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Author: Subject: Switching supply for electrolysis
12AX7
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[*] posted on 19-7-2009 at 20:05
Switching supply for electrolysis


Hey, would anyone be interested in buying kits or prebuilt power supplies for electrolysis? I'm thinking 0-5V, up to 50A (at any voltage), output ripple probably good enough for your computer if you were that desperate.

I don't have a design on hand at the moment but it's really a pretty simple thing. Say 10 people wanted one, I could design and build them in a month or two, plus little lead time for any additional units. I would guess cost in the $100 range.

Tim




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[*] posted on 20-7-2009 at 18:40


@12AX7 Having looked into some laboratory DC supplies that seems a reasonable price range for that kind of constant amperage.I would definitely be interested,although shipping to Australia would probably kill it for me price wise.



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12AX7
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[*] posted on 20-7-2009 at 20:20


What's shipping to .au usually run, I'm guessing a few bucks a pound? That's not too horrible. At least it isn't a linear supply with a laminated iron transformer!

Tim




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woelen
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[*] posted on 21-7-2009 at 07:49


I must give one word of warning with switching power supplies. They are very good for electrolysis purposes and of course for many low-voltage electronics experiments, but they are VERY easily killed by HV-equipment. I killed two switching power supplies, simply by attaching a 12V --> 15 kV converter to it. The electrostatics, produced by this 15 kV converter simply kill the switching power supply.

This of course only is relevant if the power supply is used as a general purpose power supply for both low-voltage and high-voltage experimenting.

Another thing is that the supplied voltage probably should be somewhat higher. Some cells do not draw much current at 5 V. Maybe the usefulness can be extended quite a lot if the maximum output voltage can go as high as 7 volts.

[Edited on 21-7-09 by woelen]




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Polverone
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21-7-2009 at 08:52
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[*] posted on 21-7-2009 at 10:04


Hello,

Don't want one myself even though I mess around alot with Chlorate/Perchlorate/Anodes etc. I am up to my eye-balls in power supplies. Another one and 'her indoors' would put me outdoors.
A specification that I would rather see (for Chlorate etc) would be something like:
An open circuit Voltage of 7 Volts and a current capability variable from 0 to 50 amps (ie. a constant current supply). Is that easily done with SM stuff?

Going off topic for this thread I will give a quote from here

"For any power transformer, the maximum flux density is obtained when the transformer is idle"

Is this what the fracas was about.
Also size of power transformers is frequency related as you get smaller and lighter packages for same power as freqeuncy goes up.

Dann2

[Edited on 21-7-2009 by dann2]
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[*] posted on 21-7-2009 at 12:03
Potentiostat


I have been thinking about a homebrew system for controlled potential/current electrochemical work. These devices would have far more value then just a simple power supply. Even a simple unit with reasonable stability would open the doors for amateur work in electrochemistry, not to mention a wide class of synthetic pathways to organic chemists. Like most scientific equipment, their price precludes them from the home lab.

http://en.wikipedia.org/wiki/Potentiostat
http://www.gamry.com/App_Notes/Potentiostat_Primer.htm




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12AX7
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[*] posted on 21-7-2009 at 15:50


The supply could have an operational input which would allow any generalized sort of control, constant voltage, constant current, potentiostatic, etc. Such an input would also require some electronics knowledge to use properly.

On the other hand, I'm guessing most uses for a potentiostat would be much lower current, allowing one to simply use, for example, a power op-amp (e.g. LM1875) to drive the cell. Add supply (a linear supply would be fine) and off you go. It would be good for whatever voltage you're using (10-30V?) and a couple of amps. A discrete model could easily be built for many more amps. Matter of fact, I have the parts to make a +/-20V, 20A bench supply... I need to build that some day. :)

Tim




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[*] posted on 21-7-2009 at 17:47


Constant current at greater than about 3V@50amp range would suit my purposes nicely.As long as shipping runs at under 50% of the unit cost you can put me down for one.I like this kind of initiative on the forum,surprised we haven't seen a glassblower offering custom glass to order.
Should you proceed with this 12AX7 please U2U details.




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chromium
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[*] posted on 22-7-2009 at 12:59


I would not buy SMPS for lab use if its design is not well tested for reliability. Like woelen sayd switchmode PSU-s are sometimes very easy to kill. Some years ago when i had access to computer power supplys with almost no cost i choose ones for lab use by short-circuiting all outputs in nearly every possible combination several times. About one third or quarter of PSU types survived this mistreatment and no one of them has failed afterwards. Some of those wich did not survive were killed by just one-time short from 5 or 12V to ground.



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[*] posted on 22-7-2009 at 16:15


Fixed voltage supplies can be used, but after using a true variable supply, it is like comparing a Yugo with a Porsche. A true CC/CV supply is a joy.

I've used both switchers and linears for chlorate/perchlorate cells, and the switchers do work fine, at 1/5 the weight and lower cost too, but yes you do need to know that they cannot be abused quite like a good linear supply can.

A 1 kw linear supply will probably weight 40 to 60 pounds. They are big, heavy, expensive, and getting harder to find at a decent price. If I was on a budget, I wouldn't hesitate to go with a switching supply for the stuff we generally do.

If the kit can be set up variable voltage at a minimum, I think it'd do well.
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densest
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[*] posted on 22-8-2009 at 22:28


Mr. 12AX7's project overlaps with some stuff at my chaotic corner. I'm not trying to take over anything - it just happens I've got some parts which might help :D...

I've got quite a number of Vicor BAT-MOD 0-56V 0-4.2A constant current/constant voltage DC-DC converter modules I'd be happy to sell for a very reasonable amount each. They require:
  • a nominal 300VDC input (250W per module)
  • a fuse per module
  • a heat sink definitely and a fan if not positioned to get good cooling
  • an input noise filter to protect the module from the mains and the mains from the switching noise generated by the module
  • an output filter to protect the module from the load and the general environment from switching noise.
  • 0-5V (or so) DC control voltages in.
It produces voltage outputs for current, and I think (IIRC), that they can be paralleled in constant current mode. If there's interest, perhaps in collaboration with 12AX7, a circuit board to hold one of these could be made, also containing:
  • a universal input (100-250VAC 50-60Hz) PFC AC-DC chip/module
  • a fuseholder
  • terminals to connect everything
  • a couple of control pots
  • provisions for either analog or digital meters
Of course, there's always the alternative of attaching a USB module with 2 DACs and 3 ADCs for computer control, or a microcontroller for local programming.

Any thoughts?

Also, I've got two or three Vicor Mega-Pack 2KW universal input PFC power units which accept these modules on plug-in circuit boards, holding up to 7 boards, also accepting other Vicor modules for 5V, 12V, 15V, etc. etc. They're shoe-box sized and not too heavy (5Kg?) for shipping. If someone has one of these, a Bat-Mod can be put on one of the carrier boards instead of one of the fixed output units.



[Edited on 23-8-2009 by densest]
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