Custom Power Supply for Electrolyser

Thread Starter

JulesP

Joined Dec 7, 2018
265
Hi all,

For my OxyHydrogen brazing electrolyser (pic), I need to condition the plates with a consistent 5-10A at 12V. The cheap eBay power supply I have, although fine for low power requirements, is not up to the job and can only muster 3-4V at 9A (reviews are pretty dire actually). I could use a car battery but there doesn't seem to be an easy way to fine-tune the current draw.

So I'm proposing I build a custom power supply as laid out in the pic. This uses the power transformer from an old microwave, removing the secondary winding and putting in about 15 turns of 1mm2 solid core wire. An off the shelf power rectifier and a couple of smoothing components.

My query is, firstly, are there any modifications I should make to this for effective operation? (The transformer will be inside a box and I will have a fuse)

Secondly, what is the red tube entity with the transformer? A choke, noise suppression, the capacitor they mention?

Thanks

Jules
 

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Dodgydave

Joined Jun 22, 2012
9,460
Do you need to control the Current or Voltage, as you can only do one .?
So do you need 12V DC with upto 10A output if so use an Atx PSU .
 

Thread Starter

JulesP

Joined Dec 7, 2018
265
Do you need to control the Current or Voltage, as you can only do one .?
So do you need 12V DC with upto 10A output if so use an Atx PSU .
I need to set the voltage via the number of turns on the secondary and then control the current supplied to 5-10A. I do t know what an Atx PSU is but the point of my query is to build a PSU at next to no cost.
 

jpanhalt

Joined Jan 18, 2008
10,246
Almost any discarded desktop computer will give you an ATX power supply at virtually no cost.

Given the way you describe it, you cannot control voltage and current independently.. That is, if 12 V (constant voltage) is across the plates of your electrolyzer produces 10 A, you cannot reduce the amperage at the same voltage drop across the plates without changing something else. That something else can be the electrolyte composition, plate area, or any other change that changes the conductivity of the cell.

You cannot change the supply and reduce the current while maintaining the same voltage across the plates.

Edit: Emphasis added
 
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Thread Starter

JulesP

Joined Dec 7, 2018
265
Almost any discarded desktop computer will give you an ATX power supply at virtually no cost.

Given the way you describe it, you cannot control voltage and current independently.. That is, if 12 V (constant voltage) is across the plates of your electrolyzer produces 10 A, you cannot reduce the amperage at the same voltage drop across the plates without changing something else. That something else can be the electrolyte composition, plate area, or any other change that changes the conductivity of the cell.

You cannot change the supply and reduce the current while maintaining the same voltage across the plates.
I think I understand what you’re saying. So why wouldn’t the SCR adjust the power into the primary and hence the output? Would that reduce voltage instead of current?

If I could find an old computer supply (any suggested brands?) is there a circuit I can use to set it up for adjustment of both I and V and up to say 12A max?
 

Delta prime

Joined Nov 15, 2019
504
Hello :) So your going rip out the secondary windings a good known properly working Step Down Transformer that came out of a microwave.
A step down transformer is a device which reduces a higher AC potential to a lower AC potential as per its winding ratio and specifications.
The power supplied by the secondary is in fact transmitted from the primary, although at a voltage level dependent on the winding ratio of the a pair of windings
The quantity of turns on the primary and secondary winding is determined using the formula for turns per volt ratio
Turns per volt = 1/ (4.44 x 10-4 frequency x core area x flux density)
The flux density could be considered as approximately 1.0 Weber/ sq. m. intended for ordinary steel stamping and approximately 1.3 Weber/ sq. m. for CRGO ( Cold Rolled Grain Oriented)
The quantity of turns on the secondary is calculated in the identical method when it comes to primary, but around 3% excess turns should be included to reimburse for the internal drop of secondary winding voltage of the transformer, upon loading.
Secondary turns = 1.03 (turns per volt x secondary volts)
electrostatic shielding between the primary and secondary winding to circumvent electrical interference from moving across to the secondary from the primary. I'm just giving you a hard time I did the same thing. Dirt cheap good luck. ;)
 
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Thread Starter

JulesP

Joined Dec 7, 2018
265
Hello :) So your going rip out the secondary windings a good known properly working Step Down Transformer that came out of a microwave.
A step down transformer is a device which reduces a higher AC potential to a lower AC potential as per its winding ratio and specifications.
The power supplied by the secondary is in fact transmitted from the primary, although at a voltage level dependent on the winding ratio of the a pair of windings
The quantity of turns on the primary and secondary winding is determined using the formula for turns per volt ratio
Turns per volt = 1/ (4.44 x 10-4 frequency x core area x flux density)
The flux density could be considered as approximately 1.0 Weber/ sq. m. intended for ordinary steel stamping and approximately 1.3 Weber/ sq. m. for CRGO ( Cold Rolled Grain Oriented)
The quantity of turns on the secondary is calculated in the identical method when it comes to primary, but around 3% excess turns should be included to reimburse for the internal drop of secondary winding voltage of the transformer, upon loading.
Secondary turns = 1.03 (turns per volt x secondary volts)
electrostatic shielding between the primary and secondary winding to circumvent electrical interference from moving across to the secondary from the primary. I'm just giving you a hard time I did the same thing. Dirt cheap good luck. ;)
No, my plan was to convert a step up transformer to a step down one by changing the secondary windings. From what the other member says, I can get I and V control at lot easier with an old computer PSU but I don’t yet know the setup or what make/model would be best for my needs.
 

Dodgydave

Joined Jun 22, 2012
9,460
Your best solution is a computer psu (atx) as I said earlier you can only control either Voltage or Current,.

reading up on electrolysis of Oxygen and Hydrogen it sounds like the bigger the voltage the better the process of more bubbles, so maybe a 30V supply from your Microwave Transformer would be better. Try using two car batteries or a 24V psu and see which is best, then you can modify the Transformer.
 

Thread Starter

JulesP

Joined Dec 7, 2018
265
Your best solution is a computer psu (atx) as I said earlier you can only control either Voltage or Current,.

reading up on electrolysis of Oxygen and Hydrogen it sounds like the bigger the voltage the better the process of more bubbles, so maybe a 30V supply from your Microwave Transformer would be better. Try using two car batteries or a 24V psu and see which is best, then you can modify the Transformer.
That’s not what I need for plate conditioning. The main running of the Electrolyser will be using hf square wave resonant pulses so the normal ideas of 30A etc don’t apply.

12V, 10A will be fine so are these atx PSUs in most desktop pcs? How would I make them adjustable to adjust I and V? Hence my earlier question.
 

MrChips

Joined Oct 2, 2009
21,879
Please note that your voltage and current settings are maximum limits, not operating values. You cannot operate at both values at the same time, as already pointed out.

The two operating values are not independent. They are governed by Ohm’s Law.

I = V / R

Hence, when the PSU is operating at 9A @ 4V it is doing what it is required to do, that is, obey Ohm’s Law.
 

jpanhalt

Joined Jan 18, 2008
10,246
That’s not what I need for plate conditioning. The main running of the Electrolyser will be using hf square wave resonant pulses so the normal ideas of 30A etc don’t apply.

12V, 10A will be fine so are these atx PSUs in most desktop pcs? How would I make them adjustable to adjust I and V? Hence my earlier question.
Sorry I couldn't help. I don't deal with metaphysics. Maybe someone expert in that area will chime in.
 

Thread Starter

JulesP

Joined Dec 7, 2018
265
Ok here goes again. It seems that different parts of the forum have a very different vibe

So, given that my present PSU is unable to deliver 12V at 10A then I’m looking to build a more robust one cheaply out of a second hand HV step up power transformer by replacing it’s secondary winding to make it a step down one and deliver 12V. My plan was to regulate the current using an SCR with the primary winding feed. This is all shown in the attached figure.

Having thought all that it has been suggested that an ATX unit from an old computer would do the job and also allow independent control or voltage and current.

So that’s where I’m at so far.
 

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ElectricSpidey

Joined Dec 2, 2017
1,249
If you do decide to go with an ATX supply, be sure to check the current rating at 12 volts, modern supplies produce most of the current @ 5 and 3.3 volts.
 

shortbus

Joined Sep 30, 2009
7,946
You guys aren't seeing the real danger the TS is doing. The electronics part will sort it's self out do to Ohms law, no matter what he ends up doing. The big problem is his "electrolizer". If the photo in the post is his, he is making a mix of hydrogen and oxygen, an explosive mixture. Look close, only one out let through a flow meter! That is a Darwin Award experiment waiting to happen.
 

MrChips

Joined Oct 2, 2009
21,879
Photo posted by TS shows a 10A @ 30V DC PSU.

TS needs to understand the meaning of and how to use a constant voltage, constant current PSU.
 

Alec_t

Joined Sep 17, 2013
11,650
Judging by the display on the PSU, and according to Ohm's Law, the electrolyser was presenting a load resistance of 0.62Ω. So if the load resistance were constant (which it probably isn't) and you applied 12V to it you would expect a current of ~12V/0.6Ω=20A. Clearly the PSU can't provide that. If you want a load current of 10A then you must apply only ~6V to the load.
I agree with Shortbus (post #16) re the hazardous setup without the hydrogen and oxygen being separated. Re-design of the electrolyser should be a first priority ahead of power supply considerations.
 
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