Build your own Variable Lab Bench Power Supply

a variable lab bench power supply is one of the most important tools an electronics maker can own it's mandatory while testing circuits because you can now limit the current if something goes wrong during prototyping then this means most things will not blow up anymore you can also use it to charge lithium-ion batteries or reliably determine the forward voltage of a high power LED this list goes on and on so in this video I will show you how you can build your own very easily without making your own circuits it's all modular let's get started the star of this supply is this LTC of three 780 step up step down converter it combines an efficient and really powerful buck and boost converter for the price of 21 US dollars let's test this thing before we put it in an enclosure I connected my wire adapters with the power wires of my voltage current display to the input of the board the outputs positive connects to one loose wire and the voltage sense wire of my display the black wire of my current measuring path connects to the negative outputs this loose wire represents the positive voltage and the red wire ground this configuration stays the same when the supply is inside the enclosure now I can turn on my bench power supply set the voltage to 12 volts and connect the wires everything powers up and we can play with the three potentiometers the far-right one controls the under voltage protection and is mostly used for solar charging we do not care about that so don't touch it the far left one controls our voltage the minimal voltage is not zero volts but it's very close with 0.8 volts it's not a tragedy that we cannot reach below 0.8 volts because such low voltage values are not that useful anyway the maximum voltage is around 29 point 4 volts so I would say it's a pretty neat range the potentiometer in the middle can limit our currents the minimum is around 300 milliamps which is still quite high for many circuits but we cannot do much about it the maximum current is limited by my display which only indoors up to 3 amps but small peaks of higher current should not destroy it immediately now let's find out whether the built on heatsink is enough for our project I created this Frankenstein power resistor and soldered it to my outputs if you are asking yourself right now why am i placing the resistor on top of a glass of water then just wait a second I cranked up the voltage and shortly reach the maximum of my bench power supply this means we need more power I got this 12 volt 5 amp power supply which should power quite a lot of things with 60 watts of power this supply uses a screw terminal so a wire up my old school plug and connect the AC wires to the terminal and if you have no experience with electronics whatsoever then better buy yourself a variable bench power supply because this AC voltage can kill you so be careful now we'll let's plug it in and set the voltage to exactly 12 volts this supply connects to my board just like before and now we can properly heat up the resistors right now I'm using around 60 watts of power with 29 volts on the output and fair enough there goes my solder connections now you know why I use the glass of water I did this before without it and got a nice burn mark on my table because I'm such a genius the heat sink on the other hand just warmed up a little bit and definitely does not need to be beefed up this is basically the whole structure for the supply all just simple wire connections so let's take a look at the enclosure I went with this gray beauty which even has ventilation slits the front and back panel are made of metal and will make this look awesome in the end additionally I also used in AC inputs an AC switch two binding posts two potentiometers with knobs and a couple of screws the parts list and more pictures always always on Instructables firstly let's replace the 500 kilo ohm and 200 kilo ohm potentiometer of the LTC 3 780 I just heated up the pins of the pots and shortly after they fell out on their own afterwards the shaft of the new potentiometers got shorted with my rotary tool because the knobs would otherwise stick too far out when mounted then I sold out three wires to my new pots at a drinking tube and all of those wires to the solar joins of the old ones now I cover the front and back panel with white tape and did some basic measurements where I want my external ports to be placed I marked those spots and use the drill to make small holes which I could enlarge later two squares with my saw or bigger holes with my drill again it took quite a lot of patience to make those cutouts look good but it worked out somehow okay time to mount the poles nothing special to say about most of them but it is very important that you make sure your binding posts are isolated from the front plate and make sure that you're protective conductor of the AC inputs has a proper connection with all metal parts of the enclosure I drilled small holes for this and secured the wire with a nut and a washer please don't forget that it's an important safety feature now it's time for the other wiring the AC input connects the main switch which then connects to the input of the 12 volt supply and I'm using flexible 2.5 square millimeter wire if you are curious all the other wiring is the same as before except for the binding post which connects to the positive output of the LTC 3 7 ad and the red wire of the current path of the display now let's secure everything with screws and hot glue close it all up and we are done like I said super useful and with a maximum of 6 amps much more powerful than my upper bench power supply if you liked this video then please don't forget to like share and subscribe stay creative and I will see you next time

Channel: GreatScott!

Views: 2,019,754

Keywords: Power Supply Unit, build, your own, variable lab bench power supply, adjustable power supply, DIY, how-to, tutorial, Do It Yourself (Hobby), LTC3780, modular, buck boost converter, greatscott!, make your own, 12V Input, variable power supply, step up step down converter, converter, 60W

Id: wI-KYRdmx-E

Length: 7min 10sec (430 seconds)

Published: Sun May 03 2015

Reddit Comments

[u/FullFrontalNoodly]

You should do another video showing the output of the supply on a scope.

[u/Linker3000]

Min current limit approx 300mA - yeah, as the video says, not great. Would be much better if that would go down to around a few mA, but a simple build for a beginner.

[u/[deleted]]

Hey man, I really enjoy your videos (I think I've seen all of them, and one of your older videos helped me build my own lab bench supply).

It would be really cool to see you make an indoor, self-monitoring, self-watering garden system sometime.

[u/stahlous]

Great video, and I will see you... next time!

[u/Enlightenment777]

Video = Missing too many details.

Detailed Article + Video = Far better.

[u/wsender]

One place where you shouldn't cheap out is with lab equipment.

[u/MoserLabs]

Congrats on making an instructable feature! Just got this on their email

[u/59923]

My bench power will only do 23 v @ 23 amp but i think it needs a friend