Advice on a Bench Supply (£100 limit) - Page 1
Forum section: electronics / testgear

author: CpHarding
author_rank: Contributor
timestamp: February 26, 2015, 12:57:42 am
content: Hi guys, i'm looking to upgrade my bench supply (currently using a converted ATX Psu)I'm seeing alot of what look like cheap chinese stuff around at the sub £100 mark, but hard to get a feel for quality until you get to hold them and test the output.something like this will probably be what i'll go for unless someone can point me at a better product or a reason why I shouldn't go for this!http://www.amazon.co.uk/Bench-Supply-Switch-Adjustable-3003SM/dp/B00BCME5AQ/ref=sr_1_1?s=diy&ie=UTF8&qid=1424910757&sr=1-1&keywords=dc+bench+power+supply#productDetailsorhttp://www.ebay.co.uk/itm/DC-Bench-Power-Supply-Adjustable-Voltage-Variable-Current-Limit-3Yr-Warranty-/161558312612?pt=LH_DefaultDomain_3&var=&hash=item259da036a4Any advice welcome!

author: radhaz
author_rank: Regular Contributor
timestamp: February 26, 2015, 04:07:11 am
content: Have a look at this one:KORAD KA3005DIt's a linear, and has an output on/off switch.

author: Obin
author_rank: Contributor
timestamp: February 26, 2015, 09:09:45 am
content: +1 on the korad, I use them in the lab at our school.Look on local second-hand websites, i managed to score a triple output supply for 80 euros onceedit: The one from the second link looks fine thoughhaving a spare 5V out can always come in handy

author: EEVblog
author_rank: Unknown
timestamp: February 26, 2015, 10:27:37 am
content: I'd look for a 2nd hand unit, like this:http://www.ebay.co.uk/itm/THURLBY-THANDAR-PL320QMD-TWIN-POWERSUPPLY-/151598123010?pt=LH_DefaultDomain_3&hash=item234bf3c802orhttp://www.ebay.co.uk/itm/GW-Instek-GPC-3030DQ-Bench-Powersupply-3CH-30V-3A-1-Fixed-5V-3A-/181671176569?pt=LH_DefaultDomain_3&hash=item2a4c722979

author: Fungus
author_rank: Super Contributor
timestamp: February 26, 2015, 10:29:17 am
content: Quote from: Obin on February 26, 2015, 09:09:45 amIsn't that the one that failed miserably in Dave's test?https://www.eevblog.com/forum/blog/eevblog-315-korad-ka3005p-reviewfail/

author: EEVblog
author_rank: Unknown
timestamp: February 26, 2015, 10:38:39 am
content: Quote from: Fungus on February 26, 2015, 10:29:17 amThey fixed it. But I haven't retested it. People have confirmed it though.

author: tmbinc
author_rank: Frequent Contributor
timestamp: February 26, 2015, 11:14:26 am
content: Agilent 6632B can be ridiculously cheap; I paid ~150EUR+shipping for mine. They are 0-20V, 0-5A, have OCP (i.e. they can be set to switch off instead of going into CC), and they can sink current. They are also programmable (GPIB and RS232). They are generally very awesome, especially for their money.Be warned though: they are _loud_. At least compared to the E3646A that I have. And they aren't very efficient (apparently by design).For day-to-day stuff though I have two E3646A simply because they are not as loud, but I think I paid ~200EUR for each, so they are out of range. And they don't have a lot of power >8V (only 1.5A per output), and miss overcurrent protection (they still have CC of course).

author: necessaryevil
author_rank: Regular Contributor
timestamp: February 26, 2015, 11:18:00 am
content: Have you considered DIY'ing it?You can do that for 100 pounds (translated: $150) if you buy the case, the transformer and the heat sinks second hand. Use decent potmeters!A good option would be the design published in Elektor December 1982. Onfortunately, I only have the article in dutch.

author: VK5RC
author_rank: Unknown
timestamp: February 26, 2015, 11:23:19 am
content: +1 for the good but older second-hand gear, if it was good it will be full of nice stuff e.g. transformer etc and even better if you can get the schematic / service manual. HP gear e.g. 66xx 65xx 63xx etc fits the bill quite nicely but a little noisy acoustically but not electrically.

author: bookaboo
author_rank: Frequent Contributor
timestamp: February 26, 2015, 11:32:44 am
content: Quote from: CpHarding on February 26, 2015, 12:57:42 amI have the MCH-K305b and it's very stable, smooth and no overshoot or undershoot on startup. Certainly can recommend it as a base level power supply.Definitely get a linear type, i.e. one with a transformer rather than a switchmode. A switchmode will have more ripple which is not what you want for electronics work.

author: rolycat
author_rank: Super Contributor
timestamp: February 26, 2015, 12:38:19 pm
content: KJDS and TopLoser who are both UK-based members of this forum often have high quality second-hand PSUs for sale, and are both really good guys to deal with.KJDS has sold a lot of the HP/Agilent 6632B previously recommended, although he doesn't seem to have any at the moment. He does have some Statron 32V 3.2A suppliesherewhich look solidly constructed if a bit battered for just £50. Also a Weir 30V 2A supply for £75here. These may be a bit cheaper if you buy through the forum rather than via eBay.

author: KJDS
author_rank: Super Contributor
timestamp: February 26, 2015, 02:03:57 pm
content: I've got assorted power supplies lying about and am indeed cheaper if I don't have to pay ebay fees. Even cheaper if you can collect from Leicester.What we really need to know is what does the OP need, single or dual supply, voltage and current range? programmable? Size and noise restrictions?I've recently picked up some Farnell TSV 70 mk1. The mark 2 are big, and weigh 30kg. The mark 1 make the mk2 look tiny and I've yet to weight any, so if anyone wants to collect these for £35 each then it's a great 35V 10A or 70V 5A linear supply without a fan to make any noise.I've still got a couple of HP6632A hiding somewhere, excellent accuracy, the lcd display isn't quite as nice as the VFD on the HP6632B but they are still great if noisy displays. There's a few more of various others about too, depending on requirements.

author: rdl
author_rank: Super Contributor
timestamp: February 26, 2015, 03:19:16 pm
content: If you buy used, and I certainly won't recommend it, be sure you get a warranty and right of return on the seller's dime. Be sure you get plenty of time to test it. Many used power supplies have problems that don't show up in the typical eBay testing (powers on and voltage is close to what my multimeter says). I've bought a number of used power supplies on eBay and about half suffered from defects that don't show up in that kind of "testing", yet all were advertised as "works perfect", "great condition", "excellent working order", etc.

author: Fungus
author_rank: Super Contributor
timestamp: February 26, 2015, 03:26:04 pm
content: Quote from: VK5RC on February 26, 2015, 11:23:19 amOnly problem is they tend to be massive/heavy. For people with plenty of space only.

author: dom0
author_rank: Super Contributor
timestamp: February 26, 2015, 03:33:17 pm
content: That is really a thing of the system supplies, because they always come in the 19" × 400-600 mm form factor.OTOH there is plenty of other gear 19" or half-width 19", so it makes a lot of sense to have space for at least one '19" tower'.But I'd personally wouldn't buy system supplies for everyday use. Not because they're too pricey (they aren't) or because their performance is lacking (it is most definitely not!), butsimply because they are all loud- at least older units. Because they're designed to run at ambient temperatures of 50+ °C...However, if you find yourself to need much power, and have it nicely regulated too, then those system supplies are a no-brainer, really. Also, if you need accurate, programmable supplies, then there isn't much around these, especially since there are units with multiple channels, some even with independent (isolated) channels...!Older bench-top supplies are usually not _much_ larger than a bench supply of today, at least if both are indeed of the same specs and technology (i.e. linear). Todays units are a bit smaller, tough, because they often come in the "slim" form factor (more tall than wide). OTOH: if you put two slim units side by side or stack two wider units on top of each other - not really a big difference.

author: 6sigma
author_rank: Newbie
timestamp: February 26, 2015, 04:47:18 pm
content: Quote from: Obin on February 26, 2015, 09:09:45 amLooking for something similar to the OP, I'm curious about the convenience vs. necessity of a dual or triple output supply for most/many hobbyists. Two questions, how often or what kinds of projects make a dual or triple output supply necessary and, other than bench space, how is a dual supply superior to a pair of single output supplies?Thanks...the answers will point me (USA) to the Korad OR Agilent E3610A OR E3620A/30A.

author: dom0
author_rank: Super Contributor
timestamp: February 26, 2015, 05:02:51 pm
content: Analog/mixed signal circuits often need at least one digital supply and one higher analog supply, or a symmetric analog supply (although the industry trend is to use single supply of/c).Dual supply gives you automatic tracking, which is not possible with many single channel supplies.

author: CpHarding
author_rank: Contributor
timestamp: February 28, 2015, 09:51:51 am
content: wow guys, thanks for all the help!I live in a small ish flat, so size is a concern. For my expected usage, a single output would be enough, and I know going dual supply will increase the cost! (but would be nice). As for voltage and power, I don't currently do anything with high power, so anything up to about 20V would probably be OK with current limit of more than 2AI like the look of the Instek GPC-3030DQ, sensibly sized, more than enough power and 2 variable +1 fixed output. I wonder how much the price will go up before it sells though.I've thought about DIY-ing it, but I have so many projects on the go at the moment, time is a issue, along with wanting something I know will work!I'll have a proper look at all the ones you've suggested, and i'll let you know what I go for.Thanks alot guys!

author: AnalysIR
author_rank: Contributor
timestamp: February 28, 2015, 11:53:25 am
content: QuoteDon't know, but I am planning to bid on it.....given that its local...at least I know your budgetsmall world.

author: CpHarding
author_rank: Contributor
timestamp: February 28, 2015, 11:16:22 pm
content: Quote from: AnalysIR on February 28, 2015, 11:53:25 amHaha may the best man win!

author: Pasky
author_rank: Regular Contributor
timestamp: March 04, 2015, 10:40:10 pm
content: Can the Korad KA3005D do negative voltages as well?

author: dom0
author_rank: Super Contributor
timestamp: March 04, 2015, 11:07:23 pm
content: Quote from: Pasky on March 04, 2015, 10:40:10 pmCan a battery do negative voltages as well?

author: Pasky
author_rank: Regular Contributor
timestamp: March 05, 2015, 03:04:51 am
content: Forgive me, I've never used a bench power supply. I wasn't sure if there was any limitations on them, reading up on it I see more or less how they work now.

author: dom0
author_rank: Super Contributor
timestamp: March 05, 2015, 09:06:21 am
content: Quote from: Pasky on March 05, 2015, 03:04:51 amNo, I just wanted you to think for yourself and not just accept something someone said in some forum

author: Fungus
author_rank: Super Contributor
timestamp: March 05, 2015, 09:23:50 am
content: Quote from: Pasky on March 05, 2015, 03:04:51 amIt's nothing to do with the power supply, bench or otherwise.*Any* voltage source can be positiveornegative, depending on how you connect the wires.

author: jpb
author_rank: Super Contributor
timestamp: March 05, 2015, 10:02:51 am
content: Quote from: Fungus on March 05, 2015, 09:23:50 amThat is true for floating supplies and batteries. It may not be true for a power supply with one terminal earthed being used to power a circuit which is also earthed - or could lead to some confusion if the circuit is being measured with a scope that is earthed.The bench supply that I use (TTi320QMD) has a separate earth connector so either terminal can be earthed but I'm sure some cheaper supplies don't. It may be that all supplies are floating - this isn't true for AWGs where some are and some aren't.

author: BillyD
author_rank: Regular Contributor
timestamp: March 05, 2015, 10:22:36 am
content: Recommend those Thurlby Thandar supplies as well, something like this:http://www.ebay.co.uk/itm/THURLBY-THANDAR-PL-154-15V-4-AMP-LABORATORY-POWER-SUPPLY-/400875312567?pt=LH_DefaultDomain_3&hash=item5d5607d5b7These come up very regularly on ebay.co.uk, often around £50 to £60 for the single channel units.Simple, silent, reliable and not too big.Note that there are a few different models - 15v/30v , 1A, 2A, 4A, etc - and the example above is 15V, so be sure the specs suit you.

author: Ericho
author_rank: Regular Contributor
timestamp: March 05, 2015, 10:49:14 am
content: I would advice on a double supply for a starterI got an older version of the LABPS23023, you can find this close to £100 (they are €149 in Belgium)Heavy and bulky, no fan, specs OK for the price, multiturn pots.I have 2 single and 2 tripple supply's and still feel I running out of supply's at times, So don't worry to much about it. In time you'll end up building or buying a few more anyway.

author: Fungus
author_rank: Super Contributor
timestamp: March 05, 2015, 10:55:06 am
content: Quote from: jpb on March 05, 2015, 10:02:51 amNo, it's true for all power supplies.Quote from: jpb on March 05, 2015, 10:02:51 amIn that case you'd connect the common ground (or the scope's earth clip) to the 'positive' supply rail.Thought and care may be needed, yes.(And please correct me if I'm wrong in saying that most/all bench supplies are either isolated or have a way of isolating them...)

author: KJDS
author_rank: Super Contributor
timestamp: March 05, 2015, 11:05:15 am
content: Whilst most bench supplies have isolated outputs, it's not that unusual for big switchers to have one output tied to mains ground, in which case you just can't connect the other one to ground.

author: sainter
author_rank: Regular Contributor
timestamp: March 05, 2015, 01:35:09 pm
content: Quote from: radhaz on February 26, 2015, 04:07:11 am+1 on KA3005D, i bought it as my first power supply and I'm very happy with it. Memory is very useful, easy voltage and current setting. About the one Dave had, if i remember correctly, he had the wrong model for the country. I never had any problems with mine.

author: Fungus
author_rank: Super Contributor
timestamp: March 05, 2015, 01:44:00 pm
content: Quote from: KJDS on March 05, 2015, 11:05:15 amMoral: Check before you buy. Don't buy a 'big switcher' if you're going to be wiring them up for negative voltages...

author: dom0
author_rank: Super Contributor
timestamp: March 05, 2015, 01:52:07 pm
content: The grounded secondary on many industrial-type SMPS has mainly safety (insulation) and EMI reasons. Floating SMPS usually have a self-healing etc. capacitor to achieve a similar effect ("stitching capacitor"). You'll need similar measures with inductive isolators, btw.

author: engiadina
author_rank: Contributor
timestamp: March 19, 2015, 10:33:56 pm
content: Just what I did ...I bought a bunch of Agilent E3610A, about 140€ each. Quiet, reliable, good for everydays work, dont take too much space.We have a couple of 6632B as well, they did cost about the same. Way better meter, remote controllable, huge, loud and reliable.I would miss both of them ...Guido