To filter the pulsating voltage we get the output of the rectifier, a capacitor must be placed for continued tension as possible. To achieve this it is necessary that the capacity of the capacitor is high, the bigger and less ripple is desired. The disadvantage is that large capacity occupy a large space, so in our design we have chosen the value of 2200 F and 35 V. We have also placed a 100 nF ceramic capacitor to suppress voltage transients on the input.
To stabilize the supply voltage to the required voltage of 12 V, it is necessary to use a voltage stabilizer circuit. The circuit is formed by a limiting resistor and a zener diode biased at 12 V reverse elbow. We measured the ripple voltage on the capacitor filter is 75 mV about 22 V, therefore max Vcc = Vcc min = 22,075 and 21,925. The maximum and minimum current is 55 mA zener and 1 mA respectively.
The value of limiting resistor can be calculated from the following formula: (max Vcc-Vz) / (Iz max + I max) "rlim" (Vcc min-Vz) / (max + I max Iz) (22,075 - 12) / (55mA +30 mA) "rlim" (21.925-12) / (1 mA +30 mA) 118! "Rlim" 321 For our case we choose a resistance of 220!. Maximum output of the zener should be: Pz max = Vz x (Vcc max - Vz) / rlim = 0.5 W
And the maximum power dissipated by the limiting resistor is: P rlim = (Vcc max - Vz) ² / W = 0.45 rlim To ensure the smooth operation of the circuit due to overheating of the circuit, both the power zener like rlim shall 2 W. We finished the design of the source by placing a capacitor of 100 nF in parallel with the zener diode to filter any transition occurring in the source output.
'Lighting circuits' Figure 2 Diagram of the power supply to all components calculated. Vu-meter initially calculate the collector resistors of the transistors. We have chosen transistor type BC547 for high gain and a transistor that is suitable for general applications. In our case we used four equal blocks, one for each led, and since each LED should have the same brightness, the resistance will be equal for all.
As seen in Figure 1, the value of collector resistance is given by Rc = (Vcc-Vce-Vled) / iLED Having set the current through the LED at 4 mA, Vled = 2 V and assuming that the transistor is in saturation, therefore Vce = 0.2V: Rc = (12-2-0.2) / 4mA = 2450 "2K7


To filter the pulsating voltage we get the output of the rectifier, a capacitor must be placed for continued tension as possible. To achieve this it is necessary that the capacity of the capacitor is high, the bigger and less ripple is desired. The disadvantage is that large capacity occupy a large space, so in our design we have chosen the value of 2200 F and 35 V. We have also placed a 100 nF ceramic capacitor to suppress voltage transients on the input.
To stabilize the supply voltage to the required voltage of 12 V, it is necessary to use a voltage stabilizer circuit. The circuit is formed by a limiting resistor and a zener diode biased at 12 V reverse elbow. We measured the ripple voltage on the capacitor filter is 75 mV about 22 V, therefore max Vcc = Vcc min = 22,075 and 21,925. The maximum and minimum current is 55 mA zener and 1 mA respectively.
The value of limiting resistor can be calculated from the following formula: (max Vcc-Vz) / (Iz max + I max) "rlim" (Vcc min-Vz) / (max + I max Iz) (22,075 - 12) / (55mA +30 mA) "rlim" (21.925-12) / (1 mA +30 mA) 118! "Rlim" 321 For our case we choose a resistance of 220!. Maximum output of the zener should be: Pz max = Vz x (Vcc max - Vz) / rlim = 0.5 W
And the maximum power dissipated by the limiting resistor is: P rlim = (Vcc max - Vz) ² / W = 0.45 rlim To ensure the smooth operation of the circuit due to overheating of the circuit, both the power zener like rlim shall 2 W. We finished the design of the source by placing a capacitor of 100 nF in parallel with the zener diode to filter any transition occurring in the source output.
'Lighting circuits' Figure 2 Diagram of the power supply to all components calculated. Vu-meter initially calculate the collector resistors of the transistors. We have chosen transistor type BC547 for high gain and a transistor that is suitable for general applications. In our case we used four equal blocks, one for each led, and since each LED should have the same brightness, the resistance will be equal for all.
As seen in Figure 1, the value of collector resistance is given by Rc = (Vcc-Vce-Vled) / iLED Having set the current through the LED at 4 mA, Vled = 2 V and assuming that the transistor is in saturation, therefore Vce = 0.2V: Rc = (12-2-0.2) / 4mA = 2450 "2K7