Power Supplies [Basics]

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From: Bob Masta on 29 Mar 2010 09:40

From: Kari Laine on 30 Mar 2010 05:30

Bob Masta wrote:
> On Sun, 28 Mar 2010 22:07:59 +0300, Kari Laine

Thanks Bob,

yep I will do +/- 12V 1.0A supply.
I have already all the parts except housing.

To make housing right seems to be another graft to master.

The "super" switching PSUs. I was more interested to know how they are
implemented rather than building one. If I ever need such power I will
buy a ready made supply. Reasons are that the currents in that range are
so huge that I will surely burn my house with a self made supply.

One question I have though. I am thinking that one cannot use soldering
with that kind of currents - can one? If not then how the connections
are made?

Anyway thanks to all in this group. This is a great resource.

And about the mains. Before I try to measure it in any way(if there
really is need - witch I doubt) I will borrow a book and ask someone how
exactly to do that. I don't want to blow up my equipment or kill myself.

Best Regards
Kari

--
PIC - ARM - DISPLAYS - RELAYS - MODULES - CONVERTERS - I2C - SPI -
KEYPADS - ACCESSORIES
http://www.byvac.com (I am just a satisfied customer)

From: Bob Masta on 30 Mar 2010 09:20

On Tue, 30 Mar 2010 12:30:06 +0300, Kari Laine
<klaine8(a)gmail.com> wrote:

>Bob Masta wrote:
>> On Sun, 28 Mar 2010 22:07:59 +0300, Kari Laine
>
>Thanks Bob,
>
>yep I will do +/- 12V 1.0A supply.
>I have already all the parts except housing.
>
>To make housing right seems to be another graft to master.
>
>The "super" switching PSUs. I was more interested to know how they are
>implemented rather than building one. If I ever need such power I will
>buy a ready made supply. Reasons are that the currents in that range are
>so huge that I will surely burn my house with a self made supply.
>
>One question I have though. I am thinking that one cannot use soldering
>with that kind of currents - can one? If not then how the connections
>are made?

All the switchmode PSUs I've seen are soldered.
The important thing at higher currents is to make
the copper circuit board traces wide enough. I've
never run into problems with this, but it's
certainly possible. After all, if you make the
trace narrow enough it starts to look a lot like a
fuse!

Best regards,

Bob Masta

DAQARTA v5.10
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, FREE Signal Generator
Pitch Track, Pitch-to-MIDI
DaqMusic - FREE MUSIC, Forever!
(Some assembly required)
Science (and fun!) with your sound card!

From: Hammy on 30 Mar 2010 11:48

On Tue, 30 Mar 2010 13:20:00 GMT, N0Spam(a)daqarta.com (Bob Masta)
wrote:

>On Tue, 30 Mar 2010 12:30:06 +0300, Kari Laine
><klaine8(a)gmail.com> wrote:
>
>>Bob Masta wrote:
>>> On Sun, 28 Mar 2010 22:07:59 +0300, Kari Laine
>>
>>Thanks Bob,
>>
>>yep I will do +/- 12V 1.0A supply.
>>I have already all the parts except housing.
>>
>>To make housing right seems to be another graft to master.
>>
>>The "super" switching PSUs. I was more interested to know how they are
>>implemented rather than building one. If I ever need such power I will
>>buy a ready made supply. Reasons are that the currents in that range are
>>so huge that I will surely burn my house with a self made supply.
>>
>>One question I have though. I am thinking that one cannot use soldering
>>with that kind of currents - can one? If not then how the connections
>>are made?
>
>All the switchmode PSUs I've seen are soldered.
>The important thing at higher currents is to make
>the copper circuit board traces wide enough. I've
>never run into problems with this, but it's
>certainly possible. After all, if you make the
>trace narrow enough it starts to look a lot like a
>fuse!
>
>Best regards,
>
>
>Bob Masta
>
> DAQARTA v5.10
> Data AcQuisition And Real-Time Analysis
> www.daqarta.com
>Scope, Spectrum, Spectrogram, Sound Level Meter
> Frequency Counter, FREE Signal Generator
> Pitch Track, Pitch-to-MIDI
> DaqMusic - FREE MUSIC, Forever!
> (Some assembly required)
> Science (and fun!) with your sound card!

This trace width calculator wil give you an idea. It seems pretty
accurate compared a few with a chart of conductor width for current
for a given temp rise in my power electronics book.

http://circuitcalculator.com/wordpress/2006/01/31/pcb-trace-width-calculator/

But for an SMPS you also have to consider RMS handling for the
switching loops.

http://circuitcalculator.com/rms.php

From: default on 30 Mar 2010 19:31

On Sun, 28 Mar 2010 22:07:59 +0300, Kari Laine <klaine8(a)gmail.com>
wrote:

>Hi,
>
>I am trying to find schematics for PSUs. I found one, probably good one,
>but it was very complicated and used an IC, which I probably won't get
>anywhere.
>So any good links welcome.
>
>I understand the sub 3A PSUs somehow. But for example a 12V/60A ones are
>mystery to me. One person told me that they use FET's. Are they
>basically like the PC Power supply? But how they make the controllable
>between 1.5 -- 12V with full load?
>
>Any schema ?
>
>I hope my continued questions are not regarded as spam...
>
>Best Regards
>Kari

Like bob already said - a basic three terminal regulator is a good
place to start. I would find a variable supply more useful, if I just
had one. Plus and Minus supplies find most of the applications in
linear electronics - and from you sig file, I get the idea that
perhaps you are more interested in digital (learning to run before
walking?)

I keep one small variable three terminal supply, two independent 12
VDC fixed supplies (separate cases and line cords), and one 12-24
unregulated heathen (lot of amps with circuit breakers), and a
variable (variac controlled) 0-18 / 5 amp with circuit breakers, and
one I call my "come along" brute force ~15 Volts with no protection
and enough output to start an outboard motor , and motorcycle (maybe a
small car too).

My tinkering is mostly with the variable 1 amp supply (a volt meter
mounted to it would be nice - read: "damn near necessary" yet I never
get around to it). The "picaxe" is mostly with 2-3 AA batteries (only
needs some micro amps), or a 5V regulated supply for the axe, and an X
voltage for the peripherals (mostly for the convenience of having one
switch control everything)

Check out the picaxe. Really amazing fun device. Low cost. No
programmer required. Free software. Just an RS232 serial port on
your computer, and three resistors to program, using BASIC, and maybe
a breadboard with three AA cells on it. Total outlay <$20 (or zero if
you have a junk box). Extra fast learning. And, from the forum, I
deduce there's a lot of folks learning to fly, run, and walk from
square one. (e.g. "how do I connect a transistor?" to "which
communications protocol does my flat panel display take?")

Cost of the chips is <~$3 to ~$12 US depending on which flavor you get
(8-40 pins). The 08M is the most basic chip - has on board music, PWM
out, a couple of programmable A/D inputs, etc.. All the regular BASIC
commands, plus some controller commands to make a pin an output and
have it go high or low. Only integer math - no decimals (so you work
around that).

I'm old. Learned vacuum tooobs back in the day, but I have become an
apostle for the 'axe. I have them working inside my computer, working
my electric range, time elapsed cameras, etc.. Even did a switching
(buck PS) - using an N channel mosfet switching to ground. These
things are just plain fun.

Site with all the skinny and program software, and manuals:
http://www.rev-ed.co.uk/picaxe/

Best place in the US to get them, IMO:
http://www.phanderson.com/picaxe/picaxe.html

UK AU NZ and EU have other outlets
--

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Prev: Idiots, we all will be killed in a couple of days. Write to Genevaand plead the citizens of Geneva to block the entrances to LHC.
Next: Tomorrow, the 30-th of March, despite to our protests, CERN plans to perform the first collisions of protons with the energy 3.5 TeV per proton (7 TeV per collision).