Bench Power Supply

[TheJay]

Hey there, I have a number of projects where I want to convert battery powered stuff to mains/want to be able to test my projects as I work on them without connecting batteries to them.

At the moment for example, one of my projects involves 12v lights. I don't have any suitable batteries and would rather connect to a steady supply whilst testing.

I'm thinking about getting a bench power supply. What would I need to look out for? Can any deal with AC and DC? How many amps? Should I be looking at something supplying more than 12v? Can deal with series and parallel? I'd like something with a digital display.

 

[danadak]

AC use a variac, and if isolation from line is important, an isolation transformer feeding the Variac.

DC

1) Dual
2) V and I control
3) Series the dual for higher V useful
4) V and I displays

What is your budget ? There are even intelligent supplies, that allow you to
ramp power, quite useful for checking powerup circuits.


Regards, Dana.

 

[Nigel Goodwin]

AC use a variac, and if isolation from line is important, an isolation transformer feeding the Variac.

Talking of which I was looking at a stack of large variacs the other week - at the Computer Museum at Bletchley Park. They have rebuilt a copy of the worlds first computer, Colossus - and have a large bank of BIG variacs feeding it, presumably to power it up slowly to preserve the 80 year old valves

Interestingly, running along the sides of it's frame are 'welding' sized cables, presumably the heater feeds for the valves.

 

[TheJay]

Thanks for your replies, I don't know about budget. I don't want to go mad butt at the same time I don't want to find I am missing essential features. Also, not bothered if new or used.

 

[Nigel Goodwin]

Thanks for your replies, I don't know about budget. I don't want to go mad butt at the same time I don't want to find I am missing essential features. Also, not bothered if new or used.

It really depends what you end up using it for - but generally the vast majority of your requirements are met by simple 30V 3A one, with digital displays.

They are pretty cheap off Amazon, and I would recommend ones with digital controls (rotary encoders), where you just dial the voltage in, and press the knob - this means you can't easily accidentally disturb the voltage, as with the ones where you just have potentiometers (usually two, one coarse, one fine). However, the ones with pot's are stupidly cheap

The one I'm using at work is a Tenma 72-2685 30V 3A, and it's been excellent. We've got two of them, plus an older one with the fine/coarse knobs, which I tend to avoid

While variable AC is 'nice' it's something you only VERY, VERY rarely require - I'm using my DC PSU now, testing a partially completed board charging it's Li-Ion batteries. It's pretty rare that a day goes by when I don't use it.

 

[TheJay]

Thanks for your recommendation, that looks like a good one.

At what point does someone need a higher amperage from 5A to 13A?

 

[danadak]

I use a triple, 2 adjustable, one fixed 5V. But there is a problem
with it, it generates large V transients when turning off, which
can fry a circuit if you are not aware. So I unplug loads, then turn
off. Pain in the hiney, otherwise its a good supply. Problem with
this is you dont know when you purchase. I recommend you google
this as a problem for a specific model you are interested in to see
if anyone else reporting the problem.

You could always buy and return on eval, but shipping costs to do so
a burden. If you do this set your scope on one shot, say 1 mS sweep,
and a trig V just above the current V you have it set for. See if you
get any significant transient. Mine produces 50V+ transients..... I need
to add this to my fixit list ....

This happens to be model

Arksen 303-2D 30V Triple Output DC Power Supply | Proxibid

Bid in a Proxibid online auction to acquire a Arksen 303-2D 30V Triple Output DC Power Supply from SD Surplus Auctions.

www.proxibid.com

Regards, Dana.

 

[AnalogKid]

At what point does someone need a higher amperage from 5A to 13A?

At the point when they need it. That's not a snotty answer. Only you can tell us what kinds of projects you are doing in the future. If all of your projects need only a few watts, then, never. If you want to play around with automobile headlights, then, now.

The reason there are so many bench supplies in the 24 V to 30 V range is because that is a little more than many people need. Same for the output current. Do you think you will be working on a circuit that needs +/-15 V power rails that track each other in the next 5 years? How about 5 V at 6 A? 3 V at 20 A?

Make a list of the *kinds* of things you anticipate doing. Not necessarily specific projects, but project types. Then think about the power levels of those types. Then buy.

ak

 

[For The Popcorn]

Take a look at Handy Bench Power Supply. It may meet your needs nicely, and be cheap to make.

 

[TheJay]

Good point, the first project does involve car headlights (LED angel eyes). So that means I need at least 5A? If I were modifying mains powered stuff, it would need to be able to cope with 13A right? Then again, household supplies are 240v, yet these supply peak at 30v?

 

[crutschow]

the first project does involve car headlights (LED angel eyes). So that means I need at least 5A?

LEDs don't necessarily take that much power.
Determine how much they really require.

If I were modifying mains powered stuff, it would need to be able to cope with 13A right? Then again, household supplies are 240v, yet these supply peak at 30v?

Yes, but you seldom need to vary the household voltage when testing AC powered devices.
The 30V peak is for DC output supplies.
The internal DC voltage of AC powered devices is seldom above 30V.

 

[TheJay]

Hopefully this is sufficient for my purposes:

Tenma 72-2540 Single Output DC Bench Power Supply with RS-232 and USB Interfaces, 30V, 5A​

 

[AnalogKid]

Link?

 

[For The Popcorn]

Link?

Literally, this link to the power supply took 5 seconds to find.

 

[AnalogKid]

That is a link to a product, but not necessarily the link to the exact product the OP is considering.

Besides eliminating ambiguity, it is simple etiquette, when asking about a thing, to provide a link to that thing so we all are literally on the same page.

ak

 

[TheJay]

There's no ambiguity, the product linked is the same one. The product code matches.

 

[For The Popcorn]

....as would be the case since the manufacturer, model number and description are exactly identical.

 

[ZipZapOuch]

That one has a datasheet with a 2012 copyright and 9-years since the last datasheet revision. I'm surprised there is no revision A or B or C by now. A very logical question to validate exact model number with the OP.

Over the last 10-years, SMPS have been built with smaller inductors and higher frequencies (using GaN transistors) thanks to high speed SiC-MOSFETs and GaN-FETs to make them both cheaper and more easily transported while offering lower noise - even suitable for high quality audio applications - and faster response to load changes. I'd get something newer. Even the CUI power brick sent with my Sound Bar was based on GaN technology.

Whatever you buy now, you'll have for the next 20 to 40-years. Get a decent one. Farnell is always expensive for this kind of stuff.

 

[AnalogKid]

Despite all of the digital goop on the front panel, that is a 150 W supply in a big box with lotsa vents and an exhaust fan, and weighs almost 10 pounds.

Smells like a linear supply to me.

It could be a variable-output switcher with a tracking linear post-regulator, but Tenma is not known for that level of complexity in its power products. AND - neither the sides nor the rear of the case have good vent patterns for a 200 W switcher.

ak

 

[Nigel Goodwin]

That one has a datasheet with a 2012 copyright and 9-years since the last datasheet revision. I'm surprised there is no revision A or B or C by now. A very logical question to validate exact model number with the OP.

Over the last 10-years, SMPS have been built with smaller inductors and higher frequencies (using GaN transistors) thanks to high speed SiC-MOSFETs and GaN-FETs to make them both cheaper and more easily transported while offering lower noise - even suitable for high quality audio applications - and faster response to load changes. I'd get something newer. Even the CUI power brick sent with my Sound Bar was based on GaN technology.

Whatever you buy now, you'll have for the next 20 to 40-years. Get a decent one. Farnell is always expensive for this kind of stuff.

CPC, while part of the Farnell group, often has MUCH lower prices - and often uses the same part numbers, so CPC is well worth a look, and is a good source for many decent priced items. As always, hunt round and see where is the best value - sometimes even Farnell can be cheaper than CPC, but it's rare.

I just ordered a TV mounting bracket from CPC, and a cheap 55 inch TV from Amazon - it's just for mounting at work, for doing presentations. I checked on CPC first for the bracket, and a suitable one was about £49 + 20% VAT, then I checked round for a TV, and ended up on Amazon with one for £299 (inc. VAT). So I then checked the price of a bracket on Amazon (because I'd feel pretty stupid if it was cheaper), and was shocked when the identical one was £120 (inc. VAT). So bracket from CPC (which has arrived) and TV from Amazon (due 2nd May).