| Electronics > Beginners |
| Power supply advice please (I live in the UK) |
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| bd139:
--- Quote from: spec on December 07, 2018, 09:25:57 am --- --- Quote from: bd139 on December 07, 2018, 08:53:35 am ---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! --- End quote --- There 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. --- End quote --- Yes indeed. Current limit is killer feature number one. --- Quote from: spec on December 07, 2018, 09:25:57 am --- --- Quote from: bd139 on December 07, 2018, 08:53:35 am ---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. --- End quote --- AFAIK 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. --- End quote --- On 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 am --- --- Quote from: bd139 on December 07, 2018, 08:53:35 am ---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. --- End quote --- That 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. :) --- End quote --- I'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 am ---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. --- End quote --- Minimum 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. |
| amlu:
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.1.42b692b7mWKYGc Power it up with SMPS of your choice, can be old laptop adapter, can be a meanwell brick. |
| CJay:
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. |
| bd139:
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. |
| max_torque:
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....... :bullshit: |
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