DPS5020 dual power supply build

[Dannyx]

Re: DPS5020 dual power supply build

Not having a 1MEG and Y-cap I disagree with megaraider, although I'm not clear what "hot side ground" and "analog ground" are.

I believe he's referring to the primary of the transformer (hot) and the secondary of the transformer ("analog") respectively, though I would like a confirmation indeed.
Sure sounds industry-standard to have a y-cap between your regulated ("cold") output and chassis (earth) GND....true, SMPSs are not designed with series-connection in mind, so I'm not sure how well the concept would transfer to our build here.

[redwire]

Re: DPS5020 dual power supply build

It's good to have a reverse-diode across each output. P600 is good.
If you put the power supplies in series for more voltage, but something goes wrong (overload) the weaker PSU gets forced reverse voltage on its output.
The other reason is if you connect a battery backwards (smoke!) or connect an inductive load like motor, car coil etc there would be -ve voltage spikes.

Not having a 1MEG and Y-cap I disagree with megaraider, although I'm not clear what "hot side ground" and "analog ground" are.
For sure you don't want stray leakage currents lifting up the DPS voltages floating, so you need a path to earth ground. Prove it by measuring the AC leakage voltage and current (to PE, or between channels) without any 1MEG 10nF kind of thing. Or look at it with a scope.

I've always drawn non-polarized capacitors with a curved plate.
Old film caps have polarity as an "outside foil wrap", which you want connected to GND for shielding or to the output of a stage. This is a very old reason for the curved (-) plate (stripe mark) on a non-polarized film cap.
https://www.youtube.com/watch?v=BnR_DLd1PDI

[Dannyx]

Re: DPS5020 dual power supply build

THIS popped up in my suggested articles on Ali today...I think it's starting to enter the realm of ridiculous for such an application Also, I think inrush of that thing would.....kill !

[megaraider]

Re: DPS5020 dual power supply build

So you're saying I should not use the 1 meg resistors +caps ?
As for grounding the 230v input, the filter I showed in post #27 does that internally I believe.

Yes that's it.

[Dannyx]

Re: DPS5020 dual power supply build

So you're saying I should not use the 1 meg resistors +caps ?

As for grounding the 230v input, the filter I showed in post #27 does that internally I believe.

[megaraider]

Re: DPS5020 dual power supply build

I need to scrounge up some Y caps (in parallel with the 1 meg resistors)

*ONLY* the hot side ground should be connected to earth ground (using either Y cap or RC)!
The analog ground (i.e. to the power transformer right) should not!

If you do connect them say goodbye to the 2 DPS working in series.
Even worst:
a human heavy electric static discharge on the analog terminal, i.e.: power supply analog ground output,
will make the main power electric differential to actuate and cut the power

[stj]

Re: DPS5020 dual power supply build

templates & guides fixes that.

[Dannyx]

Re: DPS5020 dual power supply build

That's precisely what I said: I DO measure a dozen times and it all seems perfect, but somehow I STILL mess up the final cut and it all turns to sh!t

[megaraider]

Re: DPS5020 dual power supply build

I'm the kind of guy who measures a dozen times, everything seems perfect, but when it's time to finally make the cut, I F it all up BIG TIME !

My father usually said: measure twice, cut once

[stj]

Re: DPS5020 dual power supply build

diode should be schottky or very fast, with a nice safety area.
if it's schottky - the highest voltage you can find.

[Dannyx]

Re: DPS5020 dual power supply build

Thank you redwire for the schematic. We'll stick with this I think.

I need to scrounge up some Y caps (in parallel with the 1 meg resistors), though I believe they're misrepresented in the schematic as polarized ones.

Also, what diode should go on the output there ? I have a P600K on my current supply just tied between the output terminals as an after-thought, simply because that's the only type I had which had long enough leads to go from one binding post to the other

[stj]

Re: DPS5020 dual power supply build

aluminium is anoying to cut, because it's soft the flakes get stuck in your cutter!

[Dannyx]

Re: DPS5020 dual power supply build

and a hacksaw blade - can be used/blunt/fucked,.

Took me a few tries to catch this part, especially the last bit, but I finally got it and started laughing like a retard for some reason

I shall discuss this idea with my blacksmith to make his life easier Those panels the box has are rather thick aluminium...

[stj]

Re: DPS5020 dual power supply build

if you get a couple of small clamps, 4 bits of thick tape - so the clamps dont scratch, and a hacksaw blade - can be used/blunt/fucked,.

clamp the blade onto the target like a ruler for cutting - using the rear smooth edge - not the teeth edge.
it's spring-steel and will resist most cutters.
then just run a small cutting wheel along it.
just dont go to far.

[Dannyx]

Re: DPS5020 dual power supply build

Must admit my dad is the master metalworker when it comes to stuff like this, since I don't have the skills for precision cuts and measurements....I just suck at them...I'm the kind of guy who measures a dozen times, everything seems perfect, but when it's time to finally make the cut, I F it all up BIG TIME !

[stj]

Re: DPS5020 dual power supply build

mini dremel with a disc and a scrap bar of stainless/spring steel as a guide cuts a clean line.

[redwire]

Re: DPS5020 dual power supply build

The biggest hassle is cutting out the hole on the front panel to fit the DPS module.
I looked into buying a DIN-size square metal punch that can do it, but it's like $400. I wanted one for all those cheap chinese panel meters too.

Russian build of dual DPS unit.
The dummy load resistor is kind of hilarious. It arcs really good at 20A! It's like a long heating element or spring on a 2x4 with some nails.
The fan is not moving on the DPS, so I have no idea what he is doing.
He's using 48vdc 20a smps.

[Dannyx]

Re: DPS5020 dual power supply build

Just received my banana terminals which I'm going to install in the front panel to allow me to stick standard multimeter probes in them. I thought they looked a bit cheap, but they're actually decent. The plastic outer shell that is - I'm not sure about the properties of the metal inside them like resistance and current rating and all that.....

[Dannyx]

Re: DPS5020 dual power supply build

In the case of my first supply, with the single DPS module, earth ground is not actually connected to the negative side of the bridge rectifier - it's only connected to the chassis of the transformer and that's it. By "earth-ground" I refer to the third prong of the IEC 13 plug on the back, so I don't know if my meter would actually measure anything between this prong and GND. I now realize I should've probably tied GND and that earth terminal together - seems industry-standard. Even better add those Y-caps+1meg resistors you suggested.

I noticed on some Samsung TVs I worked on that cold GND (GND of the 5/12/etc. power rails of the SMPS) is connected directly to the metal frame which is then tied to the earth prong on the mains lead with no Y cap in-between. I definitely remember seeing blue Y-caps on SMPS boards, somewhere in the corners near the metal mounting lugs but I can't remember for sure where they go. I think they're between HOT GND and earth (chassis).

[redwire]

Re: DPS5020 dual power supply build

All you do is measure ACV between each output to earth ground, with the DPS on but output disabled. That will tell you if it's floating at high potential, enough to damage the mosfet.
I take extra care against things floating up or ESD hits to the DPS jacks when I'm connecting things. The mosfet takes the hit. Normally it's not a concern in power supplies because things are always connected both jacks- there is no mosfet switch that can be off. I could be wrong too.