Variable bench power supply

[moijk]

I made a bench power supply from an atx psu and that works well for the 5v and 12v applications I got, but when I want to test stuff that requires something else or test voltage cutoffs and such I'm out of help. I see there are such things on eBay like this:

https://www.ebay.com/itm/30V-5A-Adj...egulated-Power-Supply-110V-220V/332845817555?

But I'm an amateur so I'm really not knowing what I need or don't need. I just know what I need it for. So any suggestion. There is an Manson EP-925 sold locally, but that's not cheaper, it has analog gauges and it seems to be a model that has been around for decades which lead me to believe modern supplies might be better.

 

[Bryce]

Hi moijk,
a few tips. First to the device you've linked to. These are no-name devices that many companies slap their name onto, so you will probably find it under several names, maybe even locally. Secondly, it only has one output and in many cases you'll need to supply more than one rail, so I would advise you spend a bit more on a dual supply now, rather than discovering you need it later. It is also a switched-mode PSU which will not be suitable for all jobs, I'd recommend you look for a linear supply. Also, by spending a bit more you can get one where you can set the OVP/OCP and CC levels. This one doesn't offer any of those. What's your budget barrier, then maybe I can make some suggestions?


Bryce.

P.s. I hope your ATX supply has fuses, otherwise you could destroy some prized retro gear if it has a failure!


Edit: Had a quick look and here's some options. All more expensive than the one you pointed to, but all have dual/triple output and a lot more features. starting from the cheapest. The Siglent is the most expensive, but the most reputable of the three companies. The cheapest seems to be a clone of a reputable brand and as far as value for money goes, if you are on a tight budget, probably your best option.

https://www.ebay.de/itm/Duales-DC-L...3003CIII-Netzgerat-Labornetzteil/312210509672

https://www.ebay.de/itm/Netzgerat-D...ornetzteil-LED-0-15-30-V-0-1-5-A/123587123608 (The S-LS-24 Model)

https://www.ebay.de/itm/Siglent-SPD...-3V3-5V-NT-USB-Software-PinSonne/132947464395

 

[moijk]

Well, I went around to read up on the subject a bit more given the pointers I looked upmarket and downmarked to see what more or less money would yeld, but when I saw there was a national importer of the Siglent it was hard to go through the hassle of buying overseas.

I mean, the X model of the Siglent has a proper screen but I really didn't see a hundred pounds more worth in that for my use, and going downmarket I didn't find anything that gave me as much. I mean, it even have the third channel that is not variable or cc-ed but perfect for my constant 3.3 & 5v needs.

So thank you, I went and ordered it.

 

[moijk]

by the way, given I'm not that good at this. I started to look at the projects I've got. I have a newbrain without a psu. I need 13.5v, 6.5v and -12v. 13.5 and 6.5 is no problem, but minus 12v? If I bridge two channels in serie at 12v I seem to recall I get -12 and 12, but without doing that given I would need all.

 

[Bryce]

The X series isn't just a fancy screen, it also has other functions. However, these extras are things you would mainly need for test and development when you are designing your own hardware, so possibly not what you would need, so pointless to get unless you intend getting into electronic design.
As far as the superbrain is concerned, yes, that would all be possible, but read the manual carefully when series or parallelling channels, you don't want to destroy your new toy on the first project.
Siglent is a wise choice, not only because of the local distributor, but also because they are a class or three above the cheaper devices.

Bryce.

 

[moijk]

I'm usually buying the next step up "just in case", but the main thing here was timings and I went so far I watched videos to try grasp what that would be for. Could I trouble you with a scenario that it would be useful? My oscilloscope has a signal generator which I see can be useful down the road (not yet), but to flip with voltages like that?

 

[Bryce]

A few things you can do with a fully programmable PSU:

Battery simulation: Upload the discharge curve of a battery and simulate how (and how long) your device functions with certain types of batteries, what functions fail first and how.
Dirty supply simulation: Add ripple, spikes and other random crap to analyse what your device can get away with (or survive). Or in the case of a PSU or filter design, how much it can filter out.
Power plots: Gather data of the voltage/current/power requirements over time.

Bryce.

 

[BloodyCactus]

the things you dont see are safety features. fuses, shorting protection, over current, over voltage, isolated outputs etc. The Siglent PSU is just a copy of the GWInstek PSU (I think every chinese brand on the planet copied GW PSU design).

If you can find old AIM/TTI PSU, Hameg, Lambda/TDK, they are good value. Siglent is eh.. its ok. just remember its a chinese brand built to price with crappy caps and components.

 

[Bryce]

The Siglent has shorting protection. It doesn't have OVP or OCP, however it has current limiting which is usually enough for retro repair as it will then switch to CC mode and the voltage will drop and protect the DUT. The Siglent isn't a GW Instek clone, Siglent develop their own devices now and unlike the past, also use pretty high quality components too. I have used many of the newer Siglent devices and they can't be compared with the devices they were selling 15 years ago.
The older TTI/Hameg devices you've mentioned are all good devices, but they will be secondhand and possibly have a history of abuse, so without knowing how to check / restore / repair them it would be unwise for moijk to invest in one.

Bryce.

 

[moijk]

Got it today, looks and feels like a piece of professional grade kit. Not sure how well it works yet, I have just tested with the multimeter for fun, but once I get some new leads I'll give that a go. I'm pretty sure it'll be good enough for my use. Thanks for the help and patience, Bryce.

 

[Bryce]

Nothing like a piece of new test gear to make you smile the whole weekend. Congratulations. Read the manual fully before you start pressing buttons.

Bryce.