Sciencemadness Discussion Board

Getting me a lab power supply.

nannah - 18-8-2014 at 10:58

Hi, i am thinking about getting a power supply to run a electrochem cell, but im not sure which one i should buy.
I have found this one that has a reasonable price, 140W, 10A (12A Peak) and 13,8 +0,12V, 140W.

Does it sound enough for the needs of a amateur experimenter?

What should you look for when shopping for a power supply? I mean, what matters, for example the amount of ampere or volt.

anks in advance. Love Nannah.

[Edited on 18-8-2014 by nannah]

TheChemiKid - 18-8-2014 at 16:04

Do you have any specific experiments that you would use this for?

hyfalcon - 18-8-2014 at 20:20

I think this would be a better solution.

http://woelen.homescience.net/science/chem/misc/psu.html

I like this one

quantime - 18-8-2014 at 20:27

http://www.ebay.com/itm/30V-10A-10AMP-110-220V-Precision-Var...

For chemistry, adjustable current regulation is important.

nannah - 19-8-2014 at 09:38

Im not really sure what experiments i want to try. I am curious maybe making some bromine at first.

I checked the link out, and it seem like a good one. I will keep it in mind.

So what i should look for is that i can adjust the amp? And the more ampere it have it will be able to do all kinds of different size experiments?

I dont want to buy one and later figure out that it doesnt have power enough to perform the experiments i want to try. I figure its best to get one thats powerful enough right away.

Thanks for taking time to help me. :)

/Nannah.

Zyklon-A - 19-8-2014 at 11:30

You should probably get one that can allows you to adjust the amps as well as the volts.
Many experiments will require different volts, and if you use too much or too little voltage, the reaction will not go as expected. Voltage is critical.
Amperage will determine how fast the reaction goes and how hot the solution gets. So if you can't adjust the current (amperage) then you will be limited to using only a solution quantity that fits your amps. In other words, if you use to little solution, for the amount of amps you supply, your solution will boil. Not enough solution, it might not get warm enough, if the reaction requires heat.
Both of these are relatively easy to fix, by using a heating/ cooling bath. But more importantly, if you can't supply enough current, the reaction may take a long time.

BromicAcid - 19-8-2014 at 13:37

I've always wondered how a cheap tattoo gun power supply would work for these sorts of things. The voltage is varied by the dial on the unit. Amps could be controlled by immersion level and distance between the electrodes. Even the cheap <$20 units are usually 2 amps which is plenty to play with.

I.e.
http://www.ebay.com/itm/Red-Pro-LCD-Digital-Power-Supply-Uni...

[Edited on 8/19/2014 by BromicAcid]

nannah - 19-8-2014 at 15:01

Thanks Zyklon. That helped alot. :) I will definently get one that adjust both. I am looking at a Pyramid, and it adjust amp, and volt between fine and coarse. Is this standard?

Also it seem like the higher the price, the lower the amp.

I am searching ebay and found a couple interesting ones. There are many cheap chinese units, that seem pretty good. Can the low price indicate that the quality is bad. Anybody here have experience with them?
I live in the EU, so i couldnt get an american unit becouse it wouldnt maybe run over here. I have already made that mistake once. :)

I have heard of people using car battery chargers. Can that be an option?

/Nannah.

mrTrifaziux - 19-8-2014 at 15:25

If you manage to find a charger that has adjustable current it might be me an option, but still no match for a lab supply. I've seen people make bromine with car battery chargers. And you can't adjust voltage on a car battery charger so that's a big minus.
I too live in EU and I got my PSU from local electronics shop, not the best one but does the job.

IrC - 20-8-2014 at 08:56

One thing many fail to consider is can the supply run bathed in high heat for long periods of time. Something common in runs of electrochemical cells. In the Pyramid example you have pass transistors which will eventually fail. In others words just because a supply says it can do X amperes, the real question should be can it do X amperes for say 100 hours nonstop. Example is looking at the surge current rating. Useless if you expect that current level for days on end. It will fail. The car battery charger idea is actually not a bad one if you add a Variac. Also you should consider de-rating, meaning use a supply rated for twice your expected load.

Your local TV station runs 24/7 because if they want a hundred kilowatts out they use a 200 kilowatt amplifier. Using a charger and a variac rated for twice the current you will be running, odds are it will do this for long time periods without failures. The main advantage of using the car charger - Variac combination is elimination of the pass transistors. Probably the only bad thing is if you are doing some experiment requiring precise voltage or current regulation. In this case you would need a supply such as the Pyramid, though this brand is rather cheaply built as is Trip-lite and many others. Perhaps woelen with his preference of switching supplies has already concluded many of these thoughts. A switching supply can operate for long time frames without the heat failures common with supplies using pass transistors. In any case before you run out and buy a supply give careful thought to what it can take over what time frame nonstop VS what you intend to use it for.

Metacelsus - 20-8-2014 at 09:28

A variac (1.2 kVA) connected to a rectifier and smoothing capacitors is what I use for most stuff, including electrochemical cells.

nannah - 20-8-2014 at 10:39

I found this one that is in the link. From what i know it seems like a good choice, but i wanted to check with you guys if you would recommend this one.

http://www.circuitspecialists.eu/switch-mode-dc-bench-power-...

IrC - 20-8-2014 at 11:06

I studied your link and it looks like a very nice power supply. Being able to set voltage and current independently is a plus. I imagine this supply would be a very good addition to your lab. Overload and thermal protection as well. I do not think you would need anything else for your experiments other than maybe something producing high voltage if you ever decide to delve into plasma experiments. If you did you could build a high voltage supply and use this one to power it.

hyfalcon - 20-8-2014 at 12:14

I've bought from them before myself. Soldering station and hot air rework station I have came from them. Only not the ones in the EU. There's one here in the states also.

[Edited on 20-8-2014 by hyfalcon]

nannah - 21-8-2014 at 11:59

I think i will go for it and buy that one. It seem great, but the only thing that i wonder is that it say that it runs 8 hrs continously or something like that. I dont know what that mean, but i hope not it means that it shuts down after 8 hrs. In that case its not that great.
What would you do to cool down your p.s if it gets too hot. This one has a overload/over heat protection, but you dont want it to come to that, right.

Have a great day, and thaks to everybody. :)

/N

IrC - 21-8-2014 at 12:02

Quote: Originally posted by nannah  
I think i will go for it and buy that one. It seem great, but the only thing that i wonder is that it say that it runs 8 hrs continously or something like that. I dont know what that mean, but i hope not it means that it shuts down after 8 hrs. In that case its not that great.
What would you do to cool down your p.s if it gets too hot. This one has a overload/over heat protection, but you dont want it to come to that, right.

Have a great day, and thaks to everybody. :)

/N


It may mean 8 hours at maximum ratings, which I doubt you will do anyway.

nannah - 23-8-2014 at 10:23

Yeah, you got a point there. :)

One thing i was thinking about is that a Hg pool cathode is pretty common used, but for someone like me its pretty hard to aquire that much Hg. That got me thinking of a thread here on the forum about the use of Ga to substitute mercury salts in Al/Hg amalgam. As i understand it worked out pretty good, right? Eventhough Al/Hg use Hg salts, and the Hg cathode use Hg metal i wanted to hear with you guys about this thing i was wondering about.

Its just a thought, but i wonder if you think that a pool of Ga as cathode could successfully substitute Hg? It would require the temperature of the reaction to start up at 30C.
Even if it works, i don't know if it is even worth it. If i could use other kinds of metals for cathode that are much cheaper, and that may get the same end results as Hg would, or better, i would not use Ga for my cathode.

As i understand, in electrochemistry different metals have different properties (ofcourse), and they are used for different types of redox. Im no expert in this field, as you already know. But i going to read up on over potential.

Take care.

gdflp - 23-8-2014 at 13:34

For lots of instances gallium won't work, either because the higher temperature needed to keep the gallium molten is unfavorable for the reaction, or the products will dissolve the gallium (such as making sodium hydroxide from sodium chloride). The success with amalgams has to do with reductions in organic chemistry and doesn't have much in common with electrolysis.

Fantasma4500 - 24-8-2014 at 03:39

i bought a 5V 40A power supply from china (i recall it was?)
it works well but one day it killed my 1x3'' MMO anode in saturated KBr solution, it still seems to run in NaCl solution however..

if you are thinking about electrolysis as in for chlorates, iodates and bromates you want to go for 5V, 3.3V being the lowest for electrolysis -- i recall

the more voltage the more heat, using 24V can easily get a beaker shockboiling

the amperage shouldnt be a problem, you can simply dilute solutions to get it running abit less aggressive, but 1.5L NaCl solution usually went abit past 50*C after 3 days of electrolysis

if you want to use it for electrocoating you might want to get one abit smaller where you can adjust voltage/amperage, which of what i have come by on this forum plays a big role

you could perhaps buy a few, now that they are so cheap anyways..
http://www.ebay.de/itm/5V-5A-10A-20A-40A-60A-Power-Supply-Tr...

note its free shipping

jock88 - 24-8-2014 at 11:51


Folks need to stop obsessing about 'the voltage needed' for electrolysis.
Statements like '24 volts can easily get a beaker boiling' are and very poor way (if not downright inaccurate) of describing a situation.
You do need to have a certain voltage to do the job of course. You need a sufficient voltage to 'shove' the required (desirable) current (current will depend on electrode surface areas and perhaps total volume of cell).
The best thing for this job is a controlled current supply, as described above in some posts/links. Set the desired current and let the voltage be what it will be at the that current.
Get a supply with a maximum voltage in the region of 10 volts and as many amps as your pocked can withstand.
You will then used this supply in the 'controlled output current' mode.
Forget about a controlled voltage source (whether or not the output voltage is fixed or variable).
If you are short on cash a fixed (or variable) controlled voltage source WILL do the job but you are then STUCK with only being able to put (say if its a computer power supply (controlled voltage source)) either 5 or 12 volts to the cell. You can put resister in series to get the current you desire in this situation.

Stop obsessing about 'the voltage needed to get the cell to run'. Think in terms of the current I want to pass through my cell.

There are people here who can put this more elegantly than I!!!



[Edited on 24-8-2014 by jock88]

Fantasma4500 - 25-8-2014 at 10:06

perhaps i was not very accurate.. i mean to recall the amperage went to 20-30 at that time, meaning 24x25 approx, giving 600 watt

but really, using excess voltage would be entirely counter productive, perhaps not if you have too much electrolyte to get the cell running at a decent temperature

jock88 - 25-8-2014 at 14:03



For electrochemical cells fix the amperage and let the voltage be what it will be (you need a controlled current source or supply with a 'current source facility', (as above in some of the links)). If the voltage required to do this is some crazy high number then you are putting far to many amps into the cell or there is something wrong with the set up.
Obtain a controlled current source for your cells. Try to avoid controlled voltage sources (most power supplies are controlled voltage).
Some of the lab supplies above have both options which is great. Controlled current source for cells etc.
Controlled voltage source for other stuff (like running your 5v logic stuff).

When you read a statement like 'such and such a reaction product forms at a voltage of 2.1 Volts' in a scientific paper, the author is NOT measuring the voltage across the terminals of the cell using a voltmeter. They are using a third reference electrode in the cell (like a saturated calomel electrode (sce), or a hydrogen electrode or some other) to measure 'the voltage that the substance forms at'.

No one on this board has ever (to my knowledge) used a reference electrode and reported using it on the board. (They may used them professionally etc etc and know lots about them of course).

Stop obsessing about the voltage across cells!!

The next best thing to having a saturated calomel electrode (or some other reference electrode) is to quote the current density on the electrodes.


If I here anyone ever again on this board saying something like "Ya need 6 volts to get perchlorate to form" (or something like that) I am going to contact Pulveriser and have them banned for a week (I have no doubt he will entertain me!!)

[Edited on 25-8-2014 by jock88]

nannah - 26-8-2014 at 07:49

I have reconsidered the adjustable 0-30V, 0-20A power supply, and will start looking for one thats not quite that powerful. I figure that a 5A or 10A that adjusts only the current is fine for me.

I have heard that you can use a car battery charger can be used. What are the downsides to that?

Thanks boys.

Fantasma4500 - 26-8-2014 at 08:04

Quote:

and a voltage somewhere between 3.5 and 10 Volts.


http://www.oocities.org/capecanaveral/campus/5361/chlorate/p...

jock88 - 26-8-2014 at 10:21

A more up to date copy of the Geocities page is here

http://oxidizing.typhoonguitars.com/

Link to power supplies here
http://oxidizing.typhoonguitars.com/chlorate/powersup.html


Some modern car battery chargers are quite sophisticated devices.
The older ones consist of a transformer, bridge rectifier and a resistor.

If you are going to do some experimentation you are best with a controlled current power supply with a current meter (and if you like a voltage meter)


Zyklon-A - 26-8-2014 at 10:45

This might be a stupid question, but can alternating current be used for chlorate production? I generally use MMO for the anode as well as the cathode, so if the positive and negative terminals alternate (about 60 times per second) each electrode is an anode and cathode half of the time. Would this not work?
If not, why?
[EDIT] One reason I can think of is as each product is produced, it might reverse and reduce anything that was just oxidized, and oxidize anything just reduced because there isn't enough time for it to migrate to the other electrode. Is this the reason?
I though ions would move fast enough for this to not affect anything much, maybe not...?

[Edited on 26-8-2014 by Zyklon-A]

nannah - 29-8-2014 at 01:29

How do you scale down the bromine, (and other electrochemical experiments) so a power supply with 5A can be used?

/Nannah.

gdflp - 29-8-2014 at 20:13

To scale down electrochemical experiments you need to figure out the surface area of your electrodes. Generally the amount of current needed is directly proportional to the surface area of the electrode you are using. So, to scale down experiments by two for example, halve the amount of reagents you are using and use electrodes with half of the surface area. Even if the current is lower than specified by the experiment, you could still use the 5A supply, it will just take longer due to less electrons being conducted through the solution, again time is directly proportional to current.

nannah - 30-8-2014 at 02:50

Ofcourse. It sounds so obvious when you say it. Why couldnt i thought of that? :)

I am planning on converting a old computer psu to bench power supply. I have been under the impression that its a very complex process, but yesterday i saw a video on youtube, and it is ridiculously simple to do if you have the parts, and the tools.

What amps can you get with a apx psu? It say that the output is +3,3V - 14A max, +5V - 22A max, and +12V- 10A max.
Is it really possible to get up to 22A then? :/

/N.

gdflp - 30-8-2014 at 05:58

Yes each output can be one of three voltages, and each of these voltages is connected to a fuse. So at 5V you can pull 22A, and at 3.3V you can pull 14A etc.

nannah - 30-8-2014 at 11:47

Ok, but its not possible to adjust the current or voltage, so you have to keep it at 10A, 14A or 22A, right?

WChase501 - 9-10-2014 at 10:11

Have you thought about a computer power supply unit?

jock88 - 9-10-2014 at 15:21

http://www.sciencemadness.org/talk/viewthread.php?tid=3885&a...

Circuit for constant current out below

using irfz44n You can get bigger ones.


http://oxidizing.typhoonguitars.com/chlorate/cpsu.html