Colloidal Silver and Gold Forum
Production Techniques and Chemistry => Colloidal Silver Production => Topic started by: Stefan on February 15, 2019, 05:57:13 PM
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Very simple
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Thank you for this!
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Willingly ;)
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Thank Stefan,nice and simple. Even someone as confused by electrickery as me could build that I believe.
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I would like to try and build this, but have a few questions as I have a very limited understanding of electronics.
What are the power ratings/wattage values of the resistors?
What are the specifications of the rotary switch, other than 12 positions?
The circuit shows that you can supply 12-60V, but wouldn't the current and voltage that is output be dependent on the initial input voltage and change depending on what input voltage is, as the resistors drop the voltage to its target? Or is this regulated to the target output values (1ma, 2ma etc) by the transistors?
Is there an upper limit of current the the circuit can handle from the power supply?
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Thats the simple 2 transistor current limiter using PNP transistors instead of the normal NPN ones. The top resistors set the current. You could also replace all that (expensive) stuff with one of those little 3/8" or so square blue 10 turn trimmer pots. They're cheap and rated at 1/2 watt and you'll never get there because there's only 0.7v across it so even at 20ma, thats only 14mw (0.014 watts).
You absolutely need a 10 turn pot if you're doing it this way but so long as you're OK with a eyeglass screwdriver adjustment (I usually set it and forget it), the pot makes this much simpler. If you wanted to mount it in a box and have the current setting external, you can get a panel mount 10 turn pot but expect to pay a couple dollars for one.
Also, with that resistor schematic, usually the best tolerance you can get for a resistor easily is 1%. That means current setting is at best +/-1% from where you set it. For example, 10ma would be in the range of 9.9 to 10.1ma. You're going to have to measure each current setting and make a note of exactly what it is so the Farday's electrolysis law equation provides accurate time. This usually isn't a problem with a pot as you can tweak it to be dead on or really close.
You can get 0.1% resistors but they're not as common, you may not be able to get all values and they're more expensive.
Also, given the sense element is the diode that makes up the base-emitter junction of the transistor, thats really not very accurate and the voltage changes some if the transistor heats up or cools down which will cause the current set-point to drift some. Also, the base-emitter voltage changes a bit from transistor to transistor and type to type. If you go with the resistor rotary switch version, you're still going to have to measure each current setting and write it down so you can accurately compute the run time.
Lets also talk about power rating of the right transistor (pass transistor). If you're running say 20ma and feeding in 60V and the voltage across your cell is 10V, that means 50V at 20ma needs to be dissipated within the transistor and thats 50*0.02 = 1 watt (no kidding). I don't know of any small TO-92 package transistor that can handle this much power. You'll need to use a TO-220 sized transistor for this one. The BC556 transistor listed is not capable of dissipating 1 watt and its not available in a TO-220 package. Its max (and for safe area, stay 30-40% lower than this so you don't brand yourself as it'll get noticably hot if you don't) is 0.625 watts. You really want a TO-220 transistor for this one if you're using higher voltages where a lot of that power needs to be dissipated in the transistor as its going to get somewhat hot.
At 30V supply with 10V across your cell, thats 20*0.02 = 400mw and here, the specified transistor should do it for you.
Remember, transistors are linear devices. If you put a voltage on one end and the voltage coming out the other is noticeably lower (supply, cell voltage), that voltage difference times current (watts) has to be absorbed by the transistor as heat.
A TO-220 transistor should easily be able to handle 2watts+ without a heatsink.
Whatever you do, keep the pass transistor (right one) as far away from the left one (sense transistor) as you can because if the right one gets hot or warm, if its close, it'll change the temperature of the left one and the current set point will drift a little. Even if you're going for broke and going with a TO-220 package, the same holds true. Using a transistor as a sense element, the base-emitter junction voltage will drift some with heat so keep it as far away from the pass transistor as you can.
Voltage regulator IC's use a circuit called a bandgap reference which produces about 1V as a reference and its rock solid stable over a very wide temperature range. You can get voltage reference IC's but then you're talking about needing to use an op-amp or comparator circuit to compare the reference voltage to that of the sense element and thats more complexity than its worth dealing with.
Everything in life is a compromise. The best you can do is make good choices. There is no such thing as "perfect".
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Thanks for the informative response Gene.
I've since looked into using an lm317 instead, it seems to be more reliable and less complicated to make a simple constant current circuit with it. If I understand correctly all it needs is a resistor, a potentiometer and maybe a capacitor. It's just a matter of getting the parts without paying too much for shipping.
I also realized, after playing around with some resistors I had left over from a previous project involving LEDs that I was confused about the function of the resistor, I thought it dropped voltage and amps, but it only drops the amperage.
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There's only one issue with an LM317 current limiter. It bottom ends around 10ma (lowest current).
I could be misremembering but I'm thinking its just a cap, the regulator and a resistor (fixed current) or a pot (variable).
Either way, so long as you're OK with 10ma minimum and about a 3V differential between output voltage and input voltage (a.k.a "headroom"), you're fine. If not, you'll have to use a 2 transistor regulator (less than 1V headroom requirement) or something else or find another variable regulator that consumes much less ground pin current (quiescent current) to make a current limiter with.
I should actually look because that does sound like a good idea and yes, there are other variable low dropout regulators (the LM317 isn't low dropout - low dropout means well less than 1V across the regulator to keep it functioning) that have very low ground pin currents (well below 1ma) and some of them have been around for decades and as such not very expensive.
Resistor "resist" current flow. For a given resistance and applied voltage, the current through the thing is fixed. If you vary the input voltage, the output current will change based on Ohms law. A pot is a variable resistor - at least in the application we're talking about here. You can set its resistance to whatever you want within the range it supports from max value (how they're rated) to about 5% of max value. None of them ever achieve 0 Ohms. Some higher quality, tighter tolerance ones (read: more expensive) are 2% tolerance meaning they may be able to hit 2% of full scale on the low end.
How a current limiter works is that it acts like a variable resistor feeding your load and it changes its resistance to absorb the excess voltage to your load which keeps the current flow constant. The only thing you have to consider is that you need to use a high enough input voltage that whats across the cell in a worst case (highest voltage) plus the headroom requirement of the limiter doesn't exceed the input voltage and for safe area, you want at least 3-5V higher than this as your supply.
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If I am reading the data sheet correctly, the minimum current of lm317L (from Texas Instruments) is 1.2-2.5mA and you can get them in 20mA-1.5A versions. but limiting it to only 10ma seems to be reasonable for Colloidal Silver production, as, If I understand correctly you don't really want to go over 15ma. A 3 volt differential shouldn't be an issue either as you can supply a maximum of 37V to these ICs and even at 24 volts you have 11 volts to play with.
Having said that, I have made a bunch of solutions using higher then recommended mA calculating the proper time for a give ppm and the color and clarity came out to be somewhat reasonable. But I am not the best judge of this because I am new to this in general.
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I was not aware the LM317L existed. The only THD package it comes in is a TO-92 which has a power limit, usually, around 330mw. If you want it to stay cool, try not to shoot for more than 2/3 that. I was looking at TO-220 regulators (the LM317) and the specs seem to be different on those which kind of surprises me but OK.
10V across the regulator times 15ma is 150mw.
Power is voltage times current so (10v * 0.015). If the voltage goes up, for a fixed current, so too will the power the regulator has to absorb.
15ma is not a limit. It depends on the size of your anode. With a 1ozt silver bullion anode, if you have a stirrer, you could probably easily push it to 20ma. A wire anode? I'd recommend not pushing it over 10ma and only if you have a stirrer and are heating the solution. If not, probably 5ma.
Looks like the LM317L can run down to about 2.5ma which is much better than the LM317.
If you have any non-reduced silver (still ionic), your Colloidal Silver will have a slight metallic taste. If it doesn't, you can probably call it good.
With the right amount of electrolyte, at 10ma which I run, I'm able to get the cell voltage even below 10V (which I never do - shoot for about 12v) with adjusting the cathode. To give me a finer adjustment I use a piece of 24 gauge copper wire. Using a piece of 18 gauge wire was just too touchy. Sure, with the 24 gauge wire you may have to submerse 1-1.5" but that lends a lot to fine-tuning cell voltage AND it minimizes voltage change if you're running the cell heated where the level will change based on evaporation if you're making higher PPM and running for a goodly while. Remember, if the liquid level drops due to evaporation below the cathode, the cell will stop working and then you don't have ANY clue what PPM you made.
I'd build a full range adjustable limiter - go for broke - 2.5ma to 20ma. You never know when you might need a different current in that range.
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Thanks again gene.
I couldn't actually find the lm317l after I posted that, mouser seems to have taken it down or it wasn't in stock. I have since purchased a few lm317, some resistors and a pot from digikey anyhow. I looked up some other circuits based on this chip and if I understand how to make this properly and calculated it properly it should be able to do 3.7ma - 31ma from a 14V-37V supply based on a 10V load. If it works out I'll post the schematics. But feel kind of bad because I sort of hijacked this thread.
I couldn't notice any metallic taste, but it's pretty subtle so it's hard to tell
Thanks for the suggestion of the 24 gauge copper wire. I've got a bunch of old telephone wire which I believe is around 24 gauge I can use.
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I realize that you already purchased the standard LM317, but the L version is still available at Mouser, part number (one example):
926-LM317LZ/NOPB
Depending upon the input/output voltage differential can go as low as 2.5 ma
Data sheet:
http://www.ti.com/general/docs/suppproductinfo.tsp?distId=26&gotoUrl=http%3A%2F%2Fwww.ti.com%2Flit%2Fgpn%2Flm317l-n
As for the cathode, a piece of wire from phone wiring is what I used. Works great. Note that this is the wire used for internal house use running from the junction block to the station jacks.
Argentum
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Regarding cathode wire, if you have an old broken ethernet cable, this is 24 gauge solid for CAT3 or CAT4 and 23 gauge for CAT5 - this works equally as well.
Cross connect wire (whats used to connect telecom connections in wiring closets in office buildings) works well also. Thats 24 gauge solid wire.
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I realize that you already purchased the standard LM317, but the L version is still available at Mouser, part number (one example):
926-LM317LZ/NOPB
Depending upon the input/output voltage differential can go as low as 2.5 ma
Data sheet:
http://www.ti.com/general/docs/suppproductinfo.tsp?distId=26&gotoUrl=http%3A%2F%2Fwww.ti.com%2Flit%2Fgpn%2Flm317l-n
As for the cathode, a piece of wire from phone wiring is what I used. Works great. Note that this is the wire used for internal house use running from the junction block to the station jacks.
Argentum
Oh well, digikey sells similar ones too, I guess I over looked it when searching, as I was focusing on the TO-220 packages at the time. There's so many of them to look at. I just found one that goes as low as 1.5 ma. at 35V too the LM317LZ/LFT1, but the minimum order is 2000. That's too bad as I've already bought a couple lm317kct and the shipping cost more then the products lol.
I do have a whole bunch of old ethernet cables I could sacrifice too. I also have a wire gauge I can use to check the size. Now that I think about it, the telephone wire is probably closer to 22 gauge.
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Regarding cathode wire, if you have an old broken Ethernet cable, this is 24 gauge solid for CAT3 or CAT4 and 23 gauge for CAT5 - this works equally as well.
Cross connect wire (whats used to connect telecom connections in wiring closets in office buildings) works well also. That's 24 gauge solid wire.
Gene, should the copper wire, (once extracted) be conducive, or shall we take some fine sandpaper and remove coating?
Thank you much,
Nix
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I'd clean it a little just to take off any oxide and anything on the surface the process of putting the insulation on may have left behind but don't go overboard. Even just wiping it with a tissue or paper towel with a bit of alcohol on it should be enough. It'll be plenty conductive enough without doing this but I'd suggest you do this to make sure its good and clean.
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Thank you Gene.
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Here's what I've come up with. I was trying to follow the circuit in the first picture, but the calculations I made didn't work out and the amps couldn't go below 6ma and above about 22ma, depending on how it was wired. I also wasn't sure how to properly wire the potentiometer into the circuit with regards to the 3 pins on the potentiometer. So maybe I was originally wiring the circuit improperly, I'm not sure.
I ended up putting 3 332omh resistors in series and it works, it can be regulated all the way from about 3ma to 20ma. It would probably be best to use a larger valued potentiometer and lower valued resistors. Unfortunately while I was testing this, my milliamp setting on my multimeter stopped functioning properly so I can't get a precise milliamp reading, but I can still use the amperage setting to check the proper amperage of the circuit. I am not sure why this happened as I don't believe I overloaded it and I can't figure out how to get it open to check if a fuse blew.
The lm317 needs to have at least 3 volts more then then load uses to maintain amperage regulation, so the minimum voltage input in our case to maintain 10V in the solution is 13V. The lm317 can also take up to 37V before it overloads. The vout and adjust pin takes the input supply and regulate it to 1.25V, so the resistors values can be calculated based on this.
In reality you can simply put a resistor and a potentiometer on the vout pin and have a track running from the adjust pin to the end of the pot/resistor combo and it'll function the same. There is a picture of this in another thread from one of the users here. But supposedly this way, if the potentiometer loses track or fails for whatever reason, the resistors will keep the amperage low in the circuit and it won't overheat.