Thanks, Les I tested a homemade cap as per your video using only acetone...accidentally left it for 2+ weeks! WORKED GREAT. capacitance measures the same...if I could only remember the kV rating......
Holy crap! That was way simpler that I thought it would be, and the result was very presentable! This channel is so underrated, but someday you will get that 100k plaque, im sure.
Thanks! Yep, in the end it is pretty straightforward. I reckon it is possible to do all sorts of things with these dielectrics, maybe stack them and make a Megavolt capacitor or something ;-)
@@LesLaboratory oooh, I would absolutely LOVE to see a video like that! Maby even pass the full output through different components to see what they do and just mess around!
You need silver based eutectic solder to be able to solder to silver deposited on ceramics; this is actually fairly common, that's how you can solder onto ceramic capacitors and piezo crystals.
Regarding soldering directly to the silver plating: this should be possible using a solder that contains a few percent silver. Tektronix used to use silver-plated ceramic terminal strips in their vacuum tube-era scopes and included a small roll of suitable solder tucked away in each chassis. The reason this works is that solder (at least, the old 60/40 kind) has a very limited capacity to absorb silver; the silver goes into solution when you melt the joint but the alloy saturates at a few % silver. If you use solder that's already 'fully loaded', no more will dissolve off your electrode. It's possible that SAC305 would work but I have not checked the chemistry to see if the tin or the lead was the dominant factor.
Good idea, I will maybe give that a go. An additional Idea, might be to thicken the plating by electroplating those surfaces as well. I have some Ideas about stacking a few in series to make a peaking capacitor for a Marx Generator :-)
i'm not sure i'm getting it... so you are saying that if solder already contains silver it will take no more and not peel off the silver plating? this interests me for various purposes
Hi Les, I am planning to make a better cap. It's skinned already. I plan to use short brass screws as you did, but tighten a short round inside-threaded brass (+lock washer) tube screwed tight to the centered screws for female connectors as in the real doorknobs. I will place it in a cut pill bottle. Arranged for one terminal to come out of the bottom and a circular top for 2nd terminal. Filled with hardening poly. A bit of JB-weld + the dried poly to prevent turning. (you know, perhaps hex instead of round terminals) BTW: I think it is the dark orange Rx bottles that have 'MONSTER' dielectric strength (tested this during a project for spark plug panel connectors) FYI: I found that these bottles are 'barely' 'slightly' beveled. ...just thought I'd share the thought...
Yep, honestly I thought it would be much harder. I suppose if I repeated the process, it would be about 15 minutes work. All the rest of the time is waiting for the Acetone to do its job, and waiting for epoxy to fully cure.
It'd be really interesting to see some comparative measurement of the parasitic inductance between these, "real" doorknobs and the basic wire-ended caps. Obviously you'd need some specialist equipment to do this directly but just comparing the discharge pulse shapes on the oscilloscope would give us some idea of how they compare.
I was under the impression if you use high silver content solder you can solder to silver ok. As I understand it the solder absorbs silver but if its loaded with 3-5% silver it doesn't leach the silver substrate. However it do have to be protected from humidity or you will get silver migration whiskers across potential difference points.
interesting how easily acetone acted on that coating, i'll take a note on that, anyways you should check if those capacitor leads are iron based, low quality capacitors often are, not only chinese knock-offs, grab a magnet and "magic wand" over em, just in case
Like in your experiments, I'm not sure about even weak acids as they'll all attack the metal parts to some degree... but if acetone doesn't work for some plastic coatings, you can always try DCM / dichloromethane or toluene / methyl benzene..... both of which can be got from E. Bay.... but acetone is always the best bet.
You can also use conductive epoxy, basically silver or copper loaded epoxy. If you encapsulate it all afterwards you don’t mind the reduced strength of the conductive epoxy. Well done in getting a neat alternative capacitor.
Already got some ;-) When I stripped the coating, I was looking at ways to re-coat them. As I discovered you cant just glue foil to them, since no matter how thin the layer of glue, you have introduced a tiny series capacitance, that drops the overall capacitance of the assembly, but silver conductive paints seem to work very well in terms of getting back to the original capacitance. How well they fare under a pulsed load of thousands of Amps is an experiment for another day.
What about copper plating the ends to make them solderable? Copper sulphate is quite available and plates quite well to most surfaces. I've made plated thermocouples with copper plating and they were quite robust.
It should do. The catch is the solderable bit. These things are not very happy about heat. I suppose I could use some low melting point Gallium based solder.
Nice hack! I was wondering about the stability of the laser. You say that it's quite stable, however in the video there appear to be large variations in the pulse intensity. Is that due to the pulses and camera frame rate out of sync?
Mostly yes. The shots often occur between frames. Filming pulsed Lasers is a Major PITA! Generally to the eye, it looks pretty reasonable. If you run the repetition rate way up, the output will tail off, unless you also turn the gas up as well. I suspect there is quite a bit of shot to shot variation however that my eyeballs can't discern, as the Spark gap is not triggered. I recently acquired a Laser Micro Joule Meter sensor, so I am going to measure all these and share the results in an upcoming video.
I recently got a nitrogen laser from ebay, an old soviet unit, it lased for a couple of pulses but then it stopped lasing. It still has an output, but it's like not fucussed anymore. It makes some crackle noises. I guess a doorkbob cap is broken. But everything is potted in jelly :(
Do you know If it´s possible to metalize them at home and resolder the bolts directly? Maybe that would improve the pulse current and inductance of the cap ! Otherwise thanks for the idea !
The (perhaps too obvious) question I have is: Why not just pot the "hack" at 0:51 into a PVC tube with epoxy and end up with something similar to the result at 3:27 without the week-long soak in acetone? I'm pretty sure that epoxy potting should stop it flashing-over without altering the capacitor itself, but I am prepared to be wrong.
Yes, it would work, however the long leads of the capacitor add unwanted inductance. The switching speed in TEA Nitrogen lasers is critical. The faster we can dump the stored charge, the more optimal the output will be. This is a follow up from a previous video where the goal was to do the job in such a way as to have a really good analog to a genuine doorknob cap. Originally I had intended to solder the bolts directly to the dielectric.
It is notable that the existing wires have been soldered so what is the manufacture using? Perhaps this is a silver bearing solder to prevents the silver film from dissolving into the solder.
@@LesLaboratory Perhaps some conductive silver bearing epoxy some are very conductive. I have used this on other projects but the current density probably is very high. Finding an exact spec for resistance has proven difficult.
..thanks again : ) ....please wear gloves, i do not know if that stinky juice is toxic, or if something disolved in solution would get better absorbed thru the skin etc..i learned of the acetone a while back and since then, irrelevant- i will do outdoors and latex gloves to be sure- ....anyway, the same "solder" problem is with ultrasonic disks- try using silver solder, that worked on them- but the heat might compromise the PZT..you got me charged up again, getting a bunch of em and make like a rail configuration.. excellent video, presentation, diction, content, etc, thank you
Thanks! Acetone isn't the worst solvent. There are worse ones as far as trans-dermal absorption are concerned (like DMSO), but sure, gloves would be a good idea. Yeah, I considered re-coating (even tried it using various methods), but in the end, went with the simplest solution.
I have not characterised them proper, however internally the Dielectrics at least are similar, if not the same. There will be some inductance present (though minimal) due to the short leads, though this is negligible for this application. They do however have much improved stand off voltage, and are probably more then adequate for small Lasers, Marx generators and so on.
I tried this annnndd my capacitors broke to pieces. I would say "shattered" but that implies it broke quickly resulting from a strike. It definitely appears to be a result of some internal stress within the ceramic; I'm not sure how acetone would weaken the ceramic enough to cause it to break apart though. At first I thought that I just overvolted my caps and I was uncovering previous damage, but I saw one that was intact that subsequently broke later. The ceramic doesn't appear to be porous or absorbing the acetone... So it's possible I had some micro fissures from use that then propagated due to differential cooling. I ordered some more, I may try it again with completely unused caps to confirm.
I think it's a dielectric manufacturing thing. I had some huge wire ended caps that when de-potted seemed to break into thousands of small sharp pieces, whereas others remain good and solid.
I know this is old video but am missing something, why not just bend theas apart and pot the wire lead cap as is? I have done so in wax up to 40kv and it works ok
They don't dissolve, some epoxies however will swell and soften. My best guess is that the acetone penetrates in between the long chain molecules. Note, this is a best guess, any physical chemists want to jump in?
Have you heard of anyone trying to power this type of laser with radio frequencies or a Tesla coil? To me seems like the next reasonable step, a lot less power out but faster repetitive shots, may be useless but I was thinking uv resist due in laser printer or cutter design, ok I'm just out there.
Not that I am aware of. The literature says they can be run at repetition rates of >1kHz with flowing gas. At really high frequencies, you would need extremely high gas flow rates. These days, research departments tent to used Tripled Nd:YAG/YVO4 at 355nm in place of Nitrogen Lasers, that are capable of 10's of kHz at millijoule pulse energies.
Has anyone in the US ever thought that if it burns on the inside of a door with a knob, it is impossible to open the door because the skin `melts` off the hand!
Noticed the smiley face on the dye vial. Cute touch!
Thanks, Les
I tested a homemade cap as per your video using only acetone...accidentally left it for 2+ weeks! WORKED GREAT. capacitance measures the same...if I could only remember the kV rating......
Holy crap! That was way simpler that I thought it would be, and the result was very presentable! This channel is so underrated, but someday you will get that 100k plaque, im sure.
Thanks! Yep, in the end it is pretty straightforward. I reckon it is possible to do all sorts of things with these dielectrics, maybe stack them and make a Megavolt capacitor or something ;-)
@@LesLaboratory ooh, and then a massive voltage multilpier!
@@justin.campbell I have a nice home made 150kv Marx I could hit it with...
@@LesLaboratory oooh, I would absolutely LOVE to see a video like that! Maby even pass the full output through different components to see what they do and just mess around!
@@justin.campbell yeah, I have been thinking about that. The channel can't all be about Lasers right? :-D
You need silver based eutectic solder to be able to solder to silver deposited on ceramics; this is actually fairly common, that's how you can solder onto ceramic capacitors and piezo crystals.
Regarding soldering directly to the silver plating: this should be possible using a solder that contains a few percent silver. Tektronix used to use silver-plated ceramic terminal strips in their vacuum tube-era scopes and included a small roll of suitable solder tucked away in each chassis. The reason this works is that solder (at least, the old 60/40 kind) has a very limited capacity to absorb silver; the silver goes into solution when you melt the joint but the alloy saturates at a few % silver. If you use solder that's already 'fully loaded', no more will dissolve off your electrode. It's possible that SAC305 would work but I have not checked the chemistry to see if the tin or the lead was the dominant factor.
Good idea, I will maybe give that a go. An additional Idea, might be to thicken the plating by electroplating those surfaces as well. I have some Ideas about stacking a few in series to make a peaking capacitor for a Marx Generator :-)
i'm not sure i'm getting it... so you are saying that if solder already contains silver it will take no more and not peel off the silver plating? this interests me for various purposes
Wow ! result, looks great and seems to work great, I won't be paying a tenner on e-bay for them...cheers.
Great ideas are those that are simple and work!
Well done!
Thanks!
Hi Les, I am planning to make a better cap. It's skinned already. I plan to use short brass screws as you did, but tighten a short round inside-threaded brass (+lock washer) tube screwed tight to the centered screws for female connectors as in the real doorknobs. I will place it in a cut pill bottle. Arranged for one terminal to come out of the bottom and a circular top for 2nd terminal. Filled with hardening poly. A bit of JB-weld + the dried poly to prevent turning. (you know, perhaps hex instead of round terminals)
BTW: I think it is the dark orange Rx bottles that have 'MONSTER' dielectric strength (tested this during a project for spark plug panel connectors)
FYI: I found that these bottles are 'barely' 'slightly' beveled.
...just thought I'd share the thought...
That worked extremely well for the price of the HV cap.
Yep, honestly I thought it would be much harder. I suppose if I repeated the process, it would be about 15 minutes work. All the rest of the time is waiting for the Acetone to do its job, and waiting for epoxy to fully cure.
Fantastic! I have been trying ways to remove that coating recently. I did not think acetone would work this well.
It almost seems like it won't, but leave it a week and it practically falls off.
Those capacitors are simpler inside than I thought!
It'd be really interesting to see some comparative measurement of the parasitic inductance between these, "real" doorknobs and the basic wire-ended caps. Obviously you'd need some specialist equipment to do this directly but just comparing the discharge pulse shapes on the oscilloscope would give us some idea of how they compare.
Hmm pickled capacitors.... i like them with chips and solder 😁🤓❤
I was under the impression if you use high silver content solder you can solder to silver ok. As I understand it the solder absorbs silver but if its loaded with 3-5% silver it doesn't leach the silver substrate. However it do have to be protected from humidity or you will get silver migration whiskers across potential difference points.
Probably, but temperature is a consideration. The dielectric cracks easily.
Subscribed! Great info and great video! Thanks bro!🤘
I was just watching the other video and wondering if you could crack it open and replace it's wires with something beefier.
interesting how easily acetone acted on that coating, i'll take a note on that, anyways you should check if those capacitor leads are iron based, low quality capacitors often are, not only chinese knock-offs, grab a magnet and "magic wand" over em, just in case
Like in your experiments, I'm not sure about even weak acids as they'll all attack the metal parts to some degree... but if acetone doesn't work for some plastic coatings, you can always try DCM / dichloromethane or toluene / methyl benzene..... both of which can be got from E. Bay.... but acetone is always the best bet.
That is absolutely Awesome. It has been two years now and how are these home made doorknob capacitors?
Thanks! They are doing just fine!
You can also use conductive epoxy, basically silver or copper loaded epoxy. If you encapsulate it all afterwards you don’t mind the reduced strength of the conductive epoxy. Well done in getting a neat alternative capacitor.
Already got some ;-) When I stripped the coating, I was looking at ways to re-coat them. As I discovered you cant just glue foil to them, since no matter how thin the layer of glue, you have introduced a tiny series capacitance, that drops the overall capacitance of the assembly, but silver conductive paints seem to work very well in terms of getting back to the original capacitance.
How well they fare under a pulsed load of thousands of Amps is an experiment for another day.
I saw you pull that acetone dripping cap out onto your cuting mat and thought "nooooo" and yes you've erased your lines hah
LOL yup! Never mind, there will be plenty more erasing and scorching before it gets replaced!
What about copper plating the ends to make them solderable? Copper sulphate is quite available and plates quite well to most surfaces.
I've made plated thermocouples with copper plating and they were quite robust.
It should do. The catch is the solderable bit. These things are not very happy about heat. I suppose I could use some low melting point Gallium based solder.
@@LesLaboratory old tektronix scoped used silver solder for this reason
Nice hack! I was wondering about the stability of the laser. You say that it's quite stable, however in the video there appear to be large variations in the pulse intensity. Is that due to the pulses and camera frame rate out of sync?
Mostly yes. The shots often occur between frames. Filming pulsed Lasers is a Major PITA! Generally to the eye, it looks pretty reasonable. If you run the repetition rate way up, the output will tail off, unless you also turn the gas up as well. I suspect there is quite a bit of shot to shot variation however that my eyeballs can't discern, as the Spark gap is not triggered. I recently acquired a Laser Micro Joule Meter sensor, so I am going to measure all these and share the results in an upcoming video.
I recently got a nitrogen laser from ebay, an old soviet unit, it lased for a couple of pulses but then it stopped lasing. It still has an output, but it's like not fucussed anymore. It makes some crackle noises. I guess a doorkbob cap is broken. But everything is potted in jelly :(
I think I saw it, and nearly bought it! The breakdown could be anywhere including the PSU. If you are so inclined you could carefully depot the thing.
@@LesLaboratory Yeah the blue one. Grey cover. Pretty neat unit. Fun while it lased.
@@PiratCarribean Don't give up. Carefully strip it and see...
Do you know If it´s possible to metalize them at home and resolder the bolts directly? Maybe that would improve the pulse current and inductance of the cap ! Otherwise thanks for the idea !
Probably! I would imagine you could sputter a thin layer of copper, then thicken it by electroplating. This would involve quite a set-up though.
@@LesLaboratory check with applied science chanel he built one of those.
"have corona inside them" is certainly a thing one should worry about in many contextx-s, this year. :)
The (perhaps too obvious) question I have is: Why not just pot the "hack" at 0:51 into a PVC tube with epoxy and end up with something similar to the result at 3:27 without the week-long soak in acetone?
I'm pretty sure that epoxy potting should stop it flashing-over without altering the capacitor itself, but I am prepared to be wrong.
Yes, it would work, however the long leads of the capacitor add unwanted inductance. The switching speed in TEA Nitrogen lasers is critical. The faster we can dump the stored charge, the more optimal the output will be.
This is a follow up from a previous video where the goal was to do the job in such a way as to have a really good analog to a genuine doorknob cap. Originally I had intended to solder the bolts directly to the dielectric.
It is notable that the existing wires have been soldered so what is the manufacture
using? Perhaps this is a silver bearing solder to prevents the silver film from dissolving into the solder.
Quite possibly a silver solder right enough. It is a very thin coating though, and excessive heat damages the dielectric.
@@LesLaboratory Perhaps some conductive silver
bearing epoxy some are very conductive.
I have used this on other projects but the current density probably is very high. Finding an exact
spec for resistance has proven difficult.
..thanks again : )
....please wear gloves, i do not know if that stinky juice is toxic, or if something disolved in solution would get better absorbed thru the skin etc..i learned of the acetone a while back and since then, irrelevant- i will do outdoors and latex gloves to be sure-
....anyway, the same "solder" problem is with ultrasonic disks- try using silver solder, that worked on them- but the heat might compromise the PZT..you got me charged up again, getting a bunch of em and make like a rail configuration..
excellent video, presentation, diction, content, etc, thank you
Thanks! Acetone isn't the worst solvent. There are worse ones as far as trans-dermal absorption are concerned (like DMSO), but sure, gloves would be a good idea. Yeah, I considered re-coating (even tried it using various methods), but in the end, went with the simplest solution.
do these 'homemade' doorknob capacitors have all the same parameters as regular doorknob capacitors?
I have not characterised them proper, however internally the Dielectrics at least are similar, if not the same. There will be some inductance present (though minimal) due to the short leads, though this is negligible for this application. They do however have much improved stand off voltage, and are probably more then adequate for small Lasers, Marx generators and so on.
I tried this annnndd my capacitors broke to pieces. I would say "shattered" but that implies it broke quickly resulting from a strike. It definitely appears to be a result of some internal stress within the ceramic; I'm not sure how acetone would weaken the ceramic enough to cause it to break apart though. At first I thought that I just overvolted my caps and I was uncovering previous damage, but I saw one that was intact that subsequently broke later. The ceramic doesn't appear to be porous or absorbing the acetone... So it's possible I had some micro fissures from use that then propagated due to differential cooling. I ordered some more, I may try it again with completely unused caps to confirm.
Just had a thought... maybe a dumb one. Do ceramic capacitors have any "parasitic" piezoelectric effect?
@@jonathanseagraves8140 probably. I have never tried to squeeze them.
I think it's a dielectric manufacturing thing. I had some huge wire ended caps that when de-potted seemed to break into thousands of small sharp pieces, whereas others remain good and solid.
I know this is old video but am missing something, why not just bend theas apart and pot the wire lead cap as is? I have done so in wax up to 40kv and it works ok
All epoxies dissolve under acetone or formic acid, even the IC caps? what is the reason?
They don't dissolve, some epoxies however will swell and soften. My best guess is that the acetone penetrates in between the long chain molecules. Note, this is a best guess, any physical chemists want to jump in?
Have you heard of anyone trying to power this type of laser with radio frequencies or a Tesla coil? To me seems like the next reasonable step, a lot less power out but faster repetitive shots, may be useless but I was thinking uv resist due in laser printer or cutter design, ok I'm just out there.
Not that I am aware of. The literature says they can be run at repetition rates of >1kHz with flowing gas. At really high frequencies, you would need extremely high gas flow rates. These days, research departments tent to used Tripled Nd:YAG/YVO4 at 355nm in place of Nitrogen Lasers, that are capable of 10's of kHz at millijoule pulse energies.
Has anyone in the US ever thought that if it burns on the inside of a door with a knob, it is impossible to open the door because the skin `melts` off the hand!