Is it okay to get single output power supply as a beginner ?

[electronic_guy]

Hi,

I'm still preparing my home lab setup for electronics. I've seen the advice on getting, dual or triple output power supplies.

Is it that bad to get a single output power supply ? I know this sounds like a no brainer, but l couldn't find a decent multiple output power supply from a reputable brand like Agilent or HP on used equipment market.

My focus on start is to spend only about $ 250 on my first supply without shipping, and I will be working on getting experience of PCB prototyping and OPAMPs. My target is to reach RF circuit designs. 

Your advice on this would be supportive to me.

Thanks.

[Nusa]

Of course it's ok. And if you end up needing multiple voltages, there's no reason you can't get another one. Having multiple supplies in the same box is mostly a convenience, not a requirement.

[25 CPS]

You mentioned op-amps specifically so this is a bit of a tough situation.

There's nothing inherently wrong with starting out using a single output power supply and it's by far better to have a single output power supply instead of no power supply and getting by using wall-wart adapters or batteries.  When I was starting out, I ended up looking for a power supply pretty quickly after discovering how far 9 volt batteries went for powering circuits I was working on.

Op-amps are definitely devices that typically work best with a dual +/- supply, ideally a dual tracking supply where one side follows the other for voltage in opposite polarity.  Most supplies like this are two or three supplies in one cabinet as Nusa mentioned but this doesn't necessarily have to be the case.  The idea I was kicking around my head for your situation was this:  If you're stuck getting a single output supply, see if you can get a Hewlett-Packard power supply that has the full set of output, sense and programming terminals on the back.  That'll get you started.  Then when you save up a bit more, you can get a second one and then change the strapping on the terminals to operate them in multiple unit to get more current, more voltage, or a dual tracking, opposite polarity setup ideal for op-amps and end up with a two output supply but in two boxes bought at different times.  It might be worth thinking about this idea depending on what's available on the used market in your area.

[james_s]

I'll second that, if you have any interest in working with op amps then get at least a 2 channel power supply that is capable of tracking, even if you can't find one from an A-list brand. For years I used an old Heathkit triple power supply and it still lives on the shelf above my bench, it isn't the most feature rich thing but it does the job. Find some models you're interested in and then set up a saved search on ebay and something will turn up eventually. Or go ahead and buy a single output supply now and then keep looking for something with at least two channels, having extra power supplies is often nice.

[David Hess]

I worked with a single output power supply for a long time, but quickly built a couple of fixed +/-15 volt power supplies using of 7815s and 7915s.

[GerryR]

There are many linear triple-output supplies on Ebay, like BK Precision, Protek, etc. with switches for series/parallel operation, current limiting, with two variable outputs 0-30v @ 2.5-3.0A and a fixed 5v output, for well under $250.00.  Power supplies are generally pretty bulletproof, and most reputable sellers have a good return policy.  You might want to check some of them out.

[David Hess]

Also, it is relatively easy to make a simple variable bipolar tracking supply with a 317 and 337 for +/- 1.25 to 15 volts or higher, as shown below from the Linear Technology LT137 datasheet.  Projects for simple test equipment are a good way to gain experience.

Note that nothing prevents using the design shown below for a 2.5 to 40+ volt power supply.

[MarkF]

I have several small single output supplies now
but very quickly built a couple fixed +/- supplies
just for the convince of not having to configure and set the voltages each time.

I built a +/-12V and a +/-15V.  Thinking the 15V for really old op-amps (741).
But if I were to build just one, I would build a +/-12V. 
Then, you have a +12V output readily available for those battery operated projects.

I just love these little HP supplies (I have four now.  Brings back the old school days. ):
Can be had for $50 on eBay.


But, I would lean toward a Siglent SPD1305X and build a +/-12V from 7812 and 7912 regulators to get started.
Sense lines. Plus USB & LAN available for automation testing.

[Fungus]

Is it that bad to get a single output power supply ? I know this sounds like a no brainer, but l couldn't find a decent multiple output power supply from a reputable brand like Agilent or HP on used equipment market.

My focus on start is to spend only about $ 250 on my first supply without shipping, and I will be working on getting experience of PCB prototyping and OPAMPs. My target is to reach RF circuit designs. 

You really need two outputs for opamps (+/- rails).

l couldn't find a decent multiple output power supply from a reputable brand like Agilent or HP on used equipment market.

It should be easy in the USA, eg: https://www.ebay.com/itm/304190908203

Or get two cheap supplies (eg. the ones suggested by MarkF) and stack them:

I just love these little HP supplies (I have four now.  Brings back the old school days. ):
Can be had for $50 on eBay.

Or ... get a fancy, modern single-output supply for the positive rail (ie. with functions like current limiting, etc) and one of those little supplies for the negative rail (all you need is something linear/low noise, current draw is minimal, almost anything will do).

[m k]

Some years back I thought I need something not analog in one case.
Can't remember why I have two 1803D designs and not 3005 versions.
Maybe it was a need, maybe value.

Not so long a go I tried to update those two and my auction skills are clearly inadequate.

What I found was that 3010 seems to be SMPS.
Few 3005 versions were also available but their weights were mostly suspicious, less than 2kg or so.

One thing I'd like to note.
Indicating vs. measuring.

[ledtester]

My focus on start is to spend only about $ 250 on my first supply without shipping, and I will be working on getting experience of PCB prototyping and OPAMPs. My target is to reach RF circuit designs. 

A lot of op-amps today only need a single rail. Op amps are generally not very power hungry devices, so for dual rail applications you could use two 9V batteries which will also give you very clean power.

[Fungus]

A lot of op-amps today only need a single rail. Op amps are generally not very power hungry devices, so for dual rail applications you could use two 9V batteries which will also give you very clean power.

I once used a 9V battery for the negative rail on a project with the positive rail from a single-output power supply.

OP-amp circuits only use a few mA so they last quite a long time.

(...and $50 buys a lot of 9V batteries.  )

[electronic_guy]

Is it that bad to get a single output power supply ? I know this sounds like a no brainer, but l couldn't find a decent multiple output power supply from a reputable brand like Agilent or HP on used equipment market.

My focus on start is to spend only about $ 250 on my first supply without shipping, and I will be working on getting experience of PCB prototyping and OPAMPs. My target is to reach RF circuit designs. 

You really need two outputs for opamps (+/- rails).

l couldn't find a decent multiple output power supply from a reputable brand like Agilent or HP on used equipment market.

It should be easy in the USA, eg: https://www.ebay.com/itm/304190908203

Or get two cheap supplies (eg. the ones suggested by MarkF) and stack them:

I just love these little HP supplies (I have four now.  Brings back the old school days. ):
Can be had for $50 on eBay.

Or ... get a fancy, modern single-output supply for the positive rail (ie. with functions like current limiting, etc) and one of those little supplies for the negative rail (all you need is something linear/low noise, current draw is minimal, almost anything will do).

Thank you all for your regard to my problem and the knowledge shared.

Going with what @Fungus proposed here, would those two supplies be a good selection that can cover my needs in general ?

As a modern power supply for positive rail I can buy a HP/Agilent 3632A and for the negative rail I can get a HP/Agilent 3610A.

Here I would not be having tracking for the dual supply. Would that be a big issue when it comes to OPAMPs ?

[james_s]

Tracking isn't strictly necessary, you can always adjust the two separately and most of the time you'll set it to a specific voltage and leave it there. It's just a convenience.

[Shock]

Not that it's entirely necessary to have a triple output power supply, it's the utility of having one or two of them replace a bunch of other supplies.

[MarkF]

A lot of times, I find myself with a project that has a micro-controller and an op-amp.
It's a nice convenience to just flip a switch (and not fiddling with adjusting voltages) for the op-amp power and a third supply for the MCU (3.3V or 5V).
All having low power requirements. 

And then there are cases when you need a good variable output.  Or need a single output with a higher current capabilities.

IMHO..  Everyone builds a bunch of simple low power supplies and most projects only need a few 100 mA. 
But, higher output power (over 1A) is more difficult to build.  I actually prefer a fixed dual supply for op-amp work.
That's why starting with a supply with higher output power (i.e. 5A max) and a few small DIY supplies might be the way to go.
Or spend more and get a triple output supply with more capabilities.
You will always need more than one supply.  So, it all boils down to personal preference.  A triple supply, or a few single supplies, or some combination.

[Fungus]

It's a nice convenience to just flip a switch (and not fiddling with adjusting voltages) for the op-amp power and a third supply for the MCU (3.3V or 5V).
All having low power requirements. 

Of course it's nice ... but sometimes bench space and/or budget are limiting factors so we have to make do. 

[Tomorokoshi]

You mentioned op-amps specifically so this is a bit of a tough situation.

There's nothing inherently wrong with starting out using a single output power supply and it's by far better to have a single output power supply instead of no power supply and getting by using wall-wart adapters or batteries.  When I was starting out, I ended up looking for a power supply pretty quickly after discovering how far 9 volt batteries went for powering circuits I was working on.

Op-amps are definitely devices that typically work best with a dual +/- supply, ideally a dual tracking supply where one side follows the other for voltage in opposite polarity.  Most supplies like this are two or three supplies in one cabinet as Nusa mentioned but this doesn't necessarily have to be the case.  The idea I was kicking around my head for your situation was this:  If you're stuck getting a single output supply, see if you can get a Hewlett-Packard power supply that has the full set of output, sense and programming terminals on the back.  That'll get you started.  Then when you save up a bit more, you can get a second one and then change the strapping on the terminals to operate them in multiple unit to get more current, more voltage, or a dual tracking, opposite polarity setup ideal for op-amps and end up with a two output supply but in two boxes bought at different times.  It might be worth thinking about this idea depending on what's available on the used market in your area.

Examples are the HP 6227B and 6228B. These tend to be in the $150 to $200 range on ebay.

https://www.keysight.com/us/en/product/6227B/power-supply.html
https://www.keysight.com/us/en/product/6228B/power-supply.html

I hope that describing them as simultaneously both robust and repairable isn't too much of a contradiction.

[MarkF]

It's a nice convenience to just flip a switch (and not fiddling with adjusting voltages) for the op-amp power and a third supply for the MCU (3.3V or 5V).
All having low power requirements. 

Of course it's nice ... but sometimes bench space and/or budget are limiting factors so we have to make do. 

Exactly my point.
To answer the OP original question:
Modern projects will most likely consist of both an analog and a digital sections requiring 3 or even more voltages.  You might need +/- voltages for an analog section and 5V and/or 3.3V for a digital control MCU section.  You will typically only need one variable voltage and the rest are going to be fixed voltages.

When just starting, the OP is not going to know what his evolving requirements will be.  You can get a big triple output supply and still need more.  Or save some money now by getting a single output lab supply and building a few cheap dual supplies.  He can put the saved money toward other lab equipment.  A second multi-meter for example.

The physical bench space would be about the same for a bulky triple supply or a single lab supply with a small DIY dual supply.  On my humble bench table (no shelving), I currently have 8 power supplies.  Four lab supplies and four DIY supplies.  I have only needed a higher power (30V @ 5A output) supply and the others have been fixed low power (500mA) voltages.  But, everyone has different requirements.

[tautech]

But, everyone has different requirements.

This ^^

Some designs need power rails properly sequenced at power ON and a programmable multi channel PSU is required for that.
Unlikely the novice will need such things initially but maybe one day.
Decisions.......

[nctnico]

I have several small single output supplies now
but very quickly built a couple fixed +/- supplies
just for the convince of not having to configure and set the voltages each time.

I built a +/-12V and a +/-15V.  Thinking the 15V for really old op-amps (741).
But if I were to build just one, I would build a +/-12V. 
Then, you have a +12V output readily available for those battery operated projects.

I just love these little HP supplies (I have four now.  Brings back the old school days. ):
Can be had for $50 on eBay.

That is a lot of money for an old clunker if you compare it to the Korad PSUs you can buy new with better features. One of the things you'll want is adjustable current limit down the tens of mA. With a current limit you won't fry your circuit when it turns out it has a short or something isn't right.

[YurkshireLad]

I'm an absolute beginner and I would say get a single bench power supply, like the Korad. Once you've worked out how deep you want to get into electronics, you can buy or build to meet your requirements and budget. I bought a Korad recently and it's perfect for my needs.

[MarkF]

I have several small single output supplies now
but very quickly built a couple fixed +/- supplies
just for the convince of not having to configure and set the voltages each time.

I built a +/-12V and a +/-15V.  Thinking the 15V for really old op-amps (741).
But if I were to build just one, I would build a +/-12V. 
Then, you have a +12V output readily available for those battery operated projects.

I just love these little HP supplies (I have four now.  Brings back the old school days. ):
Can be had for $50 on eBay.

That is a lot of money for an old clunker if you compare it to the Korad PSUs you can buy new with better features. One of the things you'll want is adjustable current limit down the tens of mA. With a current limit you won't fry your circuit when it turns out it has a short or something isn't right.

It's a nostalgia thing for me and totally quiet (no fan).
They are designed to be placed in parallel or series.

By the way, you can set the current limit down in the tens of mA. 
F.Y.I.  The max output of these power supplies is 500mA. 
Without taking time to go test them, I believe you could set the current limit to 1 or 2mA.


Edit:
Note that there are some reports of overshoot when switching on/off.
https://www.eevblog.com/forum/repair/power-supply-overshoot-when-disabling-output/
https://www.eevblog.com/forum/testgear/korad-kd3005d-bench-supply-power-on-spike/

Edit #2:
Just tested the old clunker.  I found that with a steady hand, I can adjust the current in 100uA (yes. micro amp) steps, starting at 100uA.  Test done at 6V plugged directly into a DMM.

[Fungus]

Can be had for $50 on eBay.

That is a lot of money for an old clunker

Here's one for $35: https://www.ebay.com/itm/304190918453

I might buy it if I was in the USA but I'm not, so... I'll let you guys fight over it. 

[Wallace Gasiewicz]

There are several bench supplies available in Indianapolis IN at a radio shop. If you are near you can go and check them out, Plug them in and measure voltage etc.
Includes a triple and some singles.
I cannot quote prices as they are not mine but they are cheap.
Also lots of Linear supplies for 14 Volt and at least one for 28 Volt.
If anyone is interested PM me. I will give you location.