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current limiting diode

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plumber

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Much lower than newbie, in pipe fitting almost everything is in line and parallel connections rarely effect the main. The diode is essentially a FET with the gate shorted to the source...I barely know what this means! The following explains the application and failure. I need help. Would someone tell me what I need to do to make this work? Thanks plumber. = Hello, I recently purchased a current limiting diode, but it did not limit the current. I am sure the fault lies with me and not your product. I need to buy more, but first I must find out what went wrong. Please forgive the lack of proper terminology as I describe what I did: this is for electrolysis, in which I need to keep the current from climbing above 1.5 mA.
30 volt dc unregulated power (wall adaptor) + output to striped end of CDL. (+) output from diode then goes through multimeter (in line) and then out to the (+) anode. - output from wall adaptor goes through (-) side of multimeter and then to the (-) cathode. Starting current was
228u. As the process advanced, the current climbed past 2.88mA after the tenth hour. The CDL was rated for a current limit of 1.2mA .Stock #610-1n5299 / MFG PN 1n5299 (Central Semi Conductors) I will test the diode a little later and report back. How susceptible are these diodes to static discharge? I was reasonably careful, touching my grounded project box as I handled and soldered the diode in place. Didn't use a grounding strap. So please, tell me what basic circuit knowledge I messed up with? "series" / "parallel" did I need a Zen. diode or resistor somewhere? I know the set up was ultra simple...made sense to a plumber! Any input would be appreciated.
thank you for your time
 

plumber

New Member
electrolysis.jpg
Now I know you are entertaining yourselves! I told you, I was lower than a newbie! So here is my very first ...er ah...er ah, electronic diagram ( I couldnt bring myself to call it a schematic)
 

kchriste

New Member
Forum Supporter
30 volt dc unregulated power (wall adaptor) + output to striped end of CDL. (+) output from diode then goes through multimeter (in line) and then out to the (+) anode. - output from wall adaptor goes through (-) side of multimeter and then to the (-) cathode.
It looks like you connected the "diode" backwards. ie: The "cathode" is the striped end. Do you have another one to try? As long as the current didn't climb too high (Diode got very hot), then the diode is probably still OK. A safe way to test the circuit is to substitute a 3.3KΩ 1/2 watt resistor for the distilled water bath. If you have the diode backwards, the meter will read apx 8-9ma. If the diode is installed correctly, the meter will read apx 1.2ma. No damage can occur while the 3.3KΩ resistor is substituted for the water bath even if the diode is installed backwards.
 
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ericgibbs

Well-Known Member
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View attachment 34463
Now I know you are entertaining yourselves! I told you, I was lower than a newbie! So here is my very first ...er ah...er ah, electronic diagram ( I couldnt bring myself to call it a schematic)

hi,
Can you tell us what is the purpose of this project, I see you say electrolysis, but why.?:)

Why start with distilled water.?

You can buy constant current 'diodes' that will limit at 1.5mA.
 

plumber

New Member
thank you kchriste and others

I read the pdf notes on the applications for the "cld". Of course, simply limiting current was not listed, and "constant current" was listed as an additional use for the diode...only as a reference with no example or schematic. A simple ac clipper circuit with back to back cld's seems to indicate that no other components are required in the circuit. And that reverse polarities wouldn't arm this specific cld. The diode never even got warm...by the way, is heat dissipation the way this diode shunts excess current with out a gate or drain? Ok, I just got back from fiddling around with things, resistance is 00.6 on the diode, I put the striped end of the diode opposite of the power source, I shorted my leads to simulate load and my amp meter would not go past 1.14 mA while holding (-) (+) together. the cld is rated to limit current to 1.2 mA...is this good news? Did I just have the diode backwards? No complicated circuit needed? I used a 12 vdc source for this test...I am assuming I'll get the same result from a 30 vdc source? the diode is rated to 100 volts max. I really don't know what I am doing...something happened to my multimeter (before I shorted the test leads) the regular fused jack for low amp testing no longer conveys power through the meter to the the load and wont read amps. the fuse looks fine and the leads actually read voltage when set to dc volts. but the meter circuit wont power a motor. I switched the (+) jack to the non fused 10 amp meter circuit and it reads amps and conveys power to a test motor just fine. So maybe I fried something besides the fuse?
 

plumber

New Member
hey ericgibbs

hi,
Can you tell us what is the purpose of this project, I see you say electrolysis, but why.?

Hi ericgibbs, as for the purpose, I'm too tired to go into it, suffice it to say, ion transfer with as little agglomeration as possible. That requires a slow process, the longer I can run the process the better. Mechanical stirring only controls the current until ion saturation becomes uniform throughout the solution. To avoid clustering of the ions which result in large suspended particles ( nano sized but still too large) the process has to be stopped. Ion concentration and ppm being less than optimum. So, a constant current of 1.5
mA or less will allow me to "gently" strip ions into the distilled water without sintering off large particles from the anode. This way, I can saturate until the first signs of precipitation, knowing I've got max ppm and ion count. Approx. 18 hours for two liters. Distilled water is a horrible conductor, but it is to avoid formation of any kind of salts or reactionary products. If you have any suggestions or input I'd appreciate it, I think I figured out that I had the diode backwards and that it still works, but the low amp jack on my meter no longer works in line. If you see potential problems please let me know.
Take care, plumber.
 

ke5frf

New Member
Check the suspect fuse with your ohm function. It should read as a short, 000 ohms.

Thanks for posting the schematic. I was suspicious you had the diode backwards from your text description. Where did you get the idea for this circuit? Plumber eh? interesting a plumber would choose a circuit with an electronic check valve :)

And you said you are driving a motor with your meter? Must be an older analog style I'm guessing. I personally would find another voltage source for that purpose.
 

plumber

New Member
Hey ke5frf

Check the suspect fuse with your ohm function. It should read as a short

I got the idea for this circuit after turning my brain to mush trying to absorb and understand all the posts and schematics about JFETS, MOSFETS, here a transistor, there a transistor, sine wave, square wave bipolar junction n channel p channel gate dump shunt drain short to source old symbol new symbol American euro symbols rectified scramblized brain is fried field effected
comparator selected galenium siliconized v=I-r ohm is a good friend of mine. You get the idea. I just had to find the beloved current limiting diode. I can do in and out. Two terminals yeah. No parts left over.
A lot of folks told me cld's are not very popular anymore...I better stock up, because it is going to take me awhile to learn a working knowledge of this stuff. I admit it is very intriguing and addictive. As for a motor...who keeps saying motor? Maybe my meter symbol looks like a motor. I have a 6vdc gear motor mounted to the electrolysis tank lid for very low rpm stirring. But it has it's own power supply and creates just enough movement in the solution to disperse the ion stream, reduce the current, and prevent agglomeration of ions into large particle clusters. Thanks for the challenge of drawing my first electronic diagram in windows paint program.
 

audioguru

Well-Known Member
Most Helpful Member
The datasheet for the current-regulating "diode" does not show which polarity it should be connected to regulate DC current.
I guess originally you had the polarity backwards since reversing its connections made it work properly.
 

kchriste

New Member
Forum Supporter
I put the striped end of the diode opposite of the power source, I shorted my leads to simulate load and my amp meter would not go past 1.14 mA while holding (-) (+) together. the cld is rated to limit current to 1.2 mA...is this good news? Did I just have the diode backwards?
Yes, looks like good news. As I suspected, you just had the "diode" backwards the first time. ( Put "diode" in quotes because it is really a special JFET with the gate and source terminals shorted together.)
 
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