Hi /diy/nos!
Listen, not much of an electro guy. Yet.
I'm into chemistry and I'm playing with electrolisys reactions, or at least i want to.
I need SOMETHING that will convert my AC current in DC current with known voltage and current.
For the little i know, a recifier is used to convert AC to DC, yet current and voltage are variables that i can't understand how to control in this process. So, i ask to you:
Can such a thing as a rectifier-voltage-current-controler-o-tron be built?
If yes, which is it's real name for googling purposes?
Can an old PC power suply be adapted to the purpose?
I'm reading!!
Pic totally related
>>993082
>I need SOMETHING that will convert my AC current in DC current with known voltage and current
See pic. Anything there will work.
>Can an old PC power suply be adapted to the purpose?
Yes but it wouldn't be worth the waste
>>993082
>Can such a thing as a rectifier-voltage-current-controler-o-tron be built?
Yes but once again, it isn't worth a chemist's time.
>>993085
But it's worth my money, ATM my finances are exactly -$100.000 at my local currency, yet I have an spared power supply and a box full of old electronic stuff that i've gathered throug years. I can read resistors and capacitors values and i can solder almost decently, building this is worth, specially if it can allow me to gather experimental data for some reactions that i need (complex salts system that can't be fully predicted by theory), but as you say and http://www.finishing.com/324/39.shtml confirms, it's dificult at least
Now, back to track: >>993084 is pretty useless to me,since i can't manage (per se) voltage or current. I'm looking for something that allows me to have a voltage span of -3/+3 volts and a definition/precission of 0,01V and a current of.... i dunno the span, the bigger the better, but 15-20 is known for being for hardcore job, yet, 0,01 A of definition is neede for my purposes.
Now, how can i convert a power supply or adapter into my desired arrange? Just using V=IR till i get it? I think i have a protoboard, so could come easy to mount/dismount all of this
cute/horny jap with cocoa for your troubles.
>>993121
Your computer power supply would put out like 12v probably not tons of current all depends on supply in question. You can build your own relatively easily but as it has been previously stated buy since your looking for a high current output you would need to make one yourself. You would use a resistor to set the current out of the supply if your load(what ever kind of frankenstien shit your doing) doesn't manage to pull that much power, which it probably won't. With high current supply's you would need to make sure your diodes can handle the current as those will melt first quickly fallowed by the other componants.
http://www.circuitstoday.com/regulated-power-supply
Probably start there.
>>993121
>since i can't manage (per se) voltage or current. I'm looking for something that allows me to have a voltage span of -3/+3 volts and a definition/precission of 0,01V
A small voltage reg circuit and >>993084 should do that
What chemicals are you trying you preform electrolysis with anyway?
>inb4 H2O >>>H2 and O
You can do that with 12v dc at >1 amp fine
>>993172
want to run electrolisys in sea water with the semireactions
2Cl- => Cl2+2e
2H2O +2e => 2OH- + H2
the reaction needs 3 volts, but I THINK I'll need high output if I need to proceed to pilot plant. For starters, few amps and area regulation can help to fix the current density (needed parameter) but I get the feeling that building the curve can take some more of power. Still running the numbers, but i'd rather have a big kit if i go large, wich is a probable outcome.
Power supplys provide from 0,3 to 30 amp, so I should be able to find a suitable one in a long range, so now i'm worrying about how to produce exact output
>>993186
Why do you want chlorine gas?
Anyway, this is an interesting topic, I've made some small H2 burners before, however, none the scale(?) of yours thusfar. Firstly, you don't need just 3V. I presume 3V is the minimum cell potential needed to drive the reaction, so, with changing temperatures and concentration of solute with time, the needed voltage will likely rise. Also, a pretty well known tip is to use high surface area neutral plates to divide the potential across the electric field, but the outcome is that you can't reliably isolate H2 and Cl2, unless you build a pipeline that alternates between H2 and Cl2. Current determines how fast the reaction can take place, but you'll have to mind that water has resistivity, and an issue with my older cells was heat production, and some of the water evaporated due to the massive heat generated. Perhaps joining cells in parallel can mitigate this.
Good luck..
Basically, you can choose either the current or the voltage, and the other will be dictated by the chemistry (i.e. the solution, its concentration, the size of and distance between plates).
The usual constant-current circuit for non-trivial amounts of current is a buck regulator. While you can get dedicated buck-regulator ICs (e.g. MC34063), most of them are designed for constant voltage and require a sense voltage of 1.25V, which can translate to high power dissipation in the sense resistor at high currents. Ones designed for driving LEDs (e.g. LM3404) typically only need 0.2V sense but tend to be limited to an amp or so.
>>993082
You're on the right track. In order to get the voltage you want you'll have to look into transformers. That will change your AC from one voltage to another (say 120 from the wall to 12). Next you'll need a full bridge rectifier (like you already mentioned). This will convert from AC to DC. You'll probably want some caps to clean up the signal, not sure how much that will matter in your situation. As far as constant current, current is dependent on the load you give the source. If you just connect the + and - with no load you'll have a short circuit with infinite current, if you have a giant load with low voltage then you'll get hardly any current. Look up V=IR for more explenation on that.
Moral of the story: buy a pre-built AC/DC converter. They're about 10 bucks.
>>993224
Okay anon i just actually read all the posts before me. Get a bench top power supply. You can get one for relatively cheap. They allow you to control the voltage they put out as well as put a limit on the current they put out. Seems like your best bet. I bought mine for 50ish on amazoooon.
>>993189
I don't want to obtain Cl2, it's a by product. I'm trying to manage pH through electrolisys of seawater. Eventually, heat accumulation will not be a problem since it's gonna be operated continuously, but for this part of the job i need to meassure reaction kinetics, that's why the known voltage and current needed.
Have any bibliography around?
>>993204
I couldn't understand less. I'll try later,got job by now.
>>993224
I gonna use a PC power supply, since no money, and I'll use V=IR to build the cell. Problem is: how do I build cells that have fixed voltage?
Gonna have to brain this one I guess.
>>993227
The money, that's my arch enemy now.
What OP wants is variable voltage and (I think) controlled current. IIRC electrolysis needs high voltage and moderate current. OP, if you could find the voltage rage you need and the current range you need that would help a lot.
Because, at it's most simple, you could take a light dimmer and a beefy bridge rectifier and go with that.
Pic related. That'll go to 50 amps but it's probably more then you need.
http://www.ebay.com/itm/2PCS-50A-1000V-Metal-Case-Single-Phases-Diode-Bridge-Rectifier-KBPC5010-/221950605426
So, I´ve got the PowerSupplyUnit, and went here http://www.instructables.com/id/Convert-an-ATX-Power-Supply-Into-a-Regular-DC-Powe/?ALLSTEPS
So, pretty much gonna do this for now, but, I've come to notice: PSU has V and -V, what does that mean??? i know that a current has to enter the cell, some has to leave, but i supposed that if i used the PSU it should act as a battery, fixing current direction by it self. Do I need to fix it? does this mean that I can/must have a wire with -5V and another with 5V and both go to ground wire?
Don't know really.
Care to explain?
>>995107
>PSU has V and -V,
V in your system are arbitrarily placed
Whatever the voltage "is at" on -V, call it zero
The difference between them is what matters.
>>995108
YEah,got that part, but my problem is current.
Since reactions must go anodic (throwing electrons in the solution) or cathodic (pumping electrons out), I'm concerned if -V or V affects current direction and if being that the case I need to conect both wires to the solution and a 3rd wire for grounding the system.
I believe that if current direction changes it's a lot easier to build multiple cells, I´m on that now.
>>995123
So, all wires are gonna flow from "positive"to ground,and I must set the electrodes accordingly, -V and V do not interfere with current direction and as -V & V have different currents, i can have same voltage at 2 different currents, that's what I´m getting of this.
>>995123
Oh, just need a cheaper way to control pH than additives.
Gonnalet you hanging a while with the final aplication. Can as well guess, could be fun.
I'm a chemical engineer trying to get my hands on a little project-
Practical electrochemistry is new to me.
>>995127
>cheaper than additives
Soooo your plan is to increase the pH of water thru electrolysis? Considered the cost of electricity yet?
>>995234
Baking soda is very expensive, dontchyaknow?
>>995234
Considered the loss of lime due to higroscopy?
Some times a cheap operation becomes inefficient due to environmental reasons and expensive treatments end up being cheaper since they're not environmental ridden
>>995127
What are you controlling the pH of?
>>995327
seawater, as stated above.
>>993457
I'll go with the PSU that I'm modding and will ADD a dimmer to the 5V wire that i need, that should do the trick,no?
>>995371
>add a dimmer
not really.
like a light dimmer?
they usually work by clipping the tail of the AC sin wave so who knows, if the controller needs mains to run it won't do shit.
simplest way is variable resistor to set the voltage but its obviously open loop so you need to monitor the voltage current through your setup.
you really need to monitor it anyway because the impedance of what you are bubbling will vary wildly (with temperature, because its not homogeneous, because you are altering its chemistry)
if you want a regulated voltage source then that is what you need. if your experiment impedance suddenly drops and the supply can't pump out the current the voltage will drop to maintain V=IR
>>995374
>variable resistor
I assume that this is no more than a resistance, therefor, with V=3V and I=30A (PSU output), P=VI=90W, 90 watts lost to heating air. Can even a VR manage that?
Excuse so many questions, but only thing i've got is will, no money and few knoweledge
>>995381
Use an autotransformer then.
Basically just get a welder.
>>995384
But a transformer won't give me 2.7V, and that's what i need. PErhaps transformer + resitors will work
>>995371
Like in a saltwater aquarium tank? I really want to tell you it will work, because that's an incredibly horrible idea. You will inevitably produce some sodium hypochlorite AKA bleach.
>>995410
And that's exactly the point, as you produce NaOH pH raises, accomplishing the purpose of the pretreatment.
>>995410
And, no, it's not for aquarium, it's for running water
So, I've found that purple wire outputs some nice and easy 5V and 2A, so using resitors or even variable resistors is a viable option.
Guess I'll keep going with this PSU till it works
![DSC_0050[1].jpg](https://i.imgur.com/Ao4H2bE.jpg "DSC_0050[1].jpg")
MMMMMWWWWWWWWWWWWWWAAAAAAAAAAAAAHAHAHAHHAAHAHAHAHA
I've tamed the power of the PSU!!!!!
So, I've got a nice PSU with 6 outputs, being each:
12V, 18A
5V, 35A
3,3, 25A
-5V, 0,5A
-12V, 0,8A
5V, 2A
I'll try to run the reaction with a potentciometer of dunno, 10k i guess, don't remember, in the 5V,2A output so it won't kill the potentiometer.
Now, have some pic to share.
![DSC_0051[1].jpg](https://i.imgur.com/M9odV9L.jpg "DSC_0051[1].jpg")
some more wiring
![DSC_0052[1].jpg](https://i.imgur.com/NSreeWD.jpg "DSC_0052[1].jpg")
Aaand all cased now
>>995970
you're going to want to recheck your I and V calculations.
>>995978
I just realized, a 10k pot will allow 0,7 mA, so nothing. Is there a way to reducevV, have high I and don't burn out 90W in the process?
It seems now that the only real way to achieve this is by getting an special transformer, like wielding machines.
>>995981
You can use voltage regulators in parallel, but you'd lose a lot of heat. Someone mentioned the MC34063 chip, but that requires more parts, and these days, you can buy say, an LED driver circuit for lamps, because those tend to deliver tons of amps for DC.
The problem you're probably not expecting is how much resistance water has. Even with large electrodes and a small distance, electrolysis is a pain in the ass if you want something done in less than a week.
>>996126
Wait, what?
Look, I'm not looking for plating or electrodepositation, I'm trying to lower pH in a continuous operation, so, can't afford to leave water for days trying to reach operating pH.
In an industrial aproach, i can just ask for the electrolysis rectifier equipment to be purchased, but i'm still not there and for justifying the purchase of such equipment i need bacl up info first. Such back up info is related to design and for design i need to prepare certain curves, wichi'll get from this.
At lab scale i can afford to lose some power trough heat, as long as that doesn't imply to burn my house, or burn the components.
Electrolite resistivity is to be studied here as well, so i'll look more carefull in it.
If you know something or can lead me to some good books, i'll apreciate it. I'm trying Faulkner's and some old notes from teachers.
>>996174
I'm telling you from being into old free energy shit and learning the truth: electrolysis is very difficult, talking 50% efficiency without very effective technology. Even if you had some incredible amount of surface area and high voltage, and only used pure carbon electrodes, you'd have gunk build up pretty quickly and it still would not be quick.
Electrolysis is the application of electricity for ANY chemical reaction.
>>996205
How sure are you about it? as far as i know, electrodepositation is slow because it takes time to produce a fine finishing, as in copper EW, where kinetics for proper grain obtention are fundamental, but i want to eliminate Cl2 in order to produce OH- in not so big scale( few grams per ton,few tons per hour).
If you tell me that it's 50% energy efficient, i can deal with it, ifyou tell me it's 50% TIME efficient, i'm in trouble. Not so much, any way, just build an additional tank for the process, even if it's an expensive investment, as long as operational costs drop significantly, i will abide.
Again, have you something to read about? Not that i don't care for your advice, but it's pretty complicated take your exp anly throug this media.
>>996205
and the problem with voltage is not have a high one,is getting the righ one, redox reactions depend on V and pH, so there are displacements of equilibria that do not require more voltage, but less or even you can have reactions being strongly inhibited by pH
Good work kids, probably helping ISIS make chlorine gas.
>>993082
You are controlling the Ph of seawater? To what end?
Basically you need to account for plate current density like electroplating. The solution is almost a short circuit so you need to build a current controlled power supply.
Besides you are cranking 3V of potential from + to - so you will be removing metals and organics that are polar in which I assume is dirty sea water straight from the ocean.
So after you deplate the metals out, you will get more Chlorine eventually.
You are going to dissolve your positive anode plate into the solution which should be stainless to prevent that.
For the anode/ - side use a carbon rod or a metal that is not going to be dissolved into the solution easily. Avoid things like lead.
The actual chemical electropotential mention in Chemistry books is somewhat close to the real world, but you realize that you have to go a bit above that to get plating or electro-polishing (the reverse) to work.
A dc welder at 30-45 VDC then a series of cells to give the same voltage potential you need will do the trick. Lots of amps.
You could build one with an old microwave oven transformer wired backwards (output to input and get lots of AC to rectify).
Thoe other poster was right put some filter caps of a few 1000 uf at the working voltage to clean it up. The square packaged regulators have a hole in the middle to bolt them to a heat sink with thermal compound for a reason. They get hot and fail otherwise.
I would suggest a primer on electroplating and electro polishing.
You can plate small objects with minimal currents from a few D sized batteries or a solar panel if you need a thin coating in the micrometer range. But mass changing the chemistry is a lots of coulombs of electrons.
Lookup Faraday's law.
https://en.wikipedia.org/wiki/Faraday%27s_laws_of_electrolysis
https://en.wikipedia.org/wiki/Electrolysis
A bench grade power supply for up to 5A 0-60VDC is about $80 usually works in .01 gradients of voltage and amperage.
Batteries run DC dude, i that would be your best bet rather than using an alternator/transformer combo which is what uour suggesting $.$. Also you can just choose a battery with an appropriate voltage or whatever. Does electrolysis require very spesific volt/current needs? I might be wrong but i dont think it does, probably want to use less for flammable stuff? Literally just get two wires on either side of said battery one anode ones cathode. Hope thathelped man
Read a bit more of thread but not all of it cba but, get a battery and a variable resister hook it all up to a volt and amp meter so you can see whats running through it and job should be a goodun.
![DSC_0053[1].jpg](https://i.imgur.com/qqpdrcU.jpg "DSC_0053[1].jpg")
Ok, update:
PSU was built, water was electrocuted. Shit happened.
As 2 Amperages where available, 2 experiments where done. Electrolysis at 2V and 0,8A and 2A, but resistance variated in each case; did it wrong and used same resistance for both currents, so experiments where useless.
As a result of the experiments, 2A current produced brown (shit) colored flocs and 0,8A produced dark green/blue flocules. Must be noticed that 0,8A current used -5V so i'm not shure if electrodes changed place.
As i laked of a pH indicator atthe time, had to wait a little. When pH-paper was obtained 4 experiments where programed:
-seawater 2V-0,8A
-seawater 2V-2A
-saltwater 2V-0,8A.
-saltwater 2V-2A
each measuring i=I/surface; I,pH, t, and phenomenological data (shape, colour changes, etc)
Had time to run 1st exp only, yielding insatisfactory pH results and green flocs.
Next morning PSU wouldn't run. Dead brick.
I'm stuck making another, had other stuff to do, so slow development.
I think pH wouln'd change because of mixing and i need therefore separating membranes. Gotta check that.
As soon as i build the new box (tomorrow i hope) i can keep the exp. so, that's it by now.
Never the less... I HAVE PICS FOR EVERY BODY!
![DSC_0054[1].jpg](https://i.imgur.com/PQmcdJl.jpg "DSC_0054[1].jpg")
>>999288
![DSC_0055[1].jpg](https://i.imgur.com/EB8AISM.jpg "DSC_0055[1].jpg")
>>999289
Used a board now, first resisntances were soldered just in cables
![DSC_0059[1].jpg](https://i.imgur.com/7AP6WfZ.jpg "DSC_0059[1].jpg")
>>999291
![DSC_0068[1].jpg](https://i.imgur.com/xJjlIrD.jpg "DSC_0068[1].jpg")
>>999293
Floc are kept now in a glass, cba to take pics now
>>996558
OP will probably poison himself to death first.
>>999362
I have not. Yet
New equipment.
Succesfuly managed to build another PSU and now started new experiments.
In the pic, you can see the PSU, a board with resistors to achieve proper voltage and the new cell developed,which presents a songe used as semipermeable membrane.
Previous experiments led (lead?) neutral pH, yet 2 cell design presented diferent pH in each cell
