Introduction: Digital Bench Power Supply From Broken ATX PSU
It's about time I get a proper lab bench power supply. The only problem is I don't want one of those big expensive ones. So its time I made my own.
IN: 100v-240v AC
OUT: 0-32V 5A DC
Features: Constant Voltage, Constant Current, 10 Storage Slots (two quick access)
Output voltage resolution: 0.01V Output current resolution: 0.001A Output Voltage accuracy: +/- (0.5% + 1 digit) Output Current accuracy: +/- (0.5% + 2 digits)
Full Project Video
Broken/Old ATX power supply: Free/Scrap
Power Supply Adjustable Module: https://amzn.to/3qIHuOg
AC Power Supply Module https://amzn.to/3qK0VGf
Total price~ : $59.57
I had these lying around from my previous projects but these are official links for them.
Banana Plugs Sockets https://amzn.to/33Yreim
Test Lead Set https://amzn.to/2W0gPhG
1x Voltage Regulator: https://amzn.to/2Z7B7YL
Foam Seal Tape https://amzn.to/3qHUvrr
Male-Female Brass Spacer Standoff https://amzn.to/3iKzCrK
Tools used (not bought for this video just general stuff I have):
Solder Iron: https://amzn.to/2VWtUsf
Repair Mat: https://amzn.to/37IwpUw
Lead-Free Solder Wire: https://amzn.to/3oHIcJB
Magnetic Helping Hands: https://amzn.to/2W5q3ZX
Dremel - https://amzn.to/3miCNbf (or Any Rotary Tool with metal cutting disk)
My Drill Press https://amzn.to/3qC6Xsy
Drilling and Driving kit https://amzn.to/3qHULGS
Wire Terminals Crimping Tool Kit: https://amzn.to/2JGj47x
File Set: https://amzn.to/3bG1Ws9
3D printer: https://amzn.to/330MtzX (newer version)
Step 1: 3D Printed Front Plate
I first started by measuring the front of the ATX power supply where I was gonna put the display and connectors. I also measured the dimensions of the UCTRONICS Variable Bench Power Supply DSP5005 And the banana sockets. I then headed over to fusion 360. This is gonna be the first design I would be putting on Thingiverse.
Supports: No Resolution: 0.12 Infill: 20% PLA
I added a space for USB connectors if anyone wants to add one, but I think stupid me might accidentally send 12v and kill my phone in the process. So I wouldn't be adding that.
Once done, I sent it to my 3d printer. And lucky enough this was perfect on the first try.
Step 2: Test Your Power Supply and Scrap It
To test if your power supply is still good, you need to plug it in, power it on and use a wire to connect the green wire to a black ground wire on the 24 pin connector and see if at least the fan come on. In my case, nothing happened. Next, use a multimeter to check the voltage on the pin and make sure the respective voltages are present.
Again in my case, there was no voltage on any of the other pins so this power supply was dead.
So I am going to scrap this power supply and leave the Fan, AC port and switch to be used later.
I am also gonna save all this wire for future projects. I am not sure what else I can salvage from this power supply, so I'll leave that for another Instructables.
Step 3: Cutting Out the Face
I used the 3d printed plate as a stencil and marked off the drill holes and cutouts on the PSU housing. I then headed over to my drill press. Safety glasses on.
I first drilled the 4 corner holes to secure the front plate. I am using half-inch tek point screws here, and I had to widen the holes on the 3d printed plate a bit for them to fit.
Next was the holes for the banana sockets. For these, I used a 1/4 inch bit.
I clapped the housing on my table vice, and cut out the hole for the display slightly wider than the one outlined. It didn't need to be perfect since I have the #D printed front plate. I put on a metal cutting disk on the Dremel to cut out the rest of the hole for the display. I used a file to get rid of the sharp corners and check that everything was fitting in unobstructed.
The last thing to do was drill the holes to mount the AC to DC power supply and the small voltage regulator for the fan. I lined up where I wanted them to go and just used a fine tip marker to mark out the holes. I would use some metal standoff to rase them off the base. But you can use any bit of plastic washers and some nut and bolts. Also, You kinda have to make sure that everything is not obstructing each other. Once done It just a matter of assembling everything.
Step 4: Putting It All Together
Using the same cable I salvage from before, I cut 6 of these about 6 inches long. The first Two would connect the ac to dc power supply to the power module. Two would connect the power module to the banana plugs which added some ring crips to the end.
I solder the last two wires to the inputs of the buck converter for the Fan. On the output, I added the JST connect I got from the power supply circuit board.
I Added the standoffs to the housing.
Added the banana sockets, making sure it fits in the grove, and use the plastic spacer at the back to prevent it from touching the metal. Then I added the connected ring wire and then the nut.
Then I screw up the wires to the AC-DC converter. Note the live wire, The brown cable, in this case, should be connected to the screw terminal connected to the fuse which was the one closer to the corner. It would still work either way because it is AC voltage, but this is just incased of anything the live would be cut off.
I passed the wires through the cutout for the digital regulator. The ac-dc module goes to the input of the electronics power supply module, and the output goes to the banana sockets.
I use the multimeter her to make sure nothing was shorting on the case, and everything was connected correctly. A flip of the switch to do A quick power-on test here showed that everything is working.
I used my multimeter to set the out voltage of the regulator for the fan to 12v. I then plugged in the fan and realized this thing was spinning really fast, and it was loud. So I further reduced the voltage until the fan was producing a very light breeze to keep the noise level down while still removing any excess heat. This was almost silent.
I tested the voltage features of the digital power module with my multimeter to see how accurate it was. I must say I was pretty impressed with this little module.
I snapped it into the housing, and this thing was looking great.
Step 5: Fan Problem
The last problem was the fan could no longer fit inside of the housing as the heat sink for the module was sticking out.
Literally, the worst situation that I could have been in. I can either leave out the fan and add a small one to the back, or I can just put the fan on the top. Would that even look good? And you know with electronics looks are everything.
Turns out this didn't change the look that much and if anything made it look a lot cooler.
I was happy.
Step 6: Finishing Touches
Lasting to do was to add some feet, so I used this foam tape on the underside to prevent the power supply from scratch up the table and sliding around. This is some foam insulation tape use between doors.
Flipping the switch at the back Puts on the display, and it loads up beautifully.
Step 7: Done
I used some banana plugs to alligator clips here and I tested out the power supply on a small motor with a fan. I can enable and disable the output with the on and off button.
Also, I can control the output voltage and see the corresponding current and power usage. A click of the set button and encoder button, I can move the cursor over the voltage digits and use the knob to increase and decrease the values. I am moving up in increments of 0.1 volts here.
I can also control the current output just as easily.
I can also store up to 10 voltages, two of which can be quickly accessed by holding down m1 or m2.
In the menu, I can set the levels of protection.
So all in all, a pretty cool module.
Full Project video