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Reversing polarity for electrolysis project

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by BHinote, Jun 16, 2011.

  1. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    I thought B meant without the current limiter?

    It's possible that the Widlar current source is effectively optimized for a single current or close range of currents.

    There is no "out of compliance" indicator like there usually is on a typical CC supply. This might be a voltage comparitor looking at the rail vs, the drop across the current regulator.
     
  2. ronv

    ronv Well-Known Member Most Helpful Member

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    The high resistance of the soultion is the current limiter until it gets going. Some on line info suggests seeding with a previous batch to speed up the process.
     
  3. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    That sounds like a better idea than moving the electrodes closer.

    What I'm saying, is that you have no idea when the circuit is say working at the 1 mA level.
     
  4. dave

    Dave New Member

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  5. ronv

    ronv Well-Known Member Most Helpful Member

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    What confuses me is how do you decide on 1 ma vs 10 ma. Most of what I read just proposes 12 to 30 volts as the magic number which should be ok as is. (no current limit) but I could see where a current limit might work for better consistency.

    http://www.elixa.com/silver/lindmn.htm
     
  6. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    Thanks for the link.

    It appears that it's described here: http://www.elixa.com/silver/TDS.htm

    Which basically is an electrometer ohmmeter with temperature compensation. That looks like how it determines ppm. 0-9999 uS is in the unit micro siemens. micto is 1e-6 and a Siemen is 1/ohms. This 1uS is 1 Meg ohm and 9999 uS is 100 ohms. Usually the units of Siemens are preferred for high resistance values. The Siemen is a unit of conductance.

    From the article, it suggests that high quality of water be used so there are very little particles to bond to. Cutoff is reached when a particular temperature compensated conductance is reached. i.e. 10 ppm.
     
  7. ronv

    ronv Well-Known Member Most Helpful Member

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    Guess we will need to wait for B to come back. Using that formula would make 10ppm about 100k ohms. Cant get 1 ma that way.
     
  8. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    The theory is basically here: http://www.mbhes.com/conductivity_measurement.htm

    2 uS/C = 1 ppm

    Pure water is 18.3 Mohms-cm

    Note that the unit is effectively a resistivity unit R = rL/A where R = 18.3 M-Ohms, and A would be the cross sectional area of the electrode and L is the distance between the electrodes.

    Somewhere in this thread is the electrode size. We don't know his spacing. I didn't look at the article for the temperature compensation equation, but we know it's lower at higher temperature. Ok, I looked. It's about 2% per deg C.
     
    Last edited: Aug 3, 2011
  9. ronv

    ronv Well-Known Member Most Helpful Member

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    For the silver solution it is .6 per ppm.
     
  10. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    What are you trying to say? Is that where you want to stop the reaction? I thought I saw 10 ppm somewhere and this should be a do not exceed amount.

    An example problem: Suppose electrodes are 2 x 3 cm and the distance is 1 cm, then R = rL/A; R = 3 M ohms. At 100 C, this would be about 150 % less or about 20K.

    So, temperature and separation distance is a BIG factor.

    Thus, I am proposing a (in complianace) LED for the circuit. This would allow you to set the spacing. Using 1 mA and 40 volts, this means 40K would be the minimum resistance. As the reaction proceeds, you could move the electrodes apart.

    A way to achieve this is to be able to differentially amplify the voltage across the electrodes. I bet we can do it using a discrete FET differential amplifier followed by say and AMP02 from analog devices. I'm nor sure how to design the animal.

    One he had separation distance, the area of the electrodes, the current, the temperature he can then determine when to terminate the reaction. A DVM cannot be used to do this.

    Alternatively, he can buy one of those meters and measure the conductivity. Apply the temperature equation (possibly) and then set the initial separation of the plates start. With 1 mA, this means he has to see 40K resistance (possibly temperature compensated)

    I suppose, that using the meter is a better choice than incorporating a voltage measuring device for the electrodes.

    If the current source is well behaved, you could look at the voltage difference across the source and compare it to the supply, Suppose the source had 2 diode drops. You could say, that if 3 drops or more was seen across the source, then it's working. I think that mod should be essential.

    Use the same OP amp as in your current source. Put say three diodes to the + supply (assuming it normally drops at least 2) and a resistor to ground. Set the comparitor to look at the output and compare it the the supply less 3 diode drops.

    Now, he has a way to set the initial position of the electrodes. He could then at various times, move the electrodes farther away.

    The process is useless UNLESS the circuit sees 40 K minimum resistance.
     
  11. ronv

    ronv Well-Known Member Most Helpful Member

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    Fix me up.
    Use your example of 2X3X1. To get 1 ma you need 40K ohms or less. (25 us) Lets leave it at 25 c so it's simple. If the solution gets to the point that 1 ma flows the process should have already stopped. 0.6/ppm X 25 =16 ppm. So why a 1 ma current source? Particle size?
    I would think you would want it to be hands off otherwise you have to stand around and watch the grass grow.:D
     
  12. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    I keep loosing my input and I finally figured out why. I'm typing a ^R (Refresh) vs a Shift R and I can't recover. The laptop keyboard has limited travel and it's easy to goof. It's geting late and I'm recovering from a headache. 60 mg of Oxycontin and 2 Fiorinals (Aspirin/Cafeine/(Barbituate sedative) in the past 12 hours.
     
  13. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    2 uS per cm = 1 ppm. This is the key. 10 ppm = 20 uS/cm. If I did my math right, that's 50 ohm-cm, not ohms and that's p which is really the Greek letter Rho.

    To get ohms, you need R = pL/A

    Now we have a bunch or oranges and apples to sort out.

    40K ohms and 50 ohm-cm and 2 x 3 x 1 (lets assume cm and no inches) and 18 Mohm-cm which is 55 uS/per cm.

    This is where electrode size and spacing come into play.

    In the first case, from R= rL/A we have; L = (R*A)/r ; so if the electrode is 2 x 3, we have L = 40,000*(2*3)/(55/0.001); so our electrode spacing should be a minimum of about 4 cm.
    That's for a compliance of 40V, 1mA or 40K

    Now we need to continue until p = 20 uS/cm or 50 ohm-cm

    R= pL/A; Plug in R = 50*4/6; This means R has to equal ~ 33 ohms.

    That's a big difference.

    With all 4 sides of the electrodes exposed, your going to have some generation from the back and the sides. That generation represents an error term. The ppm would be higher because the cross-sectional area is higher.

    The current determines particle size and the initial purity determines particle size. If the purity is low, you have nucleation sites which the silver would adhere to. Those particles would not be 100% silver.
     
  14. ronv

    ronv Well-Known Member Most Helpful Member

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  15. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    1/S = ohms. micro is 1e-3. There is no area in uS. There is in uS/cm

    If you ignore the uS for the time being, 1/(S/cm) is the unit ohm-cm

    .6 us is 0.6 micoseconds. ppm is a volume unit or bulk property. Ohm-cm or resistivity is volume unit too ( a bulk property)

    if anything it would have to be 0.6 uS/cm = 1 ppm silver

    Sorry, units were drilled in my head and I got problems wrong if there were no units. Siemen is a proper name. seconds is not, that's why Siemens is capitalized.

    micro is part of the milli, micro, nano, pico, femto, atto set.
     
    Last edited: Aug 4, 2011
  16. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    Last edited: Aug 4, 2011
  17. ptm82379

    ptm82379 New Member

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    colloidal silver generator

    Im thinking of making one of these and i wantes to get some opinions...

    These things typically use 9-24 volts with 2 ultra pure silver wires used as electrodesimmersed in water to release the silver particles into water.

    I want to use a transformerto do this off of the 120v mains. Is there a safe way to do it... it should produce around 40 mA at 18 vdc...any ideas or should i just go for it...lol
     
  18. Mikebits

    Mikebits Well-Known Member

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  19. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    Last edited by a moderator: Sep 29, 2011

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