Electronics > Projects, Designs, and Technical Stuff
Open HV Probe 40kV
joeqsmith:
Looks like a nice old transformer.
You could try using the uA range as well. Can you go across the output of the transformer instead? You could also try a shorter distance. Maybe try going through the sidewall of the case.
beanflying:
Transformer is an Allanson 277V, 60Hz, 15kV, for anyone playing along at home (Running nominal 240-250V in my case) ;)
I have started prepping the Probe for Epoxy coating so no more testing for a bit. Floating a decent DMM that far above ground was worrying me so I didn't. I do have a couple of old Victor 86B's with mA and uA ranges that I care quite a bit less about so maybe I will look at that when the coating is done.
Having a look at what ArthurDent raised I think I will extend the inner tube further toward the handle by a bit at a reduced diameter again and add some Tinned Copper Sleeve and bond it to the Earth and LV connection to the meter to it. Belts and braces a bit but it certainly cant hurt.
I have ordered some more PLA which should be in tomorrow and I have planned to print a second one as a Chicken stick for the Neon Transformer with HV cable going in right at the tip part of a Lanthanum TIG electrode (longer barrel again). While I am going I can do a second barrel with multiple points to connect to along the Barrel.
Easy to add these as small raised knobs or holes/divots to help connect to? Let me know what may work best?
For interest I have attached some cutaways of the actual Sliced Gcode for the upper Barrel. It was 6 inner and 6 outer layers and it is well down into the tip before there is any infill/voids. They could be eliminated easily if it looks like being an issue with a simple setting change to the infill from 40% to 100%.
tggzzz:
--- Quote from: kony on April 24, 2019, 07:13:58 pm ---Someone notify the Darwin awards commission, they might get a special serial entry brought you by the open source community (TM).
No, NO, and FUCK NO to the material and manufacturing selection for the insulator of the probe. Having dealt with reliability of manufacturing processes of 20kV PSU assemblies in the past, I am very painfully aware of how deep the rabbit hole goes to even start thinking about passing the design for production after several iterations of debug and validation of BOTH the design and manufacturing process. And you are attempting to get this out in a way such everyone can wing it with the leftovers just lying around? Gotta be shittin me! I am sorry, but I am not sorry for my languague, it is fully apropraite for the magnitude of the possible consequences this can have.
OP, do you have a single fucking clue about the E field distribution on the probe insulation, what air pocket inclusion or surface defect or grit contamination will do to it? Sensitivtity to moisture, long term stability of the plastic (selection of which you, BTW, have absolutely zero control over)? Corona resistance of the material should partial discharge occur - and what certanity is there it won't avelanche in the degradation? How about air gaps in the insulation to the center isntalled divider or elsewhere - do you at least understand what relative permitivity discontuinuity implies for local electric field magnitude?
Can you imagine the consequences of some poor bastard using such thing handheld on hard power supply?
--- End quote ---
Some of us have tried asking pointed questions, and been rebuffed, and bowed out of the discussion.
beanflying:
I chose to roll past Mr Fuck this that or the other before as he offered no factual information to back up spurious claims that would be true of HV probes commercial or otherwise in the hands of a numpty. If we use this thinking anyone who spends money on evilbay or aliexpress and buys Probe X can injure of kill themselves and that's ok?
It is really simple SHOW ME EVIDENCE of the material or process not being suitable. When offered video of the material being tested under HV for breakdown you didn't watch and then went on again without looking further for yourself. You chose to dimiss the people as 'Talking Heads'. When offered further information about the material you went on again with no evidence to back up your claims about it.
--- Quote ---PLA and many thermoplastics are hygroscopic to some extent. Unless proven otherwise I would assume that would change the electric properties over time, e.g. it becomes more conductive.
I have not seen (because I haven't looked for) any measurements indicating whether or not that would be sigificant in this application.
--- End quote ---
I have done some additional research into moisture and all plastics absorb water to a greater or lesser degeree with Teflon being a bit of an exception. The ABS for example used in a lot of these probes commercially will hold water in the order of 0.2-0.3% based on my reading and for PLA it seems to vary but at around the 0.4-0.6% range is what I have read and all plastics absorb more moisture as the Temperature rises. What have you done and what did you find?
You have sought at every possible point to add zero constructively to the project and only tell the world it cant and shouldn't be done because you say so. :-//
As I thought may be obvious by now I have a set of files ready for release that work and quite deliberately haven't and won't be generally releasing them until I am happy that tests carried out be me and hopefully a few others independently give more confidence in the design.
The Soulman:
--- Quote from: beanflying on April 25, 2019, 07:29:50 am ---It is really simple SHOW ME EVIDENCE of the material or process not being suitable.
--- End quote ---
Engineers are used to it being the other way around.
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