I need an circuit suggestion

Databyter

Enlightened
Joined
Oct 12, 2005
Messages
525
Location
San Diego
I wasn't quite sure where to post this but it says non-flashlight electronics.

I need one of you genius's to help me figure out what components and plan I would need to make a circuit that would regulate a circuit's current.

This is for making ionic colloidal silver which in my case I make by useing 4, 9 volt batteries in series as a power supply but I've let them run down so that they have long life at a slightly lower voltage (33-35).

It is not necesary to know what colloidal silver is and what it's for or anything but here is a short description of the "problem" I am trying to solve for background because I know I'll get the questions about what the usage of the circuit is for..

I use distilled water and two silver wires spaced a 2 inches apart connected to the 4 batteries supply directly. initially the resistance of the water is very high and the current is very low..and this is a good thing because the current being low causes the best quality silver solution composed of positivly charged very minute silver ions and very small silver particles. The current flows through the water and carries silver ions and particles from one wire through the solution and plates the other wire. Eventually the water itself takes on various properties depending on how you controll the process.

As the process progresses however the high resistance of the water lowers (because it is becoming filled with silver particles) and the current rises. This is ok up to a point but then the current becomes to high and the process occurs to violently and too quickly which produces much less of the desired minute silver ions and much more of the silver particles of increasing size which for my purposes is not a good thing. I want small particle sizes (1 to 4 microns) of preferably positivly charged silver ions.

I am told that limiting the current to 5 to 20 milliamps as the conductivity increases will slow down the process and allow a more controlled reaction of smaller particles entering the water which is important to allow them time to spread into the solution and become hydrated and to prevent them from sticking together (conglomeration) and basically make a worthless mess instead of a nice clear small particle size ionic colloidal solution.

So basically I need a circuit designed that operates from a 35 volt dc power supply and when the current reaches say 10 milliamps it is kept there.

Any help?
 

Steelwolf

Flashlight Enthusiast
Joined
Feb 6, 2001
Messages
1,208
Location
Perth, Western Australia
Off the cuff, I would suggest using the LM317 IC in current regulator configuration. It can deal with a difference of 37V between its input and output terminals, so it should handle your 4 x 9V batteries without difficulty. However, I would suggest bolting on a small heatsink to the transitor to help with any heat generated. If you can imagine it, the LM317 basically acts like a variable resistor, changing its resistance continuously to deliver the voltage or current you want.

If you do a search with the terms "LM317" and "data", you should find the data sheet. The circuit you are looking for is in the "Typical Applications" section under "Precision Current Limiter".

Alternatively, go to http://www.worldtorch.com/schematics.php
The schematic is the simplest one there, next to the blurb "This drawing is the LM317 based regulator circuit." Just substitute the LED for your 2 silver rods and use a 120 ohm resistor. This will limit the current to 10mA.

PM me if you need more help.
 
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