Programmable Power Supply 42V 6A




Intro: Programmable Power Supply 42V 6A

My new project was inspired by programmable power supply, module Ruideng. It is fantastic, very powerful, precise and for reasonable price. There are few models available, concerning output voltage and current. The newest ones are equipped with communication options (USB and Bluetooth).

Programmable - variable Power Supply described in this article, is dedicated for DIY electronic bench. It was originally based on Ruideng model DPS 5015 without communication. During writing my Instructable, modules with communication were introduced to the market. I have added this option as version B.


  • AC input: 100 - 220V
  • AC frequency: 50Hz/60Hz
  • DC voltage output: 0 - 42V
  • DC current output: 0 - min. 4A, max 5A (DPS5005) or 6A (DPS5015)
  • Output voltage resolution: 0.01V
  • Output current resolution: 0.01A, (0.001A for DPS5005)
  • Output power: 200W
  • Output voltage accuracy: +/-(0.5% +1 digit)
  • Output current accuracy: +/-(0.5% +2 digits)
  • Number of memories: 9 sets of data groups plus the last setting (memory 0)

What means Programmable?

  1. Power supply Ruideng DPS 5015 or DPS 5005. You can adjust parameters of the power supply and save them to its memory internally, from the front panel. You can not adjust and program any parameters externally. There is not any connector and any link to program parameters from outside. Version A.
  2. Power supply Ruideng DPS 5005 communication version. These Ruideng module allows communication from the outside of instrument via USB micro connector or Bluetooth. You can adjust and program all parameters from PC. Version B.

Main programmable parameters are:

  1. Voltage
  2. Current
  3. Over-(voltage, current and power)


  • Small jig saw
  • Drill
  • Soldering iron
  • Multimeter

Step 1: Parts

In my case, main part is programmable power supply Ruideng DPS5015. This module contain colour LCD, which displays all necessary data. DPS5015 was available for low price. The module could provide maximum DC output 50V and current 15A. Current value DPS 5015 is not fully exploited here, but I have purchased it, in temporary discount for less than 20€. The best solution for this case, there is model DPS5005, communication version, I recommanded it.

Any DPS module Ruideng require on its input some other power supply, (switching or not switching) with ability to deliver about 50V and 5A or more. Such power supply could be made on main transformer 220V/50V and some other components. This solution is very heavy and big size and not very efficient. Switching power supply is more economical. Therefore I decided for switching power supply, to change 220V AC to 48V DC. I could not find suitable one, so I have used two modules 220VDC/24VAC. Modules are connected in parallel on theirs inputs and in serial on outputs.

Parts are:

  • Switching power supply Geekcreit 24V/4-6A, 2pcs, Banggood
  • A version, without communication, Programmable PS Ruideng DPS5005, (or DPS5015) Banggood
  • B communication version, Programmable PS Ruideng DPS5005 communication, DPS Banggood
  • Plastic instrument box, Banggood
  • Main power switch, Banggood
  • Fan 12V, as for instance ebay
  • Adapter 220VDC/12VDC, as for instance, ebay
  • Female bannana jack sockets, 2pcs, ebay
  • Thermistor, 10kohm, ebay
  • Driver for fan, built on small protoboard, Banggood
  • Power main cable 220V, 2.5A from local store, depends on the plug type.

Parts in driver for fan:

  • Transistor 2N5401or BC337, Banggood
  • Diode universal 1N4148, Banggood
  • Trimmer resistor 1kohm, Banggood
  • JST female connector 2.5mm on board, 3pcs, Banggood
  • JST male connector 2.5mm with cable, 3pcs, Banggood

Step 2: Wiring Diagram - Version a - No Communication

Connections between all blocks is drown on picture above. On the left side, there is input 220V, main cable and main switch. On the middle there are two modules AC/DC 220V/24V. These modules are connected in parallel on input, voltage AC 220V. Both module are connected on their outputs in series and attached to the input of programmable PS. Each module deliver 24V DC, so total output voltage is 48V. Programmable PS DPS 5015 is attached to output connectors (plus and minus of the instruments output voltage) and by ribbon cables to LCD display. On the picture in upper part is adapter 220V/12V, fan driver and the fan 12V. There is not displayed thermistor on the picture. Thermistor with negative temperature coefficient, NTC is mount inside one of aluminium cooler.

Programmable DPS 5005, following drawing, contains all electronic circuitry located inside display part. You have more space in plastic box. Wires are connected directly from switching power supplies to display and from display to banana connectors.

Scheme for hardware of fan driver is on next picture. Connection is very simple, just few components. Transistor T1 switch on the fan according value of thermistor. If thermistor is exposed to higher temperature, his resistor value is decreased and transistor conduct more current, fan is running. Diode D1 protect transistor.

Generally, there is not necessary cooling fan for all modules. Programming PS 5015 is equipped with its own small fan. DPS5005 does not need any cooling. Both switching modules require cooling in case of higher power output. Therefore, I have provided block of two switching modules with fan. Fan is switched on, just in case of higher temperature of aluminium cooler on one of two module boards.The most operating time is programmable power supply quiet.

Special adapter 220V/12V deliver voltage 12V for fan. I choose this solution, because I prefer separate power supply for fan.

Step 3: Wiring Diagram - Version B Communication

Wiring diagram is the same like version A, module Ruideng DPS5005, just USB communication board is added. It is on picture above. USB board is connected by its original cable with connectors on both sides.

If you order Ruideng communication model with two communication boards, USB and Bluetooth, you can connect just one board in time, because the display module contains one connector only.

There could be solution for both boards, but I did not check functionality of next described circuit. Mount on free space of plastic bottom box both modules. I suggest connect as priority board - Bluetooth and USB is connected just in case of connected USB cable. Wires could be fed through 12V relay 4PST, or through two relays DPST. Independent 12V DC voltage is available at adapter output. Place micro switch in place, where USB connector is inserted, such a way, that inserted connector activate switch. By switch could be energized relay and switch wires to USB board.

Four wires coming to communication boards supposed to be: VCC, GND, TX, RX. If you able to identify VCC and GND, just remaining two wires should be switched by one relay DPST. Both boards could be connected to power permanently if instrument is switched on.

Step 4: Construction

Construction steps, version A

Power supply is placed to the ready made plastic instrument box. This save time and simplify construction. Next steps are for DPS5015. In case of DPS5005 in step 3. just mount voltage adapter and you get some free space on bottom part of plastic box::

  1. Prepare plastic box: remove same plastic mounting feet from bottom part of box, (marked by circle with black pen). Drill holes and cut windows in plastic front panel and back panel according to above pictures.
  2. Mount both switching PS and fan together in one assembly. Use metal right angle joints and screws. Mount this assembly to bottom plastic case using mentioned joints and screws. Do not forgot to attach wires to terminals, because later it is not possible or not so easy. On wires going to programmable module solder fork connectors.
  3. Mount programmable PS 5015 module and adapter to bottom plastic case using joints and screws. Prepare wires for output connectors and solder on them fork terminals. On adapter output solder two wires with JST connector to fan driver and two input wires to screw terminal 220V.
  4. Solder parts of fan driver on small print circuit board or protoboard. Size of this board is about 15 x 25 mm. Cut connector wires to proper length and solder them to fan, thermistor and adapter output 12V.
  5. Place and fix thermistor on one of aluminium cooler. I fix it by inserting thermistor inside hole of heat sink.
  6. Mount parts on front panel. Power switch, two banana connectors and LCD display.
  7. Place front and back panel and connect all wires.

Construction, version B.

Mount USB communication board on free space of plastic bottom part such a way, that connector is faced to the right. On the USB board, there are two holes and using standoff, screw board to plastic box. Cut a hole for connector on side of the box.

Front panel

On the last picture,there is front panel. You can use it as template. Drawing was made in Paint program in Windows 10. You can modify design very easy. Drawing is done exactly in the size of front panel (scale in mm). By printing there is necessary to choose print size 100%. To make it nice, choose photo paper and protect it by transparent adhesive foil.


There is a good practice to check all modules and parts in the process of mounting. I recommand to check fan driver connected to fan and attached to 12V at first from some other power supply. Fan should run or not run depending on trimmer position. Somewhere in the middle of trimmer trace fan just stop. If you place thermistor to some hot place (like solder iron), fan should start rotate.

By next check both switching power supplies. Connect 220V from screw terminal to their inputs and connect their output to serial. You should measure the final voltage 48V. Both modules should be equal concerning output voltage and current. If you can choose them, take two with the output voltage exactly the same. In this case power supplies are well balanced.

If voltage 48V is correct, connect programmable PS. Be careful, do not mix input and output, and plus and minus on input, programmable module can be destroyed.

At the end connect driver board for fan and all remaining cables. Cables drawn like thick on wiring diagram should be thicker, because of higher current. On input 220V, wires diameter should be about 1mm (max. current 2A), on output 48V should be diameter 1.5mm (max current 6A).

Step 5: Communication

Visit site with link communication software and download DPS5005 PC software for communication. Detailed information, how to install software and how to use it, how to configure serial port for USB, how to configure Bluetooth, is on video: communication .

On PC software, functions in Basic tab (the first picture) are very similar to settings on non communication version. On Advanced tab (the second picture) are more sophisticated functions which could be used for automatic component measurements. Except more clear and simplified memories for data groups there are functions:

  • Auto test - allows to adjust number of steps (maximum 10), time intervals by delay value for each step, voltage and current for each step.
  • Voltage scan -allows to adjust output current, start stop and step value of voltage, one delay common for each step.
  • Current - scan. Function the same like voltage scan. Adjustment of output voltage, start stop and step value of current, one delay common for each step.

Step 6: Conclusion

User manual for Programmable PS Ruideng is including in shipment. Just a few comments:

Very good feature is possibility to connect or to disconnect load on output connectors by switch. That way during voltage and current adjustment should be load switched off and protected.

On above pictures, there are example of constant current mode. On top line of LCD are displayed set voltage and current. On output connectors is connected resistor 4.7 ohm. Although voltage is set to 10V, voltage on output is about 4.7V, because current is set to 1A and was achieved.

On the next picture there is Zener diode attached to output without resistor. Current is set to value about 0.05A and voltage line is showing directly Zener voltage 4.28V. By such component measurements there is important to check displayed power on the third big line (0.25W in example). I have destroyed a Zener diode for 30V, because adjusting 0.05A, I had missed power over 1.5W!

In 9 memory places could be stored very often used voltages, like 3.3V, 5V, 6V, 9V, 12V and so on, with its expected currents, over voltages and over currents.

Communication version allows some automation for component testing. It is like measurement of voltage to ampere characteristics or some battery charging with time and current depending voltage.

Comment about front panel. There was too big space on the left side of LCD display. I was thinking to put there something crazy, like LCD thermometer for inside temperature or sedentary reminder, but finally I decided for picture, because of using photo paper as front cover. Between nice nature (mountains) and the most beautiful city, win the city.

Hope you will enjoy doing the nice power supply yourself.



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    4 Discussions


    8 months ago

    This is a good single output variable power supply project and it will work. Series connecting the 24V supplies is an acceptable method for increasing the input voltage to the final DC-DC converter. As you mentioned, 24V supplies are available in greater power and size packages than are 48V supplies so using two 24V supplies is a good compromise.

    I only have a few comments:

    A 24V fan could be driven by one of the 24V supplies eliminating the small 12V converter. The fan control circuit would need to be redesigned. The control presented here is quick and simple but with just a little more work could be better.

    The 24V switching supplies have input fuse protection but the small 12V converter for the fan does not appear to be input fused. You might want to consider adding a small inline fuse at the 12V converter just to be safe.

    If you use different 24V supplies than specified by the author, be sure to verify with a multi-meter that the PCB mounting holes are electrically isolated from the DC outputs before you stack them together.

    The 24V supplies are specified as 100W converters which would make their maximum working output current approximately 4A. I'm not sure why Bangood is suggesting that they can operate at 5A unless that is a surge current rating. It's probably best to be conservative and call these 4A supplies.

    The 24V supplies are 120V/220V rated so if you live in the US, or another country with 120V AC you can use this power supply project with no problem. All you have to do is change the power cord to a NEMA 5-15P instead of the Europlug used by the author.

    I think the Ruideng 5005 with Communication is the better choice. The 5015 uses the large PCB board used in the first picture of the Instructable while the 5005 contains the display and converter in one piece. Much less space in the case and easier to build. And besides, the 24V supplies are only conservatively rated at 4A so there's no need for the larger 5015.

    I think the output power is overstated a little at 200W if the author meant it to be a working power, not a peak power. The combined 24V power supply is conservatively 192W. Buck converter efficiency in the Ruideng isn't specified but is not likely to be much better than 90% so the output power is going to be around 173W. The input voltage to the Ruideng must be 10% higher than the maximum output voltage. So the maximum output voltage will be pretty close to that specified by the author (42V). A conservative maximum output current is approximately 4A at 42V. Pretty good actually and sure to be more than most circuits will need.

    Inexpensive DC-DC converters typically have between 50mV and 100mV of ripple between 50KHz and 100Khz so be aware of that if you plan to use this power supply on sensitive radio or Op-Amp circuits. From experience the power supply design presented here works extremely well for most analog and digital projects. But it can cause some very weird problems with high impedance or noise sensitive circuits.

    This is a good Instructable for a nice power supply that looks really cool. It can be used globally with only a power cord change. Some might find the digital voltage and current increments a bit limiting but you really don't need exact voltages when good design practices are used. Close enough should be good enough for most projects.


    3 replies

    Reply 8 months ago

    Hi NetZener,

    thank you for thorough comment. You are right about some weeks points, but I need to explain some properties of my design:

    24V separated power supply for fan was used, because I did not want to charge both 24V outputs (in series) by asymmetrical load. In that case is internal resistance different and can depreciate output parameters.

    Circuit for fan I was using, was as simple as possible. The reason is that fan is not very necessary, just in a few cases of big (low resistor) load. But I agree, if it must be perfect it should be other circuit.

    Mounting both 24V boards together through PCB holes is dangerous, I agree. Boards should not be connected!

    Concerning output current. In Banggood specification for 24V power supply is stated 4 to 6A, but if power is to 100W. It means for voltages until about 33V (2x100W) it could deliver 6A. I have tested it and it is true.

    Output voltage is OK, more than 42V, it is just above 43V.

    Ripple for Ruideng should be less than 100mV according some testing on YouTube, for 24V module is not tested. Anyway I agree, for very sensitive circuits it is not the best power.


    The best choice is DPS5005.


    Reply 8 months ago

    It's a nice looking project and you did a great job on it. It takes a lot of time to document a project like this as well as you have.

    A while ago I used the same approach you presented for a switch-mode variable power supply. The project in the image below is a dual supply 0-20V 0-2A so not on the same scale as the one you built but similar in concept. I use mine all the time for general analog and digital design. I like it because I made it, but it's also much smaller and lighter than an equivalent transformer-fed linear supply.

    For anyone reading through the article on Kamil47's power supply, the design does work quite well and his use of a programmable final converter is a nice touch. Don't settle for mangling an old ATX supply and attaching an LM317. Give this project a try and press the "I Made It" button.



    Reply 8 months ago

    I was looking to your power supply. It is unbelievable. Not just electronic solution, but your whole Instructable. Such perfect and professional processing I had never seen. You should spent many hours on it. I would write some comments directly. Congratulation.