If you are beginners who want to use the simple variable power supply 0-30V 2A. This circuit is best for you. Because it has a few parts, small, and cheapest than others circuit that same power. The features of this handset are the DC voltage continuously from 0-30 volts and apply current up to 2 amperes and can put easily in a large pro box.
There are LED1 to show power on and R1 limit current to a safe value.
R2-100ohms and ZD1-30V are connected together as the 30V steady DC regulators.
The variable resistors VR1 is used to adjust the output voltage between 0V to 30V, that have transistors Q1, Q2 increase the output current up to 2A. Also, there is the short-Circuit protection include Q3, R3.
How to builds
The circuit assembly is very simple Because the devices are less Can assemble down on the perforated board. While the power transistor Q3 – 2N3055 is working, will hot so we always use a heat sink on it.
Should use low wattage soldering iron does not exceed 30 watts. The soldering the legs of transistors and diodes we should use the pliers with leg devices Because these devices cannot be very hot.
Adjustment and usage
The prototype works well, have ripple voltage at output lower than 1 mV and the output voltage will drop lower than 0.1 volts
In real usage that although it off, LED power ON will still light up for a moment. Because the LED gets current from C1 that does not discharge fully.
If you want to stop LED immediately. You may move R1 and LED1 to across the secondary of T1. Then, add the diode-1N4001 series with LED to protects voltage backward which LED may be damaged as Figure 2
We change the rectifier section to new, from a Full-wave into the bridge and use the two secondary coil; 24V 2A. Then, apply the negative and positive of each channel to the ground as Figure 3
The parts you need
Q2, Q3: 2N3055 Power NPN transistor
Q1: BC548,BC549, 45V 100mA NPN Transistor
D1, D2: 1N5402 3A 100V Diode
D3: 1N4002 1A 100V Diode
ZD1: 30V 1W Zener
VR1: 10K Potentiometer
R1: 3.3K, 0.25W resistor
R2: 100 ohms, 0.5W resistor
R3: 0.3 ohms 10W resistor.
Be careful Components pinouts
Some parts on this have different pins. You need to put it in the correct way only!
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