35. Emitter
 Pin 4 of 4N35 is used for the control logic circuitry.
 All the line-/phase-sensing circuits are similar as explained above.
The control logic circuit is isolated from the phase-sensing circuit by
optocoupler 4N35.

12. Control Logic Description
 From the truth table, we can easily arrive at the following Boolean
equations:
 R= R phase
_______
 Y=R phase. Y phase
______________
 B= R phase. Y phase. B phase
_______
 INV. = R phase. Y phase. B phase. Inverter
 The working of the control logic circuit is as simple as its structure.
The presence of any of four phase lines, namely R, Y, B and
inverter, makes the corresponding variable high (logic 1). The
glowing of a particular LED, bearing the same name as the output
variable, will indicate top priority.

13. Components Used
Inverter Circuits (CD4069UBC)
The CD4069UB consists of six inverter circuits and is manufactured using
complementary MOS (CMOS) to achieve wide power supply operating
range, low power consumption, high noise immunity, and symmetric
controlled rise and fall times.
 Features:
 Wide supply voltage range: 3.0V to 15V
 High noise immunity

14. DIODE
This is a junction Diode. If the positive terminal of the battery is connected to
the p-type material (cathode) and the negative terminal to the N-type
material (Anode), a large current will flow.
If the connections are reversed, a very little current will flow.

15. RELAY
Relay is a common, simple application of electromagnetism. It uses an
electromagnet made from an iron rod wound with hundreds of fine copper
wire. When electricity is applied to the wire, the rod becomes magnetic. A
movable contact arm above the rod is then pulled toward the rod until it
closes a switch contact. When the electricity is removed, a small spring pulls
the contract arm away from the rod until it closes a second switch contact.
By means of relay, a current circuit can be broken or closed in one circuit as
a result of a current in another circuit.

16. RESISTANCE
Resistance is the opposition of a material to the current. It is measured in Ohms (W). All
conductors represent a certain amount of resistance, since no conductor is 100% efficient. To
control the electron flow (current) in a predictable manner, we use resistors. Electronic circuits
use calibrated lumped resistance to control the flow of current. Broadly speaking, resistor can be
divided into two groups viz. fixed & adjustable (variable) resistors. In fixed resistors, the value is
fixed & cannot be varied. In variable resistors, the resistance value can be varied by an adjuster
knob. It can be divided into (a) Carbon composition (b) Wire wound (c) Special type. The most
common type of resistors used in our projects is carbon type. The resistance value is normally
indicated by colour bands. Each resistance has four colours, one of the band on either side will
be gold or silver, this is called fourth band and indicates the tolerance, others three band will give
the value of resistance.
COLOURS CODE
 Black 0
 Brown 1
 Red 2
 Orange 3
 Yellow 4
 Green 5
 Blue 6
 Violet 7
 Grey 8
 White 9


17. IC ULN 2003
The output from the logic control circuit is fed to relay
driver ULN2003 (IC7). IC ULN2003 is a high-voltage,
high-current Darlington array containing open-collector
Darlington pairs with common emitters. Each channel is
rated at 500 mA and can withstand peak current of
600mA.
The ULN2003 is high voltage, high current Darlington
arrays each containing seven open collectors Darlington
pairs with common emitters

18. Optocoupler
 In electronics, an opto-isolator, also called an optocoupler,
photocoupler, or optical isolator, is "an electronic device
designed to transfer electrical signals by utilizing light waves to
provide coupling with electrical isolation between its input and
output". The main purpose of an opto-isolator is "to prevent high
voltages or rapidly changing voltages on one side of the circuit from
damaging components or distorting transmissions on the other
side." Commercially available opto-isolators withstand input-to-
output voltages up to 10 kV and voltage transients with speeds up to
10 kV/μs.

19. Conclusion
The DIGITAL PHASE SELECTOR is an advanced
technique which is not only used for automation.
It is one of the techniques for the power quality
improvement.
This is a safe mode of change over of phase as it uses ic
4N35 optocoupler which is high frequency switch.
It does not contain any mechanical contacts and hence
losses are negligible.