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Author: Subject: Power Supplies
The_Davster
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[*] posted on 11-7-2005 at 22:04


Eh...I have no idea what I am talking about...In Craig's link:

I assumed the double circles in pin 11 meant 2 wires, and was confused when mine had only a single wire...oops

[Edited on 12-7-2005 by rogue chemist]




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IrC
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[*] posted on 11-7-2005 at 23:01


I see what you mean. Wouldn't worry about it though, as long as you have the rectangular connector like the pic you have an ATX supply. I don't see why you couldn't use one for an experimental supply though, I do it all the time, and like 12AX7 mentioned I parallel all the reds (5 volt) together, and the yellows (12 volt), and blacks (ground), to have the maximum output from both the 12 and 5 volt sources. Of course this is for limited voltage selections. I still firmly believe in a brute force transformer supply when I want lots of amps with fully adjustable voltage. If they were not so expensive and hard to find two variacs (one for current, one for voltage control), a big transformer, and some big bridges combined with about a one farad capacitor (pay attention to maximum possible voltage output to pick the voltage rating needed, or put two in series for a half a farad) make a very good all around supply.

A MOT transformer rewound for low voltage high current (with about a 30 uF 300 volt AC capacitor across the primary) makes a very good transformer if you wind it correctly. Sola power supplies also work well if you need good voltage regulation, if you can find one surplus.
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Lambda
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[*] posted on 12-7-2005 at 12:22
Pinlayouts and schems for connectors


For pinlayouts and schems for connectors just go here, and you will be able to sleep at night:

http://pinouts.ru/

Download the offline-manual here:

http://www.hardwarebook.net/download/index.html
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Lambda
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[*] posted on 12-7-2005 at 15:01
ATX power supply pinlayout and schems


And here you will find your ATX connector's pinlayout and schems (on this same website):

http://pinouts.ru/pin_Power.shtml
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Archimede
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[*] posted on 18-7-2005 at 14:42


If I remember this right, the power supply used in computers are called 'switching'.
If you look at that with an oscilloscope you will see a serie of constant pulses like a square wave. Thats how they can get soo much current output with the components used. Its probably ok with most of the work you are trying to do , as many people use it.
The car battery its interesting eccept that the voltage is probably too high and you cannot limit the current.
Of course more expensive (this one is selling now for around $100) seems to me the best equipment to use.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=75304...

It let you set the Volt output (0-40V) and the max current output (up to 30A) so you can limit it if you need to.
Something like this would also let you recharge your car battery (set Volts at 13.8 and Current to around 5A) or any rechargable battery pack just setting the right Voltage and Current.

[Edited on 18-7-2005 by Archimede]
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Twospoons
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[*] posted on 18-7-2005 at 23:21


Oh dear...

A 'switching' supply is one that uses internal switching to regulate the output. It does not mean the output is a square wave! The output is flat DC.

Switching supply topologies are used because they are (or can be :D ) more efficient than linear supplies. So they don't get so hot.
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12AX7
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[*] posted on 19-7-2005 at 08:21


Quote:
Originally posted by Twospoons
Switching supply topologies are used because they are (or can be :D ) more efficient than linear supplies. So they don't get so hot.


They are also much lighter, smaller, and cheaper once it's been designed and a few ten thousand units have been produced. :)

Tim




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[*] posted on 19-7-2005 at 08:29


Why do you guys need so much current. What you will get is all kind of reactions taking place as one kind of ion is discharged near the electrode another will take over. It will depend on how much convection and external mixing is taking place. Or maybe you're trying to boil the electrolyte.
I use a 317 to keep the current constant, and I would never use more than 100 mA if I wanted to get a clean reaction.
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12AX7
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[*] posted on 19-7-2005 at 10:27


I guess you've never wanted to oxidize more than ten grams of a salt per week, or had to plate something larger than a ring.

100 amperes on a good two square feet of graphite, lead dioxide or platinum will go through a lot of chloride > chlorate nice and fast.

Oh, and it's not the amps that melt the cell, it's the volts.

Tim




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IrC
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[*] posted on 19-7-2005 at 10:56


"Oh, and it's not the amps that melt the cell, it's the volts."

Come on guys, you are bumming me out here, as I know you are smarter than that. It is the power, a product of volts times amps called watts, that produces cell melting heat. Not just volts, or amps alone. Heat is molecular or atomic vibration, needing energy in ergs per second (or joules/sec or watts/sec if you prefer) per unit area.

So it is the volts times amps per unit area that melts the cell.
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12AX7
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[*] posted on 19-7-2005 at 11:26


I mean okay you can physically boil a cell with just a few watts, if you wrap it in thermal blankets. But a cell with the proper electrode surface area and voltage for the reaction taking place inside is going to be a certain size and that size is going to dissipate most of that power quite nicely. Yes, some reactions will need extra cooling or heating. In general, excess voltage (beyond what's needed for the reaction) still causes ohmic heating and unwanted side reactions, not to mention is a waste of power.

So yes, quite the wild generalization, but there are more (and more common) cell reactions in use that prove rather than disprove it, so it works!

(Salt is a good exception, typically being ran in the 10-20V range, well above the 4.1V required to split the ions. This is simply for convienience, using the excess 6-16V to heat the electrolyte and keep it molten, heat that could otherwise be supplied by fire or whatever.)

Tim




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[*] posted on 19-7-2005 at 12:13


Ok fair enough if you're into industrial production. I'm normally doing something more subtle ever tried Hittoff's method if you put in more than 10mA you're wasting your time.
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The_Davster
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[*] posted on 28-7-2005 at 09:32


Done building the powersupply.:D

powersupply.JPG - 199kB




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[*] posted on 29-7-2005 at 08:25


where would be without hot glue?????

if the outputs (secondaries) of the power supplies are floating (not grounded) you can indeed series or parallel them.

Use MOTs all the time in this configuration to gain either voltage and or current.

also if you get a defunct large transformer like a old welder or large battery xformer.

use it on a large variac (variable transformer) through a full wave bridge with or without filtration.

got a welder that delivers up to 225 amps at what ever voltage i desire by varitying the input accordingly.

duty cycle is dependent on percentage usage of therating of the unit

10amps @ 12vdc goes much better than

100amps @ 30vdc.

[Edited on 29-7-2005 by jimwig]

[Edited on 29-7-2005 by jimwig]
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Archimede
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[*] posted on 31-7-2005 at 08:14


Quote:
Originally posted by 12AX7
Quote:
Originally posted by Twospoons
Switching supply topologies are used because they are (or can be :D ) more efficient than linear supplies. So they don't get so hot.


They are also much lighter, smaller, and cheaper once it's been designed and a few ten thousand units have been produced. :)

Tim



Yea, but they are also designed to work between a range of loads. I don't know about the ATX power supply , but some old ones used on computers wouldnt even turn on without a certain load connected on it.
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[*] posted on 31-7-2005 at 14:19


Has anyone thought about using an old arc welder as high power supply. They normally give 100A or much more at something around 28V. They are really hard to kill, and they won't overheat.
The ionly problem is that they give 28V.
Mayby it's possible to connect their primary side (120V/240V) in serie and connect their secondary side parallel, so it should be possible to get 14V with two transformers, 9V with 3 transformers and so on.
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12AX7
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[*] posted on 31-7-2005 at 21:35


MIG welder maybe, but stick or TIG has a constant-current output so the voltage varies from say 70V open (zero amperes) to 20V arc (at say 100A). One solution may be to max out the current control, which would work reasonably on my stick welder, which uses a variable magnetic shunt and tops out at 225A. Using it at something less, say 50-100A should have acceptable regulation.

Reducing the primary voltage would be an ideal solution, but then you need a massive buck transformer or variac. Droooool, 240V variac. :D

Tim




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Twospoons
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[*] posted on 31-7-2005 at 22:17


Quote:
Originally posted by jimwig
where would be without hot glue?????



A lot better off! The problem with hot glue is
1/ if it gets hot - it lets go.
2/ usually it lets go anyway because most hot glue is useless for anything other than cardboard.




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Lambda
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[*] posted on 13-8-2005 at 18:13
Power supply and electronics in general


13.8 V / 15 A from a PC power supply:
http://www.qrp4u.de/docs/en/powersupply/

13.8V 20A power supply:
http://www.electronics-lab.com/projects/power/028/

200W ATX PC power supply (please check out the links on this page for power supply modification):
http://www.pavouk.org/hw/en_atxps.html

Power supplies and control schematics:
http://www.commlinx.com.au/Power.htm

And for more schematics on the same website in various fields of electronics:

Alarms and security related schematics
Audio power amplifier schematics
Audio preamp circuits
Automative, car and motorcycle schematics
Data acquisition and data logging schematics
Filter schematics
Games and fun stuff (schematics)
Infrared based schematics
Laser related power supplies and data transmission
LED related schematics
Lighting schematics
Medical and health related schematics
Microcontroller based schematics
Misc audio (also see Music, Amplifiers, Preamp)
Miscellaneous schematics
Model and remote control schematics
Motor and general control schematics
Music related schematics (also see Audio)
PC related schematics
PDA interfaces and related schematics
Power supplies and control schematics
Radio-frequency schematics (also see Transmitters)
Solar-powered schematics
Telephone and intercom related schematics
Test equipment schematics
Timing, oscillators etc. (schematics)
Transmitter schematics (also see RF)
http://www.commlinx.com.au/schematics.htm
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neutrino
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[*] posted on 22-11-2005 at 17:25


Just to make sure I've got this right: to get 5V, connect all the +5V wires for the positive terminal and all the ground wires for the negative one, correct?

For an AT, this do I use red or orange for +5V? I'm guessing red because there are a lot of red wires and only one orange.

Is there any use for the -5V wires? I notice they have a very low amperage rating on my ancient AT, so I'm guessing that the answer is no.

[Edited on 23-11-2005 by neutrino]
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12AX7
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[*] posted on 22-11-2005 at 22:06


Leave the other wires alone, +5 and +12 are the only ones with enough snuff behind them to be of use. -5 and -12 are almost always rated under an ampere, so unless you have an experiment you *know* will be safe and use less than rated current, leave 'em alone. ;)

If in doubt, you can open the case (mind the high voltage parts, they might carry a charge) and trace what wires go where. Usually, the red wires meet in a tight grove for +5V (something printed on the circuit board, or nearby such as a capacitor, should say something in that range), and likewise for the yellow +12V lines and a whole mess of black ground leads. Those are the most powerful so need the most wires.

Newer supplies may have a few 3.3V lines BTW. I forget what color that is.

Tim




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neutrino
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[*] posted on 23-11-2005 at 03:07


So red and black, then.

I have an older supply, the better part of a decade probably. None of that ATX junk. :D

One more little thing. When I got the unit, there was no power button to turn it on, just a bunch of wires where a switch once was. To get the thing working, I connected the wires labled 'L' with each other where the switch would have been, likewise with the 'N'. Sound good?
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12AX7
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[*] posted on 27-11-2005 at 13:04


Careful with that. It'll probably work, but I'd check the circuit board or wiring to make sure you aren't either swapping wires (not too big a problem, but could cause trouble to a grounded power cord), or worse, shorting both sides! :o

Tim




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neutrino
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[*] posted on 27-11-2005 at 13:52


It seems to work fine the way I have it now. Don't worry, I was careful not to cross - and +.
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[*] posted on 23-1-2006 at 15:38


Can two PC powersupplies be hooked up in parallel to get around 40A output on the 5V line? Or would bad things happen? And is there a limit for how many could be put into parallel?(I just got access to a large number of old computer parts :cool: ). I imagine at some point they would have to be plugged into separate wall outlets though...

[Edited on 23-1-2006 by rogue chemist]




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