Whatfor do i need a LAB PSU ?

[JanJansen]

Hi, why do i need a laboratory power supply ?
Now i use a cheap thing like this :


I listen with my ear how much noise it makes for short circuit !
So i might need the lab supply for reading how much power the circuit takes ?

What is exact the money for, since they are very expensive.
I dont wanto buy a cheap chinese one : try and die ?

So whats the best choises ?,
i also wanto buy a scope and digital multimeter, is it best to first buy a good power supply ?

Thanks in advance, greetings

[tszaboo]

The lab PSU is needed, that you dont die, the circuit doesnt die, and it makes your life easier. It has current limit, which can be controlled by a knob, so if the circuit misbehaves, it will not start a fire or blow up. If you are serious about electronics, this should be the second thing you buy, first being a multimeter.

BTW, there is nothing wrong with the power supply you showed. When I was young, I've used a power supply designed for model train speed control. Thinking back, I should have bought something nice, it would be still usable now.
There are OK quality chinese power supplies, the trick is to know which one. Farnell sells Tenma branded power supplies, they are OK, has some quirks, but they work, and they are safe. The cheapest is about 70 EUR.

mod: Now I'm seeing, that yours is also Tenma.

[JanJansen]

Hi, i switched it on and off to many times, the on/off button is going to break, so i remove the powercable from the wall all the time, i need a new one for sure.
I have a multimeter, it works only the screen displays only 4 characters, just like my very old analog scope, it works only i want a nice digital one.
So i wanto replace all 3 things sooner or later : DMM Scope & PSU, i cannot afford all in one buy ( to bad ), else i needed at least 2000+ euro.

What do i buy ?, i realy like the Hameg / R&S gear, only the PSU is to expensive, what PSU do you reccommend and why ?, or are all brands good quality for such a simple thing ?

[WackyGerman]

You could also buy second hand stuff too . My first PSU I bought for 30 Eur was a really old one , made in White Russia . Still works good and it was fitted with screws , not with hot snot like the newer ones . Also got the manual with a parts list and the schematics . So it is repairable . If you find such an old puppy at ebay or somewhere else for a good bargain , then get for it . I made a teardown of it here in the forum

https://www.eevblog.com/forum/testgear/universal-power-source-made-in-belarus-teardown/msg485318/#msg485318

[JanJansen]

Hi, i,m looking to a PEAKTECH 6225 A,
not so expensive and new for around €75,-
Is it good ?

[rstofer]

I have been messing around in electronics at various levels for nearly 60 years and I FINALLY bought a Rigol DP832.  I have gotten by with fixed voltage linear supplies, batteries, wall warts, whatever, for a very long time.  I always wanted a decent lab PS but I can't say I have ever really needed one.  I bought it just because I could.  A true bench power supply, like the DP832, has a lot of very nice features and having 3 outputs, I can power up dual-rail op amps and a microcontroller all from one source.  That's pretty handy compared to what I was doing.

In my corner of the electronics sandbox, I would put a decent scope far ahead of a power supply.  Most of my projects are uC based and are usually powered by USB.  I can get along without the PS but I can't get along without a scope.

[The Soulman]

Or if you are in the Netherlands:

http://www.marktplaats.nl/a/hobby-en-vrije-tijd/elektronica-componenten/m1098225876-dubbele-tandar-type-ts3022-regelbare-voeding-30-volt-2-amp.html?c=a2384ef0ece270f44503df9f8598c624&previousPage=lr&pos=13

A TTI ts3022, I will let others comment on that one..

[MosherIV]

Hi

Yes, where are you based exactly?

As Soulman says, TTI (or Thurlby Thandar Instruments) have made very good basic lab PSUs for decades now.
If you are in the UK, they are very common and relatively cheap used.

If you are in the USA - then HP PSUs are probably common and relatively cheap used.

[ProBang2]

Peaktech does not build devices themself. It does only rebadging chinese OEMs.
Personaly I have prefered the Korad KD3005P (as D a little cheaper, also sold as Tenma and Vellemann).
Display with one more digit resolution, precise setting with rotary encoders and a dedicated switch for turning the load on/off.
(Costs around 90,- €)

I would avoid used PSUs. Sure, they can be great bargains.
But often enough: You only bought the sorrows from an other...

[JanJansen]

Peaktech does not build devices themself. It does only rebadging chinese OEMs.
Personaly I have prefered the Korad KD3005P (as D a little cheaper, also sold as Tenma and Vellemann).
Display with one more digit resolution, precise setting with rotary encoders and a dedicated switch for turning the load on/off.

If you look at Peaktech and Reichelt site you see the 6225A is the new version of the 6225, available from 14 november. ( i can think about it for 2 weeks before buying )
It has also exact what you say, on off button i think & more accuracy, looking good.

If this Peaktech is rebaged, what would be the original brand ?, maybe that one is even cheaper ?
I readed bad things about the Korad brand : try and die, Peaktech sounds somewhat more trustworthy to me.

I would avoid used PSUs. Sure, they can be great bargains.
But often enough: You only bought the sorrows from an other...

I agree, i dont wanto take any risk.

Or if you are in the Netherlands:

I updated my profile, look my flag now !, thanks for the link, i better buy new gear not second hand.

@ rstofer : LOL, after 60 years you bought a LAB PSU!
Thanks for the reply`s all

[JacquesBBB]

If you are serious in electronics, the first thing you should do is to fix your power supply. From what you say it is just changing the switch.

[PotatoBox]

You might want to consider building your own. A linear power supply is simple to make and is a good learning experience.

[JanJansen]

I am affraid for 220 volt, i only use 15 volt max, so repairing or builing that : no thanks.

[tszaboo]

I don't use a lab power supply (well, I have one, but I just use it as a normal 5V/12V PSU). I put all power management functions on board, so all of my boards only require one power jack input, and they generate their own voltage rails using on board converters.
If you design like me, you can safely use just a 12V or 5V power adapter to power up your boards. Don't forget to test for short using a DMM before applying power, and also put a fuse on board.
However, if you don't do complete product design, instead, you are more interested in building quick proto boards to verify circuits, then a programmable PSU can help a lot.

It is still better to power it with a lab PSU. You can create shorts when probing around, or the device can go into self-destruct mode. The fuse is used to protect the cable (catching fire), not safety or current limitation. Also some awful plugpacks can float themselves to half mains voltage. It will not shock you, but i can disrupt communication.

[JanJansen]

Ok, i agree it can save time with having a 3 output PSU unit.
I dont mind hooking up some 7805 and 3.3v regulators, still i would like to have a 3 out PSU,
Only why are those brands so expensive ?, Rstofer has a Rigol, its about the cheapest brand, still it cost 500.

So what is the big difference between the €75,- PEAKTECH 6225 A, and other brands like Rigol ?,
ok it has no 3 outputs, take for example a 1 output device from a brand, the casings look much bigger then the PEAKTECH 6225 A.

And what is the Earth (green) terminal for ?, on my current adapter i have only + (red) and - (black), i always thought earth was the same as - ?

[cs.dk]

A lab psu is floating. If you for some reason wanna ground it, you can use a shorting-bar between negative and earth.

Your own psu is probably also floating with respect to mains earth. Is the 230V cable with 2 or 3 pins?

[JanJansen]

Hi, the cable is 2 pins.

[cs.dk]

Then it is floating..

Floating lab psu's can be series or paralled coupled to gain more power output. Or to make a ie. +/- 15V supply. Don't do that with grounded psu's

http://powersupply.blogs.keysight.com/2014/03/what-is-floating-power-supply-output.html

[JanJansen]

Thanks, i try to understand, maybe i just dont use the earth at all, since i see no use for it, my final projects dont have earth also.

1 more thing about the peaktech, i read here all peaktech PSU`s are rebranded :
https://www.eevblog.com/forum/testgear/bk-precision-peaktech-only-rebranded-objects/
I try to find out what the original brand is of the PEAKTECH 6225 A, they say Manson or GW instek.
When i visit the Manson site i get a virus warning, what kind of brand is that ?

[FlyingHacker]

Lab supplies are useful mainly due to the current limiter. This will save you many $ in parts. 

Personally, I like older Linear supplies (Lambda). They are reasonably priced on eBay if you look around. They are through hole, and come with schematics/service manuals. You can learn a ton from repairing things.

Modern supplies, especially anything from China, are difficult to repair, as they are surface mount and have no schematics, and will end up in the landfill while the older supplies will keep running for many decades. I don't just st mean cheap supplies either. Nobody wants users to repair things anymore.

[ProBang2]

Hmmm...  "Peaktech" and "trustworthy". Somehow paradox.

Peaktech DMMs are usually from CEM. They are the OEM for many DMMs from Extech, too. And have ruined their reputation.
The Peaktech 6225 PSU is manufactured from MCH. http://www.china-mch.com/index.php/en/info/250.html
Just for interest: Teardown of a MCH-K305D (6225)
This company even managed to have a cheaper copy ("SM-8145", 33000 Counts) of the Vici VC-8145 (80000 Counts) benchmultimeter...

Unfortunatly: There is no information about the "6225 A" at this time. Too new? Hence: No confirmation right now possible.
 

[JanJansen]

Ok, i dont wanto try and die, i have some more money.
I dont get it why Reichelt sells it then ?
Luxury choises are difficult.

Wow, i,m looking to the Rigol DP832 YouTube movie, it makes a lot of noise,
i,m busy with audio, so i dont want any Rigol gear, those scopes also makes noise.

[Dave]

What sorts of currents do you need your power supply to deliver?
If your demands aren't too high, you might like HP/Agilent/Keysight E361xA series supplies. Lovely linear supplies, low noise output and no fans - just one hefty heatsink at the back. Exactly what you need for designing audio circuits.

[gamalot]

Hi, i switched it on and off to many times, the on/off button is going to break, so i remove the powercable from the wall all the time, i need a new one for sure.
I have a multimeter, it works only the screen displays only 4 characters, just like my very old analog scope, it works only i want a nice digital one.
So i wanto replace all 3 things sooner or later : DMM Scope & PSU, i cannot afford all in one buy ( to bad ), else i needed at least 2000+ euro.

What do i buy ?, i realy like the Hameg / R&S gear, only the PSU is to expensive, what PSU do you reccommend and why ?, or are all brands good quality for such a simple thing ?

Spend 1000 euros you can get Rigol DS1054z oscilloscope, Rigol DP832 bench power supply, and UNI-T UT61E multimeter from eBay. I think they are good enough to a beginner.

[CraigHB]

Earlier in this thread someone said a lab PSU is the second thing you should buy, the first being a multi-meter.  I would agree, but possibly a scope is second with a lab PSU third.  Good ones are expensive.  I was using those el cheapo Chinese ones, but the pots wear out fast and adjustments get jumpy.  I ended up replacing a couple of those units sooner than later. 

I bought a relatively cheap Chinese lab PSU with a rotary encoder.  It's great because there's no pots to wear out, but still wasn't particularly cheap at about 200 USD.  I'm actually on my second one.  The first one failed shortly after I bought it and fortunately the vendor warrantied it for me at no cost.  Even so the firmware is buggy and sometimes it reacts incorrectly to button pushes. 

Sometimes you end up paying more by cheaping out which I probably have on benchtop supplies.  I really, really need to get a good brand name supply, but don't have the money for it right now.  Has to have digital controls, don't want pots wearing out on me. I also need higher current and voltage limits since I've got a couple projects I want to do that need it.  Digital lab supplies with higher limits get really pricey.  It will probably be the most expensive of any test equipment I've bought so far. 

Don't really understand why quality benchtop supplies are so expensive considering you can get a decent scope for around four hundred USD.  A brand name digital lab supply with higher limits is greatly more than that.

[julian1]

This is Dave's review of the E3610A. They can be picked up on Ebay around $100, (although postage is an issue is you have to source it from overseas).



The advantages are simple, linear, no fan noise, top-brand, schematics are available. Disadvantages - you need two if doing dual rail. Definitely don't spend $400 on a power supply if you don't have a scope yet.

[bitseeker]

Disadvantages - you need two if doing dual rail. Definitely don't spend $400 on a power supply if you don't have a scope yet.

Note that the E3620A has two outputs and the E3630A has three (although the third is negative-only relative to common).

[julian1]

the E3620A has two outputs

Do those have current limiting? - it's a bit hard to tell the front-panel. They also command a higher-price - which means they compete against the features of more modern models (tracking, programmable etc).

[The Soulman]

i,m busy with audio

What are you doing with audio? dac, active filters, amplifiers?
solid state, tubes?
And more importantly, what do you want to learn from it?
I was like you 25 years ago.. 

[bitseeker]

the E3620A has two outputs

Do those have current limiting? - it's a bit hard to tell the front-panel. They also command a higher-price - which means they compete against the features of more modern models (tracking, programmable etc).

Unfortunately, they do not have adjustable current limiting, just short-circuit protection. Same story on the E3630A. However, they cost less than buying two (or three) single-channel models. They were HPs budget line, so not as much power or features as, say, the E3631A (triple-channel) or E364xA (dual channel) models.

[FlyingHacker]

I see no point in a "lab" supply without an adjustable current limit. You might as well use wall warts or batteries at that point.

[CraigHB]

That's pretty much the whole point of using a lab supply, ammeter and adjustable current limits.  I use the ammeter all the time and often rely on the set current limit.  Otherwise you could just use any ol' power supply.

[JanJansen]

What sorts of currents do you need your power supply to deliver?

Not much, not more then 1A maybe a half, that Peaktech PSU is overkill already.

Spend 1000 euros you can get Rigol DS1054z oscilloscope, Rigol DP832 bench power supply, and UNI-T UT61E multimeter from eBay. I think they are good enough to a beginner.

Noisey X 2, i rather have that €800 Hameg/R&S scope without noise.

You need 3 of these for audio (totally $2700). 2 for bipolar 15V/18V for OPAMP, and one for +12V or +5V for logic.
Make sure your bench top is free from any RFID equipment before using any Keysight gears .

Yeah, only i use single supply audio, the final build is powered from a wall adapter, i dont trust 220volt, i always find out the hard way.
Huh, RFID in Keysight gear ?, i,m not buying that brand or a rebadged brand, they are crazy, what is the use for that ?

What are you doing with audio? dac, active filters, amplifiers?
solid state, tubes?
And more importantly, what do you want to learn from it?
I was like you 25 years ago.. 

Hi, i make synthesizers instead of buying, not learning anything special, just to build more cheap synthesizers.
Right now at the moment, i re-make 25+ years old digital synthesizers like Yamaha DX7 & Casio CZ in 1 chip.
Did you have PIC chips with build in audio DAC + 128KB Program & 16,384 RAM Bytes 25 years ago ? 

I see no point in a "lab" supply without an adjustable current limit. You might as well use wall warts or batteries at that point.

That Peaktech has that, right ?, i going to buy that one not that noisey Rigol brand.
http://www.peaktech.de/productdetail/kategorie/schaltnetzteile/produkt/peaktech-6225-a.html

[FlyingHacker]

I see no point in a "lab" supply without an adjustable current limit. You might as well use wall warts or batteries at that point.

That Peaktech has that, right ?, i going to buy that one not that noisey Rigol brand.
http://www.peaktech.de/productdetail/kategorie/schaltnetzteile/produkt/peaktech-6225-a.html

I can't imagine the Peaktech is much less noisy. As others have pointed out a switchmode power supply is probably not a good idea for audio.

I might go with one of these:

http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2047675.m570.l1313.TR0.TRC0.H0.XLambda+LPT-7202-FM.TRS0&_nkw=Lambda+LPT-7202-FM&_sacat=0

[tautech]

I see no point in a "lab" supply without an adjustable current limit. You might as well use wall warts or batteries at that point.

That Peaktech has that, right ?, i going to buy that one not that noisey Rigol brand.
http://www.peaktech.de/productdetail/kategorie/schaltnetzteile/produkt/peaktech-6225-a.html

I can't imagine the Peaktech is much less noisy. As others have pointed out a switchmode power supply is probably not a good idea for audio.

That Peaktech ^^ is SMPS and somewhat noisy but quite OK for tinkering around with IF you add additional local smoothing capacitance to your projects.
As others have pointed out it's made by MCH and here's an older thread examining them in little detail:
https://www.eevblog.com/forum/testgear/cheap-variable-switching-power-supply/
 

[JanJansen]

Yes i always use big cap where the power goes in, then a 100ohm resistor and then again a cap.

I have the Peaktech 6225 A, i am very happy with it, glad i did not wait 60 years.
It is looking realy good, makes no noise at all, it dont get hot, and dont smell ( my old adapter alway get hot and smell ).

Ok, you can see its made in china :
The banana plugs dont go in totally, a half centimeter you see the metal.
When removing the plasic from the display, the display comes loose from the device ( it did not break and went back in place when the plasic was removed ).
One time when rotating the voltage encoder down, the voltage goes up instead of down.

Still for that money ( around 75 euros ), i am very happy, it measures how many mAh it takes, and very presice setting the voltage and max mAh.

[JanJansen]

I am not so happy no more with my Peaktech 6225 A :

[FlyingHacker]

Just get a older Lambda lab supply and be done with it. Linear, silent, bombproof, through hole, with schematics.

Lambda makes the power supplies for many of the big players. A lot of HPs and Agilent/Keysights, and others are Lambda supplies with some extra circuit board thrown in, and a much higher price. Those companies know if they want a good, reliable supply they start with a Lambda.

[rstofer]

Wow, i,m looking to the Rigol DP832 YouTube movie, it makes a lot of noise,
i,m busy with audio, so i dont want any Rigol gear, those scopes also makes noise.

Which kind of 'noise'.  If it is audible, well, that will be a function of load current on the DP832 but, yes, it is noisy enough to remind me that it is on.  For the DS1054Z, many people, myself included, have changed out the fan.  Details elsewhere.  I did it but I didn't really have to.  None of this stuff is anywhere near as noisy as one of my tower computers which already has sound absorbing padding.

If you're talking about electrical noise, I would expect to have to add both bulk and decoupling capacitance to the circuit anyway.  Long leads from the PSU to the project aren't really such a great idea.  Measuring noise with a scope just brings in the scope's own noise floor and that isn't anywhere near 0V.  If I use my handy dandy EEVBlog Brymen meter to measure electrical noise from the DP832, I get around 0.01 mV AC (unloaded).  My Fluke 189 gets a somewhat higher reading (like 0.15 mV AC) but, either way, well under 1 mV.

I have been messing around with this stuff for a very long time without a lab quality PSU.  It would be my last piece of equipment, not my first.  There are lots of ways to power circuits that don't involve spending a lot of money.  My order would be: DMM, Scope, Signal Generator then PSU.  Wall warts and USB work for me!

[james_s]

You don't *need* a lab PSU, it just makes life easier. I've always built my own, these days there are so many really cheap modules you can get that make it even easier. Surplus power bricks can be used as the source.

[JanJansen]

Its my first choise, i like it if it worked good, before i was blind, now i can see ( milliampere usage ), i dont wanto always use multimeter for that, besides i dont have the extra cables.
Also this thing is small, fits great in my house, it would be perfect, it makes no sound at all.

Now i am looking to a bit more expensive, 3 channel GW instek GPS-3303, since i was reading only good things about that brand.
The first thing i see on YouTube : GW INSTEK GPS-3303 CH1 malfunction


If i had the money i would invest 1000+ in a good 3 channel PSU, i hope the shop will replace mine with a updated working model or fix it, for 75 i cannot buy anything else, i need 75 and more on top of 1000 bwha.

[bingo600]

This is Dave's review of the E3610A. They can be picked up on Ebay around $100, (although postage is an issue is you have to source it from overseas).



The advantages are simple, linear, no fan noise, top-brand, schematics are available. Disadvantages - you need two if doing dual rail. Definitely don't spend $400 on a power supply if you don't have a scope yet.

Watch out getting especially the E3610A from overseas , Dave says in the video that they aren't switchable between 110v <--> 220v

/Bingo

[bghende]

If its in your budget, try to get a supply with an enable button. Nothing scarier than turning on the main power switch on a power supply connected to a load without knowing what the voltage and current limit settings are.

[james_s]

I always turn on the supply and then connect the load, I suppose an enable button would be more convenient though.

Power supplies are something I've always built myself. They make good beginner projects, you can start building simple ones and then move on to more advanced features.

[JanJansen]

The shop fixed the PSU, i removed the movies from youtube.

[VEGETA]

Lab supply is a must for me, but if you don't have money now maybe you can see this:



^ adjusted after  a stupid mistake!

[ProBang2]

Lab supply is a must for me, but if you don't have money now maybe you can see this:

https://www.youtube.com/edit?o=U&video_id=CJEQZV30sc8

Ahhh.... - nope. Nothing to see. Zero videos.   

[VEGETA]

OMG I am so stupid!

here is the link:

I copied the first one from my channel dashboard!!! 

gonna adjust it now;