When I start experimenting on the breadboard...
Im setting aside a table, getting a meter, etc...
I have in my mind a thought that it might be cool to have the ability to be able to generate different voltages .....
Say....1vdc to 12vdc.....
1.) is that a good idea ?
2.) is it cheaper to build a power supply that does that or buy one?
Using something youve built is to my mind cooler than buying something...
What say all of you...?

 

1) I think it's a very good idea.
2) I have done both, building one is fun if you haven't already, but after building my first one, I would prefer buying one, it's a lot easier and better.

 

Speaking as a total amateur, building one is great, especially if you design it yourself and adapt it as you go. So simple basic unregulated design first, then voltage regulator next, and then adding V+A meters to it, current regulation, digital control, and so on, and so on.

BUT, if you want to do other things at the same time, and you can't because you are still building your PSU to power it all, buying one is good.

 

If you ambitious you can modify an old ATX to variable output 2V to 28V, i can give you a link to my site to show you.

 

If you ambitious you can modify an old ATX to variable output 2V to 28V, i can give you a link to my site to show you.

Please do , I'll be converting a PC CPU into a bench power supply in a few weeks so i'm interested in what you did

 

Please do , I'll be converting a PC CPU into a bench power supply in a few weeks so i'm interested in what you did

Dodgydave

Depends on which chip you have in the atx, let me know

 

I don't speak for everyone but me I just bought one on Ebay for about $50 bucks (MASTECH DC POWER SUPPLY HY3003D)... I was finding all kinds schematics to build one but found out that they don't have any real safety features.. So I just bought one because it's less likely to burn down my house ,But right now I am working a really small voltage power supply with voltage display for a breadboard ...

When I start experimenting on the breadboard...
Im setting aside a table, getting a meter, etc...
I have in my mind a thought that it might be cool to have the ability to be able to generate different voltages .....
Say....1vdc to 12vdc.....
1.) is that a good idea ?
2.) is it cheaper to build a power supply that does that or buy one?
Using something youve built is to my mind cooler than buying something...
What say all of you...?

Please do , I'll be converting a PC CPU into a bench power supply in a few weeks so i'm interested in what you did

Here Check this out ..
http://dangerousprototypes.com/2012/06/28/new-prototype-atx-breakout-board/

 

I don't speak for everyone but me I just bought one on Ebay for about $50 bucks (MASTECH DC POWER SUPPLY HY3003D)... I was finding all kinds schematics to build one but found out that they don't have any real safety features.. So I just bought one because it's less likely to burn down my house

Actually a very good point. A bench supply will be your friend for life: they are very hard to kill (though I've killed some) so they will survive much abuse from your circuits going bad, they can help protect your circuit form your mistakes (current limiting), and they have every voltage possible from zero to their max.

Here Check this out ..
http://dangerousprototypes.com/2012/06/28/new-prototype-atx-breakout-board/

I would *never* use a computer power supply to power my circuits. While it does provide some nice stable voltages it does so with enough unlimited current for you to put your eye out.

I had a boss once who insisted I use a battery to power development units... until the day there was a short and the board went up in flames (literally). A current limited supply would not make that happen... a computer supply will do it's best to get a fire going.

 

If you are seriously building up your experimental electronics knowledge I recommend getting one of the books by Michael Tooley. They really are first class.

In particular the 1990 edition of Electronic Circuits is designed to teach about components and circuit configurations by experiment. It is all superbly explained.

You build up a series of modules

AC power supply
Fixed DC power supply
Variable DC power supply
Digital panel meter
Transistor tester
Digital ohmeter
Function generator
Pulse generator
Output stage
Crystal Calibrator

and learn a great deal in the process.

 

I would *never* use a computer power supply to power my circuits. While it does provide some nice stable voltages it does so with enough unlimited current for you to put your eye out.

.

Isn't there this thing called a 'Fuse' that prevents our circuits from blowing up in case of a short or overcurrent?

 

If you are seriously building up your experimental electronics knowledge I recommend getting one of the books by Michael Tooley. They really are first class.


and learn a great deal in the process.

I checked out the name . Any books in particular that you would reccomend?

 

There are two Tooley brothers who have written some good stuff for magazines plus several books together. IHMO they are much better than the Penfold offerings.

The book I recommended ( Electronics Circuits ) has been renamed in recent editions and I'm not sure if it has quite the same format.

My old copy was ISBN 0 434 91968 3

Incidentally fuses are fine to protect electrical equipment, but are several order of magnitude too slow to protect electronic kit.

The best sort of protection is called 'foldback' as it does more than limit the current, it actually reduces it above a certain level.

A contined fault condition is protected against by a 'crowbar' circuit', which protects the actual power supply components, rather than the load.

 

Hmm but even an ordinary fast blow fuse will protect from smoke and fire won't it ? Even if the components will fry there won't be current supplied for long enough to induce a fire or anything of that sort no?

 

A contined fault condition is protected against by a 'crowbar' circuit', which protects the actual power supply components, rather than the load.

Doesn't the crowbar circuit require a certain amount of voltage in order for it to work properly???

 

Isn't there this thing called a 'Fuse' that prevents our circuits from blowing up in case of a short or overcurrent?

Sure is. It's best used for field failures, unless you happen to own an infinite stock of these components.

A current limited lab supply is a standard piece of development equipment. I own several, each with multiple outputs.

I suggest anyone who is serious and can afford these get some.

 

The purpose of a crowbar circuit is to rapidly divert excess current from the load through another path until a fuse ruptures or breaker trips, thus isolating the fault condition until it can be properly fixed.

Yes this takes voltage until the disconnection, at which point there is no voltage.

The crowbar itself may be sacrificial and is often a thryristor.

 

Dave...I got your PM ......thank you very much.
Enjoyed your other videos also...
You guys never let me down...
I think I'll file this for the future and stay with the "store bought" version for now....
Many thanks
D.

 

Basic Bench Top Power Supplies

Power supplies are about the only thing left that is economical to build, especially with a high current high voltage wall wart (such as is used in laptops).

I did buy this one,

Even with current limiting you have to be careful, as the caps filtering the output will pop an LED. To feed a good constant current source start with the outputs shorted.

http://www.vellemanusa.com/products/view/?id=522797

 

I'm going to have to side with the current limiting crew.

I feel like even this unit for $89 (http://www.circuitspecialists.com/csi5003xe.html) will pay for itself in headaches and parts if it saves you but a few boards from getting zapped.

I do still have an old ATX with a 3.3 rail I may still use for a voltage source at the bench, but I'll be back to the current limiting variable for development.

 

Check out mastech power supplies ...
They are made in china ,but are pretty cheap to buy and really not bad made ..