WTB: Variable Power Supply

A Variable PS is something that I've always "needed" in my life...

(merely to fuel my laser and flashlight 'addiction' ), so I've finally decided to get one.

I'd like to keep costs below $100 if possible.

my requirements are pretty basic, up to 10A would be nice but is not essential.

Perusing the fleebay there are quite a few offerings from Australian sellers
that have sold in excess of 300+ units. It is rated for 5A up to 30V and costs $73AUD.

New 30V 5A Variable DC Power Supply Digital Display Lab Grade Adjustable




Considering how cheap they are I am obviously quite skeptical of the quality. Sure enough,
a post on EEvblog states that this particular model has a fare amount of overshoot.

Be aware: Yihua YH-305D bench PSU

Bearing this in mind there is also another post which indicates that the more expensive
10A iteration of this particular PS has much less overshoot.

Yihua 305D, 3010D.. Myth?

Should I risk the potential overall quality issues and purchase the 10A version
or is there another viable option without shelling out hundreds of bucks?

I think if you search more on eBay you can find some good ones for less than $100, but off the top of my head I cannot remember if they ship to your location. Thanks

Yeah sure... Like what for example? As you can tell I am not well versed in this area at all.

Perhaps some members here have a specific brand or model which has been proven reliable?

Search for "power supply" in the google box below. There are a number of threads on this subject already.

Thank you for the advice Bionic,

However, you are forgetting that unfortunately I live in Australia. That means two things. One, is that all the suggestions made by
yourself and Cyparagon in previous threads from the likes of Agilent, Maxtech, Lambda, Leader, Xantrex, Sorenso, Kepco etc are all
American companies, meaning that in order to purchase one, I would end up paying in excess of $100 just for shipping, not to mention
the plummeting Australian dollar. Two, is that the majority of the aforementioned power supplies are based on Linear AC to DC
circuitry's. Besides from the inherent inefficiency's associated with Linear power supplies, unlike switch-mode PS's they also have
a very limited input range, meaning that any linear power supply that was designed to run off 110VAC, will require the transformer
caps to be changed in order to accept 240VAC. Something which I do not have the skill to perform.

Bionic-Badger said:

Search for "power supply" in the google box below. There are a number of threads on this subject already.

Click to expand...

In regards to your comment I am quite against the classic "This has been discussed countless times, use the search bar!" response
(there are of course exceptions). It severely limits the amount of constructive threads that surface each day and the few threads
that are available on a particular subject become severely outdated. The majority of threads that came up under "power supplies"
where more than three years old, not to mention the vagueness of the terms suggested to search.

Or perhaps I should be shot down for having the audacity to request that someone
should take the time out of their day to answer such a ridiculous question...


Perhaps I should be slightly more specific when asking questions...

I would like to purchase a variable power supply that I can use to power LD's, LED's up to 10A and DC motors up to 30V.
For those specific requirements I assume that a linear power supply would be best due to its reliability, lower electrical ripple
and higher transient response (compared to switch-mode power supplies). However, the Australian ebay market is
extremely scarce of linear variable power supplies and scarcer still of name brand companies.

Besides from the dual output, how does this stack up for example?

LCD Dual Output Variable Adjustable Linear DC Power Supply 30V 5A

There are a few power supplies on ebay that Cyparagon and other's have mentioned in the past, but they would set me back
in excess of $300 to get them posted to Aus. Which sucks since the power supplies below went for roughly $45USD back in 2012.

Leader 718-5D DC Power Supply 18V 5A

Agilent HP E3614A 0 8V 0 6A DC Power Supply | eBay

any decent brand/quality power supply is going to cost you upwards of $350-$500 for a 5A supply. I recently purchased this ultra cheap $60 bench supply from a aliexpress store and it looks like a winner..

this one here is even more compact and newer model.
New Design MCH K305D Mini Switching Regulated Adjustable DC Power Supply SMPS Single Channel 30V 5A Variable MCH K305D-in Voltage Regulators/Stabilizers from Electrical Equipment & Supplies on Aliexpress.com | Alibaba Group

cheap but works, until the magic smoke comes out..

Hi Sinner is correct I also found a 30V/. 5A for around 60.00 and its on the money.
Just shop around and read the feed backs . You will eventually find a good one for a great price. Make sure they come with leads, some do not. Ask the seller if they do.
Good luck and be safe glasses are not an option there a must.

I usually recommend used supplies. A quality, name-brand 10A will run you $60 if you look around on the US ebay. Hell, I was lucky enough to get a 0-5A 0-325A supply for $50 once. This won't really work for you since the selection is really small in Australia. The issue with buying chinese supplies is many of them don't give 2 shits about constant current regulation, since it's a niche requirement. My suggestion is get a scope (DSO, or something with single-shot) to accompany your PSU, so you can test it for power quality yourself.

Hook up a test load like you would any driver you're used to. Watch the current (ie shunt voltage) on the scope while fiddling with the pots, during power up, and during power down. If it's garbage, at least you'll know before popping diodes. Then write a review of your findings so others know, and buy a different supply to try again. Garbage supplies are still good enough for most other applications anyway, so it won't be a total loss. There are some decent chinese supplies out there, and even if you have to buy 5 before you get one, it'll be cheaper than buying a new name-brand supply. :undecided:

Oh, one more thing. DO NOT use the leads that come with chinese supplies, or at least check the size first. They really cheap-out on copper, often to the point of using 30awg, which throws your voltage-under-load regulation right in the trash. Buy some banana plugs and clips and make your own leads. 18awg or bigger for 5A; 16awg or bigger for 10A.

I wonder if fitting a 555 timer controlled relay with LED to the cheaper supplies which delays the output for a few seconds during the switch on phase, would solve any problems of a switch on spike, giving the uC a chance to catch up and adjust regulation? Surely there would be room inside and a suitable DC rail to hook the delay circuit up to?

Peeps playing with PSU and stuff should be able to veroboard a 555, a couple of resistors, a relay and a few caps to make this happen

Cyparagon said:

I usually recommend used supplies. A quality, name-brand 10A will run you $60 if you look around on the US ebay. Hell, I was lucky enough to get a 0-5A 0-325A supply for $50 once. This won't really work for you since the selection is really small in Australia. The issue with buying chinese supplies is many of them don't give 2 shits about constant current regulation, since it's a niche requirement. My suggestion is get a scope (DSO, or something with single-shot) to accompany your PSU, so you can test it for power quality yourself.

Hook up a test load like you would any driver you're used to. Watch the current (ie shunt voltage) on the scope while fiddling with the pots, during power up, and during power down. If it's garbage, at least you'll know before popping diodes. Then write a review of your findings so others know, and buy a different supply to try again. Garbage supplies are still good enough for most other applications anyway, so it won't be a total loss. There are some decent chinese supplies out there, and even if you have to buy 5 before you get one, it'll be cheaper than buying a new name-brand supply. :undecided:

Oh, one more thing. DO NOT use the leads that come with chinese supplies, or at least check the size first. They really cheap-out on copper, often to the point of using 30awg, which throws your voltage-under-load regulation right in the trash. Buy some banana plugs and clips and make your own leads. 18awg or bigger for 5A; 16awg or bigger for 10A.

Click to expand...

The route that you suggested appears to be the only sensible outcome considering geographical constraints.

You've given me a lot to consider, it would seem to be the wisest choice to hook up an oscilloscope to check current ripple and start-up spikes, no matter what PS I end up purchasing. Which naturally leads me to start asking more questions Such as what should I look for when buying a digital storage oscilloscope, although I won't bore you with my ridiculous questions, since it should be perfectly reasonable to suggest that I should simply google these inquiries. I won't bore you any longer with my abysmal lack of basic electronics knowledge

I'll udpate this thread when I purchase a PS and DSO and then (hopefully) post my findings in the very near future :beer:

vk2fro said:

I wonder if fitting a 555 timer controlled relay with LED to the cheaper supplies which delays the output for a few seconds during the switch on phase, would solve any problems of a switch on spike, giving the uC a chance to catch up and adjust regulation? Surely there would be room inside and a suitable DC rail to hook the delay circuit up to?

Peeps playing with PSU and stuff should be able to veroboard a 555, a couple of resistors, a relay and a few caps to make this happen

Click to expand...

I'm sure that this would definitely be feasible, although whether it would be effective or not is another matter, perhaps someone else could chime in? Either way I'm definitely not the person to ask to implement such an idea

will manners said:

...what should I look for when buying a digital storage oscilloscope...

Click to expand...

Last I checked, a Rigol product is the best for the money. It will have everything you need. Just stay away from phone-sized things; UI is terrible and they have lots of annoying limitations. Get a proper bench version.

You could try building your own power supply too. Plus, that site is out of Australia.

You might also just bite the bullet and get a decent power supply from eBay shipped from the US. Yeah, it may cost a bit in shipping, but often you'll be saving a bit on those older used PSUs or investing in something more top-notch.

If you try building your own I'd recommend trying to get an old stereo system and using the transformer in there. They're typically large and can handle good amounts of current, and often have a good amount of voltage behind them too letting you have a good range of adjustment.

Alternatively, an ATX power supply could also work too, though you'd have to build another regulator after if you wanted true 0-12 volt adjustment.

I recently bought a Siglent SPD3303D from Trio Test & Measurement in Sydney, via their eBay store. Siglent SPD3303D 195W DC Power Supply 30V 3A X 2 2 5V 3 3V 5V 3A X 1 | eBay

Yeah, it's $400... but it's dual-output, 0-35v, 0-3.2a, built in series/parallel modes (the 3rd output is unmonitored but in theory 2.5/3.3/5.0v ~3a - good for running logic you've already tested, but not hugely useful). All of the nice things.

And coming from Trio, there's an Australian warranty too

They also sell a nice linear single-output unit for $179 - QJE 30V 5A Regulated Linear Bench Power Supply Australian Distributor NEW | eBay which I hear good things about.

The earlier revisions of the siglent had some voltage overshoot and issues with constant-current mode stability which have been resolved in the latest versions (which Trio ship)

Well over a year and a half later my hunt continues for a cheap, reliable and capable variable power supply. As one can imagine all those
requirements rarely go together... However I believe I may have found a viable option that if proven reliable enough for LD's would no
doubt have a lot of people interested! The power supply in question is the DPS5015 50V/15A variable DC/DC power supply.



These are the claimed specifications:

• Input voltage range: 6.00-60.00V
• Output voltage range: 0V-50.00V
• Output current: 0-15.00A
• Output power range: 0-750W
• Product Weight: about 222g
• Display module size: 79*43*41(mm) (L*W*H)
• Open size: 71mm*39mm
• Power module size: 93*71*41(mm) (L*W*H)
• Length of connecting line: 200mm
• Fixed hole center distance: 86mm, 64mm
• Output voltage resolution: 0.01V
• Output current resolution: 0.01A
• Output Voltage accuracy: ± (0.5% + 1 digit)
• Output Current accuracy: ± (0.5% + 2 digits)

BLF member HJK has done a very in depth, comprehensive review of this power supply and he provides mostly all
of the necessary test data that would allow us to determine whether it is suitable/stable enough for sensitive electronics.

Test/review of Power supply DPS5015 50V/15A

Additional data for the tests performed can be found here:

lygte Power supply DPS5015 50V/15A, charts

As far as my limited experience gathered these are the most relevant test values provided in the review:

Noise at 12V 1A (Vin 40V) is 10mV rms and 62mVpp
Noise at 12V 5A (Vin 40V) is 14mV rms and 148mVpp
Noise at 12V 14A (Vin 20V) is 65mV rms and 300mVpp
Noise at 12V 14A (Vin 40V) is 30mV rms and 310mVpp
Noise at 12V 14A (Vin 60V) is 65mV rms and 420mVpp
Noise at 10V 10A constant current (Vin 40V) is 32mV rms and 255mVpp

However he does not calculate mA rms or mApp ripple... Which I would think would be more relevant for us. My question is: based from the test data provided would this be able
to serve as a viable option? If yes then potentially one could have a 50V 15A variable power supply for $78 US (cost includes a sufficient DC power supply to power the buck converter.)

Switching power supplies are great for lots of power in a small package and I use them myself, but sometimes they put out spikes or transcients which can cause a problem for our laser diodes, if directly driving them off of it. I see the specs though, noise isn't very bad, maybe it will be OK. Better to buy a linear power supply, I think, but they are heavy and won't have the features this unit has at the same current capability unless expensive. It might be OK, I've used switching power supplies to drive diodes when testing etc., but one thing to be careful of and that is turning the unit on with the diode hooked up, or even a diode with a driver between it and the power supply, I killed a diode that way. These power supplies usually put out a big spike of over voltage when first turned on, regardless of the last setting. Be aware of that and you will probably be fine.

Edit: I found this statement in the review:

Notes

When using it for constant current remember never to turn it on before the led is connected

Click to expand...

That is counter that what I was saying to never to turn it on with the laser diode connected. OK, I don't know what to say now, if you buy this check what happens when you first turn it on and see if there is a voltage spike, but you might need an oscilloscope to catch it.