I'll ignore your rudeness and suggest that you make sure the meter probe wires are plugged into the current jacks and not the voltage jacks.
BTW, the ability to read, or previous residence in Idaho, does not preclude improper use of a meter. I'm a retired EE, and I've done it a few times.

__________________
Ron

 

Mr. Plumber...

About 5 or 6 posts up, prior ro Roff's, I suggested the same scenario as he.

You have drawn us a picture of two circuits, where you claim the first one is working and the second one is not. The first one had the meter parallel to the diode and the second one in series with it.

Both configurations will read current as long as there is no failed or improperly biased component creating infinite resistance, as long as the meter is on the proper range, the fuse is not blown, all function switches on the meter are properly set, and the leads are connected to appropriate terminals.

However, the parallel configuration, which you say is working, will bypass the diode. There will be no current limiting. You might as well remove the diode from the circuit and make it a Christmas ornament.

The SECOND configuration, as long as YOU are doing everything correctly with your meter and components, all setting correct and components properly biased, assuming the components are suitable and properly functioning, and furthermore assuming this circuit is a proven design, SHOULD WORK.

If it isn't working as you expect, those of us on this end HAVE to assume either you are doing something wrong, your equipment is faulty, or the design is bogus. Exploring any of these possibilities is not an insult.

After all, you came to this site asking questions and as far as I can see some knowledgeable people have done their best to help you. My suggestion is that you take a deep breath and explore the possibility that you are doing something wrong per our suggestions.

After all, if you are claiming the first drawing is "working" but do not realize that it CAN'T be working per the design of the circuit (ie no current limiting from a bypassed diode), then we MUST explore any and all possibilities.

As Roff said, and I can personally attest, even the most skilled and experienced craftsman can have a brain glitch and improperly use the tool of his trade.

Please offer us, as I asked previously, the make and model of your meter. Is it analog, is it digital? What is the min/max current range, etc.

And if you have a digital camera, a detailed photograph of your experiment MIGHT shed some light.

 

Excellent post, ke5frf! I think you've said it all.

__________________
Ron

 

TY Roff. Don't mean to sound rude myself, but he keeps asking us to not question his intelligence when asking someone if they are using their equipment correctly has no bearing on intelligence whatsoever.

I have a feeling that he IS using his equipment correctly but the diode simply isn't conductiong when he has it set up "correctly",

Going back, he said he refuses to tell us his starting voltages, etc because he doesn't want us to "go off track" with our suggestions. In a way, that is an insult to the person from whom you are seeking advice! In fact, all the voltages and specifics of the circuit very much have a bearing on the outcome. He may not even be applying enough voltage to produce a current through that particular diode for all we know.

In one of his first posts, he said he didn't have time to look up the model number of the diode, which is extremely relevant! Yet he has time to post questions, defend his intelligence, banter, and OUR time is of no consequence.

OK, Mr. Plumber I am sorry for getting testy myself. I truly am. I think you are sincere, but you have to give us ALL pertinent information in order for us to help you, willingly and without hostility.
__________________________________________________ __________________________________________________ __________________________________________________ __________________________________________________ _________________

EDIT: As an aside comment...if the current measurement with the meter parallel to the diode is not exceeding a milliamp in that configuration, per your observations, a few things you should consider and understand...

First, conceding that I am no expert with electrolysis, it MUST be concluded that the conductivity of the electrolyte solution along with your battery voltage and the resistance of your conductor are the ONLY FACTORS limiting the current in your experiment (in the parallel meter configuration) according to Ohm's law. This is pure Physics 101 and unless you are the discoverer of a new Earth shattering phenomen this conclusion is all that is left.

What you have is two parallel conductors. IF ANYTHING is certain, your actual current is MORE than your measured current, because the forward biased diode (probably) offers only a little more resistance than the meter and leads, and the overall current will be the sum of the two branches according to Kirchoff's current law. It is entirely conceivable that you have as much as 2 mA of current passing through the circuit but will never know it because to detect it would require two ammeters.

This doesn't seem likely, however, because you say the series configuration isn't working. I would be interested to know how you define not working. In other words, is there NO measured current, or is the current more simply LESS than you expected it to be? If there is no measured current, the only reasonable conclusion is that the battery voltage along with the conductivity of the electrolyte is not enough to properly forward bias the diode and get it to conduct. If there is a current but not what you expect, the only reasonable conclusion is that the overall conductivity of your circuit and the voltage supply is not permitting the current you desire, in part because of the current limiting of the diode.

Are you an actual plumber? OK then you should be familiar with pressure regulators. Think of them for a moment. A 10 lb pressure regulator cannot regulate 5 lbs of water pressure. The supply pressure has to be more than the desired output. You need headroom. This may be the case, in terms of current, with your experiment. By pure coincidence, the electrolyte solution may offer just enough conductivity to permit 1 mA of current with no diode in place (bypassed), but with the diode in place, you simply do not have enough current for it to perform as you desire.

At any rate, without knowing the EXACT performance specifications and conditions of every component in the circuit, there is no way to give you the exact answer you are looking for, only guesses and speculation. But one thing is for certain, your "working" set-up is not working.

 

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. In your lower drawing, your current is limited to 1 ma by the diode. It may be the diode keeps the emulsion ready to work when the voltage is raised, don't know why it's there, but that's how the diode works. I think CLDs are so cool, if in series with a capacitor, the voltage will rise in a straight line instead of the usual 5 TC curve.
Enjoy,
Kinarfi

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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.

__________________
Ron

 

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.

__________________
de KI6RWX

 

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.

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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

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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)

 

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.