What do you think about these very inexpensive benchtop power supplies? - Page 1
Forum section: electronics / beginners

author: Jay112
author_rank: Regular Contributor
timestamp: November 17, 2015, 05:53:37 pm
content: Like this ($27):http://www.ebay.com/itm/15V-1A-DC-Power-Supply-Precision-Variable-Adjustable-Regulated-Cell-Phone-Repair-/321105942440Or this one ($50):http://www.ebay.com/itm/NEW-30V-2A-Digital-Adjustable-Variable-DC-Power-Supply-With-Clip-Cable-Lab-Grade-/231698395296When they are that inexpensive, is it expected that they will have problems or have very low quality?I basically only work with 12v, 5v, and 3.3v, all low amperage (<200ma). I'm just a hobbyist and don't need anything professional. It's been working fine for me to just use DC wall-warts whenever I need to work on something, but I've been thinking recently that things might be easier and faster for me if I had a stable benchtop power supply.Thanks!

author: karoru
author_rank: Regular Contributor
timestamp: November 17, 2015, 06:12:25 pm
content: This one with analog ammeter doesn't seem to have adjustable current limiting.Second one is produced (via mutual rip-off) by probably every Chinese factory that has banana sockets and LED displays at hand (under different brands), so you results may very much vary. You can see plenty of teardown of these pearls of engineering on Youtube:)The thing is, you can do awesome stuff even using a basket of wall-warts. You can also build your own one if you know what you're doing (and even if you have a good supply, for a hobby project build another one - not with LM317 and few pots, go like a real man with beefy transistor, few opamps and all that stuff, much fun troubleshooting why it oscillates:)). You can also use these Wang Hung Lou (sorry if I've misspelled, I'm bad at imitation Chinese dialect pinyin) bench power supplies, but remembering small things like "this one has big noise on low voltages, and that one has nasty spike when switching transformer windings, and overheats if used at full power" (for example) is rather counterproductive. One semi-decent will stay with you forever (excluding some occasional repairs;p). I don't say "get Rigol with big-ass display, GPIB, USB, STD, numeric keypad and assortment of fancy knobs", just something a bit better than cheapest (there are many recommendations on this forum) that you can trust.

author: KL27x
author_rank: Super Contributor
timestamp: November 17, 2015, 08:56:28 pm
content: Go for it. Sure, they might work great. At the price, it's worth a shot. Current limiting is nice for certain tests and/or for charging batteries, but in general you can do just fine without it.

author: Jay112
author_rank: Regular Contributor
timestamp: November 17, 2015, 09:02:13 pm
content: Thanks for the responses, guys! I appreciate it!I stumbled upon this thread just now:https://www.eevblog.com/forum/reviews/b3603-dcdc-buck-converter-mini-review-and-how-the-set-key-could-be-fatal/,and it seems like another decent option. It looks like those can be found on ebay for $12.50! Plus I love the small size factor, and I'm guessing it'll be suitable for my applications as long as I only use it for lower-current devices.

author: Howardlong
author_rank: Super Contributor
timestamp: November 17, 2015, 09:16:42 pm
content: Depending on what you're doing, current limiting might be essential or at the very least save your DUTs from yourself! As a matter of course, I set both current and voltage on PSUs when usng them. Saves me from all sorts of potential disasters, mostly self inflicted.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: November 17, 2015, 09:52:05 pm
content: Quote from: Jay112 on November 17, 2015, 05:53:37 pmYou should rather go for this one. Current limiting is a very useful feature, if not essential.As a first application, you can charge lipo batteries.This unit also has fine and coarse tuning, which is what you want.Of course, the quality will not be very high, but you probably can do a lot with it, and as most probablyits all through hole components, so if even it breaks down, you will be able to fix it easily.

author: Jay112
author_rank: Regular Contributor
timestamp: November 17, 2015, 09:56:52 pm
content: Thanks! I'll definitely knock the $27 unit off my list.

author: rx8pilot
author_rank: Super Contributor
timestamp: November 17, 2015, 10:00:37 pm
content: I would quit electronics if I did not have current limiting supplies.As for these cheap and random pcs, I would say keep your expectations very low. I have a pair of different but similar supplies. In general they do what they should but with some critical flaws.1. Noisy. This can be mitigated with some front-end filtering on your circuit. Not a hug limitation unless you are doing circuit with fast and delicate analog or something.2. Poor step response. If your circuits have dynamic current characteristics, you may see voltage swings beyond your liking.3. Scratchy pots. This is by far the worst in mine. After using them for a bit, the cheap pots get scratchy causing big voltage spikes on the output that can damage your circuit. I thought for a second I was going to replace them, but started to realize that some old HP supplies could be found on eBay for super cheap if you are patient.A decades old HP for a $100 is FAR better than any brand new $50 unit.

author: rdl
author_rank: Super Contributor
timestamp: November 17, 2015, 10:06:32 pm
content: I've been meaning to buy one of those cheap ones. Last time I looked they were going for $35. At $27, it's probably worth getting one just for the parts. That metal case could easily be re-purposed.I have two HP power supplies, one Tektronix and one BK Precision. All have current limiting. It's nice to have at least one supply that has it, but you can easily get by without it. I went 5 years using just a home made LM317 supply when I first started and never felt I was limited or missing anything.

author: Jay112
author_rank: Regular Contributor
timestamp: November 17, 2015, 10:14:12 pm
content: Thanks for the input, rx8 and rdl!I'm just a beginner, and most of my powering needs involves powering Arduino-type units (both 5v and 3.3v), or messing around with old random/broken 12v parts, or testing out basic transistor circuits. My last project involved using/testing a 5v SSR for my first time, and my current project involves using a ACS712 current sensor for letting me know when some 250-watt heat lamps burn out and stop drawing current.With such basic needs, and knowing that I'll probably be continuously expanding my equipment as I learn more, I'm guessing I'll be fine to start out with one of the cheaper ones. On the B3606 (like this one:http://www.ebay.com/itm/B3603-DC-Digital-controlled-Constant-Current-Voltage-Adjustable-Step-Down-Module-/252121912140), is the current-limiting feature somehow inferior to the one like on the $50 unit above (besides the lack of convenient knobs)?It seems there's a great community here. I first found this forum by studying about oscilloscopes, because I want to get my first one soon (I currently have my eyes on the Rigol DS1054Z).

author: rsjsouza
author_rank: Super Contributor
timestamp: November 17, 2015, 10:16:23 pm
content: If I were in the market for a power supply I wouldn't pay $50 for the second power supply when I could getthis HPfor just $25 more... Or eventhis Power Designsfor $30 + shipping. There are other very decent brands that are also sold for very competitive prices...

author: mtdoc
author_rank: Super Contributor
timestamp: November 17, 2015, 10:30:05 pm
content: I have one of the first ones ( $27). I bought it to use when away from the basement lab. It's on my desk in the house where I sometimes do breadboarding or other small scale projects.It works just fine and is a good value IMO. It has a very small footprint and is quiet (no fan) which made it perfect for my application.True, no adjustable current limit but it limits itself at 1 amp and an alarm goes off when it does. This has saved my butt a few times!It also has a nice extra feature which is it has a voltmeter as well. The meter and voltage setting on mine read about 0.1 V off though. Still, just fine for breadboarding, etc.

author: klunkerbus
author_rank: Unknown
timestamp: November 17, 2015, 10:47:25 pm
content: Quote from: rsjsouza on November 17, 2015, 10:16:23 pmAlthough I would question the seller on why the item condition says *power supply not included*

author: Yansi
author_rank: Super Contributor
timestamp: November 17, 2015, 11:24:59 pm
content: I don't know about the first one, but the second one, branded by thousand different names is fuck*ng pure shit. I have had one of those at home some time ago. I have photographed the internals. Disgusting cheap construction, absolutely no heatsink (the aluminium plate without any fins can't be called heatsink), all potted in red gunky stuff, wire insulation damaged by hand soldering of some components... Just ugly!And also, the potentiometers died quite quickly in there. Dunno if it was a bad solder joint or bad wiper contact. (maybe both)If I find the photos, I will post a "teardown" as a red flag for anyone, who'd like to buy this evil supply from hell.

author: wraper
author_rank: Unknown
timestamp: November 17, 2015, 11:39:29 pm
content: Both are junk, especially more expensive one.

author: xani
author_rank: Frequent Contributor
timestamp: November 18, 2015, 01:16:32 am
content: I had the second one.Current limiting lowest limit were somewhere above 0.5 A which is basically useless. And after few tests it just... stopped limiting current. Fan was also pretty loud and ofc without any PWMBut on the plus side output voltage was surprisingly noiseless and very small overshoot on powering on.

author: Yansi
author_rank: Super Contributor
timestamp: November 18, 2015, 01:32:33 am
content: xani: 0,5 amp minimum current limit means eaxactly the "FINE CURRENT" potentiometer being damaged. Had the same problem occuring, but minimum was as I remember 0,48A. But most like it is the same issue.Also other problem I've had was that the max output current wasn't 5amps but only 4,67 or thereabout.Yes, the fan is only switched on-off by using a bimetal thermostat mounted on the "heatsink" plate with the two 2N3055 chinese fakes. (Hilarious was that each one was a different ripoff brand marked).The heatsink gets astronomically hot. Longer periods of high current draws ar a big no with this supply!

author: ez24
author_rank: Super Contributor
timestamp: November 18, 2015, 02:04:47 am
content: There are a lot of discussions on this forum on Power Designs and lots for sale on ebay. Hard to find a better unit and hard to find one that does not work (but possible). Search on "power designs power supply"If you have time shop around for one on ebay. If possible get the seller to plug it in and turn the voltage dial and tell you what happens. Got two good units this way.These are quality units (especially the 2020) whereas the ones you are looking at are pure crap Just goes to the trash.Just know that 4005 means 40v .5 amps and 4050 means 40v 5 amps. So XXYY means xx voltage and YY ampsFor example here is a 32v 4amp (3240) for $60 totalhttp://www.ebay.com/itm/Power-Designs-Inc-1-32-VDC-O-4-Amps-DC-power-supply-Used-works-great-/191390426504?hash=item2c8fc22588:g:UaMAAOSwQJ5UTN6~

author: MarkF
author_rank: Super Contributor
timestamp: November 18, 2015, 02:17:46 am
content: I bought twoHP 6216A0-30V @ 500mA power supply from eBay. In the $30 to $60 range with shipping.orYou may like aHP 6234ADual Output

author: ez24
author_rank: Super Contributor
timestamp: November 18, 2015, 03:03:41 am
content: At least you know HP were made by humans. Since there is no known history of PD, I would not bet they were made by humans.

author: rx8pilot
author_rank: Super Contributor
timestamp: November 18, 2015, 03:10:02 am
content: Even as a hobby, I would consider staying away from the bottom of the barrel crap.Here is why: Your time is worth more. I hear many people saying, "It's just an Arduino....." or something similar. The reality is that you spend time and money putting a project together for fun or to learn something. If the PSU or any other piece of gear is bad enough to to cause problems that will distract you or destroy the project - its simply not worth it. I would wait, save more money or hunt for an eBay gem. That way, the learning part of your experience is not focused on what happens when you use a crap PSU and your project 'sorta kinda' works. You may spend a ton of time chasing down a problem you think is in software or your bread board only to find out that when you barely turned the 'FINE VOLTAGE' knob the scratchy pot blasted a 13v spike into your microcontroller.Anyway, I have come up as a life long low budget hobbyist from about 6 years old when I got my first radio kit. I learned to scale my projects and ambitions to my modest budget.

author: JoeB83
author_rank: Regular Contributor
timestamp: November 18, 2015, 04:31:24 am
content: Quote from: ez24 on November 18, 2015, 03:03:41 amWhat?

author: mtdoc
author_rank: Super Contributor
timestamp: November 18, 2015, 05:12:05 am
content: I own 5 HP power supplies and 2 (soon to be 3!) Power Designs supplies. I would never advocate someone buying a cheap Chinese supply if they can afford and have the bench space for a high quality supply.That said - the first supply listed is $27 shipped and is well worth that money in my experience. It will be perfectly adequate for 99% of low voltage, low current hobbyist projects and is certainly better than mucking around with batteries, wall warts or modified ATX supplies.Cheap, budget gear does have its place for many - the trick is to weed out the total crap from the just cheap but adequate stuff that provide good value for the low price. My experience with one of those $27 supplies is that it fits in the second category. YMMV.

author: dom0
author_rank: Super Contributor
timestamp: November 18, 2015, 11:59:25 am
content: Quote from: JoeB83 on November 18, 2015, 04:31:24 amI think he refers to the uncannily low output noise of some power designs units. Some have like 100 µVpp over a dozen MHz and were built in the beginning 60s. It's like - how did they even measure that back then?!

author: daqq
author_rank: Super Contributor
timestamp: November 18, 2015, 12:42:06 pm
content: I would say, that in a world where you can buy a working usedHPAgilentKeysight 6632 (and similar) for 200 USD on ebay you should save up and avoid questionable items like the ones you linked.http://www.ebay.com/itm/HP6632B-DC-power-supply-20V-5-A-/351569622176?hash=item51db2eb4a0:g:g8AAAOSwDNdVwe1DIf your only target application is to power a simple device for a limited time (just power, no fancy stuff, like, say, measurement) then they might be OK. But I'd avoid them for anything more complicated, certainly not as a lab power supply. I've seen some nasty stuff from power supplies like these - ammeter totally off (10% error), spikes and glitches when turning on, furious relay clicking...

author: Jay112
author_rank: Regular Contributor
timestamp: November 18, 2015, 01:11:24 pm
content: Thanks everyone for the excellent information and advice! This forum is really exceptional! And thanks for the ebay links!I'll probably wait a few days to let all this sink in, before purchasing anything. I'll also keep an eye on ebay deals.

author: rdl
author_rank: Super Contributor
timestamp: November 18, 2015, 01:27:09 pm
content: Here is a link to the only review I found on youtube. At least you can get some idea of what this power supply is like. Though as usual with low cost electronics from Asia, it would be a good idea to check it for serious problems before use.While a used HP or similar is better in many ways, something like this can still be useful. It's small, quiet, very low cost, and maybe good enough. It depends on what you actually need.

author: ez24
author_rank: Super Contributor
timestamp: November 18, 2015, 08:28:02 pm
content: QuoteAliens have different test instruments than humans do. This is why PD disappeared from written history (only aliens have the power to make history disappear).My guess is they used their PDs to make ships to return home and they left. My PDs will be worth a fortune if this is ever proven. Can DNA be found inside power supplies?

author: JoeB83
author_rank: Regular Contributor
timestamp: November 19, 2015, 05:59:37 am
content: Quote from: dom0 on November 18, 2015, 11:59:25 amI see what was meant now, thank you!

author: karoru
author_rank: Regular Contributor
timestamp: November 19, 2015, 03:52:34 pm
content: Quote from: rdl on November 18, 2015, 01:27:09 pmIt spikes the voltage and then cuts out on overcurrent? Seriously? Even my USSR-made el cheapo 15V, 1A lab power supply made in 80s without a single IC inside (not even an opamp) will work as constant current when it's set to too big voltage.

author: Jay112
author_rank: Regular Contributor
timestamp: November 21, 2015, 03:02:39 am
content: I ended up buying the $27 unit, and also I was the highest bidder for a new B3603 so I got one for $8 ($7 shipping, $1 bid). I'll probably play around a little with these before deciding if I need something better.Thanks everyone for your replies and suggestions!

author: mtdoc
author_rank: Super Contributor
timestamp: November 21, 2015, 03:48:08 am
content: Quote from: Jay112 on November 21, 2015, 03:02:39 amThat's a nice low budget combination. I bet it will last you longer than you expect - that is unless you catch the vintage power supply collection bug that infects some of us...Julien Ilett hason the b3603.

author: Jay112
author_rank: Regular Contributor
timestamp: November 21, 2015, 04:04:30 am
content: That was an awesome video review! Thanks for sharing!

author: nbritton
author_rank: Frequent Contributor
timestamp: November 21, 2015, 02:20:26 pm
content: http://www.aliexpress.com/item/DP30V3A-Constant-Voltage-and-Current-Step-down-Programmable-Power-Supply-Module-Buck-Voltage-Converter-LCD-Display/32254182789.html

author: nbritton
author_rank: Frequent Contributor
timestamp: November 21, 2015, 02:42:12 pm
content: Quote from: Jay112 on November 21, 2015, 04:04:30 amhttp://www.aliexpress.com/item/B3603-Precision-CNC-DC-DC-Constant-Voltage-Constant-Current-Buck-LED-Driver-Module-Solar-Charging-Power/1625052409.htmlWith an Arduino I'm thinking you could easily mod three of these boards together to make a triple output power supply.

author: AlessandroAU
author_rank: Regular Contributor
timestamp: November 24, 2015, 02:37:03 pm
content: Quote from: rdl on November 18, 2015, 01:27:09 pmThat's actually my video.I still have and use the power supply, its pretty lacklustre, but for the price I paid I can't complain. Sometimes you just want to power up a led strip or a PC fan independently.It can't handle much current, that being said I run to to where the transistor on the back could boil water and it still hasn't died.

author: jpasqua
author_rank: Newbie
timestamp: November 29, 2015, 05:20:07 am
content: I've tried both of the small units pictured above (or variants thereof). As it turns out, the Minghe B3603 (the one reviewed by Julien Ilett) happens to fit perfectly into a display case for a hockey puck. Sounds weird, but I happened to notice these boxes while looking for something else. I just drilled a couple of holes to access the control buttons, added binding posts, and a barrel connector for power in.For the DP20V2A (variant of the DP30V3A pictured above), I was able to add binding posts directly to the case and I ran wires out the back for power in via a barrel connector.Neither of these units have great user interfaces, but both have worked well so far for undemanding tasks.

author: nbritton
author_rank: Frequent Contributor
timestamp: November 29, 2015, 06:37:10 am
content: Quote from: jpasqua on November 29, 2015, 05:20:07 amWhich one do you like better? The DP30V3A is over double the price of the B3603, is it worth the extra cost? I was thinking of buying three B3603 and modding them into one triple channel PSU with the help of an Arduino. What buck converter chip is used in the DP30V3A?

author: nowlan
author_rank: Frequent Contributor
timestamp: November 29, 2015, 12:57:54 pm
content: doesnt that ebay switcher have a really long/slow ramp to set point?

author: jpasqua
author_rank: Newbie
timestamp: November 29, 2015, 05:55:18 pm
content: Quote from: nbritton on November 29, 2015, 06:37:10 amFor my use case a couple of B3603's are a better value than a single DP30V3A. I don't have my DP20V2A apart at the moment so I can't tell you what chip it uses.If you are looking for something you to mod, please check out this github repo:https://github.com/baruch/b3603. A ton of work has been done to reverse engineer the B3603. There is also work on alternative firmware.