Hi Ivan, > [ ... ] > > I'm here to probably bore most of the list to death with this > > technical crap :-). > > I'm interested. ;-)
Glad to know that someone is :-). > > [ .. ] > > So I wired up a stamp, stuck a couple 2K2 resistors from the > port pins > > in series to the probes and cobbled up a short program to do > the job. > > Why the resistors? The sole purpose of these resistors is to limit the current to aproximately 2.5 ma. The actual calculations called for 2K0, but that isn't a standard value (at least in the stuff I have :-). Turns out that it is only a safety factor to protect the port pins in case of accidental "short" and provide for a maximum current flow that will be allowed (to keep me from making the REALLY strong stuff :-). > [ ... ] > Yes, higher voltage will speed the process. I think that there is a given power factor (voltage x current) that will cause the silver probes to "outgas" (I'm not sure that is the right word, but hopefully it will convey the point :-). Just to play with numbers... Power(watts) = Voltage x current: 27V x 0.00027A = 0.00729W (my typical starting current) 27V x 0.0025A = 0.054W (my (now) max (finished) current). Seems like the 0.054W power factor might be considered the minimum to start forcing the silver into the solution (ignoring, for the moment the resistance of the solution). 5V x 0.000040 = 0.0002W (the starting current from the raw output from the microcontroller) - a long way from 0.00729. Not sure just what this means, but I think it is a good indicator of required minimum voltage?! > Some comparisons: > First the geometry of the generating container or cell; > 1 cup (200mls, 7 - 8 oz) distilled water, with electrodes in the > following > arrangement, > 2 x 2mm silver wire (14swg), wetted depth 45mm (1 3/4"), 45mm > apart. You are using MUCH shorter wires than I. mine have 4 1/2" of wetted depth. I've seen these shorter wires in looking around the net along with some that use 3 wires (still haven't figured that one out). Perhaps the wider spacing I am using (2 3/4") and the wetted depth I have are compensating for the shorter wires and the closer spacing ?!? > I used a sterilite 1 cup, soft clear lidded plastic container > with the > electrodes pushed through the lid and parallel. The container > dimensions are, 85mm (3 1/4") diameter by 65mm (2 1/2") deep. > > 9 volt ac wall adaptor (developing around 12 volts, output > connected directly to electrodes) > 10 ppm (as measured by Ion Selective Electrode) 3.0 hours > 0.05 mA initial current .... 0.59 mA final current > > 15.5 volt constant. > 10 ppm... 2:30 hours > 0.06 mA initial current ... 0.72 mA final current > > 18 volt adaptor... 21.5 volt constant. > 10 ppm ....2:20 hrs > 0.09 mA initial current ... 1.2 mA final current > > 28 volts current limited 0.5 mA > 10 ppm ... 2:20 hrs > 0.09 mA initial current ... 0.49 mA final current > 28 v initial voltage ... 11.25 v final voltage. > > All solutions stirred before measurements, about six times during > run. > Would be interesting to compare current densities of electrodes. Sigh, I get really tempted to just shelve experimentation with this until I can afford to come up with some test gear that will give me PPM metrics with some degree of accuracy, until I can do that, I just keep feeling that these experiments are ultimately meaningless, taste and Tyndal are just too relative to communicate accuracy. > A question: > How would one go about turning off the power to the electrodes at > a specific resistance as measured by voltage and current draw. > Further, would it be possible to input starting resistance > (calibrate as zero or some other nominal value) and then switch > off at some other particular resistance. > Anyone? There are ways to do this, I've had a couple of thoughts (inexpensive) on the matter but until I get the basics down I'm leaving that alone :-). There are industrial sensors and methodogies that will do it, but they are not cheap :-). One of the thoughts is to use the "pot" statement from the stamp, it is normally used to read a variable resistor returning a value from 0 to 255. I'm not sure how this would work, it would require some experimentation. Much appreciate the response! Thanks & take care, Vikki. -- Victoria Welch, WV9K, DoD#-13, Net/Sys/WebAdmin SeaStar.org, vikki.oz.net "Walking on water and developing software to specification are easy as long as both are frozen" - Edward V. Berard. Do not unto others, that which you would not have others do unto you. -- The silver-list is a moderated forum for discussion of colloidal silver. To join or quit silver-list or silver-digest send an e-mail message to: [email protected] -or- [email protected] with the word subscribe or unsubscribe in the SUBJECT line. To post, address your message to: [email protected] List maintainer: Mike Devour <[email protected]>
