Portable USB-C Lab Bench Power Supply With Magnetic Lamp

Hi, I am Giovanni Aggiustatutto and welcome to this Instructable! In this guide I will show you how you can build a variable lab bench power supply, but not the usual one: a portable, super-compact and lightweight lab bench power supply powered by a USB-C port, with a bright magnetic lamp on top to illuminate the work area and many other useful functions. For those who make electronics projects, the variable power supply is an extremely useful tool, as it can be used to easily and safely power pretty much any circuit you are working on. These tools, however, have a big problem: they are huge and heavy, so not really made to be used for repairs on the go and out of the workshop. So I designed and built a very compact and portable lab bench power supply, with lots of useful features. To start with, the power supply has a USB-C port, so it can be powered using a phone charger or even a power bank to use it on the go. On the front we can adjust voltage and current, and on the display we can see the current draw of the load. On top we have some magnetic connectors that can be used to put additional modules on the power supply, like a lamp to illuminate our work area. This system is expandable, so you could build other modules, such as a soldering fume extractor or even an entire soldering station. On the front of the power supply we have a space to store the cables, to keep them always organized. Lastly, on the lamp we have a small tray to put screws in, to avoid loosing them every time when we are repairing a piece of equipment. All in all, a very useful project for any maker that works on the go or has little space in his workshop!

As always, I've also made a video about this project, that you can find on my YouTube channel (it has English subtitles).

To make this project, I used:

1. XY-SK60X buck boost converter (link here)
2. USB-C Power Delivery trigger board (link here)
3. Black and red 45 mm crocodile clips (link here)
4. XT60 connectors (link here)
5. 16AWG red and black silicone wire (link here)
6. 22AWG red and black wire
7. Heat shrink tubes
8. 2x 2-pin magnetic connector pairs (link here)
9. 3x 1W 5600K white LEDs (link here)
10. Current limited PWM LED driver (link here or new improved version)
11. 20 to 30 mm wide flat aluminum profile (or around 30x92 mm aluminum plate)
12. Thermal paste
13. Single pole 16 mm round switch (link here)
14. 2 mm thick transparent or frosted acrylic
15. 6x M3x6 mm brass threaded inserts (link here)
16. 6x M3x14 mm black countersunk screws (link here)
17. 6x M3x8 mm round head screws (link here)
18. 6x M3 self locking nuts (link here)

Tools:

1. 3D printer with white, red and black filament
2. Soldering iron
3. Hot glue
4. Screwdrivers, pliers and other basic tools

The first step for making this portable lab bench power supply was designing the case to mount all the components. In my projects I always try to take care of the aesthetics and design of the final product, so I spent quite a lot of time in Fusion 360 to design all the different parts. When I was happy with the result, I sent them to the 3D printer. For the main body of the power supply, we need to print two parts: the main enclosure, that will house the voltage regulator and USB-C port, and the rear panel. To print these parts I used some white PLA filament, that will create a good match with the red color of the lamp. The main body has an opening on the front for storing the output cables.

Before installing any of the components in the 3D-printed box, I installed the four M3x6 mm threaded inserts on the four corners, that will be used later to secure the back panel with some screws. To install them I used my soldering iron set to 230°C.

Now that we have the two 3D-printed parts that make the enclosure, we can start assembling our lab bench power supply. First I installed the digital voltage regulator, which snaps in place in the front opening. Then came the USB-C Power Delivery trigger board, which can be secured with some hot glue in front of the opening for the USB port. This board is essential for this project, because it allows us to choose what voltage we want to receive from the USB-C power supply, starting from 5V and going all the way to 20V. After connecting a USB-C power supply to the trigger board, by pressing the button I selected the output voltage of 20V, which is perfect for powering the voltage regulator module. It is worth mentioning that not all power supply can deliver up to 20V, but in that case the board is going to negotiate the highest possible voltage, that can be 9, 12 or 15V.

After the USB-C PD trigger board was set up, I used two pieces of AWG 16 wire to connect the + and - output terminals of the trigger board to the input terminals of the voltage regulator. At this point the screw terminals of the voltage regulator will not be easily accessible, but remember that they can be pulled out thanks to a built-in connector.

After taking care of the power input of the power supply, we need to take care of the cables that we are going to use to connect its output to the circuit we need to power. The obvious choice here are two crocodile clips, one for the positive terminal and one for GND. For this projects I choose two 45 mm-long ones, in addition to some 16 AWG silicone wires in red and black colors. I soldered these cables to the crocodile clips, before sliding the plastic cover on them. I cut the wires pretty short, at around 30 cm, as I wanted to keep the power supply as compact as possible. As I said before, on the front of the 3D-printed housing there is space for storing the cables. On the top-right corner there is a hole to pass the cables through, bringing them on the inside of the power supply. There I connected them to the two output terminals on the voltage regulator module.

As I designed this tool to be used on the go, I wanted to have the option to swap the crocodile clips with other output connectors, like a DC barrel jack for powering a device I'm repairing. So I cut the output cables in half and soldered a pair of XT60 connectors, one on the wires coming from the power supply and one on the wires going to the crocodile clips. After soldering the cables I protected the joints with some heat-shrink tubing, to prevent short circuits. To connect different types of output connectors, I just soldered to them more XT60 connectors that match the one on the power supply.

The main innovation of this project is the ability to add modules on top of the lab bench power supply, expanding its capabilities and creating a fully portable electronics station. For example, I created a work light as a module that snaps on top of the power supply, to have our work area always well-lit even in dark environments. These modules work thanks to a set of magnetic pogo pins I added on the top of the case of the power supply. These connectors not only give power to the modules, but also keep them secured to the power supply and give a really nice feeling when installing them.

For this project we need two pairs of magnetic pogo pins, each one with two pins for positive and negative. Two connectors of the same type will be installed in the power supply case, in the two slots on the top. I connected the two connectors together with some wire, keeping in mind that they will be installed with opposite orientation. To avoid mistakes, I set the scheme of round side of the connector going to the positive and square side of the connector going to the negative. Installing the two connectors with opposite orientation will allow us to install the modules in both directions, without the risk of inverting the polarity. To one of the two connectors I also soldered two wires that will be used to give power to the connectors. After protecting the soldered joints with some heat-shrink tubing, I placed the connectors in the two slots, and secured them with hot glue. The two wires go to the positive and negative output terminals of the USB-C Power Delivery trigger board, where the input of the voltage regulator is also connected.

Lastly, I could close the back panel of the enclosure, using four black M3 countersunk screws.

Now that the lab bench power supply is complete, we can start focusing on the modules that can be added to it. I decided to build a work light, that will be very useful for keeping the work area bright when I'm doing some small repair or soldering on an electronic board, even if I am on the go in a not well-lit place. After a bit of work, I designed the lamp to match the aesthetics of the power supply. This time, I printed the parts using some red filament. As before, we have the main body of the lamp and the rear panel, which we are going to use to close the lamp. In addition to these parts, I also printed a thin black wall that slides on the inside of the lamp. That is used to prevent the bright light of the LEDs from spilling out the red housing of the lamp, turning making it glow in a very strange way.

Before installing the LEDs in the lamp housing, I installed two M3x6 mm threaded inserts in the holes on the two sides of the back panel, that will be used later to secure it with some screws to the lamp housing. As before, to install them I used my soldering iron set to 230°C.

Inside the lamp we are going to mount three 1W 5600K LEDs, that are going to produce the bright light that we need. The LEDs come with an aluminum PCB to dissipate some of the heat, but to improve heat dissipation I decided to mount them on an aluminum profile. I choose a strange "E" shaped on I had in my workshop, which I cut to around 92 mm and adapted with a file to fit inside the black part of the lamp enclosure, resting on the two supports on the sides. For this part, any flat aluminum profile about 20 to 30 mm wide should work great. If you have it, you could also cut a piece of an aluminum sheet to around 30x92 mm. After placing the LEDs on the aluminum part, I marked and drilled two holes to secure each LED with M3 screws. Before securing them, I put under each LED a bit of thermal paste (the one that's normally used when assembling custom PCs). Then I secured the LEDs to the aluminum profile with M3x8 mm screws and self-locking nuts. To prevent the screws from shorting the + and - pads on the PCBs of the LEDs, I 3D printed six small plastic washers.

And with that the LED assembly is finished, and we can move onto the electronics that will make the LEDs work. First off, each LED has a forward voltage of 3.4V, so with the 20V we have available from the USB-C port we can connect them in series (3.4V + 3.4V + 3.4V = 10.2V). To do this I used some short pieces of wire and connected the positive of one LED to the negative of the next one. In the end we should have two wires coming from the LED assembly, for positive and negative.

Before connecting the LEDs to power, we need a way to limit the current going to the LEDs to a safe level that will not burn them. For this purpose, we generally use a resistor, but in this case it would make use lose half of the energy in heat... and we are making a lamp, not a space heater. Looking for something more efficient, I got an LED driver circuit which uses PWM technology, making it up to 97% efficient. Connecting a load resistor to its output pads (in my case that was just an electric iron) with the multimeter in current mode connected in series, I adjusted the current going to it to about 180-200 mA by turning the small screw potentiometer on the PCB. In my case, it was impossible to achieve the right current setting as barely touching the potentiometer would result in huge changes in the current. So, I decided to desolder the potentiometer from the PCB, and replace it with two resistors of 10K Ohm and 3.3K Ohm in series to achieve the right current. Finding the right current may require a few tries with different resistor values, but apart from this the modification is not too hard. Once the right current was set, I could disconnect the load resistor and solder the two wires coming from the LEDs to the output pads of the LED driver.

If we try powering it with 20V, the LED circuit works just fine. So, it's time to connect it to the rest of the power supply using the magnetic pogo pins. First, I soldered two wires to the input terminals of the LED driver board. On the positive wire I put a single pole 16 mm round switch, that will be used to turn the lamp on and off. Then I took two magnetic connectors that matched the ones on the power supply, and connected their positive and negative pins together with two pieces of wire, following the scheme of positive-round and negative-square. To the two pins of one of the connectors I also soldered the positive wire coming from the switch and the negative wire coming from the LED driver. As before, I protected the soldered joints with some heat-shrink tubing. Before installing the circuit in the lamp, I plugged in the power supply with a USB-C power adapter and snapped the magnetic connectors of the lamp on the ones of the power supply, taking care of keeping the switch of the light on the off position. With a multimeter I checked that I had power coming from the magnetic connectors, and that the polarity was right.

Now that the circuit of the lamp is finished we can move on assembling the lamp. First, we need a diffuser for light of the LEDs. To make it, I cut a piece of 2 mm transparent acrylic to around 36x94 mm. With some 180 and 320 grit sandpaper, I sanded it on both sides to achieve a matte finish that will be perfect for diffusing the light. Of course, if you have available some matte acrylic, that would create an even better result. Before placing the acrylic inside the lamp, I cover its edges with black electrical tape, still to avoid having light spilling from the lamp housing. The acrylic piece can be secured by just sliding in the black inner wall of the lamp.

This part has on the inside two supports for the LED aluminum assembly, that can be installed with hot glue taking care of keeping the LEDs centered vertically. Then comes the power switch, that can be inserted in the hole on the top of the lamp housing. To do this, we need to temporarily desolder the wires from its terminals, which we can cover with heat-shrink tubing after soldering the wires again. Lastly we can install the magnetic pogo pins in the slots on the bottom of the lamp. To achieve a good alignment with the ones on the power supply, I put the lamp on top of the power supply and let the connectors magnetically align themselves. I then secured the connectors using some hot glue. Using a zip tie I fixed the LED driver PCB to the rest of the wiring of the lamp. The last thing we need to to is to close the rear panel of the lamp, using two black M3 countersunk screws from the two sides.

Now comes the best part: snapping the lamp on top of the power supply with the magnetic connectors. Apart from the amazing feeling given by the magnetic connectors, the lamp itself works really well, effectively illuminating the work area in front of the power supply. On top of the lamp we have a small tray that is really useful to put screws in when we are opening some electronic device. The lab bench power supply itself also works well, allowing us to adjust voltage and current using the buttons and the know while seeing the values on the display. The display also shows useful data like the current draw of the connected load. By doing some tests using a multimeter, we can say that the voltage adjustment is definitely precise enough for most use cases, while the current limiting has an offset of a few milliamps, which generally isn't a problem either. The opening on the front can be used to store the output cables of the power supply, and on the back it has a hook to secure them with a velcro tie to keep them neat and organized. The ability to power the whole lab bench power supply from a single USB-C cable makes it the perfect tool to use on the go, connecting it to the power adapter of our phone or laptop or even to a USB-C power bank.

In the end, I am really happy with how this project turned out, from the point of view of both function and design. I hope this guide was useful and inspired you to create something unique for your workshop. To see more details about the project, watch the video on my YouTube channel. Bye!