Show your favorite and most used benchtop PSU

[nuno]

Nice build.

(...) metering is not very accurate at the low range because the ADC in the ATMega is not very accurate near ground.

Can you elaborate?

[jaycee]

Nice build.

(...) metering is not very accurate at the low range because the ADC in the ATMega is not very accurate near ground.

Can you elaborate?

The ADC in the ATMega, like a lot of ADCs, are not very accurate at the extreme ends of their range. Add in compensation for offset and it becomes an issue. The ammeter on my psu cannot read any lower than 20mA for example, yet it can current limit lower than that so the problem is not in the sense amp. I could have avoided the issue by adding an offset to the sense amps so that they do not go near ground, which would have allowed enough range to both cancel the offset and avoid the nonlinearity.

I attempted to hack it a bit by adding resistors to adjust the range to the front panel display, its not perfect but workable.

I might try a further hack to add the offset I mention. A TL431 should be enough to do the job. At any rate, the power supply works well and it's better than the previous lashups of LM317's etc
I'd "Open source" it, but I really dont want some unscrupulous Chinese ebay sellers turning it into a kit.

[nuno]

Are you using a current measuring resistor? If so, what value and what amplification (if != 1) before feeding the AVR's ADC?

[jaycee]

Are you using a current measuring resistor? If so, what value and what amplification (if != 1) before feeding the AVR's ADC?

Yes, 0.1 ohms. There is a sense amp and the output feeds both the ADC and the current control error amp. The sense amp is not the problem.

Full schematic here: http://www.dark-matter.me.uk/files/electronics/psu-18v1a/main_sch.pdf
edit: Actually thats just the main board. The display board is at http://www.dark-matter.me.uk/files/electronics/psu-18v1a/front_sch.pdf

edit 2: My plan is to disconnect AGND from the star ground, and add some offset voltage there. The sense and error amps get shifted away from 0v, but they dont care about that.. the only thing that will see the difference is the ADC which is referenced to DGND

[nuno]

I have used an AVR to read small values of voltage and I didn't see any problem with it (reading a PT100, only amplification was ATtiny26's internal differential 20x gain amplifier and its internal ~2.7V Vref *). You are using different Vrefs for the pure analog part and for the display/control part, maybe your problem comes from that, what happens if they differ by, say, 40 or 50mV (or maybe not ).


* The schematic is here, it's commented in Portuguese but I think it won't be a big problem, there's nothing fancy:
https://troniquices.files.wordpress.com/2008/07/coscov.png

[Pawelr98]

This is mine.

0-30V 0-6A

Uses uA723 with extra electronics.
Negative 2.5V rail (431 stabilized), allows to go down to 0V
extra overcurrent protection on driver stage
separate 35V supply for the chip that ensures dropout of no more than the Vcesat of power transistors
14V/28V transformer tap automatic switching, 300VA toroid transformer

The output stage is 2xTungsram 2N3055 on an outside radiator.

Case is metal.

On the right there's a tube tester.
Sometimes it also works as a low-current high-ish voltage PSU as it has a primitive 0-100V adjustable voltage source.
Just a 2N60 beeing source follower, no proper regulation.

[mariush]

Not the first PSU I've built, but the first one that was more than an LM317, and built into a proper box

It looks nice. It could be improved quite a bit though, if you want to release the project at some point.

Fuse is in kind of a bad location, hard to shove your fingers in a corner to pull the fuse up.  Maybe should be on bottom left corner under that to-220 with heatsink.
Maybe add connectors for those soldered wires on the left side of pcb.
Plenty of room to lay the four diodes properly .... maybe consider also dual footprint , for regular bridge rectifier (the ones very common used in atx power supplies , gbj , gbu etc, they can be screwed to heatsinks)

Could maybe rotate the to-220 chips and align with that to-220 with heatsink and maybe even with the bridge rectifier, so that a wide heatsink could sink all those chips. Also give them rigidity and whatever.  May have to add insulators.

I'd rotate most through hole resistors 90 degrees , have most traces on top vertical and the ones on bottom horizontal ,  with ground fills or whatever for increased trace thickness.

The DISPLAY connector could probably be on the right corner/edge of the board instead of center, as the ribbon cable could block air flow going through case.

As for parts minimization, you could maybe add footprints for replacing those 47k resistors with 2 x 100k in parallel to get 50k resistors - close enough to 100k.

Not a fan of to-92 transistors, i'd rather make a board surface mount than use those.

[25 CPS]

My most frequently used bench power supply is a Canadian Research Institute TRP 20/4.   As the model number implies, it’s a 20 V, 4 A capable supply with coarse and fine adjustments and two ranges.  The range switch is a gotcha though with a centre off position and the two ranges being 0-10 V and then 10-20 V.  It isn’t possible to ease the voltage up across the whole 0-20 V range without having a really awkward changeover in the middle.





Unfortunately, as is the case with a lot of the long gone Canadian test equipment manufacturers, there’s hardly any information or documentation online and I don’t have manuals or diagrams for this machine.

[old-jo]

This is my favorite and most used benchtop PSU:



I made it after watching Build your own Variable Lab Bench Power Supply video by GreatScott!
I used the same LTC3780 module as the video. As input for the LTC3780 module, I used an old laptop charger.

Good enough for a hobbyist.

[AJ3G]

Just completed this supply using the RIDEN 6018W. Need to finish up the final wiring around the binding posts, and installation of a fan controller, and I should be ready for prime time.

Rich

[BravoV]

Wow ... so many binding posts, any plan to label them ?

[AJ3G]

Yes there are a lot of binding posts. The two mounted vertically will are attached to the rear panel terminations. I have cases where I simply set a voltage to for an RF Amplifier, and do not want cables running out of the front, but instead from the back of the supply

The binding posts below each controller are run in parallel. Again the idea is I can bring the voltage out of the RIDEN controller and have it available for multiple devices without over-stacking 4mm Banana plugs. Those are Superior Electric 5-Way Binding Posts, which were given to me in a box of ten by a mentor who got me interested in RF Filter design. He passed away a short while back, so I am glad I could put them to good use. I had no idea how expensive binding post were, and I think those posts exceed the cost of the controllers! 

Yes there is a plan to label them. Debating on placards or Adhesive labels. The idea behind their location is pretty obvious, but I agree, some sort of labeling is in order.

Rich

[BravoV]

Imo, the purpose of the labels are not for you, but for other people. 

[AJ3G]

LOL - Yes I thought that was were you were heading, and Yes eventually someone besides me may end up using it, or owning it (hopefully no time soon).

Tomorrow I plan to make some short length 4mm Banana patch cables. They will attach permanently to the controllers to the binding posts. The quality of the posts on the controller do not appear to be the best, which is another reason I opted to bring the output down to the more robust 5 Way Binding Posts.

So far I have tested everything in a quasi put together state, but not yet as one large assembly. Taming the fan noise issue has been a little more work than I expected, but I think that should be taken care of tomorrow. I did have a chance to play with the WI-FI interface to the controllers, and was rather impressed with the GUI provided.

Once I wrap up the above I would love to look into making one a Master controller, and have the other controller as a slave. Getting through that may take longer than the build did.

Rich

[lordium]

Have a few different supplies, but I really like my HP6634B the most for some reason. Not my smallest/most quiet/powerful or technically best, but still my most used one. Made a relay board for it so it can switch polarity, and added jacks to the front for easier access.

(took a closer look at the picture, and the relay board is incorrect, it does have one, but not in this picture. Goes to the right of the circled area)

[Smokey]

Welcome back power supply friends!

I've been getting a bunch of use out of my HP6632B with front terminals.
Still tweaking the Keithley 2308.  Internal display is still acting up.  Having the current monitor output is pretty great.

[Smokey]

Happy power supply new year.. How many good little engineers had Santa bring them a new PSU this Christmas?

[jaycee]

It looks nice. It could be improved quite a bit though, if you want to release the project at some point.

Fuse is in kind of a bad location, hard to shove your fingers in a corner to pull the fuse up.  Maybe should be on bottom left corner under that to-220 with heatsink.
Maybe add connectors for those soldered wires on the left side of pcb.
Plenty of room to lay the four diodes properly .... maybe consider also dual footprint , for regular bridge rectifier (the ones very common used in atx power supplies , gbj , gbu etc, they can be screwed to heatsinks)

Could maybe rotate the to-220 chips and align with that to-220 with heatsink and maybe even with the bridge rectifier, so that a wide heatsink could sink all those chips. Also give them rigidity and whatever.  May have to add insulators.

I'd rotate most through hole resistors 90 degrees , have most traces on top vertical and the ones on bottom horizontal ,  with ground fills or whatever for increased trace thickness.

The DISPLAY connector could probably be on the right corner/edge of the board instead of center, as the ribbon cable could block air flow going through case.

As for parts minimization, you could maybe add footprints for replacing those 47k resistors with 2 x 100k in parallel to get 50k resistors - close enough to 100k.

Not a fan of to-92 transistors, i'd rather make a board surface mount than use those.

If i was doing it again, it'd probably be 90% surface mount. I used what I had and it was the first time I'd had a PCB manufactured too.
I dont really see much point in making it a project because you have to wind your own transformer. That in itself would just get lots of awkward questions that I don't really want to answer