PSU Load Testers - Designs?

[PCBONEZ]

I'm interested in eventually building a load tester... someday...
.... like I'll have time anytime soon... even this year!
-
But if I trip over a surplus bulk lot of power resistors that may change....


Anyway, has anyone seen any scats or plans, interesting articles, or have one they built.

Both cheesy-basic and whamidyme hi-tech my apply.

Opened as more of a casual interest discussion topic than anything else right now.

.

[zandrax]

Re: PSU Load Testers - Designs?

I'm interested in eventually building a load tester... someday...
.... like I'll have time anytime soon... even this year!

Since good load tester are expensive, Xbitlabs reviewers made one from scratch, adding sensors and a recording interface: the whole article is about psu basis and test methodology, but at page 11 they describe their loader.
If I get into some others DIY projects, I'll post here.

Zandrax

[PCBONEZ]

Re: PSU Load Testers - Designs?

Good info Zandrax.
Thank you.

[shadow]

Re: PSU Load Testers - Designs?

The review looks quite interesting. The project seems to be fairly challenging, however not completely out of grasp for those that do not have all the required know-how yet on all these electronic circuits. Such as myself.

Good find!

[starfury1]

Re: PSU Load Testers - Designs?

yeah when I read the post thats the page that come to mind.
(of course wouldn't have a clue were it was in the book marks)

I did see another somewhere which had a stack of power resistors (big ones in heat sinks)
in I think it was an old computer case with fans and large toggle switches.

I was thinking about this awhile back and there has been a bit of discussion on it.

Yanz I think used automotive bulbs (they suck a bit of juice).

you can get those multimeter's el cheapo ones something like $10.

Get a few of them and dedicate them 2 per rail V/A with power resistors
a switched bank for each of the rails so you can vary the load
Ideally an "electronic dummy load" thats variable would really be more the go.

Another thought is a bit cruder
one of those psu testers (like here) with the voltage meters in it but a double type power lead and a salvaged MB connector to setup some real resistive loads on it

the psu tester would monitor ( not overly accurately) the voltage.
you would have to make provision for current monitoring.

Yeah somewhat crude as I said.

none of the above are a SunMoon but could be done for reasonable price if you are prepared to scrounge around for the stuff.

Digital meters are nice for accuracy but when you consider the dynamics of what your looking at a few analog meters would probably give you a better visual feel for whats going on with a psu on varying loads.

Think for the voltage (due to the small amount it should change) you would really need to have some sort of expanded range, like say between 10 and 15 for the 12 volt range etc
(I have to think about that one but you get the idea)

Anyway they were my thoughts when I was thinking about building one.

beats stuffing around with meters and loads I suppose.

another thing as JG has got, perhaps one of the USB CRO HW SW devices if you really want to get a bit more to the nitty gritty with them.
(although if you got a reasonable CRO then thats probably all you need)


OK my 2 cents worth

Hope its of some help or gives you a few ideas

Cheers

[starfury1]

Re: PSU Load Testers - Designs?

on dummy loads

I actually built something like this for testing Audio Power Amps years ago.

http://www.k4eaa.com/dummy.html

Didn't fully read this, but it looks along the lines of what you might call an
"electronic dummy load"

http://www.fraw.org.uk/download/ssp/sspji-05.html

if the unit its self isn't much use it would I think give you the theory to adapt
to your purpose I supose

Here's another and again might be the basis for a more heavy duty unit.

http://tangentsoft.net/elec/smarty-load.html

note the heat sinked power resistors


a page I found (well article really)

http://www.pcper.com/article.php?aid=187&type=expert

Here's another electronic type (doc with schematic a PDF)

http://www.geocities.com/hagtronics/load.html

just mention this anyway
Normally we talk of "resistive load", which is to say current and voltage are in phase (0 degree's phase shift)

power or wire wound resistors do have a reactive element
(being a coil of wire, inductor)

Not that I think it will overly matter with a DC psu but it is there and just something to be aware of
In the case of audio amps (depending) it can be a real problem

Hope the links help somebody anyway

Cheers all

[PCBONEZ]

Re: PSU Load Testers - Designs?

The only time I can remember using dummy loads of any size as a testing device was messing with Radar units back in school. (I have worked on equipment that had huge banks of foot long power resisters built in.)

What I had in mind for PSU's is along the lines of using banks of wire wound resisters with current controls so I can set the amps on each rail to say 60% rated, then 70% rated, and so forth. Set all the rails at a % rated point and check DC volts for a drop and the wave form for noise.
-
It wouldn't do anything for transient response measurement but it would at least verify if a PSU is actually going to handle the amps you need for the system without the voltages dropping out of spec.
-
Also if you have a situation where one rail is always low or high or too noisy you might be able to figure out a circuit mod to bring it in range.

Unfortunately my brain can think of cool projects a lot faster than my time or wallet allows actually doing them.
[Doesn't kill the interest though.]

.

[starfury1]

Re: PSU Load Testers - Designs?

Yes power resistors and switching is probably the cheapest lest headache way to go
(not after lab 12 decimal point accuracy etc)

these following articles are probably more useful for setting up pwr resistors

http://www.silentpcreview.com/article683-page1.html

This page here

now this is the one I was looking for...it also came to memory when I read the post.
(not that I am saying its a perfect idea or anything..just found it a bit of novel idea, although there is a reason behind it)

http://www.extremeoverclocking.com/a...Testing_3.html

forum page I found the links on here

Another link I found Why 99% of Power Supply Reviews Are Wrong

just skimmed it so pro and cons no real idea

for those with very very fat wallets

chromaate

Anyway plenty of ideas, and by the sounds of it bonez you got a few of your own.

Cheers

[i4004]

Re: PSU Load Testers - Designs?

Another link I found Why 99% of Power Supply Reviews Are Wrong

he says measuring is not the path only to endn up with another type of measuring.

what interests me the most is reliability and diurability, and the only way to find out about that is the real-world experiences of people who actually repair pcs.

accelleratred tests and voltage/current measuring won't do.
most psus will power the machine and work while they're new.
what i'm interested in is "HOW LONG" will it work, and as i mentioned in other thread, can i trust it won't blow up my machine; durability and reliability, with an accent on rleiability, as i don't mind it lasting 2-3years if it won't kill mobo and everything else.
my requirements are pretty low, then, aren't they?

so hooking up to right people is more important for psu testing than load testing, as majority of the pople don't do video-encoding or simillar system loading tasks(then again, system loading doesn't neccesarily mean psu is loaded etc.).

[zandrax]

Re: PSU Load Testers - Designs?

what interests me the most is reliability and diurability, and the only way to find out about that is the real-world experiences of people who actually repair pcs.

You can say if a psu is a good or a bad one by looking its components' quality and by mesauring its temps while it's running: you can estimate if it will more likely fail or survive in few months, but there isn't a thing such as a reliability test.

Zandrax

[starfury1]

Re: PSU Load Testers - Designs?

what i'm interested in is "HOW LONG" will it work,

that being the big question

yes feedback is important, I agree
and so is the conditions they are (were) being used in are important to know if one fails.

I guess the only why your going to tell with say a new production is who possibly build it (as in the design) quality of build components used
how well it handles stress
Hopefully someone that reviews it knows there stuff and what to look for.

The manufactures past reputation, that doesn't mean they wont go cheap or just possibly have a somewhat suspect lemon of a new product.

I haven't read the article was more looking for resistor setups
I suppose I should since I open my big trap and posted it

Cheers

[PCBONEZ]

Re: PSU Load Testers - Designs?

what interests me the most is reliability and diurability, and the only way to find out about that is the real-world experiences of people who actually repair pcs.

accelleratred tests and voltage/current measuring won't do.
most psus will power the machine and work while they're new.
what i'm interested in is "HOW LONG" will it work, and as i mentioned in other thread, can i trust it won't blow up my machine; durability and reliability, with an accent on rleiability, as i don't mind it lasting 2-3years if it won't kill mobo and everything else.
my requirements are pretty low, then, aren't they?

I understand where you are coming from but the problem with that idea is by the time you have the reliability data the equipment is obsolete anyway.

.

[mpilchfamily]

Re: PSU Load Testers - Designs?

Thought this may help you out in your future build plans. Just last month i completed my own Load tester. Here is the Work Log of that build.
http://www.xcpus.com/forums/other-mo...ate-984-a.html

Here are the threads for the planning stages of the build.
http://www.xcpus.com/forums/mods/458...-test-bed.html
http://www.xcpus.com/forums/mods/543...ad-tester.html
http://www.xcpus.com/forums/mods/684...esign-4-a.html

It was 4 months of research before i was able to secure funding to start the build. The system is built and ready to test save for 4 resistors that where on back order. Finally got those in the other day but haven't had the chance to install them. Its going to be a bit of a choir to pull the system apart to get the resistors installed.

Here is another custom built load tester. He hasn't finished it yet but he is going all out to make it just like a nice $10K professional tester.
http://www.themodnation-forums.com/viewtopic.php?t=333

You will also find a copy of my Work Log at The Mod Nation.

Now one of the best places for PSU information and getting your PSU testing methods right is here.
http://www.jonnyguru.com/forums/index.php

Hope some of that information will help. If you have any questions please ask.

[starfury1]

Re: PSU Load Testers - Designs?

I'll have a read later but "thanks" for the links...
wow certainly some effort went into that
(OZ slang, like that LOL)

If anyone can find me a DPDT switch that can handle no less then 41A then let me know

don't know if you got an answer to that but I think you would be shopping at an "electrical" wholesaler for something that can handle that
Like a Mains Switchboard Switch (not cheap either)
I Dont know about "double throw" thought (probably available)

Just looking at some prices for electrical gear
I thought they said Ned Kelly was Dead.

Welcome to the forums

Cheers

[i4004]

Re: PSU Load Testers - Designs?

why not load it with a bunch of car headlight lamps?

[kc8adu]

Re: PSU Load Testers - Designs?

why not load it with a bunch of car headlight lamps?

the cold surge current will likely trip ocp.
had 2 astron rs35m here that would not light a test headlight.
the ocp was that fast.

[mpilchfamily]

Re: PSU Load Testers - Designs?

Lamps will work but then you have to use allot more of them and the cost goes threw the roof. As for the DPDT i figured out that i didn't need it to handle 41A. Any DPDT will do since there is only a small amount of current and voltage passing threw it. The DPDT switches are tied to the Shunts for each Load bank. The only power going threw that is the voltage drop across the shunts which is used to measure the Load on each bank.

[starfury1]

Re: PSU Load Testers - Designs?

Lamps will present a dynamic load at startup with a large current surge.(as KC8 said)
I know there is one forum member that uses them but this is as a lighter load I think not trying to max out the psu.
doable yes,
(depending on lamps, maybe throw a power resistor in line to limit surge)
but better power resistors

This is really a side point
Don't know how really relevant it is in the real world

power resistors (wirewound) I suppose have another effect which "could be" helpful and thats "inductance."
this would to some extent (if I remember my theory correctly) soften any surge at startup

This means you do have a reactive element to your resistive load but I think thats not really an issue (it may be of some effect with regards to ripple, I dont know)

All I know for sure is they do have a measure of inductance, being wire wound

(unless its "Noble" brand which I don't think exist any more, they from what I understand were wound in a way to reduce inductance, double the wire over then coil, a mutual inductance thing)

Cheers

[mpilchfamily]

Re: PSU Load Testers - Designs?

Well there will always be some short fall to whatever you use as the load. The problem is it isn't a dynamic load. Its very hard to simulate real world conditions. Unfortunately you can't get a good review of a PSU while in a normal system. For one you can't really test the full ability of a 1KW unit. Also you have no way of knowing the actual load. The ideal way to test would be using a system that is able to fluctuate the loads similar to the way you PC does when starting up, Idling, and under heavy loads. The system would have to record the load about every 10th of a second. It would also have to keep track of the voltages at the same rate. A good PSU needs to be able to react to sudden changes in loads without the voltage dropping outside of the +/-5% tolerance in that split second. Then of course you would need to compile all that information to get the average efficiency of the unit. Placing set loads on a PSU is nice but only tells you it can sustain a certain load. But PC loads are never sustained for very long and tend to rapidly peak and fall. Many PSUs out there can easily handle a heavy and consistent load. Its the constant fluctuation that they are not able to keep up with and kills them. Especially when the load Goes quickly form a relatively small load to nearly max of the PSU's capacity. Its hard to properly test a PSU.

[starfury1]

Re: PSU Load Testers - Designs?

The problem is it isn't a dynamic load.

True a resistive load is fix, all you can really do is just have it at different load levels for the PSU

mostly here people just need a decent type of load(s) for load for testing.

Power Resistors are the best option for a somewhat cheap load
which is all thats really need for the majority repairs I suppose.

True though, to look at the dynamics & response behavior, you would need to emulate those conditions of use in a controlled way.

Me, still a bit of a noob really on switchers.... understand some of the theory and some of the problems but no design engineer here.

BTW I only mentioned the "side point on inductance" because we were talking initial surge currents
Steady state DC it wouldn't matter at all.
(if it even really does factor in with ripple I wouldn't have a clue)

for the purposes of just testing a PSU under loads, the above
(using power resistors) would be fine.
lamps too I suppose if you got nothing else
but just beware as pointed out by KC8 they could be a trap
they are probably not the best idea

Cheers