R-C
HALF WAVE FIRING CIRCUIT:
Circuit diagram :

12
Connection Diagram for RC Half wave Firing Circuit :
PROCEDURE:
1)
Make the connections as given in the circuit diagram.
2)
Connect a Resistance of 50 ohms between the load points.
3)
Vary the control pot(R) and observe the voltage waveforms across load, SCR and at different
points of the circuit.
4)
Note down the output voltage across the Load for different values of firing angle in degree.
5)Calculate the theoretical and practical output voltage.
6)
Draw the graph for input wave form, output waveforms across SCR and Load.
TABULAR COLUMN
:
Sl no.
Firing Angle
Load Voltage
Theoretical
[Vm/2
( 1 +cos
)
In Volts
Practical in Volts

13
VARIOUS WAVEFORMS FOR RC HALF WAVE CONTROL
Wave forms across Input and load:
Wave forms across Load and SCR:
Firing Angle =
X/Y
180
V
in
V
load
V
load
Vscr

14
RC FULL
–
WAVE FIRING CIRCUIT
Circuit diagram:
Connection Diagram for RC Full wave Firing

15
PROCEDURE :
1)
Make the connections as given in the circuit diagram.
2)
Connect a Rheostat of 100 ohms between the load points.
3)
Vary the pot and observe the voltage waveforms across load, SCR and at different points of the
circuit.
4)
Note down the output voltage across the Load for different values of firing angle in degree.
5)Calculate the theoretical and practical output voltage.
6)
Draw the graph for input wave form, output waveforms across SCR and Load.
VARIOUS WAVEFORMS FOR RC FULL WAVE CONTROL:
Wave forms across Input and load:
Wave forms across Load and SCR:
RESULT:-
Half and full wave R & RC triggering circuit have been rigged up and output
waveforms have
been plotted.
V
in
V
load
V
scr
V
load

16
Experiment No: 04
Date:
HALF AND FULL WAVE RECTIFIER USING UJT FIRING CIRCUIT
AIM:
To study the static characteristics of RC Half and Full wave firing circuit .
APPARATUS:
UJT Firing circuit Study unit
Theory:
UJT is highly efficient switch. The switching time is in the range of nanoseconds. Since UJT
exhibits negative resistance characteristics it can be used as relaxation oscillator. The circuit diagram is as
shown with
R
1
and
R
2
being small compared to
R
B
1
and
R
B
2
of UJT.
When V
BB
is applied, capacitor ‘C’ begins to charge through resistor ‘R’ exponentially towards
V
BB
. During this charging emitter circuit of UJT is an open circuit. The rate of charging is
1
RC
. When
this capacitor voltage, which is nothing but emitter voltage,
V
E
reaches the peak point
V
P
V
BB
V
D
, the
emitter base junction is forward biased and UJT turns on. Capacitor ‘C’ rapidly discharges through load
resistance
R
1
with time constant
2
R
1
C
. When emitter voltage decreases to valley point
V
v
, UJT turns
off. Once again the capacitor will charge towards V
BB
and the cycle continues. The resistor R in the circuit
will determine the rate of charging of the capacitor. If R is small the capacitor charges faster towards V
BB
and thus reaches V
P
faster and the SCR is triggered at a smaller firing angle. If R is large the capacitor

#### You've reached the end of your free preview.

Want to read all 75 pages?

- Summer '16
- Rectifier, SCR