Is it still worth building an adjustable bench type 5-10 amp PSU these days? - Page 1
Forum section: electronics / projects

author: nzo
author_rank: Regular Contributor
timestamp: August 23, 2011, 05:26:09 am
content: Just wondering about the economics of it (not counting DIY time and the pleasureof building it)

author: Bored@Work
author_rank: Super Contributor
timestamp: August 23, 2011, 05:55:30 am
content: It is not very economic. Already the transformer and parts like metal case will cost half of a whole Made in China bench power supply.This is typically the moment that someone chips in and tells us he build his bench power supply for 0.000314 Shekel only, and it can be done. Sure, if you happen to be lucky and happen to just have all the right parts in your parts drawer. And if they magically ended up in your parts drawer free of charge. And if you find it stylish to have an enclosure made from duct tape and chewing gum. You get the idea.

author: nzo
author_rank: Regular Contributor
timestamp: August 23, 2011, 06:02:56 am
content: LOL. I see your point.

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: August 23, 2011, 06:10:05 am
content: Speaking about cash, my Kenwood PD36-10A that is 36V 10A it has a true transformer and active cooling and the weight is 14 kilos.And it cost about 1700$ USD( just found the price today )The PSU is the only device that you will keep for ever, this is why it worth's investing some true cash,so to have something worthy for the years to come.Unfortunately , with DIY there is no chance to archive truly worthy results, except if you make a direct copy the Kenwood PD36-10A.http://www.texio.jp/english/product/power/detail/series_p.php?id=29

author: nzo
author_rank: Regular Contributor
timestamp: August 23, 2011, 06:18:29 am
content: That's a fine-looking PSUKiriakos-GR.$1700 smackeroos...phew!

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: August 23, 2011, 06:25:20 am
content: Quote from: nzo on August 23, 2011, 06:18:29 amDo not loose faith, there is lots used.In Japan they sell them for around 300$Start exploring your own area and the Ebay. Australia

author: Unknown
author_rank: Unknown
timestamp: August 23, 2011, 06:46:34 am
content: Quote from: nzo on August 23, 2011, 06:02:56 amI'd mostly agree with BAW, your DIY doesn't have to be a spit & duct-taped disaster. But you'd be hard press to produce anything that is robust and looks good for the equivalent of an off the shelf unit. Testament to that is the dearth of kitset power supplies, once they were common but looking through the catalogues there isn't much to be found. That's a pity because they were good starter projects, but commercial reality driven such kits well towards extinction.At beginner level it may be worth the exercise to produce some simple 3 terminal regulator boards for specific tasks but again hard to justify when you can get quite reasonable regulated switchplug packs for a few dollars.Looks athttp://geoffg.net/Utility_Power_Supply.htmlfor some inspiration if you'd rather DIY whatever the price. Consider mixing a combination of off the shelf SMPS with some linear regulators for a custom supply specific to your needs. But remember the cost of parts rises quickly to build anything decent.

author: RCMR
author_rank: Frequent Contributor
timestamp: August 23, 2011, 08:37:02 am
content: Why not go half way?Buy a cheap Chinese bench supply -- which will give you the nice case, knobs, terminals, displays and possibly a half-decent transformer - then, if the rest of it is crap, build your own regulator and control circuitry.You'll probably still save money over a top-of-the-line supply *and* have the fun of doing your own design/build of the exciting bits inside.I have to admit that I've done this a few times before and often, when I'm buying Chinese-made engineering equipment for my workshop, I end up having to treat their lathes or mills as a "semi-assembled kitset of parts in need of finishing, upgrade and alignment". Still, by the time you've done the extra work, you can end up with some really good equipment for a fraction the "brand-name" price and with that little bit extra functionality or performance that you might decide to add along the way.For example, I bought a Chinese lathe and decided the toolpost sucked soI made my ownwhich is far better than the original.

author: SgtRock
author_rank: Unknown
timestamp: August 23, 2011, 09:58:10 am
content: Dear nzo:--I agree with virtually all of the previous posts (although UncleV will never know, because I am on his ignore list). My recommendation is before you build one of your own, I recommend you first buy a good used bench supply from somewhere other that Hong Kong. By buying used good stuff, you get quality at a Hong Kong price. And it will give you a good idea about design, case, layout etc., you might as well learn from the masters like HP, but some of the Heathkit PSU are very nice as well.-- Have a look at this HP ALIGENT E3614A 48W 0-8V 0-6A BENCH DC POWER SUPPLY. These things are darn near bullet proof, you can get manuals, and they are repairable.Buy it now $165, free shipping.http://www.ebay.com/itm/HP-ALIGENT-E3614A-48W-0-8V-0-6A-BENCH-DC-POWER-SUPPLY-/330591680875?pt=LH_DefaultDomain_0&hash=item4cf8ccb96bBest RegardsClear Ether

author: Unknown
author_rank: Unknown
timestamp: August 23, 2011, 10:17:54 am
content: How about an old UPS? It already provides the most expensive components like case and transformer. Also the pcb is full of useful components.

author: saturation
author_rank: Super Contributor
timestamp: August 23, 2011, 11:07:25 am
content: If you've never built a PSU, it would pay to build to learn, not for practical use.Getting a used quality PSU from eBay can be challenging: is it worth $180, why is another $320, why is another $50, all the same model? Can you tell if there is a subtle fault that not even the seller knows? How do you test these PSU to know its up to snuff or repair it? From a box new PSU the manufacturer warrants the specs, but not if second hand from eBay.In my day, there were no brick power supplies; so I built linear PSU for nearly all my devices; I think in the end I built 10, and I frankly got sick of it by 5th; I wondered why does each item need its own PSU when I don't use them all at the same time? Why not modularize it and plug it in only when I need it? Well, before I could work that out as a project I found them for sale and I haven't built one since [ somewhere ~ 1976-1982]. Likewise do the same for a SMPS, a doubler, a tripler, make it, test it, then dissemble it and reuse the parts for another project.Many PSU of all sizes often end up in the garbage, and work. I find, collect and cannibalize them, and rarely have to buy any for projects ... but that's because you know how to build them, and take what you need.You needn't create a full project, with a nice case, and all the trimmings. That's worth doing maybe 1-3x, in the end, since you can buy a lot of items or find them free in the trash, modding them for your needs is more practical, you can even find nice enclosures ... just check a dumpster near you, this is particularly wonderful at the end of the year in any major school; studs dump and research labs dump a lot of working gear. Enclosures from appliances can provide the sheet metal for you to work into real project cases. At the very most, you can get meters of high quality cable and copper wires.Its also a green thing to do

author: EEVblog
author_rank: Unknown
timestamp: August 23, 2011, 11:14:06 am
content: Power supplies are great projects to build, but economic these days? Not for the general purpose ones.I'm working on a few lab power supply projects at the moment, but they are all unique in some way that you can't really buy off the shelf.Dave.

author: FreeThinker
author_rank: Frequent Contributor
timestamp: August 23, 2011, 01:46:04 pm
content: Keep your eyes open on ebay for faulty units. These can be a good source of parts if nothing else. Do a bit of research before buying (manuals, circuit diagrams etc ) If you can fix it you have a nice cheap supply if not you have a decent case etc for your own build. Repair, Reuse, Recycle

author: SgtRock
author_rank: Unknown
timestamp: August 23, 2011, 03:02:18 pm
content: Dear nzo:--Saturation is correct, I should not have recommend that you buy second hand, without the standard caveats. If you are new to eBay, you will want to observe items in your area of interest, and get an idea of how things go before charging in.--Subtle faults that not even the maker is aware of can occur with eBay, Hong Kong and DIY. Freethinker has a great idea about buying "non-working" and fixing or "parting out", but it takes a lot of research. But if the item is cheap enough you should be alright. In any case this is half way to building your own power supply. Since I am familiar with them, I buy old Heathkits and fix them up.--Still, caveats being noted, there is a reason Dave and countless others recommend buying make and model numbers of known reliability and repairability. It' because you can get darn good stuff at a darn good price.Best RegardsClear Ether

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: August 23, 2011, 03:37:36 pm
content: Quote from: HAL-42b on August 23, 2011, 10:17:54 amThe most worthy to pay characteristic is the low noise Ampere limiter.Just because of this, it worth paying and getting a respectable low noise design.The voltage control was always the easy part.For example when I watch those 11 ADJ pots on my Kenwood I feel dizzyHow in earth I am going to calibrate this monster ?And this is just the first PCB of the four in it.( The picture is not my "Japanese Bloger" )

author: nzo
author_rank: Regular Contributor
timestamp: August 24, 2011, 02:52:23 am
content: Thanks all for the great replys!!

author: Kozmyk
author_rank: Regular Contributor
timestamp: August 24, 2011, 05:51:07 am
content: I got a nice deal on one of these from eBay a while back.http://www.wattpowertest.co.uk/2-0-30v-5v-triple-linear-power-supply-digimess-hy3003-3.htmlThe two main channels (<30V <3A) can run separately, series or parallel.Nice n flexible.

author: nzo
author_rank: Regular Contributor
timestamp: August 24, 2011, 06:40:32 am
content: That's a nice looking PSU Kosmyk, and not too bad a price. I wonder if the sellers of these models follow the trend of having some or all of it made in China and then re-labelling it. Hard to tell these days.

author: Kozmyk
author_rank: Regular Contributor
timestamp: August 24, 2011, 02:15:32 pm
content: Yup. Country of Origin China.Digimess used to be Grundig.I guess most if not all mass produced electronics are made in one part of Asia or another.I got my HY3003-3 s/h for £82 delivered.I was pretty happy with that deal.

author: Bored@Work
author_rank: Super Contributor
timestamp: August 24, 2011, 05:40:34 pm
content: Quote from: Kozmyk on August 24, 2011, 02:15:32 pmA long time ago. When Grundig went bankrupt the Digimess brand was sold separately. The new owner of the brand sells a bunch of badge-engineered stuff under the brand. The web sitehttp://www.digimess.co.uk/is good for a name-the-ODM bingo card.Your Digimess looks like a Mastech power supply. People are usually satisfied with these.

author: Kozmyk
author_rank: Regular Contributor
timestamp: August 24, 2011, 10:54:18 pm
content: Well spotted. Even uses the same Model number.Much cheaper with the Mastech badge on though.I think it's allright.Having to switch the metering between V & A can be tedious though.And you have to be careful not to mess with the mode switches while switched on or connected to anything.Certain unpleasant surprises can occur.

author: SgtRock
author_rank: Unknown
timestamp: August 25, 2011, 02:29:11 am
content: Dear nzo:--Have a look at this post from a different section in this forum. I might be helpful.https://www.eevblog.com/forum/index.php?topic=4579.0;topicseenBest RegardsClear Ether

author: nzo
author_rank: Regular Contributor
timestamp: August 25, 2011, 09:32:56 pm
content: LOL! Thanks for that tip mateIt's on my things to do list.BTW, you are theonlyperson onanyforum that has ever addressed me with "Dear nzo"

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: August 25, 2011, 09:48:13 pm
content: Quote from: nzo on August 25, 2011, 09:32:56 pmI am aware of the story about the frog and the princes , and so do not expect a hag from me.LOL

author: nzo
author_rank: Regular Contributor
timestamp: August 25, 2011, 10:24:39 pm
content: Kiriakos-GR - My friends who have been to Greece tell me they are warm, welcoming, human, hugging people. Even though ordinary Greek people are now much more stressed because of the huge financial burden that began with the Olympic Games and the meddling of bean counters and politicians who themselves don't know what the hell they're doing. None of them!

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: August 26, 2011, 02:06:49 am
content: Basically your country and Greece haves some sort of a tie, there is many Greeks down there,and I have work even with Australians locally.We was working together for months and we had talk about everything.I know all the little secret words about make an OZI to go mad. LOLBut I had never use it here, because I feel like a very good friend of Dave.About the financial problems, yes the cannon ball got me to.From the start of the September your media will have plenty of videos from Greece,some times you have to fight back the injustice by your naked hands.

author: SgtRock
author_rank: Unknown
timestamp: August 26, 2011, 02:27:22 am
content: Dear Kiriakos:--Unfortunately and probably justly the USA will soon be facing the same situation. Too much month at the end of the money. But that is enough of that.--It must be very beautiful where you live. Please post some pictures when you have the time. Best RegardsClear Ether

author: shebu18
author_rank: Frequent Contributor
timestamp: August 26, 2011, 12:24:09 pm
content: The title of the topic is very good. I am in process of building such a power supply. I use a ATX supply for the 12V and arround 20-30A(will not be necessary). A LM317 circuit where i put a big tranzistor which provides the amps if i need to go over 1,5A. The schematic was took out from the datasheet of the lm317. Currently the supply is done. I am working on the Voltmeter and Ammeter, both witch IC7107.I think why not bouild one if you have all the parts around you? OK, th 7107 was not around me but the rest was. I do not need more than the 11,5V i get and i do not need to go below the 1,25V minimum, so for me is was worth.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: August 27, 2011, 11:34:49 pm
content: Well, if you're a beginner you probably can't build a really nice PS, more likely a POS. If you know what you're doing you probably already have a PS or three.It, like everything, comes down to time and money and parts. If you have time and parts, but little money, it makes sense to build a good supply. It really should have both constant voltage and constant current modes. Power supplies lend themselves to scavenging, as so many things already contain suitable parts.If money is easier for you to come by than time (you can always buy parts) it's probably best to look for a good commercial supply by a well known maker. That means HP or Kepco for used stuff. There are also some decent new supplies if you have the $$. Watch out for digitally controlled supplies with menus like the B&K. It's so cumbersome to simply turn the output on and off that it's a hazard to your projects. This is a case where switches and knobs make more sense.I use some big Kepco supplies, one for plus, one for minus, but I was lucky to find them surplus. At work we use a 3-output Xantrex bench supply that's very nice. It would be the ideal home lab supply, but probably too pricey.