DIY a variable desktop power supply

In this project you will learn how I built my own lab bench power supply. This power supply has an AC to DC converter, a step-down converter (buck converter), a temperature controller, and a display to show voltage and current. This bench power supply can provide 1.2v-24.6vDC as needed, and you can adjust the potentiometer and get the corresponding output current.

Step 1: Parts List

power cable

Power outlet

Fuse x1

Fuse holder x1

DC to DC step-down converter for temperature controller

Temperature Controller

AC to DC power converter (24v)

Voltage and current regulator (1.2-24v)

Precision Potentiometer 10kOHMX2

Potentiometer knob X2

Voltage and Current Monitor (10A)

Banana Socket

Banana connector

12vDC cooling fan (you can even buy a bigger size than this one depending on the size of your box)

Box shell (at least 23x14.4x5 cm)

Alligator Clips

Step 2: AC110/220V input

WARNING!!! 220 volt AC power supply please note, if you don't understand and don't have any knowledge of electronics or electrical science, buy a ready made bench power supply.

The power outlet has three functions in one: it has an input socket, a fuse, and a switch. This helps protect the circuit from getting damaged if we connect any appliance that consumes more than 10 amps. This power outlet arrangement makes the project look very clean. Make the connections according to the diagram above.

Step 3: Voltage and Current Regulators

This is a 300W10ADC-DC step-down converter adjustable constant voltage module, which can be used to obtain an adjustable output voltage range of 1.5V to 35V. The module provides a wide range of current output up to 10A. After installing a heat sink, it can easily run high power applications continuously (provided that to obtain continuous high power output, you need to use a cooling fan on the heat sink).

This module has onboard 3296 multi-turn potentiometers for high precision voltage and current regulation to provide good stability. Since the voltage and current are adjustable, it is very easy to use in multiple applications such as battery charging, LED driver power supply, vehicle power supply, etc. This makes this module multi-purpose and therefore it is always in demand by our manufacturers due to its wide range of applications and low cost. In the next step, we have to take out these potentiometers and replace them with precision potentiometers.

Step 4: Connect the Precision Potentiometer

I have used 10k precision potentiometers here because precision potentiometers can adjust the output, whether it is voltage or current, which can be done easily as it provides fine adjustments. As the schematic just remove the 3296 potentiometers which are usually fixed on the xl4016 buck converter to interface with the xl4016 module. The main task is to remove those using a soldering iron and then connect the 3590 precision potentiometers using good quality strip wires. Make sure the connections must be the same as given in the schematic.

Step 5: AC to DC Converter (85-220vAC-24VDC)

This is an AC to DC power converter. It can handle 85 to 265V input AC and provide a constant DC 24V output. The maximum load is about 4-6 amps depending on your load. That is: 24*4≈100W. The power converter has overload protection and short circuit protection. Just start from step 2, the + and -220vAC two wires go directly into the AC input connector (green connector), and the 24vDC is output from the other side (blue connector).

Step 6: Wiring Schematic

In this picture you can see the input socket, fuse and switch connected separately. However, you can buy the socket given in the parts list. It is recommended to buy the socket because it is easy to connect after plugging both the positive and negative wires directly into the power supply unit once all the connections have been made from step 2.

The output fuse in this circuit diagram protects the output from any short circuit. This is an optional part, if you want more protection you can add fuse on the output side, otherwise it is not required as the xl4016 itself has short circuit protection.

Step 7: Cooling System Connections

Follow the circuit diagram to make the connections. This cooling system helps the module stay cool for long term use. Load. Before powering the temperature controller, check the output voltage of the mini buck converter and set it to 12v before inputting into the temperature controller.

Step 8: Cooling System

The W1209 temperature control module has a temperature sensor, buttons, LED display, relays, and requires DC12V power supply. It is an affordable and high-quality thermostat controller. A thermostat is a device that senses the temperature of a system to keep the temperature at or near the desired set point. The NTC temperature sensor allows the module to intelligently control various electrical devices based on temperature. NTC thermistors have a negative temperature coefficient, which means that the resistance decreases as the temperature increases. The W1209 has an embedded microcontroller built in, so it does not require much programming knowledge. The module consists of three switches for configuring various parameters, including ON and OFF trigger temperatures.

The temperature is displayed in degrees Celsius and the status is shown with the help of LEDs on the W1209 module with the help of a 7-segment display and relays.

Setup steps:

Long press the "SET" button to activate the menu.

Code Description Range Default Value ---------Keep the value at 36 (set the value by pressing the + button/increment or pressing the - button/decrement).

P0 heating (C/H) ---------Set to C

P1BacklashSet (0.1-15) -----------------Set to 4

P2 upper limit 110--------no change

P3 lower limit -50 -------no change

P4 correction (-7.0~7.0)-----------------Set to 0

P5 Delay start time (0-10 minutes)---------Set to 0

P6 high temperature alarm (0-110)--------Set to off

Long pressing +- will reset all values ​​to default.

Step 9: Digital Voltmeter (0-100V) and Amperemeter (10A)

This is the digital display and we can see the output voltage and current by adjusting the potentiometer applied to the load. Make the wire connections as per the schematic, the thin yellow (voltage sense) wire goes directly to the xl4016out+ screw terminal. The thin red and black go directly to the 24vDC sockets + and - of the power supply unit. The thick black wire goes to the output of the xl4016 while the thick red wire goes to the output banana plug socket or connector.

Step 10: Conclusion