2x 48V 5A Bench Top Power Supply

This is a tutorial for assembling a bench top power supply. Don't expect any electronics development or lots of soldering, I just ordered some parts from AliExpress and put them in a box.

Please beware that I made some small adjustments on the published design so pictures might deviate slightly from what you'll be building.

Supplies

1x 10.5A 48V SMPS https://www.aliexpress.com/item/32905696401.html?s...

2x DC DPS5005 step-down converter https://www.aliexpress.com/item/32756513394.html?s...

1x IEC320 fused female power socket (AC-17) https://www.aliexpress.com/item/4000469723664.html...

2x chassis mounted terminal blocks https://www.aliexpress.com/item/32796082123.html?s...

4x female banana plug https://nl.rs-online.com/web/p/banana-connectors/1...

1x 12V 50x50mm quiet fan

1x 50x50mm finger guard https://www.aliexpress.com/item/4000104316790.html...

1x 45°C thermostat switch https://www.aliexpress.com/item/4000407678713.html...

4x rubber feet

Some M4 fasteners, some wagos, some wire and some faston terminals

Step 1: Laser Cut Panels

Cut 4mm wooden panels (or any material really).

IMPORTANT! The original design assumes a cutting width of 0.1mm. This is machine, material & panel thickness dependent and important if you want your panels to fit snugly. If you know the cutting width that is applicable for you, you can swap the original finger joints (based on a 0.1mm cutting width) with a new box design generated on makeabox.io (using your new cutting width). Internal box dimensions should be: WxHxD = 143 x x 219 x 95.5

Step 2: Make Corner Cubes

Depending on the panel thickness and type of insert you are using, you might want to adjust this piece. Currently based on 4mm panels and brass M4 inserts that require a 6mm hole in order to ensure a proper press fit.

Print it 4 times and press your brass inserts into the cubes. This should require some force. If not, you might want to redesign the cube or fixate the inserts using glue.

Step 3: Prep the SMPS

This SMPS already has active cooling but we'd like to cool not only the SMPS but also the step-down converters. Two fans would be a little ridiculous so remove the top cover of the original enclosure, which holds the cooling fan. We won't be mounting the cover back on but don't throw it away just yet as it contains the terminal labels required for wiring.

I used a new, smaller and quieter fan but if you want to recycle the one that came with the SMPS that's fine. Just remember to adjust your box design accordingly (the original fan is a little bigger).

In case of using a new (50mm) fan: cut (don't pull out) the fan cable leaving some cable length near the PCB connector and leave it sticking out of the PCB for now.

Step 4: Assemble the Box

Glue together all panels except for the top one, not forgetting about the corner cubes. These are impossible to assemble after the side panels have been joined.

IMPORTANT: ensure all panels (as they are shown in the file) are facing OUTWARDS when assembling the box.

IMPORTANT²: ensure that the BOTTOM PANEL HOLES are CLOSER to the BACK SIDE of the box than to the front side, as the SMPS will reside near the back.

IMPORTANT³: the PICTURES might be CONFUSING as they show a design where the top panel still has finger joints, which have been removed by now.

Step 5: Mount Components and Wire Everything Up

Wire everything up using common sense, no rocket engineering required. You'll see that the step-down converters have removable terminal blocks (or whatever those are called), very handy for mounting the converters into the panels later on.

I would suggest cranking up the output voltage of your SMPS (using the potmeter). The step-down converters apparently like to have some input headroom when outputting high voltages at high load.

Hook up your fan to the fan connector located on the SMPS PCB by soldering or using wagos (as I did). If you don't want to have your fan running all the time, you can put a thermal switch in between fan and PCB. Mount the fan as a final step; other wise it'll block the SMPS terminals.

Step 6: Assemble Top Cover and Rubber Feet

Please note I have a different design than the one available in this instructable. I removed the finger joints in the top panel as they are not required (corner cubes), impede easy removal if necessary and cause the front cover to be less robust near the step-down converters due to thin sections.

I considered mounting a handle on top but eventually didn't because I want my PS to be stackable.

Step 7: Testing

So far I've been able to use my PS with success but I did not test it at full load yet. To be updated.

Comments

[MichalR4]

Apologies for ignorance but I would like to ask some questions about the economics of this build.
I calculated that all the cost for this build would be in a region of £110 + cost of cutting plywood/mdf (which with rough estimations comes down to £20-40 with shipping - UPDATE I just have a quote from one online company and it would cost about £120!!! to cut this box :) )
For that kind of money one should be able to buy 2 5A adjustable PSUs on eBay (granted only up to 30V) or a beefier one 0-100V like this one https://www.aliexpress.com/item/32991796519.html
And if we are talking about joy of building it ourselves then I get it :) I was just wondering if there is another, different reason.

[andres_bm]

Hi there Michiel, nice project ... but I think there is a small problem, You can put Your 2 x 5A 48V outputs only in PARALLEL because they are attached to the same SMPS Power supply.
I think it would be better to have 2 separated SMPS with 48V 5A each, so that You can put them also in SERIES and reach a single 96V 5A output.

[Kinux1]

I have asked Rd Tech, the manufacturer of DPS Power supplies and they can not be put in Series or Parallel. Even with separate SMPS.

[andres_bm]

Well... I don't know about Rd Tech, but I use them every day in my Lab and I never had problems using them in parallel or series. Of course one thing MUST be clear... SMPS power supplies MUST have FULLY ISOLATED ouputs (like them from MeanWell)

[Kinux1]

I am very curious how yours works in serial or parallel.

Before buying my own, I sent them the plan and asked if I use two separate transformer based or normal switching power supplies to power them, let me put the output of them in Serial or Parallel.

Their answer was clear and they even put a video on YouTube indicating this.


The problem of their design is that they use a Common Positive design and their Voltage and Current Control and sensing circuits are on their Negative rail.

They have the same problem with their latest RD6006, RD6012 and RD6018 ones which have a much better interface.
No doubt they are very good power supplies, I hope one day they come up with a new design that officially support this setup.

[jc_0142]

This is NOT 2 independent power supplies as they share the same power source. A simple case is you cannot put the output in series to either doubt the output voltage nor to use the them to setup a + gnd - source for testing typical amplifier circuits. For people who are unaware of this, if you attempt to do this, it will create a short circuit. It's better to use 2x5A power sources, basically 2 separate PS in the same housing, so the unit can be more flexible. Just make sure the two units' outputs are not connected to any common grounds. You should also have a separate terminal for the chassis ground pin.

Be very careful with grounding. This is an area where you may have unexpected results like noise, burnt out boards or even electric shocks.

[Michiel Celis]

Very good remark, thanks for sharing! I don't see why I'd need more than 48V any time soon and hence would ever want to put these in series but you're absolutely right.

[jc_0142]

You're very welcome. I used to build my own amps back in those days. You'll need both a (+) and a (-) voltage plus ground, so having 2 separate PS will be necessary. I once build a beast amp way back requiring +- 35-40 volt rails, that's 70-80 volt peak to peak. It's no joke if you touch both rails. I also had some bad ass big capacitors in the power supply circuit, so it took a while before they are totally discharged. As for 2x48 max output, again be very careful, you can get electrocuted with that. You might need such high voltage to test certain circuits like old vacuum tube stuff, but they only run into milli-amp range. 5A can really fry you. Most new hobbyists should stay away from such high voltage experiments unless if you have some experienced buddy assisting you.

Nice job anyway. Keep it up and stay safe! 👍

[ohmo.1950]

Nice box, good job all around. However, there are some safety concerns with using the project, especially over any extended period of time.

At the top of the list is the fire hazard even if solarborg's suggestion to raise it several mm for air flow. Wood absorbs thing, almost everything that can be carried in the air. Over time, even if given a good strong poly or acryic coat inside and out, the box will absorb things that can lower the point at which it will sustain a flame. Depending on the environment, some of the nasties in the air can actually flash at room temperature (think about gasoline that flashes at -45 degrees).

Another consideration is the shock hazard wood presents after it has absorbed some of those nasties. A single track down to the 115 VAC input could easily shock a person, burn them, even stop their heart.

Again, nice job. Internal layout and mounting are professionally done (removable terminal boards, by the way, are called "plugs"). But there are reasons electrical/electronic devices are no longer placed inside wooden containers - it just isn't safe.

(My credentials for anyone interested: 45 years in electrical industry designing, making, troubleshooting, and repairing a wide range of electrical and electronic devices. Also taught industrial and electrical safety in formal settings as well as on the deck plates.)

[ELECTRONFLYER1]

NICE JOB. I WOULD HAVE PUT A LIGHT CHERRY STAIN AND POLY COATING ON THAT WOOD .

[solarborg]

I would rise the power supply up by 5mm to allow air flow beneath the supply. To make it mountable 2 30mm high slat mounted 15mm from the top around 3 sides then a 30mmx 30mm on the front.

[LBea2n]

Nice build. I built a virtually identical one, down to choice of parts in the build, a couple of years ago. You got a prettier chassis though. One minor thing - I put a diode across the terminals for the converters to eliminate risk of frying them with back EMF. I tend to power motors frequently though, YMMW.

[ReidSommers]

This is awesome! I've been looking for a good dual bench PSU on Instructables for a while. There are some, but this is the best, with the least adaptations and desoldering. You should enter this into the Anything Goes Contest. (I'd vote for you) 😃