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Author: Subject: Power Supplies
Rosco Bodine
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[*] posted on 23-2-2006 at 11:11


I figured out a way to get a more compact
and standard file type output from the ECAD
software which I have been using to
generate schematics , which generally only
allows viewing and printing directly from the
proprietry ECAD software .

Update :

I found an even better way to get a PDF file output
directly using the freeware Acrobat PDF Writer
" virtual printer " which I discovered can print directly
to file from the CAD , so either the CAD print output is
already Post Script or it is a file type recognized by
the Adobe PDF Writer . And as a bonus the full color
file is half the size of the black and white file generated
by the more awkward method , using Ghost Script .

The color graphic file from the CAD is useful for showing most of the interconnections highlighted in red ,
and from your printer properties you can select to print everything in black if that is desired . The color
file I have attached now is half the file size and more versatile , so I am editing the old file and substituting the better smaller newer file .

[Edited on 24-2-2006 by Rosco Bodine]

Attachment: AC Power Handler for Magnetic Stirrer Motor experimental prototype schematic final.PDF (26kB)
This file has been downloaded 684 times

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Rosco Bodine
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[*] posted on 24-2-2006 at 15:45


There is an idea which I have been looking at which
would likely improve the performance of the full power
" startup pulse " feature of the design I have been contemplating .

At the higher power settings , the need is lower for
a full power startup pulse to assist the motor with
extra starting torque , since the higher power setting
already provides higher starting torque when the power is applied . So what I am thinking is to use a dual 50K
control pot for the Main V. Adjust , with the back pot
used for the adjusting of the Full V. Starting Pulse Duration . And then the two settings would work
together towards an optimization of their interaction .
When the Main V. Adjust was set to its minimum ,
the Full Voltage Startup Pulse Duration would be set to its maximum , so that its duration would be adjusted
simultaneously with the need . A trimmer across
the 50K pot could adjust the total response range
for the Pulse Duration adjustment , and a trimmer in
series with the timing capacitor could be used to set
the minimum pulse duration . This arrangement
would be much more calibratable to the actual
performance of the motor and would give better
performance , smoother startups at various speeds
with less overshoot , and a much more closely
optimized adjustment , better control harmony and
response at different settings , especially when
the motor was being " jogged " , toggled on and off
at some intermediate speed setting .

It is likely I will put this refinement on the design into
effect in the prototype , when the actual soldering begins .
Updating the schematic may take awhile since there possibly isn't room on the present page format to draw the changes ,
and the schematic may have to be redrawn as a horizontal page to allow room for clearly showing the changes .

[Edited on 25-2-2006 by Rosco Bodine]
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Rosco Bodine
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[*] posted on 25-2-2006 at 21:25


Because it is good practice on a prototype
to have provision made for flexibility in the
calibration of something like the startup pulse
circuit , so that a good bit of adjustment is
possible concerning the way it may operate ......

I have revised the schematic to allow for more
of a mix and range of adjustments to be possible
in order to cover the various possible ways in
which any misbehavior of that startup pulse circuit
may appear, to be able to adjust the parameters
in different ways to secure the intended response for the
function . These added adjustments may prove
to be unnecessary depending upon how the motor
responds , but the adjustments will be there in
the prototype if they are needed . Good data
from the actual tests for how the motor behaves
in response to starting at various power settings
will allow me to finalize the design in terms of
exactly what control arrangement and values are
needed , but for the prototype I will err on the
side of having more adjustment options and
range of adjustment , until I know from the tests
much more about what will be the optimum
configuration for this particular startup function .

Attachment: Variable AC Power Supply for Small PSC Motor.PDF (30kB)
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The_Davster
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[*] posted on 20-6-2006 at 18:53


Just an interesting note about computer power supplies, they may say their max amperage is, for example 7A. I have been pulling 13 for 3 days out of there, and the supply is still working fine.

So take the maximum amperage with a grain of salt




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The_Davster
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biggrin.gif posted on 12-11-2006 at 13:00
The next generation of modified computer power supplies


Tired of blowing computer power supplies? I sure am. So I built this device which plugs into any ATX computer power supply.

I only paid about 30$ total, for the case, the electrode clamps, a switch and a couple binding posts. Everything else came out of computers and other equipment which I dumpster dived at uni.:D

Upper switch turns the unit on, the lower changes the voltage between 5 and 12V.

It is not variable current which would be ideal, but I lack the ability to build a variable current supply.

[Edited on 12-11-2006 by The_Davster]

POWERSUPPLY2.JPG - 48kB




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Rosco Bodine
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[*] posted on 16-11-2006 at 15:35


An ATX to Lab Power Supply converter box !

Great minds think alike :D

I have have been working on a very similar concept for
an affordable low voltage high current supply ....
only trying to make it variable voltage using some added
circuitry along with the mechanical switches .

One of the ways you can get a stepwise voltage reduction which will have some stability is to string
a series of schottky power rectifiers each on a
small to medium separate heatsink , and depending on the current you will get .3 to .7 volt drop across each
diode . Another method is just to string a coil of
heating element between ceramic insulators , and
use an alligator clip to latch onto the coil at different
distance points along the length to introduce more or less
resistance in the current path , and dump the voltage
drop as heat . If you use a Y with two alligator clips
and leave one of the clips connected as you make the
moved connections stepwise , before disconnecting
the first position clip , there will be no huge arcing from
breaking the circuit .

These are less elegant solutions than a solid state
voltage regulator adjusted by a control knob like
a volume control .......but whatever works , works ,
and every one of these uses the same electricity ,
whether it is fancy or simple .
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Rosco Bodine
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[*] posted on 18-11-2006 at 18:29


Update :

@The_Davster

Having my fingers crossed and hoping I didn't overlook
any potential snare in the design concept ......

I think I have completed the conceptual design for
the 0-100% *adjustable output * solid state
" voltage regulator " , that can be powered from an ATX power supply , and which has been discussed at length
in whimsy in the " Damn I love whimsy " thread .

The adjustable version is * not * soooo complicated
once the design is figured out , after that it is just a matter of getting parts and soldering the wires . Don't
sell yourself short with that talk of not having the
ability , this is not an advanced level construction
difficulty ......even though of course it is an extremely
advanced design :D

Thanks to 12AX7 for challenging me to attempt the
design , and discussion of design considerations ,
and also to Twospoons . The schematic isn't drawn ,
but it is so very nearly identical to an existing circuit
that I may not even bother , but just scribble noted changes on the existing schematic in the application note
and work from there .

[Edited on 19-11-2006 by Rosco Bodine]
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