Power supply advice please  (I live in the UK) - Page 1
Forum section: electronics / beginners

author: HobGoblyn
author_rank: Unknown
timestamp: December 06, 2018, 10:34:05 pm
content: Been watching EEVblog #168 How to set up an Electronics LabBeen into electronics since a kid (used to build kits from Tandy's in the 1970's), now I want to take up the hobby in a serious way.Now due to ill health, I've had to retire at 54 (don't want any sympathy), haven't got loads of spare money, but want to set up a reasonable lab, so that I can start learning properly and have most things I could need.Not to worried about components, can get them cheap as and when needed (got a load of caps, resistors etc, plus a load of Ardunio bits to be getting on with). But I want to get the big things now, due to finances, I don't want to have to plead with my lovely wife to buy big (for my finances) items in months to come, I'd rather get most of it over with now.I have some things already, have a Hantek DS05102P Oscilloscope, have a couple of meters.I've been going through the youtube blog and Dave recommends getting hold of an analogue Oscilloscope. Looking at ebay, they don't seem very cheap, I presume this isn't really needed?I do need a power supply, Dave suggests getting a kit, but I can't find any on the UK. When looking at pre-built ones, I do see a lot of similar looking (presumed made by same company and rebadged) power supplies on ebay/amazon. Was thinking about something like thishttps://www.amazon.co.uk/dp/B01E7OGHJM/?coliid=II5WG08YUD1N2&colid=L5N3DCOD52K1&psc=0&ref_=lv_ov_lig_dp_itBut reviews on things like power supplies and soldering stations all seem very mixed, or numerous so called different sites all recomending exactly the same top 10 (suspect they are fake review sites). Thoughts on a power supply for a beginner, is the one I selected suitable?My soldering iron is okish (Antex Xs25w) but not a soldering station, video says I must have a soldering station. That's a minefield as there's a load of rebadged cheap stuff out there. Any advice on a cheapish good one?Then he recommends getting a hot air rework station, again loads around, haven't a clue whether they are good or cheap crap. Any suggestions for a cheapish good one please?Most other things in the vid I already own. I know it's a bit of a how long is a piece of string question, I don't expect to be working on mains voltage stuff that much, only if repairing something that breaks.Many thanksHob

author: Totalsolutions
author_rank: Contributor
timestamp: December 06, 2018, 11:25:24 pm
content: Hi HobSame here I can fix things as they break. Take a look at “My Mate Vince “ on YouTube. I use soldering irons , Weller but 4 or 5 with different bits and wattage, but not a hot air rework station (yet). Good quality basic tools from Wera or CK or Wiha. Even Stanley and Draper pro. All good brands really. A very good programmable power supply in valuable. Get your Xmas list in.

author: Jwillis
author_rank: Super Contributor
timestamp: December 06, 2018, 11:51:14 pm
content: The biggest expense on a linear supply is the transformer so many companies get around that by using a switching supply in place of the bulky expensive transformer.So a cheap power supply will do fine that delivers 2 or 3 amps at 20 to 30 volts is fine.You don't need a soldering station right off the start .There are adjustable soldering irons that will do fine for the beginner.They won't have the power as a fancy station but 50 to 60 watts has served people well for years.If you plan on using SMC (Surface Mount Components) then a a hot air work station is a must . But you could get by with a hand held hot air gun similar to thisIt probably won't replace a large chip but smaller components it would probably be alright.Cheap and good is a hard proposition.

author: Terry01
author_rank: Frequent Contributor
timestamp: December 07, 2018, 12:06:36 am
content: I have the 30v 5A version of that power supply and it's served me well for 18 months-ish. I like it as it has all the safety features on it and is quite accurate and it also hasn't blew up or electrocuted me even though i've made loads of beginner mistakes!

author: tggzzz
author_rank: Super Contributor
timestamp: December 07, 2018, 12:21:23 am
content: There's a good argument to be made that if you can't specify what you need and why, then you don't need it.With skill and imagination, you can get away with remarkable little equipment. For example, I designed and built my first computer (6800+128bytesof RAM, switches and LEDs) with only the front panel switches and LEDs and a multimeter. Learned a heck of a lotYour question about PSUs... The answer very much depends on the required power and voltage. I have a few old Farnell/Coutant PSUs that I ought to flog.Consider going to nearby hamfests; there is a lot of surplus equipment there, some of which will be good value.Consider contacting a local Hackspace/Makerspace; they will have equipment and - more importantly - experienced people with ideas.Look on gumtree, and on fleabay for local items that you could examine before buying them with cash.

author: boffin
author_rank: Unknown
timestamp: December 07, 2018, 12:28:16 am
content: Quote from: HobGoblyn on December 06, 2018, 10:34:05 pmYour existing scope will be (more than) fine. Understanding how a scope does what it does is where an analogue is better, but yours will be more than fineIf you just need low (<12, 1A) power supply, watch Dave's video on the $20 power supply, and have a look at the eevblog thread on here for that subjectFor a cheap meter it's hard to beat the Aneng AN8008 (or 8002)For an inexpensive soldering iron, try the Yihau 947-II or Quicko T12-947 (I put a video on youtube comparing them)

author: james_s
author_rank: Super Contributor
timestamp: December 07, 2018, 12:32:50 am
content: There are lots of good power supplies out there on the used market. It depends largely on what you plan to do with it, but I generally suggest a linear bench supply with at least two independent outputs of 0-20V or so capable of delivering at least an amp. More current is always nice, a constant-current mode is highly desirable although not absolutely mandatory at least for lower current supplies.Switching PSUs have their place but I do not recommend them as a basic bench supply. I also do not like PSUs that have digital controls, they look fancy yes, but nothing beats the usability of an old fashioned analog knob. Digital meters can be nice, but again I personally prefer analog.

author: cdev
author_rank: Super Contributor
timestamp: December 07, 2018, 04:20:43 am
content: This is probably the best place in the world to ask and get advice on setting up a beginners lab. Just don't jump on the first thing you buy, Wait until you know you will use something and that its the best bang for your buck and you'll do well. Also wait until you can get a good deal.

author: spec
author_rank: Frequent Contributor
timestamp: December 07, 2018, 08:49:39 am
content: This is the best values for money lab PSU and the ideal specification for home electronics- I have three of these (they are linear by the way- one reviewer on ebay claims that they are switch mode?)https://www.ebay.co.uk/p/Adjustable-DC-Power-Supply-30v-10a-Variable-Precision-Digital-Lab-PSU-Clip-Cable/23025566378

author: bd139
author_rank: Super Contributor
timestamp: December 07, 2018, 08:53:35 am
content: I wouldn’t buy any cheap supplies when you can get a decent TTi one here in the UK for not much more and sometimes less money!Look out for Thurlby / TTi PL320/330 units on eBay. Occasionally they turn up for £30-40 or at hamfests for £20-40. They were £300-400 a piece new. I paid £40 each for mine from eBay with delivery. They are professional supplies, have service manuals available and are pretty much everything proof and have no fan.I wouldn’t buy an analogue oscilloscope now. Even the newest ones are prone to packing in. I spent a fair amount of time fixing dead ones and it’s a pain if you are only just starting out.

author: Terry01
author_rank: Frequent Contributor
timestamp: December 07, 2018, 09:14:19 am
content: Quote from: bd139 on December 07, 2018, 08:53:35 amI would agree with that. I am also relatively new to electronics too.I got an analogue scope first then a digital one a couple months later and my analogue scope is still living under the bed, where I use my digital scope 99.9% of the time.I would also advise to just get digital. You can get a decent 2nd hand Rigol or whatever quite cheap, even £250 will get you a nice one.

author: spec
author_rank: Frequent Contributor
timestamp: December 07, 2018, 09:25:57 am
content: Quote from: bd139 on December 07, 2018, 08:53:35 amThere is innuendo in what you say. If you buy wisely, cheap (value for money) does not mean not decent. It is also important to keep things in perspective. A lab PSU, after all is said and done, needs to provide stable volts and controllable amps. For home work it does not need, profiles, IEEE program interface or to make coffee. In fact, in the interests of simplicity, it is better if it does not.Quote from: bd139 on December 07, 2018, 08:53:35 amAFAIK that PSU is 32V at 3A whereas the PSU I recommended is 0V to 30V at 0A to 10A. Also if that Thurlby unit goes wrong, it will be difficult and costly to fix. BTW, I am not a big fan of Thurlby PSUs. We had a load of them at work and they were nothing but trouble.I know of quite a few people who have needlessly bought fancy equipment which goes wrong and after vain attempts to fix it, the equipment is just left to rot.The other thing is that, with a couple of mouse clicks, you could have a very serviceable PSU to use within a couple of days, and if you need another, just do the same thing again. And you would have a PSU that would be more than adequate for home electronics work. Not that long ago that ebay lab PSU would have been the most wonderful PSU imaginable, certainly much better than the lab PSUs we had at work. Buying second hand takes time and is a big risk, especially for a newbee, and going to fests also takes time.Quote from: bd139 on December 07, 2018, 08:53:35 amThat may be your experience, but it is most probably because you have been buying the wrong scopes. If you get a decent, simple scope, they last for years without any problems. BTW, you can get plenty of problems with digital scopes.On the subject of digital (storage) versus analog (real time) scopes for a beginners, that is a difficult call. Personally, I would advise an analog scope, because you get much closer to seeing what the electrons are actually doing when they are doing it.There is also a big debate about bandwidth. Some people argue that bandwidth does not matter. I take the opposite view and would say that the minimum bandwidth scope that you should get is 10MHz and ideally 100Mz. With a digital scope and a low bandwidth analogue scope you can loose a lot of the waveform which may be why a particular circuit is not working. A good example is high frequency ringing at a MOSFET gate or ground bounce on a logic signal which may be causing erroneous clocking.

author: Terry01
author_rank: Frequent Contributor
timestamp: December 07, 2018, 09:43:53 am
content: Just read back and see the OP already has a Hantek digital scope. My bad....sorry!I had a similar Hantek scope before I got my Rigol and to be honest the Hantek never caused me any problems and did everything I needed it to. It was a great very simple wee scope to learn on and if I am honest the extra features on the Rigol I have now are just a luxury, I didn't "need" them it's just nice to have them.One thing is for sure, you'll get lots of opinions from lots of people with plenty experience and knowledge so you'll have the best chance of getting the best stuff for you.

author: jpb
author_rank: Super Contributor
timestamp: December 07, 2018, 10:19:22 am
content: I would second the recommendation for TTi supplies (second hand). I have three supplies, and Agilent an Hameg and a TTi (which I bought first) but it is the TTi that I use all the time. I note that some people report trouble with TTi supplies and others that they never go wrong - my experience has been the latter. They have been around a long time and probably the more recent supplies are better than the older ones.I'd also say to get a linear supply rather than switched mode. For electronics you aren't likely to need a huge amount of current so 3A is fine and similarly you probably won't need to go above 30V (probably most circuits will be under 20V though some things like a 24V supply). Linear are simple and low noise and the low efficiency doesn't matter (in my view) in a bench supply.

author: jc101
author_rank: Frequent Contributor
timestamp: December 07, 2018, 10:20:47 am
content: Quote from: HobGoblyn on December 06, 2018, 10:34:05 pmIf your near Cambridge I have a spare Maplin N27GG PSU "80W Constant Power Switching Mode Power Supply" (you'd have to google the code for specs etc.). All complete in it's original box. I've been meaning to either put it up here or on eBay for ages but not got round to it. Pretty sure it's been kicking around here for a while and surfaced when hunting through boxes for something else. Now I keep moving the box around in my never ending game of office space tetris.

author: bd139
author_rank: Super Contributor
timestamp: December 07, 2018, 11:11:56 am
content: Quote from: spec on December 07, 2018, 09:25:57 amYes indeed. Current limit is killer feature number one.Quote from: spec on December 07, 2018, 09:25:57 amOn the subject of the Thurlby supplies, they are very easy to fix (I've only had to fix one out of the 10 or so I've owned and that was trashed when I got it) and AIM TTi still stock spares for them so you can actually get the bits. I wouldn't buy their higher end digital units exactly based on your earlier complexity argument. The basic CC/CV PL series are rock solid though. 10A in the hands of a new user is dangerous IMHO. I haven't used more than about 2-3A for years myself.The problem with the cheaper new supplies is they all universally have critical design flaws. The Tenma units for example tend to just pack in. The IC on them has the markings filed off as well so chuck it in the bin or deal with Farnell/CPC returns if it goes wrong (mightmare). The switching units like the one you suggested tend to just spontaneously explode or the displays give out in no time at all. The cheap Mastech linear ones, the tap switch relay gives out, exceeds the SOA of the pass transistor and then dumps the whole unregulated supply into your project. Phut! Not good experience. I've fixed those...You're doing yourself an injury right away if you're not using half decent equipment when learning or starting out IMHO. You don't need a brand new Keysight supply, but something that does what it says on the tin you can trust.Quote from: spec on December 07, 2018, 09:25:57 amI've fixed a lot of good quality analogue scopes - 30+ at this point across Tek, Hameg, Philips, LG, Kenwood, HP. And I worked for a T&M department back in the day. Look though my forum history. There are no decent, simple analogue scopes left now which aren't likely to give up on you.A broken analogue scope is an intellectual playground and an excellent learning tool but might interrupt your work and critical path. That's up to the buyer.Quote from: spec on December 07, 2018, 09:25:57 amMinimum 20MHz ideally 100MHz for me here. I've got a 60MHz digital (old TDS210) and 250MHz (475A) analogue at both extremes. The digital one gets most of the work because to be honest it's more covenient. I had a Rigol DS1054Z but I didn't use it for any of its strengths (mainly memory depth) so it went.I suggest a digital scope simply because at the two opposite extremes of the timebase, analogue scopes are terribly difficult to use, even the good ones. At low sweep speed there is no persistence and at the high end, even on a properly set up analogue unit, there is very little brightness. Digital scopes don't have that and all of the disadvantages of earlier digital scopes like aliasing are pretty much moot these days. The hantek is probably fine. And there's the inevitable decisive "autoset" feature which is great for new users who don't know how to get the scope into a known state.

author: amlu
author_rank: Contributor
timestamp: December 07, 2018, 01:03:30 pm
content: power supply - one of those modules, depending on how many Volts/Amps you need.https://rdtech.aliexpress.com/store/all-wholesale-products/923042.html?spm=2114.12010108.nav-list.1.42b692b7mWKYGcPower it up with SMPS of your choice, can be old laptop adapter, can be a meanwell brick.

author: CJay
author_rank: Super Contributor
timestamp: December 07, 2018, 02:05:06 pm
content: Another vote for the TTi PSUs, the GPIB programmable all singing and dancing ones don't look much fun to repair if faulty but the simple ones are trivial to repair if you manage to kill one or find a faulty one for cheap, they are pretty bombproof unless you do something really silly.The Farnell L(T)30 variants are also good, simple and pretty solid performers, again easy to repair and have bog standard parts in them. Though they are *old*, they're still very usable.The DPS Buck, boost modules are pretty good too apparently, haven't tried one myself yet (keep meaning to order one) but they look usable and can be fed from a dirt cheap laptop PSU.As for 'scopes, there are plenty of cheaper analog scopes out there, late model Hamegs are a fairly safe bet but you've already got a halfway decent digital scope so I'd spend the time learning its limitations first, you'll probably find it's more than adequate for your needs, at least in the short term and possibly far longer.Don't fall into the trap of thinking you have to have all the test gear because you really don't, there's nothing wrong with having lots of test gear (only my wallet stops me) but it's absolutely not necessary to have a 0.1PPM 27.5 digit meter and a spectrum analyser capable of DC-Light, the majority of projects and repairs only need simple gear and it's really easy to get yourself very confused when you have too much data.

author: bd139
author_rank: Super Contributor
timestamp: December 07, 2018, 02:21:17 pm
content: Warning on the Farnell supplies. The E/LT ones are missing a couple of essential diodes, one across the pass transistor and one across the output. If you charge up an SLA with one and the line power goes out, or connect a voltage source to it by accident the wrong way, you'll need to buy new pass transistor and driver. Also the push button switches on the E series wear out. Otherwise they're really nice. I use an E30/2 as a radio supply occasionally for low power stuff that is tested and doesn't need current limiting.

author: max_torque
author_rank: Super Contributor
timestamp: December 07, 2018, 02:38:24 pm
content: my 10 pence:Don't skimp or DIY it on the essentials if you really want to get projects finished.If you are just interested in electronics, and having a project is just a means to that end, then sure, you can make your own power supply or whatever,from kits, or modified existing things (like server PSUs etc). But, if you actually want to get on with a specific project, then what you need is bench equipment that just works, and that you don't need to spend ages messing around with.Thanks to china, that no longer means spending ££££.. I started with a 30V 10A Chinese power supply, a cheap Chinese hot air gun and soldering iron, and well, that was it. I bought a decent (ish) beginner scope (rigol) and got stuck in!It's easy to see say £300 on a scope be a "lot of money" but how much do you value your time. Even if you are not producing things for sale, ime, when you are doing projects, even for your own benefit, you want to be spending your time making that project work, and not on making your toolset work.......

author: CJay
author_rank: Super Contributor
timestamp: December 07, 2018, 02:53:54 pm
content: Quote from: bd139 on December 07, 2018, 02:21:17 pmHehe, I found that one out the hard way

author: bd139
author_rank: Super Contributor
timestamp: December 07, 2018, 04:34:02 pm
content: Me too

author: nfmax
author_rank: Super Contributor
timestamp: December 07, 2018, 05:06:34 pm
content: Quote from: bd139 on December 07, 2018, 02:21:17 pmThat's odd - are you sure? I have a couple of these, one L30-1 and one LT30-1. The circuit diagram, issued 1979-07-28, shows 1N4003's in both places, D202 & D203. Maybe it was missing in earlier incarnations of the design? Mind you, a 1A diode is a bit wimpy for a 1A supply, especially when they use two paralleled 2N3055's as pass transistors.Nice supplies, and the only ones I have at present that go up to 30V.

author: cdev
author_rank: Super Contributor
timestamp: December 07, 2018, 05:11:27 pm
content: If you live in the UK, I would seriously consider looking - no making it your goal to buy one of the better UK made power supply brands (like TTI or Thurlby/Thandar) used.If you do your research you'll get a much better supply value than one you buy new, one that would likely be built to last.Also, being in the UK a similar situation likely exists to the situation here for US equipment, there is more of it on the used market there, so perhaps a bit cheaper.

author: james_s
author_rank: Super Contributor
timestamp: December 07, 2018, 05:40:05 pm
content: Used is definitely a good route for power supplies, I've built most of mine, but the commercial units I have I got used.That leads into another point, if you keep at this electronics stuff you will likely accumulate multiple power supplies, so don't worry too much about trying to find the end-all, be-all PSU right off the bat.

author: bd139
author_rank: Super Contributor
timestamp: December 07, 2018, 06:25:49 pm
content: Quote from: nfmax on December 07, 2018, 05:06:34 pmThere are a few revisions, not all documented well. Many an hour head scratching there. You have to crack it open and look. It doesn’t necessarily not span later versions as I’ve seen some of the plastic fronted late ones without diodes!

author: rstofer
author_rank: Super Contributor
timestamp: December 07, 2018, 07:38:28 pm
content: Quote from: tggzzz on December 07, 2018, 12:21:23 amExactly right!I often see the suggestion to get some kind of power supply right away. Gee, I got by without one for decades! Most of my stuff was 5V and I had a fixed 5V 3A power supply. Wall warts work, even simple 78xx and 79xx supplies work. If I was playing with transistor amplifiers, I might use a 12V wall wart.I did buy a Rigol DP832 but only because I could, not because I NEEDED it.So many projects these days revolve around Arduino that are USB powered so I wonder why people buy triple output supplies. Yes, they are great for older dual-rail op amp projects and that's exactly why I bought mine.Think through the PS issue carefully. You may find that this can be deferred for a very long time.The Hakko FX888D soldering station should work well. You do not need a hot air tool until you try to desolder BGA packages. Everything else can be desoldered by cutting the leads and removing the tabs one at a time. I have a hot air tool and don't use it. I don't desolder much of anything. If you want to remove and replace a component without cutting the leads then a hot air station is required. Buy one when you need it.As to SMD soldering, when you get that far, you might consider converting a toaster oven. Post another thread...You can solder small SMD projects on a kitchen hot plate. Place the board the plate, crank the knob to high and use tweezers to remove the board after the solder flows. Then turn off the heat. Not a bit of science or math is used for this process. Cook to done, remove from heat! Obviously, the plate must be in complete contact with the board. Some hot plates don't work well for this. I saw a link yesterday talking about putting a table saw blade over the heater to spread the heat. Sounds good!The Rigol DS1054Z scope is very inexpensive, has built-in decoding and, when unlocked, is rated for 100 MHz. It's a great scope for the money. I have one but I also have an older 350 MHz Tek 485 that sits under my bench taking up space. I have a very few applications where I need anything even approaching 100 MHz so the Rigol is fine.What about an arbitrary waveform (signal) generator? There are some cheap kits around. Maybe they are adequate.================================Here's the thing: What do you want to learn? That question isn't as dumb as it seems. Do you want to become the next great op amp guru? That's a different skill set than the world's best Arduino programmer. There are probably differences in the toolset as well.If you're starting from nowhere, I recommend you buy the Analog Discovery 2 and use all of the tools it provides. There is no other investment of an equivalent amount of money that provides anywhere near the flexibility. Nothing even comes close! I would use the external wall wart to augment the power supplies of the AD2. If I was playing around with dual rail op amps, I would build a small +-15V power supply. One amp goes a long way with op amps. The idea that 30V 5A times 3 supplies is somehow required is just ludicrous. A 450 watt project is a space heater! And that doesn't account for the losses...DMM - you need a couple, maybe 3. I'm going to recommend the Aneng 8008 because it is inexpensive and super accurate. Dave did a video just search for something like 'eevblog aneng 8008 video'. These are around $25 so they won't break the bank and they have some interesting features - like a signal generator and frequency counter. There are better meters but you can get them later on. Usual warning: Don't trust the CAT ratings and don't play around with mains voltages.If you want to do lab type experiments to learn electronics, there is no better tool anywhere than the Analog Discovery 2. The thing is, people look at the pretty little box, giggle a bit, and blow it off as a toy. Huge mistake!Where else can you get a dual channel scope, dual channel arbitrary waveform generator, 16 bits of digital IO that can be used as a logic analyzer and serial stream decoder plus the software to do neat things like generate Bode' Plots of analog circuits? It's one thing to pencil whip a low pass filter, it's quite another to see the actual output versus frequency. That's real learning!Which brings us back to "what do you want to learn?".

author: tggzzz
author_rank: Super Contributor
timestamp: December 07, 2018, 08:48:30 pm
content: Quote from: rstofer on December 07, 2018, 07:38:28 pmJust so.It was a little bit of a mental wrench when I realised Icouldbuy and use a general purpose PSU!QuoteI use a (dedicated) cheap saucepan with a glass lid. The lid helps keep the heat in so the topside components aren't cold, and the glass allows you to see when the flux evaporates and the solder flows.I also use a layer of sand in the saucepan, to spread the heat and prevent hotspots, and to allow the temperature rise to be more controllable.QuoteIt isn't remotely dumb. In fact it is one of the touchstone questions: your answer shapes whether you go this way or that way.Finding the right question is usually more difficult than answering it - and more important.QuoteYes, and yes.Also remember that each and every tool has a learning curve. If you choose wisely, the tools help you learn and explore electronics. If you choose poorly, the tools help you learn which specific button to press in this version of this tool.In that respect, old analogue scopes are better than digitising scopes, since they are simpler and all the controls are on the front panel, not hidden in a menu system. But if you have a digitising scope and can use it, that isn't a reason to get aworkinganalogue scope.

author: rstofer
author_rank: Super Contributor
timestamp: December 07, 2018, 09:06:00 pm
content: Quote from: tggzzz on December 07, 2018, 08:48:30 pmHaving used my DS1054Z, I see many advantages over my Tek 485. In fact, the only thing the 485 brings to the dance is bandwidth. Bandwidth is cheaper when buying used analog scopes. For the Arduino style projects and reasonable < 100 MHz projects, a 100 MHz digital will be excellent. Four channels is more than twice as good as two channels. This shows up quickly when working with SPI transactions.If I were just learning and tending to roll around like a BB in a bowling alley, I would go for the AD2. It's easy to say that while having two of them and having used them off and on for several years but, were I a student, that's the way I would go. My lab is in my backpack alongside my laptop and slide rule. OK, programmable graphing calculator with networking and Computer Algebra System (CAS). These kids have it easy!I do a lot of modeling with LTspice and MATLAB. I also do a lot of code weenie work with Fortran and C. My Microsoft Surface Book is probably my most important tool. I use a more powerful desktop for Xilinx Vivado but the Book is adequate for everything else. One way or another, a PC of some type is becoming a required tool. Especially for embedded projects. BTW, a Bode' Plot looks pretty good on an attached 27" monitor!Electronics is played in a very large sandbox with many areas of interest. Just find a corner and dig in!

author: CJay
author_rank: Super Contributor
timestamp: December 07, 2018, 09:11:05 pm
content: Quote from: rstofer on December 07, 2018, 07:38:28 pmWell to be far, you did get a PSU right away, it just wasn't variable.A PSU of some sort is essential, doesn't matter if it's batteries, a fixed supply, home made or bought, it all depends what's available in your budget/needs, as tggzzz says, you have to be able to define your needs.

author: tggzzz
author_rank: Super Contributor
timestamp: December 07, 2018, 09:16:33 pm
content: Quote from: rstofer on December 07, 2018, 09:06:00 pm100MHz is OKprovidedthe signal integrity is good. The killer-app for DSOs is one-shot analogue events.QuoteMutter. Three is better than two, but with thought and imagination two is often sufficient. Any more and I want a logic analyser or printf statementsQuoteI have an AD1, and I agree. In fact the combination of AD+Tek485 (or equivalent) is sufficient for most amateur electronics.QuoteYes indeed.Choose a tool that will do the job at hand. A "perfect" tool will do it faster (excluding learning curve) but not necessarily better.It wlll be interesting to see if the OP is still reading

author: rstofer
author_rank: Super Contributor
timestamp: December 07, 2018, 09:42:50 pm
content: Quote from: CJay on December 07, 2018, 09:11:05 pmMy little 5V 3A power supply didn't cost anywhere near the $473 my DP832 cost. Yes, you need a source of some kind but it doesn't have to be a do-all end-all network programmable bench model.Particularly for PSs, there's a tendency to go in one of two ways: 1) Try to build a high end PS, similar to a $500 supply with voltage adjust/limit and current adjust/limit, using an entirely incompatible transformer (because real supplies use custom transformers), and do it for $29.95 OR 2) buying something that is marginal in delivered power quality because it is cheap.For 'small' projects, these Power Bricks are interesting. They work especially well if your hub as a couple of power only ports.https://store.digilentinc.com/powerbricks-breadboardable-dual-output-usb-power-supplies/I think I would try to defer the high dollar approach to buying a quality supply as long as possible - but no longer. There are other tools that are more important.I might build a triple output fixed voltage supply: +-15V and +5V each at about 1A.I just this minute won the $1 bid for a new triple output fixed supply:https://www.ebay.com/itm/POWER-ONE-HTAA-16W-A-LINEAR-TRIPLE-OUTPUT-REGULATED-POWER-SUPPLY-NEW/312347229694?$15 shipping, bummer...A supply like this will work well for just about everything. There is the downside of it not having adustable current limiting - a high end supply will have this feature and it can save a lot of money on magic smoke.Look around eBay and save the high dollar expense until much later (if ever).

author: CJay
author_rank: Super Contributor
timestamp: December 07, 2018, 09:54:32 pm
content: Quote from: rstofer on December 07, 2018, 09:42:50 pmThat's pretty much my point, you do need a PSU of some sort, the Thurlby and Farnell ones I mentioned often crop up around £30 on eBay, absolutely ideal. Those Power One supplies are really useful, LM723 based usually and bombproof as well as low noise, I used a triple output version for a number of years and probably still would if I knew where they went when I moved.

author: rstofer
author_rank: Super Contributor
timestamp: December 07, 2018, 09:55:27 pm
content: Quote from: tggzzz on December 07, 2018, 09:16:33 pmI have used imagination and gotten by for decades but there comes a point where the price of fully featured entry level scopes is compelling. Not necessary but fun to play with!printf() is my favorite way to debug digital systems. It doesn't tend to work well for FPGA projects but for embedded projects, it is the way to go.Dual channel analog scopes, particularly those with External Trigger Input, can be used. But the modern DSO is so much more fun to play with!

author: cdev
author_rank: Super Contributor
timestamp: December 07, 2018, 10:18:15 pm
content: Do beginners absolutely need current limiting ability in a power supply?So that IF something is hooked up wrong it won't fry the device-Its so that I can set a ceiling of current the supply will deliver thats just a bit above what its expected power draw will be. Most also have an indicator that tells you if that level is exceeded immediately.With the bench supply, I can ensure that even if I short something out the amount of energy available to do things is what it needs, and no more.You could get this kind of current limiting with any supply that delivers adequate voltage by adding a very inexpensive Chinese buck (DC-to-DC) converter add on. Some even add voltage output above the input voltage (buck-boost conversion)If you already have a power supply, like a re-purposed computer ATX supply, add one of those DC to DC converter modules you're all set for many kinds of things.Dave has done a video about them.That route will just cost a few bucks, in its simplest form, if you already have the power supply you use it with.These DC converters only cost a few bucks. But they have some issues. Noise is one. Build quality is another. The heat sinks they use are arguably inadequate for the tasks they try to do. But in most cases, if you enclose it in a proper case, and add a properly sized fuse to this supply so it will shut off if it has a problem, they will work fine, and be safe, and for the price are really a good deal.But whatever you use, if it lacks current limiting, it isn't really ideal for prototyping, so isn't really a bench (i.e. experimenters) supply.That why if you can find a good UK built bench supply, that you can afford, thats a very good investment you likely wont regret. As you'll likely keep it and use it frequently, for a long time.

author: bd139
author_rank: Super Contributor
timestamp: December 07, 2018, 10:24:09 pm
content: I spent most of my life using a non current limited supply, made from the remains of some scientific equipment I skip dived. I got in the habit of sticking 10 ohm 1/8W resistor in series with whatever I was building. If that disappeared in a puff of smoke, then there was too much current!Where there’s a will there’s a way!I would NEVER use an ATX. Those things can shift 100A very quickly very suddenly. Things just disappear if they go wrong.

author: boffin
author_rank: Unknown
timestamp: December 07, 2018, 10:34:53 pm
content: This is the video/thread you want to read about cheap power supplies.https://www.eevblog.com/2017/10/11/eevblog-1030-20-diy-bench-power-supply/

author: cdev
author_rank: Super Contributor
timestamp: December 07, 2018, 10:35:29 pm
content: By disappear he meansvaporize.very good point, bd139, very good point.And in one of Daves videos about the RDtech devices, maybe this one, one of the units he was testing caught on fire, it partly burned up, because a ceramic capacitor in it failed, causing a localized fire. It didn't quite totally self destruct in the Mission Impossible sense, but had he not been there it might have caused a fire.

author: cdev
author_rank: Super Contributor
timestamp: December 07, 2018, 10:46:38 pm
content: rstofer, I have one quite similar to that and its pretty decent.*It's totally silent*.It has low ripple and a self-contained transformer and a bunch of different voltages and can deliver a substantial amount of current. I got it from All Electronics ages ago for just a few bucks.It needs convection through the case. No fan, it does fine without a fan but it does need convection. So case with vents is a necessity.

author: rstofer
author_rank: Super Contributor
timestamp: December 07, 2018, 10:48:01 pm
content: I never meant to imply that I didn't like or need current limiting. It is one of the great features of the DP832. I can set a foldback limit and a shutdown limit on each of the 3 sources. This is a very powerful feature!Is it worth $500? Maybe, at some point in the evolution of the hobby. It may have saved a few chips the other day when I was building up a Z80 project and there was a bus selection conflict. But, somehow, I never trashed chips before I had the Rigol.The 10 Ohm resistor idea is good, so is a small fuse or, better, a small transistor. We joked in school that designers used transistors to protect fuses. A long time ago... It was funnier back then!Still, I got along with whatever foldback the 7805 provided and I didn't lose too many parts.Where I start to get nervous is when I see these DIY projects with multiple control loops and no real guarantee that they are stable. Designing a real PS is a non-trivial affair.There are two flavors of current setting: The old way was to short the output and adjust the current knob to get the current you wanted (because there was no calibrated current setting capability) and the newer digital schemes like with the DP832. That's another thing you don't get with DIY or low $ supplies. That digital setpoint is worth every bit of $500 - a long time later on with the hobby.There is something fundamentally wrong with shorting a PS output. It just doesn't seem right!The thing about 'learning' electronics is that you can also learn by modifying experiments to match what you have on hand. So what if the transistor amplifier circuit calls for a 6V supply and you have either 5V or 12V. Work it out! There's some good learning when you have to recalculate the bias point and the collector/emitter resistors.In fact, there is a LOT more learning when you have to calculate the components based on availability. It's all too easy to simply Copy and Paste.

author: bd139
author_rank: Super Contributor
timestamp: December 07, 2018, 10:58:26 pm
content: The TTi supplies have an output on/off switch. This also acts as a set/run switch so you set the limits with the controls. No shorting required. That annoys me too.

author: rstofer
author_rank: Super Contributor
timestamp: December 07, 2018, 11:02:13 pm
content: Quote from: bd139 on December 07, 2018, 10:24:09 pmI bought one of the Sparkfun ATX Binding Post kits and added it to a supply. I haven't used it but it's around here somewhere. Fortunately, there are fuses in each output. I wouldn't use one of the newer 1.5 kW supplies.https://www.sparkfun.com/products/12867Here's an open frame +-15V supply that should work well for dual rail op amp projectshttps://www.sparkfun.com/products/14101Here's a neat little breadboard supply for 3.3V and 5V when it comes back in stock:https://www.sparkfun.com/products/114

author: rdl
author_rank: Super Contributor
timestamp: December 08, 2018, 03:09:34 am
content: Nothing wrong with building one yourself. Back in the eighties I built my first power supply from a circuit in one of the Forest Mimms books (with Radio Shack parts of course), and I used it for years. At some point I took it apart to scavenge the enclosure for another purpose. I wish I hadn't now, but I did keep a few of the parts. I didn't realize how bad it was until I came here.

author: bd139
author_rank: Super Contributor
timestamp: December 08, 2018, 08:12:26 am
content: That’s sort of what mine looked like although yours clearly had less fires.