Here is a simple project CCTV Switcher circuit using timer IC 555 and decade counter IC 4017. The basic function of this project is to switching between different CCTV camera sequentially i.e. one CCTV output is displayed in TV at a time.
A CCTV (Close Circuit Telephone) camera is used for video surveillance by using video camera. Sometime one CCTV camera is not sufficient for surveillance entire area thus we have to use multiple camera to cover the entire area of surveillance. The circuit posted here control four CCTV camera and display output of one CCTV camera to TV monitor at a time.
Circuit description of CCTV Switcher using 555 IC
The CCTV Switcher circuit using 555 IC and 4017-decade counter is shown in figure 1. Similarly relay connection circuit is shown in figure 2. The entire circuit of CCTV Switcher circuit is built around 555 timer IC, 4017-decade counter IC, four DPDT relay with its switching circuit and few other electronics components like resistor, capacitor, diode etc. for working flawlessly.
12V DC power supply is given to the circuit through connector CON1, where diode D2 block reverse current from the circuit to power supply. Capacitors C1 and C2 filter the ripple contains in input DC supply
Timer IC 555 (IC1) is configured in astable multivibrator mode whose tome period is determined by resistor R1 and R2, variable resistor VR1 and capacitor C3. The charging of capacitor is done by resistor R1 and diode D1 where discharging is done by resistor R1 and variable resistor VR1 through discharge pin (pin 7) of IC1. The output of IC1 (555) from pin 3 is given to clock pin (pin 14) of IC2 for counting the clock pulse.
The second clock pin of IC2 is grounded through switch SW1. We had only used four (Q0 to Q4) out of 10 outputs of IC1 which ON and OFF sequentially after ever clock pulse. Generally, output Q0 goes high when circuit is reset and 1st clock pulse given to pin 14 than output Q2 goes high after second clock pulse and so on up-to output Q9 become high. After the 10th clock pulse the circuit is reset. But here in this circuit we had force reset after 4th clock pulse by connecting output pin Q4 to reset pin (pin 15). Then when 1st clock pulse is given to the IC2 output Q0 become high for fixed interval of time. Similarly, when 2nd clock pulse is given to the circuit output Q1 is high and so on up-to Q3 is high.
Switching Circuit: The switching circuit is designed around transistor. Four individual relays utilize four individual transistors. When output is high its corresponding transistor goes in saturation state as a result relay energized and CCTV camera become ON. DPDT is used here because it will switch audio and video signal coming from the camera. The four LEDs is used to indicate energize of relay i.e. glowing LED1 indicate relay RL1 is energized, LED2 indicate relay RL2 energize and so on. The four resistors (R9 to R12) connected in series to LED is current limiting resistor which protect LED from burning out. Diodes D3 to D6 is fly-back diode which protect coil of relay.
NOTE: The time period of switching between different CCTV camera can be adjusted by variable resistor VR1. IF you require large time period you can replace VR1 with 1M variable resistor.
PARTS LIST OF CCTV SWITCHER CIRCUIT USING 555 IC AND 4017 IC
|Resistors (all ¼-watt, ± 5% Carbon)|
|R1 = 10 KΩ
R2, R4 = 100 KΩ
R3, R5 – R8 = 3.3 KΩ
R9 – R12 = 680 Ω
VR1 = 470 KΩ
|C1 = 0.1 µF (Ceramic Disc)
C2 = 470 µF, 25V (Electrolytic Capacitor)
C3 = 10 µF, 25V (Electrolytic Capacitor)
C4 = 0.01 µF (Ceramic Disc)
|IC1 = NE555 (Timer IC)
IC2 = 4017B (Decade Counter)
T1 – T4 = BC547 (General purpose NPN transistor)
D1 = 1N4148 (Silicon Switching Signal Diode)
D2 – D6 = 1N4007 (Silicon Rectifier Diode)
LED1 – LED4 = 5mm any color LED
|SW1 = push-to-off Switch
RL1 – RL4 = 12V, 2C/O relay
CON1 = 2-pin connector
12V DC supply