CC/CV Power Supply

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Power supply is one of the most important tool on your workbench, but they are too expensive (like >50€ for the 30v 5 amps version).
Today I want to make a good and cheap power supply, it will not be precise like what you buy, but it will cost less than 20€.

This power supply can be used in different cases:

  • is a CC/CV that mean constant current/costant voltage so is perfect to charge lithium battery and almost any type of battery, but make attention when you do that, it can be very dangerous in case you wrong to set voltage or if the battery are damaged, so please, don't do this if you are not an expert.
  • generic power supply up to 18 v and 4 amps (in my case, depending on wich power supply you will choose)
  • you can power your new circuit with the current limitation, so if something went wrong you don't broke everything

Step 1: Component List

  • xl4015, step down 5A cc/cv (with a little heatsink)
  • generic step down to 12 v for the fan
  • 12v fan
  • 2 10 k potentiometer (with their knob and bolts)
  • 2 banana connector
  • lcd voltmeter ammeter 100 v 10 A (with the relative connector)
  • ac input connector
  • ac switch (bigger one)
  • dc switch
  • T connector (i don't know if the name is correct, but is the connector used or speaker cable)
  • project box
  • power supply, mine is from a used laptop charger, the output is around 18 v and 4 amps (~70 watt), remember, when you choose you power supply, that the xl4015 have the limit of max 5 amps and 70 watt of output power.
  • some wire

OPTIONAL

  • xt60 connector
  • 1 green led with it's relative resistor (if you want you can add also one red led connected to the 220 v)

Step 2: Tools List

For this project you will need:
-wire (different gauge)
-precision knife
-cutter
-dril
-multimeter
-pliers
-scissor
-soldering iron

Step 3: Prepare the Xl4015

First of all make sure that the xl4015 and all the other component works perfectly. After that we can desolder the potentiometers and solder 6 cable (3 for each potentiometer). Then I recommend to install a small heatsink.

Step 4: Make Hole in the Project Box.

I take a piece of paper and I draw the component layout of the panel. Then I use every tools that I have to make the hole and after that I insert In place the component.

Also I need un input so I make two hole on one side for the ac input connector and the switch as you see in the photo (make sure that the input connector is centered, not like mine).

I also make some holes for the fan and the ventilation.

Step 5: Wiring

Then I start to wiring everything like in the wiring diagram.

I connect the ac input to the switch and then to the power supply input. The otput is connected directly to the xl4015 input with his screw terminal. On the xl4015 there are two hole on each side of the screw terminal that is also for the input, from here start two pairs of wires, one pair is to power the lcd meter and the other goes to the step down converter used for the 12 volt fan. I connect the potentiometer to the two pairs of cables of the board (make sure of the orientation because it will determine the direction of the rotation) . After that I connect the fan and set the output (of his relatives step down) to around 10 v (to prevent it from being to much noisy). The negative output of the xl4015 is in series with the meter current shunt (the black one is the input of the shunt and the red is the output).

Then the positive output of the xl4015 is connected with the voltage sense wire of the meter and from here I connect a red cable (this is the adjustable output voltage) in series with a switch to controll the output. The output negative and positive are finally connected to the banana connector and to the T connector.

Step 6: End of the Project, Some Tip and Adivice

Now you only need to screw in place the front panel and the project is finished.

My tips and advice are:

  • make sure that the lcd meter has double precision when you order it (not like mine)
  • make sure that the potentiometer are connected in the right position
  • for safety reason is a good idea to use NO (normally open) thermal switch on the main input (ac for example), so if something wents wrong it will disconnect the circuit until the temperature goes down (I think that the 60 degrees version is perfect for this purpose)
  • you can use another thermal switch NC (normally closed) to controll the fan, so if the temperature is too high the fan will start to cool down everything and it will reduce the noisy when the temperature is low (I think that the 40 degrees version is perfect)
  • if you use a metal box, but remember absolutely to ground the case to avoid any risky if you use the mains voltage (for example 230v ac) in your box, and be careful to work with such high voltage
  • you can protect the input (ac) and the output (adjustable dc voltage) of the project with some fuse, it will depend on you power supply capabilities.
  • if you want you can add some led to see if the project is on or off
  • in the future I will ad a 7s battery monitor to controll the battery when they are charged with this supply and the xt60 connector to connect directly the battery
  • use smaller step down converter for the fan (like the mini converter), it's also less expensive

If you have any question just tell me in the comments and I will be grateful to answer.

Thank you for your attention and I hope you enjoyed this tutorial, we will see the next time!

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    16 Discussions

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    Jan5412

    15 days ago

    Some remarks,

    Leave the laptop power supply in its original housing and only make the low voltage side in the new box. Resolves problems with 220V and safety because the complete power supply is safe.

    For the potentiometers, use 10 strokes types for a better setting.

    An old computer power supply has a fan and usually has a separate print with temperature control.

    I would measure the voltage directly on the output terminals.

    Mvg Jan.

    3 replies
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    steparakJan5412

    Reply 15 days ago

    Thanks for your comment. I know that the power supply is safer with his relative case, but I had to remove it because the cables that goes from the supply to the outside was cutted and was impossible to solder new cable. So I opened the case but most of these case are made of molded plastic and once you open it it will broke if you are not very careful. I didn't have a new case and due of that I can't replace. In a first place I thought to cover it with some electrical isolated material to avoid any risks, but then I had choosed the option to leave without case to improve also the power supply cooling.
    I have only linear 10 k potentiometer so I use that, but I don't know if I racomend to use 10 strokes version because they will reduce the precision of the system, and also the 10 k value of the potentiometer is used from the xl4015 only if you choose a input that is equal to the maximum input (around 38 v), for example in my case the input of xl4015 is around 18 v and on the maxiumium output (18 v) the voltage potentiometers reach a value around 4.5 k.
    This type of power supply doesn't came with the fan pin and doesn't have the temperature controll unit, but I you choose fox example atx power supply they have that.
    I choose to measure the voltage before the switch so I can connect the load, set the voltage and than open the switch to power the load, I don't think that there are substantial differences.
    Thank you
    Stefano

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    Jan5412steparak

    Reply 15 days ago

    A 10-stroke potentiometer rotates 10 times while it is now 1 time. The setting is therefore much more accurate. You should experiment with setting a resistor to the left and right of the potentiometer so that you can make a very good setting range.
    Mvg Jan

    Potmeter.jpg
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    steparakJan5412

    Reply 15 days ago

    I'm sorry, I thought you meant the potentiometers with 10 step of 1 k.
    And for sure in the future I will add a resistor in parallel to limit the range

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    Killawhat

    15 days ago

    I'm amazed you fit all that in the tiny box - well done! Laptop supplies are cheap and a great way to power these types of module boards. It might have been better to save a bit of space and just have a DC input from the laptop supply to the box and save wiring up 230V inside. I just got a couple of the LCD buck/boost modules as they were dirt cheap and wanted to see how they'd go (not that I need any more power supplies)!

    2 replies
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    steparakKillawhat

    Reply 15 days ago

    Thank you, I'm happy that you like it.
    I also think to do that without the power supply as you say, but I had created this variable power supply to use only on my table bench and always connected to the grid. But I probably will make in the future a smaller version that can be more portable and powered from any dc source, like battery pack.
    Thank you
    Stefano

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    Killawhatsteparak

    Reply 15 days ago

    Yeah it all depends on the project. If I'm making something larger, I generally try and include the transformer inside. But a lot of the little projects that require less power (or if I run out of 240V sockets), I generally use wall worts where I can. They're pretty cheap these days too and just makes the build a little quicker and safer.
    Although I do tend to buy a lot of 240vac/12vdc modules (they're only about $1.50ea). I use them all the time where I need some low 12Vdc power or need to isolate power supplies (like powering meters).

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    Yuhoo1

    22 days ago

    I didn't see where you placed the fan? What size of fan?

    2 replies
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    steparakYuhoo1

    Reply 22 days ago

    I put the fan in front of the xl4015 as you can see, my fan is 40 x 40 mm, but the dimension depend on wich box you use and how you set up the component.

    IMG_20190605_071647.jpg
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    Yuhoo1steparak

    Reply 21 days ago

    Thanks. Appreciate your response.

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    Yuhoo1

    22 days ago

    What is the size of project box? Do you have a part number or link from where you bought it?

    2 replies
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    steparakYuhoo1

    Reply 22 days ago

    I bought the box from a local store, Is the box used for electrical management. The dimension depend by the dimensione of your power supply unit and the other component. In my case the internal dkmensione are: 120 mm (length) x 80 mm (width) x 50 (height) mm

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    JohnW839

    Question 22 days ago on Step 6

    Very nice looking and useful project.
    Would you please share what meter you used? Also, please explain about setting up the supply for CC. I know how to do it, but other readers may not know.

    1 answer