Lab power supply - which of these would you pick? - Page 1
Forum section: electronics / testgear

author: radian
author_rank: Contributor
timestamp: May 02, 2013, 03:08:20 am
content: Hi all,I'm looking for a cheap lab power supply to get my bench up and running. I'm mostly interested in using the supply for microcontroller-based projects, spinning up motors, etc. Your basic hobbyist projects I suppose. Ideally the PSU should be as quiet as possible. I live in Canada, so the selection of power supplies are a bit limited. From my research thus far, I think I've narrowed it down to three units:1) 30V, 5A - $58 (https://www.circuitspecialists.com/i-181791.html). Looks like a decent option. I like the form factor. A bit worried about the maximum "8 hour continuous operation time", and the obvious lack of reviews, so no guarantee on performance. Seeing as how it's a switching supply, could be harder to debug if anything were to go wrong. Should be a quiet option.2) 30V, 5A - $63 (http://www.ebay.ca/itm/30V-5A-Digital-Precision-DC-Power-Supply-Adjustable-Stable-Lab-Grade-305D-New-/121092425979?pt=LH_DefaultDomain_2&hash=item1c31abc8fb&_uhb=1#ht_2369wt_1305). A popular choice on eBay. There seems to be hundreds of these units for sale. I've read mixed reviews, but being linear, probably would be easier to debug if anything were to go wrong. May end up being quite noisy.3) 18V, 2A - $50 (https://www.circuitspecialists.com/bench-power-supply-csi1802x.html). Looks like a Mastech rebadge. I've heard decent reviews on Mastechs. Nice that they include the circuit diagram, that's great. Not a fan of the output voltage and current, but I could live with it. Perhaps a silent option? No fan in the schematic that I see.Thoughts? Which would you chose? Thanks!

author: wraper
author_rank: Unknown
timestamp: May 02, 2013, 05:55:20 am
content: A can say that second one is complete bullshit. Such power supplies don't even have proper current limiting, they just cut output. I teared apart one of clone of such and not only it was crap which doesn't meet specs. There was fake 2N3055 transistors. I cut caps from them and crystals were 5 time smaller than genuine ones. No proper cooling, there was no proper heatsink, just aluminium plate. Even transformer was without proper insulation and with aluminium secondary winding. These are just dangerous to use. I also think that first is not better claiming such specs for $58. Third one looks better. It has proper heatsink on the back and doesn't claim impossible specs. But I personally wouldn't take any of them.

author: wraper
author_rank: Unknown
timestamp: May 02, 2013, 06:07:28 am
content: Just read specs of the first one. It's switching PSU, Ripple: 200mVp-p. Maybe It will work normally and even meet specs but with such ripple it has no use in electronics lab.

author: BillyD
author_rank: Regular Contributor
timestamp: May 02, 2013, 07:44:49 am
content: I have the first one as a secondary power supply, purely because its size and weight make it handy for swapping it between the table and floor to save space, and sometimes the fine adjustment knobs can be useful.However you mentioned it should be as quiet as possible and this one is not completely quiet. As a switchmode supply it makes that high pitched whine which is very noticeable in a quiet room and personally I can only tolerate using it for short periods! There is also a fan which is noisy but which only activates when necessary, which is not often.So for me the noise and ripple would make this unsuitable as a primary power supply, but ok as an occasional backup unit.

author: eevblogfan
author_rank: Frequent Contributor
timestamp: May 02, 2013, 06:37:53 pm
content: here some good links :1)http://www.ebay.com/itm/ONE-Agilent-HP-DC-Power-Supply-6200B-6201B-6202B-6206B-6281A-6289A-YOUR-CHOICE-/140966231030?pt=LH_DefaultDomain_0&hash=item20d23dfbf62)http://www.ebay.com/itm/HP-Agilent-6255A-Dual-Output-Variable-DC-Power-Supply-40W-1-5A-Opt-010-040-/130899265927?pt=LH_DefaultDomain_0&hash=item1e7a3449873)http://www.ebay.com/itm/HP-Agilent-6200B-Single-Output-30W-Variable-DC-Power-Supply-0-40V-0-75A-20V-1-5A-/130899887179?pt=LH_DefaultDomain_0&hash=item1e7a3dc44b4)http://www.ebay.com/itm/HP-Harrison-Agilent-6205B-DUAL-DC-Power-Supply-0-40-V-0-3-A-0-20-V-0-6-A-/140949026671?pt=LH_DefaultDomain_0&hash=item20d137776f5)http://www.ebay.com/itm/HP-Agilent-Hewlett-Packard-6237B-Triple-Output-20V-5A-18V-1A-Power-Supply-/151025358390?pt=LH_DefaultDomain_0&hash=item2329d016366)http://www.ebay.com/itm/Agilent-HP-6255A-Dual-Output-Power-Supply-0-40V-0-1-5A-/140962782704?pt=LH_DefaultDomain_0&hash=item20d2095df0there are more but that's good enough in order to provide you what you need ,I would have gone for at least 2A,15V~25V power supply , preferebly dual channelDON'T YOU DEAR TOUCHING THUSE CHEAPIES "NEW" POWER SUPPLIES ! , they are real crap , you'll regret it for sure !Cheers

author: ve7xen
author_rank: Super Contributor
timestamp: May 02, 2013, 06:47:29 pm
content: Keep in mind the 6327 doesn't have adjustable current limit.

author: eevblogfan
author_rank: Frequent Contributor
timestamp: May 02, 2013, 06:51:30 pm
content: heyyup indeed , BTW . 6237*anyhow - the power supply doesn't ment to be CC one , but simply multy CH CV power supply ( IE , It is ment to feed readily working devices like op amps and anything who needs dual tracking voltages )

author: ve7xen
author_rank: Super Contributor
timestamp: May 02, 2013, 06:59:53 pm
content: Definitely a useful supply, but especially for a beginner or a careless person (like me), CC mode is invaluable and will save your project more times that you care to count.

author: eevblogfan
author_rank: Frequent Contributor
timestamp: May 02, 2013, 07:03:44 pm
content: you are correct , BUT . CC project is nice and not too costy ( simplt mosfet op amp reference and some resistors caps and pot ) not to costy I'd say , BUT power supply is very costy . Why would you buy worse power supply *only* because it can have CC as well ? while you can get some wonderfule 3 CH power supply and simply upgread it to you're needs ?

author: ve7xen
author_rank: Super Contributor
timestamp: May 02, 2013, 07:40:46 pm
content: Convenience. The same reason you buy a 3CH supply instead of 3x1CH supplies. It's nice to have it all in one box because it means you'll actually use it, reduces clutter and cabling, you can do interesting projects instead of building the same boring project 3 times etc.Also if you put a CC limit regulator outside of the CV control loop it's going to have to dissipate power.

author: radian
author_rank: Contributor
timestamp: May 03, 2013, 12:24:46 am
content: Thanks for all the suggestions folks. I'll take your advice and pass on option 1 and 2. Option 3 I'll admit is still enticing. Eevblog fan, those used supplies look pretty nice, but the power handling is on the low side for my applications, and they look quite hefty. Current limiting is pretty important for me, as is digital displays.What do you think of Atten power supplies? For instance, for a bit over $100, I could get this:http://www.ebay.ca/itm/ATTEN-Variable-DC-Power-Supply-APS3005S-30V-5A-LAB-/160684423343?pt=LH_DefaultDomain_0&hash=item256989b8af&_uhb=1#ht_5607wt_1071A decent buy?

author: ivan747
author_rank: Super Contributor
timestamp: May 03, 2013, 02:49:56 am
content: I have seen this kind of thread before. A new member wants to get a chinese power supply for under $100. Lots of people suggest used supplies. I go for the used power supply. Almost nothing can go wrong when you have a full schematic of the power supply. These chinese power supplies are just a piece of sh!t. And trust me, I don't say that phrase often. Don't be afraid to buy test equipment on eBay. With a $50 HP power supply form the 70's there's not much that can go wrong.There's absolutely NO WAY you can get a 30V, 5A power supply (that's 150W!) in that tiny-ass heatsink:You should at least have something that resembles this:And that's a 30W power supply. Granted, it doesn't have a fan, but still. Have you seen how they mount heatsinks and fans on computer processors? Those only generate 100W tops, in most cases.There is a reason why good new power supplies cost a lot. There's heaps of metal: iron, copper, aluminium (solid and bent) everywhere. They don't cut corners.

author: Monkeh
author_rank: Super Contributor
timestamp: May 03, 2013, 03:05:48 am
content: The heatsink does not have to dissipate 150W..

author: c4757p
author_rank: Super Contributor
timestamp: May 03, 2013, 04:13:01 am
content: Probably near 75W though at low output voltages and high output currents, and that heatsink isn't going to do 75W either.I know that many (even decent) power supplies cannot handle driving a short for very long, but I still personally think it shouldalwaysbe operable within its specified range, and certainly not able to self-destruct. If it can't handle that kind of dissipation, it had better damn well have a thermal cutoff, and I can say from experience that those turds do not have one.

author: staxquad
author_rank: Frequent Contributor
timestamp: May 03, 2013, 04:21:56 am
content: Quote from: Monkeh on May 03, 2013, 03:05:48 amThe HP 6002A needs 480 watts input to supply 200 watts output. So 280 watts of heat dissipation is required for 200 watts of output power.

author: c4757p
author_rank: Super Contributor
timestamp: May 03, 2013, 04:28:49 am
content: Does it really need 480W input for that, or is that just the listed power input? Those often seem to be quite pessimistic.

author: staxquad
author_rank: Frequent Contributor
timestamp: May 03, 2013, 04:48:23 am
content: Quote from: c4757p on May 03, 2013, 04:28:49 am

author: eevblogfan
author_rank: Frequent Contributor
timestamp: May 03, 2013, 07:42:52 am
content: heyOP - the reason I told you to but those oldi(SH) power supply is the quality , those "new" cheap atten or whatever is total crap , you better buy some HP6002 for higher power stuff rather then buying stupide atten , Ind I can tell you for sure that the atten transformer is about 100W , they are abusing the damm thing in order to squeez 150W out of it ( actually more like 172.5W on the AC side ) and I can tell you that within 1 Hr the transformer will be dead !you better build your own HIGH power supply *just* for that particular project ( some PWM motor controller ? ) . you need only one microwave oven transformer ( MOT) and a bit of knowledge in order to rewind the thing and adding some 20 turns to the primary in order not tu freaking burn thee damm thing , and then build your own high power regulator , it can be very fun and I can tell you , it will be around 100$ or even lessGood luck

author: ivan747
author_rank: Super Contributor
timestamp: May 03, 2013, 10:48:22 am
content: Quote from: Monkeh on May 03, 2013, 03:05:48 amThe HP won't dissipate 30W either (it has 2 modes with 2 transformer taps). Still, it cannot dissipate a whole lot of power.Edit: it can dissipate 30W, but I doubt the Atten will have more than 4 taps. (more taps means more control over the input voltage that goes though the pass transistors and more control over power dissipation). There are some traps in tap switching, specially if it is done by software. Just watch what happened to Dave with the Korad supply.

author: nctnico
author_rank: Super Contributor
timestamp: May 03, 2013, 11:51:31 pm
content: Switching between transformer windings or using an SCR are very old tricks (also seen in HP power supplies). So a small heatsink may suffice.

author: nctnico
author_rank: Super Contributor
timestamp: May 03, 2013, 11:59:45 pm
content: Quote from: c4757p on May 03, 2013, 04:28:49 amNo. I have a HP6002A and it doesn't need 480W input for sure. It is a very efficient power supply which uses several windings for different ranges of output voltages / currents. It says 600VA max. on the rear but you can't thumb-rule that to Watts.

author: radian
author_rank: Contributor
timestamp: May 04, 2013, 12:55:12 am
content: Ok, thanks everyone, I'll steer clear from those cheap supplies! The used supplies are a good option, however shipping to Canada can be quite expensive. And as much as I like the vintage analog displays, I like digital a lot more. Especially when it comes to current being drawn.Now, let's change gears a bit. I'm going to to dig deep into my pockets to get a better supply. I like Agilent as a brand, and I found this option of Newark/Element 14. They are offering a free shipping promotion, which will help a lot.http://canada.newark.com/agilent-technologies/u8001a/power-supply-dc-bench-30v-90w/dp/14N3964This is a switching supply right? Anyone have any experience with this line of supplies? I also noticed some Tektronix supplies for around $400.http://www.testequity.com/products/2579/And lastly, what about this Sorensen?http://www.testequity.com/products/2928/I think I won't mind forking over a bit more cash knowing I'll be getting something with high quality and that is properly engineered.

author: c4757p
author_rank: Super Contributor
timestamp: May 04, 2013, 01:00:27 am
content: Quote from: radian on May 04, 2013, 12:55:12 amThey don't seem to directly say on the official web page, but with those transient response and ripple characteristics (and low-ish power rating) it's got to be linear.

author: radian
author_rank: Contributor
timestamp: May 04, 2013, 01:13:53 am
content: Quote from: c4757p on May 04, 2013, 01:00:27 amAh ha, well this forum just keeps on giving! A fellow member posted a teardown here.https://www.eevblog.com/forum/testgear/review-teardown-agilent-u8001a-30v-3a-linear-power-supply/Folks replying in the thread seems to have positive words, although it sounds like the supply is on the noisy side. Hmmm...

author: wraper
author_rank: Unknown
timestamp: May 04, 2013, 01:53:25 am
content: That Sorensen is actually Thurlby EL302R.http://www.tti-test.com/products-tti/pdf-brochure/psu-elr-exr-series-7p.pdf. Should be very good power supply.

author: radian
author_rank: Contributor
timestamp: May 04, 2013, 03:20:23 am
content: Quote from: wraper on May 04, 2013, 01:53:25 amWow, I didn't know Sorensen was into re-badging too... that's a bit odd. I guess it can be expected, maybe there isn't much incentive to design power supplies from scratch.

author: staxquad
author_rank: Frequent Contributor
timestamp: May 04, 2013, 05:51:03 am
content: Quote from: nctnico on May 03, 2013, 11:59:45 pmAgilent has the 480Watts printed in the manual and the 600VA is printed on the rear of the unit. It's Agilent's specs.600VA AC = 480Watts, if the power factor is .8The 600VA tells the user what fuse to use while 480 Watts tells the user what input power is being used.Have you ever checked with a watt meter the input power required on your unit to output 200 Watts, or are you just guessing?

author: nctnico
author_rank: Super Contributor
timestamp: May 04, 2013, 09:52:50 am
content: Quote from: staxquad on May 04, 2013, 05:51:03 amI didn't but dissipating 280W with the internal heatsink assembly seems very unlikely. It would be silly for any power supply to dissipate more than the output load. IMHO the 480W figure is a misprint. You could check the service manual for the voltages and do the math based on the output voltage. Maybe add 30W for the internal electronics and transformer losses.About the Chinese power supplies: they may not be excellent but the problem with the HP supplies is that they are huge boatanchors. I'm thinking about buying the 36V /3A version of this power supply:http://www.manson.com.hk/en/dcpowersupplies_detail.php?m=3&id=16For some reason I usually end up using the power supply I made in school 20 years ago. I guess the low weight and small size make it ideal to move it around. My HP6002A OTOH is very large and heavy and has a noisy fan (I did make it temperature controlled though).

author: radian
author_rank: Contributor
timestamp: May 04, 2013, 04:06:21 pm
content: Between Agilent and Tektronix, which has a better reputation for quality power supplies?

author: wraper
author_rank: Unknown
timestamp: May 04, 2013, 04:32:39 pm
content: I can say that you shouldn't worry about Agilent, Tektronix and Thurlby (Sornensen). They all are very decent manufacturers. And quality of their supplies are overkill for you considering that you were going to buy china crap for less than 60 bucks. You can pick any of them that gives you required voltage and current ranges. Agilent makes some ultra low ripple supplies but you will get more volts/amps from Thurlby for the same price. I would go for Thurlby, you will get more for the same buck.

author: staxquad
author_rank: Frequent Contributor
timestamp: May 04, 2013, 05:47:33 pm
content: Quote from: nctnico on May 04, 2013, 09:52:50 amAligent specs stand, until proven wrong though testing, not opinionIt would be convenient if every time you didn't like distortion or ripple specs that you'd just say it was a printing error

author: Monkeh
author_rank: Super Contributor
timestamp: May 04, 2013, 06:28:23 pm
content: Quote from: staxquad on May 04, 2013, 05:47:33 pmJust because it says 480W maximum input power, doesn't mean it ever actually requires 480W to output 200W. That could easily be an inrush specification.

author: Unknown
author_rank: Unknown
timestamp: May 04, 2013, 08:11:22 pm
content: Quote from: radian on May 04, 2013, 04:06:21 pmTektronix makes power supplies? Apart from a few TM500 plugins in the seventies, all of the Tektronix power supplies are rebadge jobs as far as I know.

author: N TYPE
author_rank: Regular Contributor
timestamp: May 05, 2013, 03:27:22 am
content: Guys what do you think about this Dual Tracking Linear Power supply kithttp://www.altronics.com.au/index.asp?area=item&id=K3218which was first featured in silicon chip magazinehttp://archive.siliconchip.com.au/cms/A_112014/article.htmlI'm sure I can make my own for cheaper than the price listed here as I have the schematics, parts list and board templates already, The thing which I like is that its dual tracking, and as it's a kit I can add extra outputs or modify the existing circuit to suit. Sorry I cant post the entire article as I dont have permission but the specs are as follows:Output voltage : +- 0-19VOutput current : up to 1.6A (With current limiting feature)Noise (0-1A) : <5.25uV peak to peakRipple (0-1A) : <1mV RMS <1.7mV peak to peak

author: M0BSW
author_rank: Frequent Contributor
timestamp: May 05, 2013, 06:59:14 pm
content: I can only speak for what I have it's old it's calibrated its a Farnell D30 2, a vairiable volts & amps bench power supply up to 30 volts can push up to 31.5, and Amps are 2A, and a readout, for me it's perfect. , and there fairly cheap on E-Bay, if you don't mind a 20 Year old supply.

author: Cerebus
author_rank: Super Contributor
timestamp: August 07, 2016, 12:43:08 am
content: Quote from: AcHmed99 on May 04, 2013, 07:24:38 pmI know I'm reviving a very old thread but I came across this when I was considering bidding on an HP6002A and did a search on here for some background info. Long story short - I now have an HP6002A and I thought that I'd close the loop by making some actual measurements and posting them.So:One HP6002A attached to a 2 ohm load, voltage set to 20V and current limit to 10A - both checked with my trusty old Fluke 25. Thus output power 200W +/- 0.85%. Input power (indeed measured with a cheap plug-in power meter) 375W and 455 VA. So that's 175W being blown out of the back by the fan. This is not however the maximum output power of the supply, just the limit of its in-regulation output. The manual states that it can safely run quite some way outside the regulation envelope and indeed the front panel has an 'overload' light to tell you when you are doing so. Thus it's quite possible that it could run to another 105W of input power. I don't have a lower resistance load that I could safely throw more than 200W into, so that thesis will have to remain untested for the time being.By the way, the input power with no output load is 39W (69 VA). I suspect that at least 10W of that just goes into spinning the big-ass fan.

author: eKretz
author_rank: Frequent Contributor
timestamp: August 07, 2016, 04:42:32 am
content: Sorensen is great gear. They are owned by the same parent company as Ametek and Elgar. Those are also very good power supplies. I have a 1200 watt Sorensen switcher - it's been fantastic. Ripple on mine is about 5mV, not terrible.

author: Pheadrus
author_rank: Newbie
timestamp: July 23, 2019, 01:00:09 am
content: I know this is a very (very) old thread now, but it is still relevant and was one of my resources in researching these Chinese bench supplies prior to buying one last week.Further to Cerebus, and in the interest of coming full sphere, I thought I'd put up my measurements taken of this 30V 0-5A "Hyelec HY3005ET" courtesy of Ebay for the princely sum of £34.88 ($43.50) all in. All measurements are taken using a Pico 3423 USB scope and a Pico TA009 current clamp.Open circuit voltage display vs actual:3.28V is actually 3.30V11.97V is 12.00V19.95V is 20.00V29.94V is 30.00VDisplayed voltage vs current and ripple measurements taken:3.30V / 5W5.1R resistor: displays 0.647A = 0.665A 31mA/278mV p-p5.00V / 5W5.1R resistor: displays 0.982A = 1.011A 45mA/192mV p-p5.00V / 5W10R resistor: displays 0.507A = 0.510A 45mA/225mV p-p12.00V / 10W20R resistor: displays 0.613A = 0.629A 62mA/256mV p-p15.00V / 5W47R resistor: displays 0.321A = 0.327A 36mA/267mV p-p5.00V / 2x100W1R resistor: displays 2.26A = 2.30A 131mA/299mV p-p10.00V / 2x100W1R resistor: displays 4.20A = 4.24A 143mA/331mV p-pMax V / 2x100W1R resistor: displays 5.086A = 5.219A 202mA/587mV p-pThere are no discernible voltage spikes no matter how much I mess with the power button or pull out/plug in leads with/without a load and voltage present. The most I saw was 15.07V for 0.4ms upon powering on with 15V equivalent dialled in and a 10R load connected.The 80mm fan on the back seems to be speed controlled against the output voltage regardless of current. It becomes audible at 12V. There is a slight noise with a very low CC (<0.3A), sounds like faint radio squark, and again around the 5A range, nothing that a computer under the desk can't beat.