Dual Channel Lab Bench Power Supply With USB Port || 120 Watts

Hi! Today I will show you how you can make this extremely useful dual channel lab bench power supply, which has a USB port as well to power things like Arduino, ESP32 developer board etc. It is fully customizable, meaning you can add or remove ports according to your requirements. One channel is useful for precise low power applications while other is useful for high power application. Together they can output about 120 Watts of power. It also has the most important feature of a commercial power supply, which is the current limiting function. Now your circuit will not blow up if there is some problem with it. So, without any further ado, let’s build it.

The first channel is built around a buck-boost converter that has its own display which shows the output voltage and the current that load is currently consuming. It can provide an output current of 4A continuously with no problem. It also provides a current limiting feature, which to be honest, not a lot of converters do. It has a rotary encoder for selecting the output voltage and current instead of a potentiometer which is big plus for me. Good build quality makes it the perfect choice for a power supply.

The second channel comprises of another buck-boost converter but it is a hefty one It is rated for 80 Watts and can easily handle up to 10A of current in normal conditions. It also provides a CC mode, but I cannot get it to limit the output current yet. I am not sure it does. The output voltage and constant current value is controlled by potentiometers and CC/CV mode is depicted by a common cathode LED incorporated in the board itself. As the module does not have a display, we will use a digital voltmeter/ammeter that can measure up to 10A of current.

Finally, as all take DC input, I got a chonky power supply. It has a great build quality and feels nice too. A word of advice, try to get the power supply which is cooled by a fan. If you get the one which has lots of holes on it, it will be very hard to make multiple holes on the enclosure for its proper cooling.

Parts list and link:

INDIA:

Channel 1 module - https://amzn.to/39XyP6I

Channel 2 module - https://amzn.to/3w6J4OA

Voltmeter/Ammeter - https://amzn.to/3l5RTC2

Power supply - https://amzn.to/3M8zm3V

Better and less costly option - https://www.electronicscomp.com/power...

AC Power socket - https://amzn.to/3MaQBSd

Banana plugs and socket - https://amzn.to/3FILdU4

Potentiometer knob - https://amzn.to/3FDLCa9|

Buck Converter - https://amzn.to/3FVUSGL

US:

Channel 1 module - https://amzn.to/39PZ5zL

Channel 2 module - https://amzn.to/3FCRSz3

Voltmeter/Ammeter - https://amzn.to/3PtN57F

Power supply - https://amzn.to/3wrnQKc

AC Power socket - https://amzn.to/38i4zDb

Banana plugs and socket - https://amzn.to/3lbh0mN

Potentiometer knob - https://amzn.to/3NdBYhc

Buck Converter - https://amzn.to/3FSubD0

UK:

Channel 1 module - https://amzn.to/3waeqUJ

Channel 2 module - https://amzn.to/3FCRYXr

Voltmeter/Ammeter - https://amzn.to/3w8g6y0

Power supply - https://amzn.to/3LanMUB

AC Power socket - https://amzn.to/3wrsLe8

Banana plugs and socket - https://amzn.to/3sx9C9t

Potentiometer knob - https://amzn.to/3Mbx4B6

Buck Converter - https://amzn.to/3lfckfU

Please watch the video with detailed steps on how make this Bench Power Supply.

Test the power supply and adjust its output voltage to around 12.1 to 12.2 Volts. I will use 1 sq. mm. wire throughout the build as it is flexible enough and can easily handle 10A of current. Now take a piece of the wire and carefully connect the output of power supply to Vin of the first buck boost converter. Check if the output voltage displayed is correct or not using a multimeter. Now to show you the current limiting feature I will use 5W 1 ohm resistor. I set the limit to 1.5A and turn it on. The CC LED turns on that means the output current has reached 1.5A and now the current won’t increase but the output voltage will drop. I set it to even lower output current and the output voltage drops even further. So, our module is working perfectly. Now, leave the first module there and connect the second one to the power supply as this will be our working configuration. Connect the voltmeter/ammeter to the buck-boost module. The connection depends on the voltage we want to measure. If it is below 30V, we can use the same source to power the meter. If it above that we need to bring it down to less than 30V. Connect it according to your needs. I will not go beyond 30V that’s why I am using same source to power the meter as well. We will be using same setup to test this module. It draws around 2.9A, the module is going into CC mode, but it is not limiting the current. So now that you have tested the setup, let’s move ahead.

To make the enclosure I will be using plastic boxes because working with metal is exponentially harder, and I don’t even have the tools for it. While you are at it, get a power cord and connector for it as well. One box will be used to house the power supply, and another will be used for everything else. I will show you how in a moment. The quality of plastic boxes is really good. It has thick walls and is very sturdy. I recommend getting boxes like this for the enclosures. The power supply doesn’t fit readily in the box. The support structures are on the way, but we can easily remove and file it to make it flat. The support structures for lid are also interrupting, so we can apply the same process to it. Still the lid is not closing flush. I removed two of the extra plastic structures around the screw hole and now the lid is closing perfectly. The connector won’t fit on the side so we will have to make hole for it on the top. After applying masking tape, I drew the outline for the connector and on the back, I did the same for power supply fan. I drilled the corners first and then using a fine curve cutting blade I completed the cut. I was planning to cut a circle for the fan, but I saved myself a lot of time and hassle by cutting a square instead. It will not be visible anyways. Now we can remove the masking tape from the box.

Wiring will be a bit tricky as we will have to lay it down the opposite way because of the fan. For the AC input, I will route wires from the left of the power supply to the power socket. I will use a 3-core wire and strip it completely after measuring the length required. To reduce the complexity, we can connect earth wire to the body of the power supply as the body is connected to the earth terminal which is a common practice for safety in any electronic device. If you don’t have a cable shoe, you can intertwine the wires and make it U-shaped for added grip with the terminals. I used a fitting screw and a washer to connect the earth wire to an already present hole in the power supply metal body. For DC output, the closest hole can only accommodate one wire. So, for other one I will use another hole and route it out near the output terminals. It is safe unless the wire is insulated and not coming in way of anything inside the power supply. I connected them the same way I connected the input wires. Then I placed the power supply in its designated position and started routing the wires making sure it will not come in way of the top lid of the box. Now it’s time to solder the wires to the power connector. I will use heat shrink tubes to ensure isolation. Route the wires through the connector hole and solder it accordingly. Take special care to connect the earth terminal to its proper pin on the connector. Use continuity function to be double sure. Secure the power connector, take care of the wires and turn it on. Check the output voltage, if it 12V we are good to go. On the second box, make a hole at the center on the bottom. This will be used to route the output wires to the buck-boost modules. Corresponding to that hole, make a hole on the top lid of first box. For attaching the second box on top of the first, we will need to make another hole as it is not already present there. Corresponding to those two holes, make holes on the lid like we did earlier. Now we can permanently fix the connector using some super glue on the outside, and hot glue on the inside. Bring the DC output wires out of the hole we made, and we can close the lid using the screws provided making the preparation of the first box complete.

Attach the second box on top of the first so that we can start working on it. Get some banana sockets which will be used as the output terminals for this bench power supply. Now we must make holes for all the things on the lid of the box. Additionally, a USB port can be used but is completely up to you. The second buck-boost module uses a 1k and 100k pots for CC and CV setting respectively. We will replace it with a pot that has a knob. Also, the CC/CV LED need to be brought out too. Blue knob for voltage and red for current is to be used.

I replaced the pots on the module and while I was testing it, something devastating happened. The output voltage suddenly jumped to 55V, I heard a crackling noise and now there is no output from the module. I somehow burned something as the input terminals seem to be shorted. I didn’t debug it for long, if you have any idea of what might have happened let me know in the comments.

So anyways, I promised you a dual channel power supply, and a dual channel power supply you shall get. I have this buck-boost module, which is not as powerful, and does not have a CC mode, but it will do. I will change this when I get a replacement. I changed the pot on it and did a quick test. I will not go beyond 15V this time as it is not my use case, and I don’t want to take any risk with the only buck-boost module I have. I will use the old module as reference for making the cutouts because I am adamant to replace it once I get the replacement. I made the cutouts for everything. It turned out really great and I am very proud of it. It will need extra grooves for accommodating the grips provided on the modules.

I put everything in place and made all the connections. The connections are straight-forward, you can check attached pictures. I had to solder wires to the banana socket. If you find that the voltage displayed is not correct, there will be a pot on the back of the module to calibrate it. Use that to make it display the correct values. Both the display modules can be calibrated easily, just check their documentation. For the USB socket, I will be using this buck converter as I want only 5V through it. I will connect it to the banana socket and not the output of power supply, so as to be able to measure the current drawn by the device connected to the USB socket. The voltage at banana socket doesn’t matter as the buck converter always keeps the voltage stable at 5V, unless the input voltage falls below 6V, so make sure you don’t use the USB port if the banana socket is at voltage less than 6V. Few drops of hot glue secures both the converters at their spot and same goes for the USB socket. I arranged the wires, and we can close it all up now. Before using the USB port though, check that its wiring is correct using a breakout board. I shortened the shaft length and put the knob on it and our build is complete.

That was all for this project. I hope you liked it. If you have any questions, drop it in the comment section. Please like, share, and subscribe. Till next time!