Introduction: Linear Power Regulator
Third Prize in the
Power Supply Contest
Most of the times we do not need power supplies which can provide large currents. But when we need them, either we have to buy them or have to make one. Power supplies with high current ratings are very expensive. Further, most of the online circuit diagrams contain power supplies with maximum 1A.
As a solution for these, I worked on a power supply as my university project which can supply up to 3A at a particular voltage. The main advantages are less complexity and low cost. You might have heard about SMPS (Switch Mode Power Supply). But due to the complexity of the circuit, it's hard to build them at our home. Hence I chose linear power supplies.
Step 1: Components
Collect the following components.
- 2N3055 Transistor X 2
- 10K resistor X 1
- 1K resistor X 1
- 560 Ohms resistor X 1
- 220 Ohms resistor
- LED X 1
- 5.6v zenner diode X 1
- 100uF capacitor X 1
- 470uF capacitor X 1
- Fuse Holder X 1
Let's start building the circuit.
Step 2: Diagram
Here I will explain how this power supply works. 100uF and 470uF capacitors are working as smoothing capacitors which help to avoid ripples and to maintain a smooth voltage supply.
Initially, I didn't mention the output voltage of this because we can select any desired output voltage by changing the value of the Zener diode. The output voltage will be equal to 0.6V less than the Zener diode's voltage. As an example, here I have selected 5.6V Zener and the output voltage will be 5V.
Q1 transistor is the driving transistor which helps to regulate the voltage. The Q1 transistor heats when working as the input voltage drops across this. Therefore, a heat sink is needed to remove the dissipated heat.
LED is used to indicate that the power supply is working well.
Step 3: PCB
For this circuit, I decided to make the PCB by drawing the paths with a permanent marker as this is a very simple circuit. There are many tutorials on making PCBs, so I'm not going to explain much.
You may notice that there are only 2 pins in 2N3055 transistor. The metal cover of this transistor is acting as the collector pin. So you have to use nut and bolt to connect the collector pin to the PCB. You can notice the 2 points with soldered nuts at the above image.
Step 4: Soldering Components
The soldered circuit board will look like this. I don't have many photos to show you the procedure step by step as I captured them after finishing the project.
However, you can notice the black heat sink that I used for the Q1 transistor. It needs to be placed before soldering the transistor. You may use thermal paste between the transistor and the heat sink.
2 wires for the input voltage and another 2 wires for the output voltage are needed to solder to the circuit board.
Now our circuit is ready. You can check the output voltage by supplying an input voltage. The recommended input voltage range is 0-50V and output voltage range is 0-30V.
Step 5: Enclosure
To make the enclosure I used 2mm acrylic sheet. After cutting and gluing the pieces the enclosure was like in the above image. The size is 10cm X 18cm X 5cm.
The bottom plate is kept separately to fix the circuit board.
Additional holes are created to place the power switch, fuse holder, and power connectors.
Step 6: Finishing
2 Power connectors are used to input the voltage. The positive pin of the input voltage then goes to the power switch and after that goes to the fuse holder. Finally, the output from the fuse holder is connected to the Vcc of the circuit board.
Other 2 power connectors are used to connect the output supply.
The first image shows the power switch and the fuse holder. You may use a fuse according to your requirement. But the maximum value is 3A.
Step 7: Testing
Now you can use this bench power supply for all your testings are requirements. The most important thing is the output voltage is very stable in a range of 0-3A.
I have used the lab power supply to test my power supply. The results are very impressive.
You can save money for your other projects with this cheap power supply.
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