All-in-one AC-DC power supply with three adjustable outputs

Update 2025-01-26: Added info on adding wireless connection to PC.

I designed this so it would fit nicely on my desk under the PC monitor.

Needs no external power supply and provides me flexibly with three different voltages, so that I need only one supply even if I mix, say, microcontrollers, servos, and motors in one project. Also, I wanted current control on one of the outputs.

I use this only for small currents that will not heat up the components a lot, be warned that the ventilation might be insufficient for more heavy demands. Also be warned that this design comes with some complex wiring and soldering on little space, among them 220V/110V connections.

Parts list

• Meanwell LRS-75 AC-DC 75W Single Output Switching Power Supply, I used the 15V version
• 220V/110V IEC C14 power socket with fuse and on/off-switch (footprint 47,5 x 27,5 mm)
• DPS3005 or similar adjustable DC-DC power supply (footprint 71 x 39 mm)
• 2 LM2596 adjustable DC-DC step down converter modules (need to be modified, see below)
• 2 potentiometers with on/off switch, 6mm shaft (footprint 11,2 x 9,6 mm)
• 2 DC0-100V voltmeters with 0.28 inch LED display, 3 wire version. 2 wire works as well, but will not display very low voltages.
• front sockets, included are .stl files for screw-on covers for 2,6 mm and 4mm banana plug sockets with 2mm height
• lots of wires suitable for the respective currents and voltages (I used four different soizes for 220 V to the LRS-75; 15V from LRS-75 to DC-DC converters; DC-DC-outputs; potentiometer control)
• 220V/110V cable with IEC C13 connector
• 8 M3 countersunk screws ca. 6 mm. I used 10 mm screws made of nylon, so that I could shorten them as needed.
• 4 M3 nuts
• recommended: polyfuses for the LM2596 outputs

Print the main part standing upright on its front side. Print the back part standing on its back side, it needs no support if your printer bridges properly. Cut the thin bridging helper wall to clear the space where the wires from and to the front side go.

LM2596 module modification: desolder the blue trimmer and connect the now empty PCB pins 1 and 2 with the potentiometer. I used 5K pots and replaced the R1 resistor (usually the one between the trimmer and the LM2596) with 470 Ohm, so that I can use the full potentiometer sweep for an output range of 0V-14V. Note that the LM2596 data sheet recommends placing the pots close to the chip. I could not observe negative side effects from placing them farther apart.

The basic assembly process is (1) connect front parts, i.e. sockets, LCD voltmeters, potentiometers and DPS3005; I used the pots' switches to provide 15 V to both the LM2596 modules and their respective LCD voltmeters; use longer wires with at least 15 cm for connections to and from the back parts, leave them unconnected for the moment; (2) install front parts into main housing in a bottom to top and left to right sequence; (3) install IEC C14 power socket in the back part, connect it to the LRS-75, install LRS-75 in back part (two screws); WARNING, you'll want to make sure that high voltages are well insulated and kept away from the low voltage side; (5) insert M4 nuts in back part; (4) slide LRS-75 and back part into main part, the wires to/from the front go on the left side and under the M3 nut holder; (5) modify LM2596 modules, connect them to the LRS-75 output and the front wires and install them properly insulated in the back space; (6) close everything and hope that you and I did not forget anything!

Update 2025-01-26: I added a simple wireless serial connection so that I can control the DPS3005 module from my PC. Simply connect GND, Vcc, Tx, and Rx (labeled G, V, T, R on my board in tiny writing) to a cheap and small JDY-40 module. On the PC side use a simple TTY-USB converter and connect its GND, Vcc, Tx, and Rx pins with another JDY-40 module. Don't forget to ground CS on both JDY-40 modules, SET can be left unconnected, and of course cross Tx->Rx and Rx->Tx. Use the Manual and software found here (not my upload), on Linux you can use mbpoll or DPSsupplier for control, PyDPS did not work for me.

Feel free to contact me or use the comments for questions on further details.

Warning: Use at your own risk, you're dealing with dangerous voltages.

Category: Electronics