Hi Steve, I checked out the data sheet but I don't understand it. At the top it says the device will dissipate 600 mW. That's good. But there is a parameter called "Limiting Voltage." It is described as Vl x Il = .8 Ip. and says it is 1.35 volts for that device (1N5297). I read it as the load voltage time the load current (wattage) is equal to 800 microamps. That's bad. Can you drop more than 1.35 volts across the device before it becomes hot and doesn't work anymore? Thanks for your help.
Andy > > From: "S &J Young" <you...@konnections.net> > To: "Silver List" <silver-list@eskimo.com> > Subject: CS>Simple Current Limiting CS Generator > > Fellow CS brewers, > > Not well known is the fact that for about $5 you can easily convert your > constant voltage CS generator (e.g. a three nine-volt battery setup) to one > that limits the current to assure small particle production and prevent > current "run-away". Thus your unit would then function the same as the > better "constant current" commercial units. I will try to describe this in > non-technical terms so many can take advantage of this. > > There is a device called a silicon FET current regulator diode that does > the > trick. This is really a small integrated circuit, shaped like a small > rectifier diode, that limits current flow to a set value. The regulator > diodes are small cylinders with about a 1 inch wire coming out of each end > of the cylinder. One end of the cylinder is marked with a band around it. > > The part numbers are the series 1N5283 through 1N5314, with the current > limits in the range of 0.22 ma thru 4.7 ma, respectively. Probably the one > of most interest to us is the 1N5297 that limits the current to 1.0 ma. > One > manufacturer is Central Semiconductor Corp. Go to www.centralsemi.com and > search for 1N5297 if you want to see the specifications and a drawing of > the > device. > > Using them is super simple. For example, for a three nine-volt battery > system, just cut the wire between the minus terminal of the battery and the > silver electrode. Connect the wire from the battery minus-terminal to the > "banded" regulator diode wire. Connect the wire from the silver electrode > to the other "non-banded" regulator diode wire. One can use 2 small wire > nuts, available at any hardware store, to make the connections, alligator > clips, or solder and tape them. Congratulations - you now have a > sophisticated constant current CS generator! > > When brewing a new batch, the current will start out very small as before > -- > a few microamps--depending on water purity. As silver production proceeds, > the current will rise until it reaches the value set into the regulator > diode. Then it will stay constant (e.g. at 1.0 ma for a 1N5297) for the > remainder of the brew time. It is impossible for the current to "run away" > and increase beyond the "set point", even if the electrodes accidently > short > together. > > These regulator diodes are rated to a maximum of 100 volts. That means one > could use a higher starting voltage (e.g. 54 volts from six nine-volt > batteries) and reduce the brew time (it will take less time for the current > to reach 1.0 ma). Again, the higher voltage is perfectly safe as the > current cannot "run away" because of the current limiting effect of the > regulator diode. > > These devices are not widely used so they are not available from many > sources such as Radio Shack. One source that sells them is Mouser > Electronics. Go to www.mouser.com and search for the part # 1N5297 and you > will see the information. When I checked recently, they had about 1,500 of > them in stock for a price of $4.29 each. I suppose they have a minimum > order, so it would be a good idea for someone to volunteer to order a batch > of them for those that express an interest in a group buy. (I don't have > time to do this - sorry). > > I believe the use of a 1N5297 along with a few nine-volt batteries is by > far > simplest, goof-proof way to make a constant current CS generator. If you > give it a try, please let us know how your results. > > --Steve Young >
