current control again!

kinarfi said:

Your diode, a CLD or CRD as I learned them many years ago, will pass 1 ma regardless of applied voltage. Look at my drawing and A1 will be 1ma, A2 will be your electrolysis current, and A3 will be the same as A2 minus 1 ma.

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Not true. Current limiting diodes will pass zero current when they have zero volts across them, such as when they are shorted out by an ammeter. To do otherwise would require an internal power source. Also, see Fig. 2 in this document.

current control again

kinarfi said:

Your diode, a CLD or CRD as I learned them

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Hi kinarfi, I really appreciate your "on the subject" reply. I gather from what you are saying, that I am still missing components and that my approach is over simplified. I need to to limit current. I have a real issue that needs to be resolved soon. I have a unregulated source of 34.6 volts vdc. I have an anode and cathode. When the process begins, the current is almost dead @22-24 u. As the electrolyte becomes more conductive...the current rises. At six hours The current hits 1 mA. I NEED TO STOP THE CURRENT FROM HITTING 1.5 mA. The process is a "run away train" at this point. Mechanical stirring breaks the ion stream in the electrolyte allowing current control up to six hours. After this point, manual monitoring of the current avails nothing. Here is the kicker...I need to hold the process under 1.5mA for another 4 to six hours...preferably automatically. I have put all of this forth several times on this forum. But I have yet to encounter any help with designing a circuit that will do this simple task. I still believe a cld will work, but I don't know how to wire it. I know enough to know that the relevant values for circuit design are right here in this paragraph. If I am wrong, and you can help, please tell me what other values or numbers you would need. Again thank you for your reply. Plumber (to make straight)

Perhaps the concept could be tested with a 33k ohm resistor. It won't perform as well as the current source, but if used temporarily it could sort out a lot of issues.

try this

I have attached a simple circuit for current limiting, just use a transistor a 1.5 voltage cell and few resistors, connect the terminals A & B on the attached diagram instead of the diode and connect your meter in series.

you have to decide the value of R as per your voltage of application, i hope a 1- 10K may be ok, then connect your source only in series with meter and adjust teh value of preset until you get 1mA. then conect your system in series.

you can observe the current will increase as you said then wil not go beyound 1mA as the base current is set only by preset and the cell.

you may need some improvement or change in value of resistors if you use different transsistor etc.

plumber said:

Hi kinarfi, I really appreciate your "on the subject" reply. I gather from what you are saying, that I am still missing components and that my approach is over simplified. I need to to limit current. I have a real issue that needs to be resolved soon. I have a unregulated source of 34.6 volts vdc. I have an anode and cathode. When the process begins, the current is almost dead @22-24 u. As the electrolyte becomes more conductive...the current rises. At six hours The current hits 1 mA. I NEED TO STOP THE CURRENT FROM HITTING 1.5 mA. The process is a "run away train" at this point. Mechanical stirring breaks the ion stream in the electrolyte allowing current control up to six hours. After this point, manual monitoring of the current avails nothing. Here is the kicker...I need to hold the process under 1.5mA for another 4 to six hours...preferably automatically. I have put all of this forth several times on this forum. But I have yet to encounter any help with designing a circuit that will do this simple task. I still believe a cld will work, but I don't know how to wire it. I know enough to know that the relevant values for circuit design are right here in this paragraph. If I am wrong, and you can help, please tell me what other values or numbers you would need. Again thank you for your reply. Plumber (to make straight)

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Wow. I think we were very much trying to help you, but your rudeness and arrogance keeps getting in the way.

I hope everyone sees this and lets you do it on your own.

No, your CLD will not work, in either configuration. That's whats wrong with this thread, you keep saying that and we keep telling you something you don't want to hear.

by the way i beleive he didnt get what we are really asking from him, any how his last post gives some information to explain better than before. he need a black box to be connected in series with his stuffs... it should not allow the current to increase more than 1mA, even with unregulated supply as he mentioned.

Try building this and then apply power and adjust to get the 1.5 ma current. Then to test it, short out the 1K resistor, the current should stay the same.
Kinarfi

solutions not flak

ke5frf said:

Wow. I think we were very much trying to help you, but your rudeness and arrogance keeps getting in the way.

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kinarfi,
mbarazeen,
mneary
Wow! Thank you very much. Now I have some things to try and a lot more to learn. I am thankful you saw past my frustration and offered solutions. I am sorry for offending anyone. I was being asked questions akin to "which end of the hammer am I trying to pull nails with?" It would have offended anyone with mechanical sense. I submitted the drawings out of frustration, a different angle to the same old unanswered thread I posted weeks and months ago. When I simply posted what I needed to do, all I got was curiosity and irrelevant questions. The only value I ever left out of my original questions I think would be, how much current in the form of heat dissipation through resistors would this be subjected to by the time the process finished at twelve to fourteen hours. But this still has to do with component values, not circuit design. So, there is not "too many variables" involved. At this point, I am a bit afraid to ask for elaboration on the designs you have graciously offered. I will study some more, and then implement your designs...if I can figure out what they mean! I have a real block when it comes to electronics...this is why I go to those smarter than I...for solutions.
This isn't about money or hobby...it means more to me than you know. I will check back in time. plumber (to make straight)

plumber said:

can someone kindly explain what I have done and why it works? I am trying to learn.View attachment 35046

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Look Plumber,

I just quoted your original post. You didn't ask us for an alternative circuit design. You didn't ask us for a better idea. You asked us to "kindly" explain what you had done and "why it works"...Which we proceeded to do, we explained in great detail what you had done, but we could not explain why it works, because it doesn't. In several posts, you made it clear that you are an electronics novice. Yet, you took offense when we asked questions about your set-up, and when we considered the possibility that one or more factors were in error. You can't claim to be a novice and at the same moment scoff when someone questions your materials, design, or equipment. Many an experienced individual has found an overlooked error after days of frustration with other projects.

In a later post, as I mentioned before, you implied that you had no time to refer us to the particulars like the diode part number or the voltage source. You, the novice, made it clear that you were in charge of what questions were asked and had no patience for questions you deemed "off track". This is akin to the beggar criticizing the good Samaritan for offering his handout in change rather than paper bills.

Anyway, I'm not trying to harp, I just continue to be amazed at your rudeness. Now that someone has taken the time to draw up some alternative designs, I hope you do not criticize them for not offering them on a silver platter for you.

I have a very, very simple solution to offer you. It will take a little trial and error, but it will work, at least I think it will.

Ohm's law says your desired 1.5 milliamp current will be achieved when your circuit resistance is 2400 ohms, given an approx 35 volt DC supply.

This will be your circuit resistance as well as the inverse of the conductivity of the electrolyte.

Go get yourself a potentiometer (2k to 3kOhm) and a mechanical timer switch which is closed when the timer is set, opens when it winds down. Wire your potentiometer in parallel with it.

Determine how long it takes for your electrolyte to get to the 1 mA point from start tom finish. Given controlled conditions, it should be pretty much consistant.

Do this by running the experiment without any components in the circuit besides your ammeter and battery and electrodes and electrolyte.

Now, with fresh electrolyte material and a fully charged battery...take your switch and parallel potentiometer rig-up, with the ammeter in series with them (just like you had with your diode and ammeter in series) and set your timer to your approximate 1 mA point as you've deduced. Start your test. When the timer finishes and the switch opens, the potentiometer will take over. Monitor when this occurs. Adjust your potentiometer to bring the current back down to, perhaps half, of your target current. Lets say .5 mA. I have no idea given the conductivity of your electrolyte at this point what resistance the pot will be. Watch your setup for the duration of your test. See if the current starts climbing again, and see if it exceeds the 1.5 mA ceiling.

This may be a crude way of doing it, but I think it will work out.

Ke5frf, I think you slipped a decimal point in your pot calculation, unless I missed something.

Yes I did. 24kOhms

My bad.
So his pot should be about a 25k job.

Roff, what do you think? Too simple to work?

I mean, the ultimate goal is to get the electrolyte conductivity to the point it will draw 1.5 mA of current, correct? Putting a 25kOhm resistor from the start would cause it to take an extremely long time to get there, so an analog system would be ideal, where circuit resistance goes up as electrolyte conductivity increases.

My concept isn't analog but will get him to the threshold very quickly, then the pot will take over, slow it down, and set a limit. Sounds like he has some flexibility between 1 mA and 1.5, so the potentiometer value doesn't have to be exact.

I'm not sure what the ultimate goal of this project is, or what parameters have to be precise. I sincerely hope someone can help him find an easy solution.

ke5frf said:

I have a very, very simple solution to offer you. It will take a little trial and error, but it will work, at least I think it will.

Click to expand...

I can do simple. Thank you for the silver platter! (just kidding!) I do appreciate you taking the time to help. I am learning about forums, to me, it has been the same question I posted a couple of months ago. But I realize no one links previous threads and posts. And people respond at various points along the way. Before this thread, I did try to ask how to. Some responses were way over my head, but mostly I grew impatient with the curiosity instead of answers. Enough of that. Trust me, I am less then a novice in electronics. But I can understand and follow your suggestions. Of course I'll be back, talking about switching and commutators and the like. I am sick of monitoring this thing. When I get big enough for my britches and I can actually understand the answers you guys are capable of giving, I will need help on how to build circuitry that senses the rapid rise in current, and automatically shunts,drains,gates,switches etc. the excess current to any where else besides the electrodes. Thanks again. plumber

plumber said:

I can do simple. Thank you for the silver platter! (just kidding!) I do appreciate you taking the time to help. I am learning about forums, to me, it has been the same question I posted a couple of months ago. But I realize no one links previous threads and posts. And people respond at various points along the way. Before this thread, I did try to ask how to. Some responses were way over my head, but mostly I grew impatient with the curiosity instead of answers. Enough of that. Trust me, I am less then a novice in electronics. But I can understand and follow your suggestions. Of course I'll be back, talking about switching and commutators and the like. I am sick of monitoring this thing. When I get big enough for my britches and I can actually understand the answers you guys are capable of giving, I will need help on how to build circuitry that senses the rapid rise in current, and automatically shunts,drains,gates,switches etc. the excess current to any where else besides the electrodes. Thanks again. plumber

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OK, here is a quick draw-up, hope it is easy to follow.

I actually added a second mechanical timer (cheap, can be picked up at hardware store or Walmart possibly for around $10 or so.)

T1 would be the time you want your circuit to have no resistance, the build up time to 1 to 1.5 mA

T2 would be an intermediate timed switch, longer than T1 but shorter than the time of the final process...and includes a series resistance (fixed or a potentiometer). At this point in the sequence, the T2 branch of the circuit will be parallel to the other potentiometer (or fixed resistance). The total resistance will be less than the least of the two. If they are both the same value, say 20kOhm, then the resistance at this point will be 10kOhm.

After T2 opens, you are left with your last potentiometer, in our example we said it was 20k, so we'll go with that.

So you go this sequence...Short, T1 opens (10kOhm circuit), T2 opens (20kOhm circuit)...and 20kOhm for the final duration.

The potentiometer values will be determined to suit your time needs, as will the duration that T1 and T2 are set for.

The three branch idea permits three steps of controlled circuit resistance, and the final resistance will not permit the test to exceed your upper limit. Most likely the final resistance will be near 24kOhm to comply with Ohm's law.

This circuit is "semi-automatic", meaning it isn't a "smart" circuit, as the time and resistance values will take a few tries to get right. It won't be on complete autopilot, but once you have the volume of electrolyte, the battery voltage, and starting electrolyte condition figured out, the process should be repeatable so that you don't neccessarily NEED precise feedback type control.

ke5frf said:

I mean, the ultimate goal is to get the electrolyte conductivity to the point it will draw 1.5 mA of current, correct?

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It is probably semantics and my lack of understanding, but to make sure:
the ultimate goal is to let the current rise slowly to 1mA on it's own with only the electrolyte as resistance. Then, the real goal is to hold the process under 1.5mA for another 4-6 hours...all the while the ion concentration in the electrolyte continues to condense resulting in ever increasing conductivity. At 2mA my meter looks like a stop watch. This would continue clear up to the 600 mA rating of my power supply and beyond. This process is very slow at the beginning because the electrolyte is distilled water. This is why I dont want to use a simple resistor...it would take too long. But anything over 1.5 mA and the process is fried. done. I pull the plug and google some more. For the sake of end result and parameters, 1.5mA is the parameter. Anything over results in agglomeration- the clustering of metal ions which produces large particles. I need to produce the smallest particles possible and I am after a specific ppm of these tiny particles...see? boring. I keep expecting some one to say "why didnt you just say so! Here's how!" Thanks again plumber

Plumber, I'm going to ask what will probably sound like a stupid question. You may have even already answered it, and I missed it.
When you had the CLD, the ammeter, and the electrolyte in series, did you still expect it to require 6 hours to reach 1mA?

ke5frf said:

OK, here is a quick draw-up, hope it is easy to follow.

Click to expand...

Absolutely thanks! Brainstorming is a wonderful thing...your brain...my storm! I will check back with results. plumber

Well here is what you need to understand.
After the electrolyte gets to 1.5 mA, there HAS to be circuit resistance in order for the process to hold. This is what ANY current limiting device will be doing, it will be creating a resistance to compensate for the increased conductivity. (EDIT: I'm not sure about a CLD, but most feedback type of current limiting will be feedback oriented, meaning as the conductivity goes up, so will the circuit resistance to compensate, in an analog fashion. So, even with your ideal circuit, time will be a factor as the resistance in the circuit builds.)

My offering will permit you to get to your goal in stages. The initial, resistanceLESS circuit, due to T1 being a short circuit, will allow a QUICK surge to 1 mA (or 1.5 if it pleases you). Then, a step change will occur and add a series resistance. It will bump your current back down, but it doesn't have to be much. It will climb once again, and T2 will cause the resistance to increase a second time, eventually settling on the exact resistance required for 1 mA (or 1.5 if that is acceptable). This ultimate resistance is around 24kOhm, and no matter what kind of circuit you settle on building, that resistance will be there. Current limiting is done with resistance, or shunting, or a combination of both.

Doing it in three stages permits you to control how long it takes. It sounds like your goal is to avoid the drawn out process of having a fixed resistance for the duration, which I understand would cause it to take a very long time. With the first stage, up to that 1 mA goal, being a short, the resistance problem will not be an issue.

Think of this as like a 3 speed transmission, first gear gets you to speed A very quickly. You shift gears, 2nd gear gets you to the next level, shift again and settle out at your cruising speed.

See?

Here's another current regulator that works very well