Power Supply: Build or Buy? - Page 1
Forum section: electronics / testgear

author: br4n_d0n
author_rank: Contributor
timestamp: May 03, 2023, 09:49:15 pm
content: I could really use an adjustable power supply and since I'm new to electronics I don't know how practical it would be to try and build my own to fit my needs. My main concern is it being safe so I'd prefer not to get some cheap no name power supply that could start a fire or kill me.I would like this to be more of general discussion to help others with a similar question, but I'll leave some specifics of what I'm looking for to help guide me in a good direction.24volts @ ~3amps (for powering a soldering iron)100-120volts @ low amps (gives me the ability to electroplate/anodize in the future)Whatever voltage/amps I'll need in making some small electromagnets

author: David Hess
author_rank: Super Contributor
timestamp: May 03, 2023, 10:38:34 pm
content: I would not combine such separate applications into one power supply.

author: BeBuLamar
author_rank: Super Contributor
timestamp: May 03, 2023, 10:47:40 pm
content: The 100-120VDC power supply is kind of a specialty. I think you would want a separate unit for that. The 24VDC power supply are plenty perhaps buy a fixed 24VDC supply. I am sorry but please don't say Chinese when you mean bad products. They make products of all different level of quality.

author: AG6QR
author_rank: Frequent Contributor
timestamp: May 04, 2023, 12:16:11 am
content: When I can find multiple commercial products which will basically fit my needs, I've always found that it's very hard to save money by building my own. That's definitely the case with power supplies.I think most electronics tinkerers ought to have at least one bench power supply that offers adjustable constant voltage regulation and adjustable constant current regulation. It should probably have meters that show voltage and current. There are MANY companies that make many variations on this kind of supply. They come in many quality levels, with many levels of voltage and current capability. My most used unit is my antique linear HP E3610A which I picked up used for a bit over a hundred dollars. That doesn't mean it's the best bargain for everyone, but it meets my needs, and the quality is excellent -- good enough that for almost any purposes, I can pretend it's perfect, at least within its voltage and current limits.If you want to build a power supply as a learning exercise, it could be a good project. But it's likely to end up costing more and being of lower quality than a commercial supply. It might be worth it if you end up learning enough from the exercise, though.Having said that, I agree that the 100-120V DC supply for electroplating is a specialized beast. I don't have such a supply now. My inclination, at least to start out for occasional use, would be to use a dozen or more 9V alkaline transistor radio batteries in series, to get the high voltage and low current. In addition to very low cost, it has the advantage that the internal resistance of those small batteries limits the current somewhat. While it's not totally safe, at least an accidental short is unlikely to be as spectacular as shorting DC produced by rectifying mains power without proper current regulation. If I found that I wanted to do frequent electroplating, I'd look into other alternatives.

author: james_s
author_rank: Super Contributor
timestamp: May 04, 2023, 12:53:48 am
content: Fixed 24VDC is easy to build, that's a good beginner project.A basic adjustable power supply is not too hard, but if you have the means to get a commercial bench power supply that would probably serve you better.100-120V is very unusual, I thought electroplating typically used just a few volts and anodizing is maybe 12V or a tad higher, are you sure you need ~100V+? That's typical if you want to work with vacuum tubes.

author: br4n_d0n
author_rank: Contributor
timestamp: May 04, 2023, 01:33:25 am
content: Yeah, titanium takes higher voltages and caps out at around 120v

author: james_s
author_rank: Super Contributor
timestamp: May 04, 2023, 02:43:24 am
content: How much current does it take? You can get adjustable boost modules from China for a few dollars that will go up to a few hundred volts. You might also get away with using unfiltered rectified 120V from the wall with a resistor or lightbulb to limit the current.Either way I would not try to accomplish both of these goals with a single power supply. One that is optimized to deliver high voltage is going to be poorly suited for low voltage applications and you don't want to forget that it's set to 100V and switch it on while connected to a 3.3V microcontroller board or something.

author: Brumby
author_rank: Unknown
timestamp: May 04, 2023, 07:03:58 am
content: Quote from: james_s on May 04, 2023, 02:43:24 amNeither would I.QuoteThat was my first apprehension as well - and that sort of "oops" is bound to happen at some point.

author: armandine2
author_rank: Frequent Contributor
timestamp: May 04, 2023, 09:34:29 am
content: https://www.elektormagazine.com/magazine/elektor-199010/32232I started building the elektor 400W power supplybut ran out of steam quite quickly - not a beginners project.I've revisited it recently and was soldering smd components to meter PCBs last night.

author: Fungus
author_rank: Super Contributor
timestamp: May 04, 2023, 10:53:01 am
content: Quote from: br4n_d0n on May 03, 2023, 09:49:15 pmA home made one is just as likely to be unsafe or burn the house down.Quote from: br4n_d0n on May 03, 2023, 09:49:15 pmYou really can't go wrong with something like this:https://www.aliexpress.com/item/4000419022828.htmlMeanwell are a respected brand and they have full protection against overloads/overheating/etc.Anecdote: Two weeks ago I saw somebody in a classroom deliberately try to blow a fuse with one of those and fail. The PSU always shut down faster than the fuse could blow.(The indicator LED on the PSU turned off and the fuse was fine.)The fuse blew perfectly when we tried a different PSU

author: David Hess
author_rank: Super Contributor
timestamp: May 04, 2023, 12:53:21 pm
content: Quote from: BeBuLamar on May 03, 2023, 10:47:40 pmUnfortunately distinguishing the good produces from the bad is practically impossible, making them all bad. China has become the Nigerian Prince of counterfeit products, with companies like Ebay, Newegg (Chinese owned now), and Amazon helping.Quote from: AG6QR on May 04, 2023, 12:16:11 amA variable bench power supply is an excellent learning project. It is too bad that there are not any good kits.I would also consider rebuilding an HP/Harrison power supply, or something similar that has full documentation.

author: tunk
author_rank: Super Contributor
timestamp: May 04, 2023, 01:24:00 pm
content: What's your soldering iron?It may be able to run from an old laptop power brick.The voltage will be lower (~19V), so heat-up will be slower.

author: Fungus
author_rank: Super Contributor
timestamp: May 04, 2023, 02:01:33 pm
content: Quote from: tunk on May 04, 2023, 01:24:00 pmOr two old ATX power supplies in series.

author: BeBuLamar
author_rank: Super Contributor
timestamp: May 04, 2023, 02:31:15 pm
content: Quote from: David Hess on May 04, 2023, 12:53:21 pmYou can't too bad because even name brand power supplies are made in China too. You think this is a bad power supply that would burn down your house?https://www.testequipmentdepot.com/bk-precision-1901b-programmable-switching-dc-power-supply-32v30a-120vac-line-input.html?ref=gbase&gclid=Cj0KCQjwr82iBhCuARIsAO0EAZyxBpiROwMSLyV_I-WSqU-l_lfiNhWB-rO3-JCeLmJYt3EL1qJgSlsaAmdIEALw_wcBAnd yes it's made in China.

author: james_s
author_rank: Super Contributor
timestamp: May 04, 2023, 05:55:05 pm
content: Everybody knows that when one speaks of "Chinese products" they are referring to the no-name domestic market junk that is prolific on ebay, aliexpress and so many others, not the high quality name brand stuff that is manufactured there.

author: br4n_d0n
author_rank: Contributor
timestamp: May 04, 2023, 07:29:49 pm
content: The general consensus thus far seems to be for purchasing a power supply as there seems to be a lack of good info or kits out there for a beginner such as myself. However, if someone could find a really nice kit or great tutorial for an absolute beginner, I may take a look.So, any recommendations for one $100 or less?

author: Fungus
author_rank: Super Contributor
timestamp: May 04, 2023, 07:53:23 pm
content: Quote from: br4n_d0n on May 04, 2023, 07:29:49 pmThere's lots of modules on Aliexpress, eg.https://www.aliexpress.com/item/4000742314477.htmlQuality varies but they all need some sort of external power supply to power them, typically with a voltage higher than the maximum desired output voltage.I've got one of these:https://www.aliexpress.com/item/1005001530484759.htmlIt's really tiny and I can power it from a USB-C powerbank or a suitable phone charger up to 30V - portable bench supply! It works well enough but I don't think I'd use it as my main supply.FWIW Dave did a series of videos on those modules:

author: Fungus
author_rank: Super Contributor
timestamp: May 04, 2023, 07:54:49 pm
content: Me? I wouldn't want to power my soldering iron from my bench supply - imagine having to swap the cables around every time you want to solder something, or be switching between soldering and powering. That would get old really fast.Get yourself a fixed 24V supply for that.

author: nctnico
author_rank: Super Contributor
timestamp: May 04, 2023, 08:34:58 pm
content: Be sure to get a linear power supply as your primary lab power supply. Switchers (which includes those dc-dc converter modules) output too much noise to make meaningfull measurements to a circuit.

author: james_s
author_rank: Super Contributor
timestamp: May 04, 2023, 08:59:47 pm
content: Switchers can be very clean, it's all a matter of how well they are designed. Linear power supplies are easy to make quiet though.

author: Fungus
author_rank: Super Contributor
timestamp: May 04, 2023, 09:33:55 pm
content: Quote from: nctnico on May 04, 2023, 08:34:58 pmDepends on what you're building. Digital circuits won't care.

author: nctnico
author_rank: Super Contributor
timestamp: May 04, 2023, 10:07:25 pm
content: Quote from: Fungus on May 04, 2023, 09:33:55 pmDigital doesn't exist. As soon as you connect a scope to hunt down a problem, you can easely get a lot of noise on your display that is not coming from your circuit but from a switching PSU. So what is what?Quote from: james_s on May 04, 2023, 08:59:47 pmNo. I own and have owned quite a few of the high-end HP switching PSUs and none of them have a really clean output.

author: br4n_d0n
author_rank: Contributor
timestamp: May 04, 2023, 11:51:12 pm
content: Yeah, I was thinking of going for a linear one.

author: james_s
author_rank: Super Contributor
timestamp: May 05, 2023, 12:08:22 am
content: Quote from: nctnico on May 04, 2023, 10:07:25 pmThat doesn't mean clean switchers don't exist, merely that the specific models that you've had are noisier. For most things it doesn't matter, for some it does. It's certainly easier to find a linear supply with a really clean output but it isn't the only option.

author: Fungus
author_rank: Super Contributor
timestamp: May 05, 2023, 06:26:58 am
content: Quote from: nctnico on May 04, 2023, 10:07:25 pmI see the noise nannies are out again.Stated use cases are:Powering a soldering ironElectroplatingMaking electromagnetsAt what point would 50mV of noise make the sky fall?Quote from: james_s on May 05, 2023, 12:08:22 amIt also doesn't mean that somebody who wants to build their own from a kit can't add some filtering.

author: nctnico
author_rank: Super Contributor
timestamp: May 05, 2023, 09:21:45 am
content: Quote from: Fungus on May 05, 2023, 06:26:58 amNo, just common sense. I read: beginning with electronics. A linear Korad PSU costs about the same as a switching PSU. Due to the lower noise, the linear PSU is a much more versatile piece of equipment.

author: Caliaxy
author_rank: Frequent Contributor
timestamp: May 05, 2023, 06:33:36 pm
content: Quote from: br4n_d0n on May 04, 2023, 07:29:49 pmFor general use, I'd get a linear triple power supply, with +/- 0-15V for circuits that require differential power (e.g. op amps) and +5V (for logic circuits).This kit on Amazon seems basic but OK. It provides everything you need, including transformer and enclosure, for under $80. You have to solder it yourself. Some users improved it over time (with multi-turn pots for finer voltage adjustment and output meters - read the reviews). It doesn't limit the current output, so you have to be careful. I have no experience with it.https://www.amazon.com/Elenco-Triple-Output-Power-Supply/dp/B0002DT0GU/ref=sr_1_1?crid=1XLLSDE54UER8&keywords=elenco+triple+power+supply&qid=1683309302&sprefix=%2Caps%2C207&sr=8-1&ufe=app_do%3Aamzn1.fos.006c50ae-5d4c-4777-9bc0-4513d670b6bcIf you are in US, you might find good deals on older HP triple power supplies on eBay, such as 6326B (if under $50) or (better) E3630A (if under $80-100). Make sure they are in good shape (working, with no missing knobs and/or broken posts). I used an E3630A for a long time and was happy with it. It's nice to be able to limit the current, to protect your circuits from yourself.If you buy new, Korad KA3005D (~$110) is a more modern option (well regarded here), but it's only single output. I have one of these too, no complaints.I wouldn't power my soldering iron from a bench power supply either. I'd buy a switching power supply for everything requiring high voltage/power output. Safer and simpler.

author: james_s
author_rank: Super Contributor
timestamp: May 05, 2023, 06:45:35 pm
content: My most used power supply is a switcher based 1.2-30V that I built myself out of a cheap module and a surplus power brick, it's convenient because it's a tidy little enclosure that I can carry around wherever I need it. Next is an old Heathkit linear triple bench supply, it's a bit lacking in terms of features, it doesn't have current limiting but the variable outputs are only good for 500mA so this isn't much problem in practice. I like it because it has real analog knobs that respond instantly. I also have a big Tektronix bench PSU which is linear with digital controls, it's very capable but the user interface is pretty terrible, it's the only power supply I've ever had to read the manual to figure out how to use it. There are too many cases where the same button does multiple things. The linear supplies I have are much cleaner than the switcher, but at least 90% of the time it doesn't matter for what I'm doing.

author: br4n_d0n
author_rank: Contributor
timestamp: May 05, 2023, 09:38:48 pm
content: Quote from: Caliaxy on May 05, 2023, 06:33:36 pmThese are stupid expensive right now on "theBay" for beat up and non-functioning ones... I don't get it.

author: nctnico
author_rank: Super Contributor
timestamp: May 06, 2023, 12:19:12 am
content: My biggest problem with the old PSUs is that these don't have accurate readouts. Nowadays a lot of circuits run from low voltages. For that you need at least 2 digits after the decimal point. 3.3V chips (for example) often have maximum operaring voltages of 3.6V. You can't adjust the voltage accurately enough using a moving pointer on a scale that goes to 20V / 30V.

author: Fungus
author_rank: Super Contributor
timestamp: May 06, 2023, 04:56:54 am
content: Quote from: Caliaxy on May 05, 2023, 06:33:36 pmI wouldn't want a power supply that doesn't have readout of voltage and current. That's like using a CRO instead of a DSO.Current limiting is fairly essential for me, too. Negative rail? Not so much. I rarely use op-amps and if I do I use R2R versions to avoid having to put fancy power supplies in the finished device.The last part is just me, obviously, but the first part stands.

author: David Hess
author_rank: Super Contributor
timestamp: May 06, 2023, 01:39:54 pm
content: Quote from: Fungus on May 06, 2023, 04:56:54 amI have enough multimeters that using a power supply without built in readouts does not bother me. It is enough to have an indicator showing if the power supply is in current limit.

author: bdunham7
author_rank: Super Contributor
timestamp: May 06, 2023, 02:22:35 pm
content: Quote from: br4n_d0n on May 03, 2023, 09:49:15 pmFor your 24V soldering iron, I'd get a dedicated switching supply. I have one of these (not for soldering irons) and it seems pretty decent and is made in Taiwan. It is DIN-rail mounted and so is intended for use inside a control panel. You'd have to make up a box of some sort for it because the line voltage terminals are exposed. It's not the only choice, but it is one I know will work.https://www.ebay.com/itm/134508829833Also, the much more powerful Meanwell LRS-350-24 that powers certain 3D-printers is also a possible candidate because they are widely available, work well and are pretty cheap ($35 on Amazon) due to their popularity.For your electroplating, I'm assuming you want a limited current supply (a few mA) and I'd also recommend a simple, dedicated supply but this is one you can build. I'd start with a small, isolated step-down transformer and then a voltage multiplier circuit. You can read the Wikipedia article on voltage multipliers and I've provided a link for what I think might be an appropriate transformer.https://www.mouser.com/datasheet/2/410/F48_050_C2-781070.pdfhttps://en.wikipedia.org/wiki/Voltage_multiplierAs far as electromagnets, you'll have to clarify how big, etc. You want either something pretty well protected or something you can fix yourself since you can generate some pretty wicked inductive spikes with large coils.

author: BeBuLamar
author_rank: Super Contributor
timestamp: May 06, 2023, 02:31:19 pm
content: I don't see much point in using 24VDC power supply to power a soldering iron. Get an AC powered soldering iron and save the 24VDC iron for when you want to use it on battery.

author: br4n_d0n
author_rank: Contributor
timestamp: May 06, 2023, 04:20:06 pm
content: Quote from: BeBuLamar on May 06, 2023, 02:31:19 pmI've had the soldering iron for a few years now so purchasing another one would be a waste of money. Having a bench PSU that can do double duty when I feel like it would be more worth it IMO.

author: james_s
author_rank: Super Contributor
timestamp: May 06, 2023, 05:50:00 pm
content: Quote from: Fungus on May 06, 2023, 04:56:54 amSome of us are quite able to use a CRO effectively, or measure the output of a PSU with a multimeter if we really need a precise voltage. The one PSU I have with an analog meter goes up to 20V and I can quite easily set it to 3.3V accurately enough in most cases. It's just a matter of knowing what you're doing and how to use the tools you have at your disposal. "A poor craftsman blames his tools."Negative rail is absolutely essential for some projects, and not just those with op amps, while single rail op amps do exist, they have limitations. A split supply is hardly a "fancy supply", it's trivial to integrate into the finished product. I typically use a DC-DC converter module, they're tiny, cheap and effective. Not that it really matters, virtually all multi-output bench supplies have independent outputs that can be wired in series.

author: james_s
author_rank: Super Contributor
timestamp: May 06, 2023, 05:52:08 pm
content: Quote from: br4n_d0n on May 06, 2023, 04:20:06 pmSo lash up a salvaged transformer, rectifier and filter capacitor (assuming the iron contains electronic temperature regulation) and call it done. If the iron is not a temperature controlled soldering station then IMO it's not really worth having except as a backjup.

author: nctnico
author_rank: Super Contributor
timestamp: May 06, 2023, 05:55:23 pm
content: Quote from: james_s on May 06, 2023, 05:50:00 pmThat becomes a nuisance quickly. Especially when you are working on projects that need a couple of different voltages. Been there, done that. Even considered buying even more DMMs but made a much wiser decision in the end: buy PSUs that have proper metering built-in. Saves a lot of time & effort so I can concentrate on getting my circuits going.

author: br4n_d0n
author_rank: Contributor
timestamp: May 08, 2023, 04:44:17 am
content: As a newcomer and barely a hobbyist, this stuff is way overpriced for me. I may have to wait a long time or win some sort of contest to get something good.

author: Fungus
author_rank: Super Contributor
timestamp: May 08, 2023, 06:48:04 am
content: Quote from: james_s on May 06, 2023, 05:50:00 pmDo you also use a slide rule instead of a calculator? They're good enough for most jobs.

author: J-R
author_rank: Super Contributor
timestamp: May 08, 2023, 07:35:28 am
content: New 40W Hakko soldering iron for $7.80:https://hakkousa.com/910-convertible-40w-soldering-iron.html(free shipping @ $25)Cheapest adjustable power, recycle a laptop power brick (~20V/3-5A) and combine it with an LM2596S board:https://www.mtnelectronics.com/index.php&product_id=136Also, tons of other LM2596S boards out there on ebay with different options, such as with a built-in LED display.Add some capacitance on input/output to clean things up and replace the trimmer pots with real ones and you've got something basic for nearly no money.Some other places to window shop:https://www.jameco.comhttps://www.tequipment.nethttps://www.testequipmentdepot.comhttps://www.arrow.comFor used (prices are cheaper direct compared to their ebay stores):https://www.ntc-tech.comhttps://equiptek.com/000.htmhttps://www.sglabs.it/en/Of course:https://www.digikey.comhttps://www.mouser.comUltimately, I think you're stuck and you'll just have to buy one of those cheap bench supplies on Amazon that may or may not burn your house down... They are typically in a metal box so the odds are low...

author: nctnico
author_rank: Super Contributor
timestamp: May 08, 2023, 07:46:12 am
content: Quote from: br4n_d0n on May 08, 2023, 04:44:17 amWhat is your budget? The PSUs from Korad are a good start without breaking the bank.

author: tooki
author_rank: Super Contributor
timestamp: May 08, 2023, 07:46:42 am
content: Quote from: Fungus on May 04, 2023, 10:53:01 amIndeed, I’ve had great experiences with Mean Well, too.But why suggest buying on aliexpress? Mean Well is sold by all the major distributors (ensuring it’s genuine)at lower prices.

author: tooki
author_rank: Super Contributor
timestamp: May 08, 2023, 07:52:58 am
content: Quote from: nctnico on May 08, 2023, 07:46:12 amYep. A Korad KA3005P is my “daily driver” bench supply at home, and it works well without taking up too much space. (For example, my Agilent U8001A sits unused on the shelf most of the time because it’s so deep; I can’t dedicate that much bench space to it.)

author: 5U4GB
author_rank: Super Contributor
timestamp: May 08, 2023, 08:59:12 am
content: Quote from: David Hess on May 04, 2023, 12:53:21 pmFor power supplies specifically it's actually not that hard, just look at the components and layout around the mains side of the circuit and you can get a fairly good idea as to whether it's properly designed and built or not.

author: 5U4GB
author_rank: Super Contributor
timestamp: May 08, 2023, 09:02:01 am
content: Quote from: nctnico on May 04, 2023, 08:34:58 pmI was going to comment on that too but checked the OPs usage and it doesn't seem like there's much there that'll be too critical about noise levels, or even exact voltage levels.

author: David Hess
author_rank: Super Contributor
timestamp: May 08, 2023, 09:06:35 am
content: Quote from: 5U4GB on May 08, 2023, 08:59:12 amThe criteria that I start with is whether the power supply has a service manual, with schematics and layout. It is not like there is some secret power supply IP which needs to be protected.

author: 5U4GB
author_rank: Super Contributor
timestamp: May 08, 2023, 09:14:45 am
content: Quote from: br4n_d0n on May 08, 2023, 04:44:17 amSo that's a related question, why are most of the name-brand PSUs so incredibly expensive? I saw a Rigol product ad the other day and their lab power supplies cost as much or more than a lot of their scopes, and those are some of the cheaper ones out there. I realise there's a bit more than an LM723+2N3055 in there, but does that really justify a four-digit price for a dual 0-32V 3A PSU?

author: gjvdheiden
author_rank: Contributor
timestamp: May 08, 2023, 09:50:14 am
content: You get what you pay for.I've 2 Korad power supplies (single and a double), doing just fine for me. I'm just learning and making some simple boards. Instead of a fancy power supply I invested in nice test leads. For what I'm doing, the power supply provides a very stable output and it has current limiting. Started with a single one, nice size. Soon this was annoying enough and bought a double (and a +5V without current limit which I never use) power supply.There's a new one out, Korad KA3005PS. Suppose to have less noise according to the advertisement.

author: 5U4GB
author_rank: Super Contributor
timestamp: May 08, 2023, 10:24:02 am
content: Quote from: gjvdheiden on May 08, 2023, 09:50:14 amIs the -PS a custom version of the -P for Eleshop? That seems to be the only place that carries it, even theKorad product pagedoesn't mention it.For those who don't mind switchers, the Gophert NPS-1601 is compact, fanless, and gets reasonably good reviews.

author: br4n_d0n
author_rank: Contributor
timestamp: May 08, 2023, 12:24:26 pm
content: Quote from: 5U4GB on May 08, 2023, 09:14:45 amThis is exactly what I'm talking about; I highly doubt the parts and all that amount to even half the price of these "higher end" brands. Seems like huge price gouging to me, but I'm new to this so...

author: gjvdheiden
author_rank: Contributor
timestamp: May 08, 2023, 12:40:15 pm
content: Quote from: 5U4GB on May 08, 2023, 10:24:02 amI did got the info from Eleshop, but they seem to carry to versions. KA3005PS, which according to Eleshop is just a new version and then the KA3005PE-AN. The latterisan Eleshop only version.The knob seems a little bit better too.

author: gjvdheiden
author_rank: Contributor
timestamp: May 08, 2023, 01:09:58 pm
content: Quote from: br4n_d0n on May 08, 2023, 12:24:26 pm5U4GB was talking about a Rigol. These usually are built to a price. The only 4 digit Rigol I can find is the Rigol DP2031. Just over 1300 euro. That thing can do arbitraty waveforms, 1mV/1uA precision, 10A max per channel (banner specs), has a TFT, various control inputs and then some. I don't think I could built that cheaper myself. You pay, you get.

author: Fungus
author_rank: Super Contributor
timestamp: May 08, 2023, 01:50:35 pm
content: Quote from: tooki on May 08, 2023, 07:46:42 amI don't want to recommend any particular distributor.It's also going to depend on where you live...

author: mawyatt
author_rank: Super Contributor
timestamp: May 08, 2023, 03:45:52 pm
content: The first thing to consider for a newcomer to electronics is how many channels and what voltage current levels are necessary. As all of us at one time were newcomers "been there done that" and quickly found out for general purpose work dual channels is a must, at minimum +-20V at 1A.We also found out that all switching PSs make additional noise above a linear type, some are so bad as almost useless for anything other that driving a motor!! Altho some recent quality switching PS are not too bad and could be useful for even some analog type work.The additional cost one finds in a quality lab/bench type PS like the mentioned Rigol (and others) is they are linear types, use of torrid type transformers (low magnetic field leakage), multiple independent channels, very low output noise levels, utilize precision DACs and ADCs so the outputs are spot on (both voltage and current), don't have turn ON or OFF overshoot/undershoot (disastrous for sensitive semiconductors), behave nicely when engaging Over Current or Voltage limits, easy to read digital displays (some have/allow much larger fonts) and have multiple means to remotely communicate.All these features cost in design time, assembly, components (and customer service) and this is reflected in the end user cost.Since most of us have "been there done that", a wise newcomer would learn from others and select a PS that's linear and has a couple outputs capable of producing clean accurate voltages and currents, maybe +-20V and 1A from a reputable OEM source (or used).One thing a newcomer may not recognize, but will quickly learn (usually the hard way!!), everything in electronics starts with the Power Supply, wether a Battery, Mains PS or Solar Source, and a cheap, noisy, inaccurate PS soon finds its way to the trash. This is especially true as one gains knowledge in electronics and becomes "seasoned"Best,

author: br4n_d0n
author_rank: Contributor
timestamp: May 08, 2023, 07:49:15 pm
content: Quote from: mawyatt on May 08, 2023, 03:45:52 pmI think this is quite helpful for someone new such as myself. Thanks

author: james_s
author_rank: Super Contributor
timestamp: May 08, 2023, 08:20:23 pm
content: Something else worth noting is that you will probably end up with several power supplies of various types, it's hard to have too many. I have a mix of commercial, kit, and home built power supplies and I use all of them. When I was a kid I mostly used batteries and salvaged wall warts, I still do for some things. Then I moved on to building my own PSUs with 3 terminal regulators, and then I received an old Heathkit bench PSU as a gift which I still use. That can only do 500mA so I built several other 12V and 5V power supplies over the years and later picked up a big beefy Tek bench supply. You don't have to spend too much time finding the one power supply that will do everything, you start with what you can afford that fits the needs of the projects you want to work on and go from there.

author: dobsonr741
author_rank: Frequent Contributor
timestamp: May 08, 2023, 08:34:24 pm
content: Newcomers needs a fix point to learn and build their lab experience. Power supply is one of the best fix point, one that is professionally made and have the right features.It's easy for us to forget, who got formal education into electronics, what was our first initiation into instruments. It was certainly not a DIY, it was this power supply.Still a good starter at 0-25V, 0..1A and 5V fixed at 0..1A, even it was made 40 years ago.

author: 5U4GB
author_rank: Super Contributor
timestamp: May 09, 2023, 05:20:57 am
content: Quote from: mawyatt on May 08, 2023, 03:45:52 pmI've always maintained that buying your electronics off Pornhub is a bad idea :-).

author: 5U4GB
author_rank: Super Contributor
timestamp: May 09, 2023, 05:35:54 am
content: Quote from: gjvdheiden on May 08, 2023, 01:09:58 pmAh, sorry, the wording was a bit ambiguous, the Rigol sentence and the following one were separate comments. For the Rigol it was the DP-832, which cost more than the different models of DS-1000 listed next to it. It does have a lot of bling in there but then so do the scopes, and do you really need all that in a power supply whose principal job it is to just provide X volts at Y amps?

author: gjvdheiden
author_rank: Contributor
timestamp: May 09, 2023, 08:15:34 am
content: Quote from: 5U4GB on May 09, 2023, 05:35:54 amAll in the light of this topic, starting out and as a hobby.A Rigol DP832 costs a bit under 500 euro here (the Netherlands). I didn't compare them with others, so there might be better suited ones for the price, but it isn't a waste either. Because it is such a fundamental instrument. But I would put my money on a better scope or function gen if I could spend more. My scope is an analog Hameg from '87 bought it from a school, it works.If you're starting out, I think it is good to start with something simple. Indeed, you don'tneedthis. If you start out simple, you can always expand with a more expensive one by the time you do need one. By that time you actually need one, you'll also actually know where to look for. But when starting out, like you said, just need x voltage at max y amps. That's the sensible way, but it's a hobby, doesn't have to be all sensible. The goal is to have fun. You might just want to play with the buttons on a Rigol DP832 all day long. Or just have more fun when actually using it. Who knows but you.

author: Fungus
author_rank: Super Contributor
timestamp: May 09, 2023, 02:18:07 pm
content: Quote from: gjvdheiden on May 09, 2023, 08:15:34 amYep.If the two jobs at hand are 24V for a soldering iron and 110V for electroplating then you don't need a fancy supply at all. Get a 24V switching supply (soldering irons don't care about 50mV of noise) and look into getting 110V somehow (a boosted old wall wart?)Total outlay: About 35 bucks.Then you can dream about spending 500 Euros on a Rigol (or whatever).(A Rigol isn't going to do the 110V anyway...)

author: james_s
author_rank: Super Contributor
timestamp: May 10, 2023, 01:41:20 am
content: Yeah the two main applications listed aren't really bench supply territory anyway. It would be a bit silly to tie up an expensive bench supply running a soldering iron, and as mentioned earlier, 100V+ is a specialty thing you won't find in many bench supplies that are also suitable for low voltage work.

author: br4n_d0n
author_rank: Contributor
timestamp: May 10, 2023, 03:36:22 am
content: No one has touched on the electromagnet part; it will probably be dependent on its specifications, but I was curious if it's more voltage or current dependent.

author: bdunham7
author_rank: Super Contributor
timestamp: May 10, 2023, 03:42:47 am
content: Quote from: br4n_d0n on May 10, 2023, 03:36:22 amSmall electromagnets are not particularly challenging and I think you'd typically use a CC (current regulated) supply. But the specifics are important--you can generate huge transients with electromagnets and simple but specialized circuits would be best to drive them.

author: tautech
author_rank: Super Contributor
timestamp: May 10, 2023, 04:18:57 am
content: Quote from: br4n_d0n on May 10, 2023, 03:36:22 amBack EMF can be a huge problem and it's wise when using a PSU for powering such to take precautions to avoid subjecting the PSU outputs to back EMF. Regen motors also present the same issues and even reverse voltage protection can be exceeded and output stages damaged.

author: br4n_d0n
author_rank: Contributor
timestamp: May 10, 2023, 06:57:55 am
content: Both of you, thanks for letting me know. I was going to just start playing around with some small ones without very much knowledge and it seems like that could've been damaging.

author: james_s
author_rank: Super Contributor
timestamp: May 10, 2023, 07:07:50 am
content: You'll probably be fine, I played with electromagnets frequently when I was a kid and I never hurt anything although I did get a few shocks while leaning the principal behind a boost converter in the process. The large spike occurs when you open the circuit, which you'd normally do by disconnecting the wire that goes to the power supply and then the spike can't get to the power supply anyway.The strength of the magnetic field depends on the number of turns and the current through the turns. The more turns you have, the more voltage you will need to get the current up.

author: Fungus
author_rank: Super Contributor
timestamp: May 10, 2023, 07:33:32 am
content: Quote from: br4n_d0n on May 10, 2023, 03:36:22 amIt also won't care about noise from a switching supply.Quote from: bdunham7 on May 10, 2023, 03:42:47 amYep. You control the magnet strength by controlling the current.A CC supply will help you do that and not overheat the wires.The power supply you need for this will depend on how many amps you want. A lot of amps quickly becomes expensive.

author: mawyatt
author_rank: Super Contributor
timestamp: May 10, 2023, 12:29:20 pm
content: Quote from: tautech on May 10, 2023, 04:18:57 amSo true, and one MUST pay attention to such or likely fry the PSU!!Relays are basically solenoids electromagnetically, and should always utilize a current recovery diode to give the interrupted current a nice place to go as it decays, Ldi/dt can and will wreak havoc with things!!We are working with a controller for a high pressure DC motor that requires ~50 amps, so you can bet we are paying attention to back EMF as this can send the PS (and maybe yourself) to the grave if not properly attend tooBest,

author: tkamiya
author_rank: Super Contributor
timestamp: May 10, 2023, 12:43:46 pm
content: I think buy or make decision is all depending upon one's purpose, interest, and ability. If making one interests you, by all means, make one. Don't forget buying used one either. Older HP power supplies are big and heavy but generates very clean output. I'd choose them over brand-new inexpensive ones. Just for fun, I've purchased a $50 unit from Amazon. Awful build quality and output was full of noise. I wasn't expecting much for the price but even then, it was much worse than my expectations. I sent it back for refund.What's the use-case for 100V DC power supply? What kind of specifications are you looking for? That one may be a bit trickly. Off the top of my head, I don't know of any that covers that range and even relatively affordable.Good luck.

author: Fungus
author_rank: Super Contributor
timestamp: May 10, 2023, 12:45:55 pm
content: Quote from: mawyatt on May 10, 2023, 12:29:20 pmIt won't be easy, there's usually a big capacitor across the output that will absorb it.Quote from: mawyatt on May 10, 2023, 12:29:20 pmI like to use LEDs so you can see them flash when the spikes hit.Being able toseethe spikes really helps teach people the need for protection.

author: james_s
author_rank: Super Contributor
timestamp: May 10, 2023, 05:30:12 pm
content: Quote from: Fungus on May 10, 2023, 12:45:55 pmNot in a bench supply, a big capacitor across the output reduces the effectiveness of current limiting in the event of a short circuit.In ~35 years of playing with electronics I have never managed to damage a PSU by playing with inductive loads though.

author: tautech
author_rank: Super Contributor
timestamp: May 10, 2023, 08:46:14 pm
content: Quote from: mawyatt on May 10, 2023, 12:29:20 pmWhat PSU are you using for that development Mike ?Have you looked at the SPS5000X range ?I've been using my 40V 60A unit for charging solar array batteries lately....a remote installation so powered with a genset.

author: mawyatt
author_rank: Super Contributor
timestamp: May 11, 2023, 02:50:25 am
content: Quote from: tautech on May 10, 2023, 08:46:14 pmThe Korad KWR102, but it's not enough for the higher current pump motors which may need up to 50 amps! We should have more data on the motors soon to help with the decision, and the SPS5000X might be a candidate.Best,

author: tautech
author_rank: Super Contributor
timestamp: May 11, 2023, 03:39:13 am
content: Quote from: mawyatt on May 11, 2023, 02:50:25 amMine's a 5042X 40V/60A 780W but they do have a total output rating in W so can't do both those figures at once.They start getting up in cost and even the 40V/90A 1080W 5043X jobby might not quite meet your needs or the coming 200V 25A 1500W SPS6000X either although that's not due for a bit I believe. I did start a thread for both you can hunt out if required.

author: nctnico
author_rank: Super Contributor
timestamp: May 11, 2023, 09:42:39 am
content: Quote from: james_s on May 10, 2023, 05:30:12 pmA reasonably sized capacitor is necessary for control loop stability. But in the end there isn't much energy in it.About connecting inductive loads: the higher end power supplies from (at least) HP/Agilent/Keysight have an active load circuit inside that sinks current called a 'down programmer'. This is there to make the output voltage lower quickly AND dissipate energy coming into the power supply. You can see this in action when connecting a motor to it and turn the output off. You'll see the current go negative while the motor spins down. This active load circuit is typically engaged for a few seconds at most but it does help.

author: David Hess
author_rank: Super Contributor
timestamp: May 11, 2023, 12:22:51 pm
content: Quote from: nctnico on May 11, 2023, 09:42:39 am25 to 100 microfarads per amp is typical however with careful design, less than 0.1 microfarads per amp is possible. I just noticed that it is the later designs which always seem to include the class-AB output stage or active load.

author: mawyatt
author_rank: Super Contributor
timestamp: May 11, 2023, 01:33:21 pm
content: Quote from: tautech on May 11, 2023, 03:39:13 amWe did take a look at the 5000 series, and yes they are kind of expensive!!Once we get the pump motor profiles for the various pump motors, then we'll have a better idea of what we'll need. The KWR102 isn't going to be enough tho.The system design is leaning towards separate power supplies, rather than one unified supply. This allows a dedicated supply for the pump motor, and another for the other stuff. With this in mind the heavy load motor supply doesn't need to be accurate or low noise, just have enough to hold up the pump motor and one option is to use a Mean Well Open Frame Supply and design a quick acting current limit, as we don't need a variable voltage range, so this may work out.It's interesting to see discussions of power supply active sinking capability, IMO this should be a prerequisite in any modern quality Bench Level Supply, but few have this built-in capability. Same goes for output capacitance, this should be as low as possible in a quality Bench Supply. It doesn't take much energy to destroy/damage a modern IC, and even with a low current limit set point the output capacitance energy storage is sufficient to quickly dump into a circuit and take out various chips, as as we know Murphy will direct that energy to the most expensive and elusive chips!!Best,

author: armandine2
author_rank: Frequent Contributor
timestamp: May 11, 2023, 02:22:22 pm
content: a good time to check my kikusui manual re. sinking current

author: mawyatt
author_rank: Super Contributor
timestamp: May 11, 2023, 02:23:05 pm
content: A story related to the power supply output capacitance that some folks might find interesting. Back in 70s and 80s much effort went into nuclear survivability for electronics, and research found the levels of minimum energy in a supply line or power supply that would damage/destroy a chip. Basically a nuclear detonation will turn on all PN junctions of exposed semiconductors, this includes diodes, transistors and junction isolated chips and why for high radiation environments (space for example) insulated substrate chips are preferred.For survivability the supply line and power supply had a maximum available capacitance and discharge profile which often dictated utilizing a "Crowbar" type Power Supply, where the Crowbar (we used an SCR) would act upon an event leading edge. The available capacitance was a complex assessment of the capacitance that could quickly discharge during an event leading edge from the power supply and PCB distributed decoupling capacitances, and recall this was something on the order of ~90uF for a 10mJ energy level for a 15V supply (vaguely recall this as the maximum available discharge energy to cause chip damage).Anyway, this is kind of related to the output capacitance of a Power Supply and why one prefers a lower capacitance as an "event" could be a malfunction of the test circuit, device or even operator (scope ground lead dangling and shorting something on the PCB, been there done that)We must remember that the power supply output capacitance, or a portion of such, is generally outside current limit circuitry and the current limit can't help with the instantaneous discharge levels for the output capacitance, so lower is betterBest,

author: David Hess
author_rank: Super Contributor
timestamp: May 11, 2023, 03:13:23 pm
content: Quote from: mawyatt on May 11, 2023, 01:33:21 pmIn a majority of applications, minimum output capacitance and active sinking are not required. And both have at least the increased potential of creating oscillation with certain loads. Of course either or both may be indispensable in specific cases.Active sinking is nice, but so are readouts of current and voltage, and I can get by without the later as long as I have an indicator that the power supply is current limiting. None of these things are something that I consider indispensable.Quote from: mawyatt on May 11, 2023, 02:23:05 pm"Intrinsically safe" designs are subject to a similar analysis. Systems which support hot-plugging, including USB, also have limits on total capacitance to prevent high inrush currents which could cause glitches.

author: rsjsouza
author_rank: Super Contributor
timestamp: May 12, 2023, 10:58:04 am
content: Quote from: james_s on May 06, 2023, 05:52:08 pmPerhaps this was mentioned before but, since you are in the US, there are several relatively cheap sources of 24V power transformers that would only need four diodes, a capacitor plus a few parts to make a voltage regulator to tame the input voltage (LM317is quite versatile and can even perform current limiting and high output current applications). Look for the typical 40VA transformers for HVAC and house alarm systems. Forget about doorbell transformers, which are probably too weak for a soldering iron.

author: br4n_d0n
author_rank: Contributor
timestamp: May 16, 2023, 09:47:50 pm
content: Well, I either made a good deal or a very expensive (for me) mistake. I'll see when it arrives.

author: james_s
author_rank: Super Contributor
timestamp: May 17, 2023, 12:52:54 am
content: What did you get?

author: br4n_d0n
author_rank: Contributor
timestamp: May 17, 2023, 02:40:55 am
content: A beat up BK Precision 9206 with the hope I can get working properly; it' a gamble

author: james_s
author_rank: Super Contributor
timestamp: May 17, 2023, 02:47:17 am
content: That's a beast of a power supply. The single output and high voltage makes it quite a specialized instrument but I can see it being useful. Hopefully you can find a schematic for it, not surprisingly there isn't one in the manual.

author: br4n_d0n
author_rank: Contributor
timestamp: May 17, 2023, 02:57:44 am
content: Yeah, it fits my needs perfectly and more @ 150v/10a/600w so I hope it works out.

author: br4n_d0n
author_rank: Contributor
timestamp: May 19, 2023, 09:51:00 pm
content: F**K YEAH! This thing seems to work finethis gamble paid off for the price I got this thing.I tested the voltages from the millivolt range all the way up to 150 volts, tried testing the current which was a little more difficult for me, but seemed to be fairly close on the same amperage range all the way up to 9 amps where I stopped because my meter blows a fuse ~10 amps. The VFD is in mint condition and very bright and scrolled through the menu to test a couple other things. All seems good except for a missing encoder knob, some dings on the metal case, and a little dirty, but I can clean that up.

author: james_s
author_rank: Super Contributor
timestamp: May 23, 2023, 11:47:09 pm
content: Always nice when that happens. I've bought a surprising number of untested as-is things and even some "not working" stuff that turned out to work just fine.

author: armandine2
author_rank: Frequent Contributor
timestamp: May 30, 2023, 11:18:05 am
content: Build or Buy ?Buy , a few - attempt to buildhttps://sound-au.com/articles/bench-supply.htmI wouldn't want to build one if I didn't have one