Where have all the DIY bench power supply kits gone? - Page 1
Forum section: electronics / general

author: k_sze
author_rank: Contributor
timestamp: August 21, 2016, 08:57:16 am
content: Dave said in his basic lab setup video that one can build their own bench power supply. He shows several examples in his video and they do look like kit builds.But where can I find such kits nowadays? There are some kits on eBay, but none of them comes close to what Dave shows, in terms of specs, usability, or completeness, e.g.:no multi-turn pot; instead, they have separate coarse and fine adjustment knobsno voltage/current display;board only, no enclosure provided;The thing is, I'm a complete beginner and I don't have the knowledge to modify existing circuit designs, or to design and make my own enclosure. I need a project to get me started. Familiarising myself with reading schematics, and basic soldering skill is probably as much as I can do right now.Am I expecting too much?

author: MosherIV
author_rank: Super Contributor
timestamp: August 21, 2016, 05:02:33 pm
content: HiI see you are in Hong Kong, so I do not know if Vellamen is distributed there.The kits on ebay are aimed at hobbyiests wanting to usethe psus in a project hence no controls.I mentioned Vellemen because I know they do psu kits with voltage control.If you want a single multi turn voltage control instead of the course & fine, just replace the 2 potentiometers with the multiturn one, make it the same value as the course+fine or just the course.Not sure if they do a kit with current control, I have not looked for a long time. Ideally you should have current control. The first psu I built did not have current control but then it was only 500mA so it could not do that much dammage, so if you cannot find current control do not worry too much, this is your first psu/project.No kit that I know of just allows assembley, they usually require you to mark, drill and cut out the enclosue. This is a skill you will need to develop anyway.

author: David Hess
author_rank: Super Contributor
timestamp: August 21, 2016, 11:25:46 pm
content: The three things you list would be my preferences for a kit.no multi-turn pot; instead, they have separate coarse and fine adjustment knobsI prefer coarse and fine controls to a multi-turn potentiometer. I might want a 10 turn potentiometer on a supply intended as a low current reference.no voltage/current displayGood, so I can add my own. The design needs to have a suitable current meter output though.board only, no enclosure providedIf I am adding my own meters and maybe controls, then their enclosure might not work anyway.I used to see kits which either came with an encloser and standard options or just a bare printed circuit board and maybe critical parts.

author: klunkerbus
author_rank: Unknown
timestamp: August 22, 2016, 12:21:19 am
content: This question seems to come up on a regular basis. The only power supply kit I remember being mentioned as one that is available is from Elenco. Searching on Elenco power supply kit will get you links to sources for it.Unit-level kits that include everything through the enclosure are quite rare these days. And when you find them, they aren't typically a bargain either.

author: eugenenine
author_rank: Frequent Contributor
timestamp: August 22, 2016, 12:22:57 am
content: Do you really need a kit though? Any kit in an affordable price range will be a simple transformer and liner regulator. Pick your favorite and build one. Mine was a pair of LM317's that I used until this year when my son burned up the transformer.Mine was a kit though but I had already built a couple similar, I just kept the kit one because it was part of a competition I won.

author: Aodhan145
author_rank: Frequent Contributor
timestamp: August 22, 2016, 12:27:53 am
content: Why do you need a kit? Design it your self, it doesn't take long to learn how to do it. For components get them from a distributor like farnell. The advantage with building your own is you know what you need. Buy some components off ebay for prototyping and play around with them on a breadboard powered from a wall wart to learn how they work.How are your skills? What have you played with? Have you been using anything like an Arduino? If so you could make it digitally controlled.Things I would look in to is basic voltage regulator ICs and opamp circuits. Start looking at other schematics and try to see how they work. This may take some time but the skills you will learn are highly valuable.

author: k_sze
author_rank: Contributor
timestamp: August 22, 2016, 06:12:19 am
content: I don't actuallyneeda kit, just like I don't actuallyneedto learn electronics. I understand that I can learn a lotifI design and build my own power supply from scratch; I'm just afraid that it's too big of a bite at once.I could start with some dead simple design, and then learn more theory, iterate, and improve; but then it will take me a lot of time before I get something I feel would be useful and can move onto the next project.I'mhopingto find a kit that is versatile (i.e. good voltage and current range), well behaved (over-voltage protection, current limiting, overheat protection, no overshoot/spike at power on/off or when connecting a load), and complete (with enclosure and voltage/current meter). If I can find a kit like that, then I can build it and immediately have something working to power my next project. Eventually I can start designing my own power supply from scratch, but I don't want to do that today.I don't mind marking, drilling, and cutting the enclosure. I can probably do that. It will be good practice. But if I have to pick my own enclosure and work out where to put the knobs, meters, sockets, etc on the front and back panels right away, that's another story.In other words, it's not so much about myneedas it is about how much I would like to learn from this project, and what I want in the end product.What I would like to learn from this project:practice solderinglearn to read schematicsbasic hand crafting (the part where I mark, drill, and cut the enclosure)Ideally, what I would like to get out of it as an end product, is a power supply that has:dual trackingat least 0-15 VDC per trackat least 0-3A per trackcurrent limitingover voltage protectionoverheat protectionno overshoot at power on/off or when connecting a loadan enclosurevoltage meterscurrent meter (optional)

author: MosherIV
author_rank: Super Contributor
timestamp: August 22, 2016, 09:59:04 am
content: QuoteYou basically want a full blown bench PSU.I do not think there are many kits that provide everything you want (a full blown bench PSU).They will not be much cheaper than buying one if you could find one.You will only learn to solder if you find one.Do not start with PSUs above 1Amp, they get complicated above that.Start with the simple variable voltage only one and work up from there. You can get cheap panel volt and volt/amp meters to add to the basic variable volt PSU.

author: tszaboo
author_rank: Super Contributor
timestamp: August 22, 2016, 10:04:25 am
content: You dont find kits, because these things require a transformer, a big heatsink (and you even specified a case) You either ship it with these mechanical things, and it becomes bulky and expensive to ship, so you just buy a pre made power supply. Or you ship it without it, and nobody can build it, because they cannot buy your intended power supply and heatsink (and it needs holes and such).

author: k_sze
author_rank: Contributor
timestamp: August 22, 2016, 10:17:12 am
content: Right now, the closest thingsavailableseem to be one of these:Elenco XP720K (http://www.elenco.com/product/productdetails/power_supply=ODU=/same_as_xp720_in_kit_form=NTc4)RSR 3010/3040 (http://www.elexp.com/ProductDetails.aspx?item_no=01PS3040K&CatId=2d6558c8-938e-4373-927d-951d70d0a048)Altronics K3218 (http://www.altronics.com.au/p/k3218-dual-tracking-0-19v-power-supply-kit/)Out of curiosity, why doesn't any of them specify the input power on the product page?

author: MosherIV
author_rank: Super Contributor
timestamp: August 22, 2016, 10:38:27 am
content: For $200 you may as well just buy a pre-built PSU.You should be able to find them on ebay or since you are in Hong Kong - do you know where the electronics shopping sector is?

author: k_sze
author_rank: Contributor
timestamp: August 22, 2016, 10:41:15 am
content: Quote from: MosherIV on August 22, 2016, 10:38:27 amI only know SSP/Ap Liu Street. And the biggest shop there seems to be WECL (http://www.wecl.com.hk/).

author: MosherIV
author_rank: Super Contributor
timestamp: August 22, 2016, 11:03:41 am
content: QuoteI just googled Ap Liu Street, Hong Kong.Sounds good, just keep going to the flea market, and look around for cheap 2nd hand bench PSU. Try to get an assurance it will work.You are local so the traders should figure that out and not give you the tourist price.If your heart is set on building one, look for transformers, heat sinks, case and largish capacitors in the market - these are the most costly parts of PSUsThe look up the LM317 Adjustable Voltage regulator, most people built their first PSUs from this device.

author: singapol
author_rank: Frequent Contributor
timestamp: August 30, 2016, 05:00:23 pm
content: Quote from: k_sze on August 22, 2016, 10:41:15 amHeavens..You are at the doorstep to the factory of the world. Use use internet to arrive here and you can'ttype "Aliexpress variable power supply"? You will be like a kid in a candy store. You can buy a lab PSU . For a little more you can have a programable one.

author: Rbastler
author_rank: Frequent Contributor
timestamp: August 30, 2016, 05:23:38 pm
content: Aliexpress and Bangood offer some power supply kits. The second one currently has it's 10th anniversary and therefore bargains.http://www.banggood.com/0-28V-0_01-2A-Adjustable-DC-Regulated-Power-Supply-DIY-Kit-Short-Circuit-Current-Limiting-Protection-p-1060253.htmlhttp://www.banggood.com/0-30V-2mA-3A-Adjustable-DC-Regulated-Power-Supply-DIY-Kit-p-958308.htmlThe cheapest programmable one with keypad is this one:http://www.banggood.com/DPS305BM-30V-5A-DC-Digital-Control-Laboratory-Adjustable-Power-Supply-p-932358.html.If it can be a switching supply there is this one:http://www.banggood.com/DP50V5A-Buck-Adjustable-DC-Power-Supply-Module-With-Integrated-Voltmeter-Ammeter-Color-Display-p-1050061.html.

author: David Hess
author_rank: Super Contributor
timestamp: August 30, 2016, 08:01:45 pm
content: Quote from: Rbastler on August 30, 2016, 05:23:38 pmI recognize that schematic; I hope they fixed the overshoot on startup.Some of the Engrish is hilarious.

author: k_sze
author_rank: Contributor
timestamp: September 04, 2016, 06:45:42 am
content: Quote from: David Hess on August 30, 2016, 08:01:45 pmThat design is everywhere. Lots of people seem to sell the same kit, on eBay, AliExpress, Banggood, etc.I think it originated from electronics-lab.com and if I understand correctly, the overshoot has never been fixed:http://electronics-lab.com/community/index.php?/topic/40835-0-30v-0-3a-latest-data/.And here is liquibyte himself discussing about that design on this forum:https://www.eevblog.com/forum/beginners/bench-power-supply-kit/msg769237/#msg769237

author: Docholiday
author_rank: Regular Contributor
timestamp: September 05, 2016, 02:31:26 am
content: Yep, I was totally mixed up on this. I stand corrected the turbine is located in the main unit and the heating element in the handle.

author: singapol
author_rank: Frequent Contributor
timestamp: September 05, 2016, 04:49:13 am
content: Quote from: k_sze on August 21, 2016, 08:57:16 amYes, you are expecting too much as you said you are a complete beginner and don't have knowledge to modify existing circuit designs. This means learning theory of electronics/electricity , basics like RLC (resistance, inductance and capacitance, their properties). Also AC and DC circuits, signal waveform generation, electronic components and their functions and how to use multimeter and oscilloscope. In fact most most basic electronics classes start by constructing a simple audio amplifier and a simple power supply ,positive without a panel meter. There is also a general review of electrical/electronic measurements and instruments.Like analog panel meters (those that use a needle rather than digital display). It's good to know some history about technology. Don't forget good old OHM's Law.QuoteI believe the above power supply requirements are good to have but then it's laboratory grade, althoughyou could but a chinese made one but given the bad rap on the cheap ones it's a gamble if you decide to use one. Also note that they are switchmode type or hybrid with large transformers. As a learning execise try a simple 3 terminal regulator like LM317 (positive) LM337 (negative) they are good to 1 ampere if properly heatsinked and if you want higher current just add a power transistor, see their respective datasheets.Power supply protection is another subject but it's not hard to implement a simple one.As for enclosure it's not difficult as you can use a plastic one (softer and easier to cut ) but you do need power drill ( that in itself is a learning curve as it poses a safety hazzard ,eyes and hands, use eye googles for protection) or use a manual hand powered drill and tapered hole enlarging reamers to make holes as some components have odd diameter size that a standard drill bit set may not have the size and a set of mini files to deburr the holes and edges. Analog panel meters for voltage and current are available but you need to know which one to get depending on your current capacity and voltage which come back to the old question ..might as well buy a commercial power supply given it's "faults" as it saves you the headaches and mistakes you are going to make along the way and concentrate on learning and building electronic circuits.First have a good read of this to understand what you really want and can realistically find and pay:DC Power Supply Handbook (AN 90) - Agilenthttp://cp.literature.agilent.com/litweb/pdf/5989-6288EN.pdf