The project phase sequence change indicator using 555 IC is used to indicate whether there is change in phase sequence occur or not by a beeper or a LED. We all know that in three phase motor phase sequence is important because change in phase sequence may cause trouble in machines.
Circuit Description of Phase Sequence Change Indicator
The circuit of phase sequence change indicator is divided into two main section i.e. controlling section and beeper section. The circuit of phase sequence change indicator is shown in figure 1.
The three transistors T1, T2 and T3 are used to charge three phase waveforms into square waveform. The resistor connected to its base and are so selected that transistor gets fully saturated when the base voltage becomes 10V. The diode connected to its base keeps the reverse voltage below 0.6V during negative cycle.
When the phase sequence is correct, the red phase lags the yellow-phase by 1200 where green phase lags the red-phase by 1200. The circuit designed here to detect any change in the sequence as above and further procedure beeping sound. Phase inversion and decrement of slope of rising and falling edge (i.e. to decrement the rise time of the square wave) is done by transistor T4. The output of transistor T4 is connected to the clock pin (pin 6 and pin 1) of IC7476 (IC1) as a result during every cycle the phase sequence is checked.
For the clock, squared waveform of the yellow-phase is used. Other phases are inverted during squaring operation. So, at the falling edge, transistor T3 is cut-off and T2 is in saturation. Collector of T2 is connected to the input J of IC1:a and K of IC1:b. So at the clock edge we got low at both the inputs. Collectors of T3 is connected to K input of IC1:a and J of IC1:b resulting in high output at the clock pulse. At the rising edge of the clock we get J low and K high for IC1:a. So it gets reset and gives high at Q. Similarly, when the J and K inputs of IC1:b are high the flip-flop is set. The Q output of IC1:a and Q output of IC1:b are ORed and fed at the base of T5 in order to switch on the beeper circuit. The beeper circuit is designed using two timer IC 555 and both are configured in astable multivibrator mode.
PARTS LIST OF PHASE SEQUENCE CHANGE INDICTOR
|Resistors (all ¼-watt, ± 5% Carbon)|
|R1, R2 = 22 KΩ
R3, R4 = 5.6 KΩ
R5 = 470 Ω
R6 – R9 = 10 KΩ
R10 – R12 = 1 MΩ
R13 = 560 Ω
|C1, C3 = 0.1 µF
C2 = 0.01 µF
C4 = 10 µF/16V
|IC1 = 7476
IC2, IC3 = NE555
T1 – T4 = BC148B
T5 = SK100
D1 – D4 = 1N4001
LED1 = 5mm Any Color LED
|LS1 = 8Ω Speaker|