Rectifier for a silver cell.

[Amol Gupta]

So I am going across this thread which I feel is dead.

https://goldrefiningforum.com/threads/designing-a-diy-silver-cell.31543/

The thread has some really neat ideas but no mention of the electronic side of things. How do I get a low voltage high current source.

There are instances where a 12V rectifier is mentioned but I'm not sure how do I convert the 12V input to a 3-4V output(given the large current values).

Any ideas...?

 

[RevMatt]

To convert a 12V rectifier (likely from a car battery) to a 3 or 4 VDC output with high current, you would need to use a buck converter circuit, which is a type of switching regulator designed to step down voltage while simultaneously increasing current capability.

Key points to consider:

• Buck converter selection:
  Choose a buck converter with a high current rating that can handle the desired amperage draw from your application.
• Voltage divider:
  You'll need to use a voltage divider circuit to accurately set the output voltage to either 3V or 4V.
• Heat dissipation:
  As you are stepping down a significant voltage, the buck converter will generate heat, so ensure proper heatsinking is implemented.
  

How it works:

1. 1. Input power:
   Connect the positive and negative terminals of your 12V rectifier to the input of the buck converter.
   
   
2. 2. Switching transistor:
   The buck converter uses a high-power switching transistor to rapidly switch the input voltage on and off at a high frequency.
   
   
3. 3. Inductor:
   This component stores energy during the "on" phase of the switch, releasing it during the "off" phase, creating a lower voltage output.
   
   
4. 4. Diode:
   A diode is used to ensure current flows in the correct direction through the inductor.
   
   
5. 5. Feedback loop:
   A feedback circuit monitors the output voltage and adjusts the switching frequency to maintain the desired voltage level.
   

Important considerations:

• Current rating: Always choose a buck converter with a current rating exceeding your anticipated load requirements.
  
  
• Efficiency: Higher efficiency buck converters will minimize heat generation.
  
  
• Component selection: Select high-quality components like inductors, capacitors, and diodes suitable for the current and voltage levels.
• last one I used I purchased on Amazon

 

[Amol Gupta]

To convert a 12V rectifier (likely from a car battery) to a 3 or 4 VDC output with high current, you would need to use a buck converter circuit, which is a type of switching regulator designed to step down voltage while simultaneously increasing current capability.

Key points to consider:

• Buck converter selection:
  Choose a buck converter with a high current rating that can handle the desired amperage draw from your application.
• Voltage divider:
  You'll need to use a voltage divider circuit to accurately set the output voltage to either 3V or 4V.
• Heat dissipation:
  As you are stepping down a significant voltage, the buck converter will generate heat, so ensure proper heatsinking is implemented.

How it works:

1. 1. Input power:
   Connect the positive and negative terminals of your 12V rectifier to the input of the buck converter.
   
   
2. 2. Switching transistor:
   The buck converter uses a high-power switching transistor to rapidly switch the input voltage on and off at a high frequency.
   
   
3. 3. Inductor:
   This component stores energy during the "on" phase of the switch, releasing it during the "off" phase, creating a lower voltage output.
   
   
4. 4. Diode:
   A diode is used to ensure current flows in the correct direction through the inductor.
   
   
5. 5. Feedback loop:
   A feedback circuit monitors the output voltage and adjusts the switching frequency to maintain the desired voltage level.

Important considerations:

• Current rating: Always choose a buck converter with a current rating exceeding your anticipated load requirements.
  
  
• Efficiency: Higher efficiency buck converters will minimize heat generation.
  
  
• Component selection: Select high-quality components like inductors, capacitors, and diodes suitable for the current and voltage levels.

last one I used I purchased on Amazon

Could you provide a link please we are talking 100's of amps here

 

[RevMatt]

I need to know more about where you're power is coming from..??. ie... batt 12 /24/36/72dc or / 110Ac / 220vac / 440 etc.??.. and what are you doing with the power 1 huge silver cell or a bunch of smaller cells???

 

[eprigge]

I have bought variable DC power supplies on eBay very cheaply. You can get variable DC supplies that output say 0-5V/100A, not too expensively if you wait for them. That would probably be better than trying to rig up your own supply. If fixed 5V will work, there are cheap high-power supplies you can get. Like this. I don't think it's terribly difficult to modify the output voltage of such a supply if say 3 or 4V were better.

 

[Amol Gupta]

I don't think it's terribly difficult to modify the output voltage of such a supply if say 3 or 4V were better

This is exactly what I feel the problem is.
One would need an additional DC-DC power supply.

 

[Amol Gupta]

I need to know more about where you're power is coming from..??. ie... batt 12 /24/36/72dc or / 110Ac / 220vac / 440 etc.??.. and what are you doing with the power 1 huge silver cell or a bunch of smaller cells???

220V is the line voltage and doing it for multiple smaller cells seems easy, ik more interested in a larger supply as suggested in the thread.

 

[goldshark]

220V is the line voltage and doing it for multiple smaller cells seems easy, ik more interested in a larger supply as suggested in the thread.

Lots of mass produced dc/ high amp power sources. What range are you specifically looking for?

 

[Amol Gupta]

Lots of mass produced dc/ high amp power sources. What range are you specifically looking for?

An atx power supply is the best I have got my hands on.

What's I would ideally want is 250A@3V.

I have been able to find atx power supplies operating at 800W which satisfies the power requirements but I'm looking for ways to step down the 12V output from the atx to 3V.

 

[eprigge]

You can modify the output voltage of a switching power supply pretty easily. You don’t need an external circuit. It comes down to changing a resistor or two on the feedback loop of the controller chip. There are tutorials for this on Youtube.

If you do this, the current rating of the supply will not change, you’re just decreasing the voltage a little. Or you can make it variable with a variable resistor. So you would want to start with a cheap high power 5V or 3.3V supply, which are plentiful due to those being standard computer logic voltages.

 

[Amol Gupta]

You can modify the output voltage of a switching power supply pretty easily. You don’t need an external circuit. It comes down to changing a resistor or two on the feedback loop of the controller chip. There are tutorials for this on Youtube.

If you do this, the current rating of the supply will not change, you’re just decreasing the voltage a little. Or you can make it variable with a variable resistor. So you would want to start with a cheap high power 5V or 3.3V supply, which are plentiful due to those being standard computer logic voltages.

Considering the case of ATX power supply, if I bring down the voltage for 12V to 3.5V the current is going to increase 4 times something that is not trivial for the wire or the PCB traces to handle.

 

[Amol Gupta]

Moreso there are undervoltage and overvoltage protections built into PSU units.

 

[eprigge]

No, as I said you can't increase the current rating, you can only drop the voltage (or make it variable). Which is why you want to start with a 5V or 3.3V supply since they will have a much higher current rating than a 12V supply.

"Moreso there are undervoltage and overvoltage protections built into PSU units."

Yes, there are some details to work out depending on what specific supply you start with. I just think this would be easier than trying to build a buck/boost converter circuit good for 100s of amps. If you have the money, buying a proper variable supply would be best but I'm assuming you want to go a cheaper route.

If 3.3V is close enough, you could just get one of those and not have to build/modify anything.

 

[Amol Gupta]

If 3.3V is close enough, you could just get one of those and not have to build/modify anything.

Looks very promising, once I have the details figured out this is the way I'd like to go.

 

[adam mizer]

Considering the case of ATX power supply, if I bring down the voltage for 12V to 3.5V the current is going to increase 4 times something that is not trivial for the wire or the PCB traces to handle.

You can use a small DCDC Buck Converter like these will work.
HERE
Use of remainder 12vdc and 5 vdc wiring on the computer power supply.

 

[Amol Gupta]

Thanks

You can use a small DCDC Buck Converter like these will work.
HERE
Use of remainder 12vdc and 5 vdc wiring on the computer power supply.

The amps are pretty low even if I choose to connect multiple ones in parallel.

 

[adam mizer]

Yes if you use for example 12vdc line and convert it to 3.5vdc at 3amp roughly just over 10 watts of that 12vdc line line.
You can hook up multiple converters on that line as it is designed for a large amount of watts.
Even with a small ATX supply you can have multiple 3.5 vdc lines (many) using the converters.
We can count the watts and stay below the limit.

 

[adam mizer]

A decent power supply like this is 70.9 amps of 12vdc and 22 amps of 5vdc.
If I want 3.5vdc 3amp is P=I x E power (watts) equals amp x volt = 10.5 watts and give a little to conversion circuit board round off to 11 watts.
So each yellow wire on a standard supply is all connected to the same rail.
I could connect many many dc converters to the supply.
Basically count the Power in Watts and leave some room not to over heat the supply.
Also for protection get those little inline fuse packages and install 3 amp fuses, so you protect the PSU.

 

[kaisernine]

I am not sure you need it, I work quite extensively with high amperage low voltage rectifiers (wireless towers and large redundant electronics that require 3.8-5vdc) but do you really think you will be throwing hundreds of amps through your electrolyte? Does your solution support it, will it remain cool?

Likely without you making your solution support it, it would only draw a few amps at best.

Even when I worked in a plating facility the amps were large due to the surface area of material and bath size, maybe I am wrong but it should only draw the power it needs you can't force it into solution.

more than open to being wrong, but this was my take while working with this type of process.

 

[adam mizer]

You could use fuse holder like this.
HERE
And fuse like this.
HERE
This would be used for a design that can run multiple silver bath setups.
Or possibly huge setup in one container.!!