Power supply advice please (I live in the UK)

[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.

That'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.

There 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! 

[rstofer]

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.

Exactly 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?".

[tggzzz]

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.

Exactly 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.

Just so.

It was a little bit of a mental wrench when I realised I could buy and use a general purpose PSU!

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!

I 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.

Here's the thing:  What do you want to learn?  That question isn't as dumb as it seems. 

It 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.

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!
...
Which brings us back to "what do you want to learn?".

Yes, 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 a working analogue scope.

[rstofer]

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 a working analogue scope.

Having 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!

[CJay]

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.

Exactly 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.

Well 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.

[tggzzz]

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 a working analogue scope.

Having 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. 

100MHz is OK provided the signal integrity is good. The killer-app for DSOs is one-shot analogue events.

Four channels is more than twice as good as two channels.  This shows up quickly when working with SPI transactions.

Mutter. Three is better than two, but with thought and imagination two is often sufficient. Any more and I want a logic analyser or printf statements

If I were just learning and tending to roll around like a BB in a bowling alley, I would go for the AD2.

I have an AD1, and I agree. In fact the combination of AD+Tek485 (or equivalent) is sufficient for most amateur electronics.

Electronics is played in a very large sandbox with many areas of interest.  Just find a corner and dig in!

Yes 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

[rstofer]

Well 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.

My 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).

[CJay]

Well 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.

My 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.

That'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.

[rstofer]

Four channels is more than twice as good as two channels.  This shows up quickly when working with SPI transactions.

Mutter. Three is better than two, but with thought and imagination two is often sufficient. Any more and I want a logic analyser or printf statements

I 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!

[cdev]

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.

[bd139]

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.

[boffin]

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/

[cdev]

By disappear he means vaporize.

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.

[cdev]

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. 

[rstofer]

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.

[bd139]

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.

[rstofer]

I would NEVER use an ATX. Those things can shift 100A very quickly very suddenly.  Things just disappear if they go wrong.

I 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/12867

Here's an open frame +-15V supply that should work well for dual rail op amp projects

https://www.sparkfun.com/products/14101

Here's a neat little breadboard supply for 3.3V and 5V when it comes back in stock:

https://www.sparkfun.com/products/114

[rdl]

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.

[bd139]

That’s sort of what mine looked like although yours clearly had less fires.