I agree. I also take some exception to the idea that using rectified
mains is somehow horrifically dangerous and never done in modern times.
There's nothing wrong with an unisolated HV supply, provided that the
case is designed in such a way that no part of the design can come in
contact with a person. Mike Harrison's design is a great example. It is
light, it is small.. It works well. I have clocks built that way
(although I don't do it anymore) that are perfectly safe and are still
in service. The biggest issue in these designs is to safely bring the
wall current into the enclosure. I'd be more worried about an accidental
short in the power connector (and ensuing fire) than from the rectified
HV. I'd like to add that you can have this same danger even with a
switching supply, if you bring the mains into your box.
True, a 180v isolated supply is safer in case you touch it (it doesn't
shock you as hard).. unisolated wall current could _potentially_ kill
you. I think that 110v through a voltage doubler is safer than 220v
rectified because the doubler will sag and there will be some current
limiting. Possibly Nick lives in England, and that is why he is so
concerned about the wall current? I admit that I wouldn't design a clock
that was meant to plug into a 220 socket and rectify the mains either.
No matter what, getting in the habit of extreme caution when dealing
with high voltage is a great idea. The lessons I've learned from getting
hit with nixie HV have taught me the caution necessary to work on my
tube transceiver without killing myself (the finals cage on my 500c has
an 800vdc plate voltage).
-Adam W7QI
On 2/27/2012 11:03 AM, Lucky wrote:
Wow, slow down chaps, must be a highly talented thing all this having
a dig.
All Michel said (in response to a comment "For future reference, the
TI SN75468 has seven MPSA42s in it") was "They are not exactly the
same, standard MPSA42s are 300V while as the SN75468 is only
100V." (which is true) then all hell breaks loose, lighten up guys,
can't we discuss variables etc?
@Michel..interesting links you gave, had not seen the first 2 before.
@Frank "It is not very common that nixies are powered with _more_ than
180V" Not common but still done which is point in question not how
many times it has been done.
@Nick. From how read it Michel has no 'beef' but is just discussing
possible concerns and provides links to where those concerns may arise
(after it being stated it does not happen!).
"then frankly you deserve all you get" Really? Surely that sort of
attitude is not becoming someone with the amount of intelligence such
as yourself?
"Just so you know for the future, Geert is the son of the sites author
" What so we must not mention his name?
"I suggest before wandering down these sorts of routes you take the
time to look through the archive" Have you ever TRIED searching
through the archives for information? (I have, not easy at all)
besides does he (Michel) need to to discuss a point or two?
"Many of the long-term members here are professional electrical or
electronic engineers and designers" And some of us not and actually
LEARN something by reading these posts! (and hopefully, like myself,
have a "high self-preservation factor"
All I would say guys is..Lighten up a bit, relax, discuss our hobby
without the snide remarks or chest beating, allow someone to have a
different opinion, point out errors in thinking because you/we want to
help each other, you know all the normal stuff that we do after
graduating sandpit lol. (Mountains and Molehills comes to mind) Either
way I thank you all for sharing your knowledge and learn a little bit
every time.
Regards, Dave.
On 27 Feb, 11:48, Nick<n...@desmith.net> wrote:
On Feb 27, 11:21 am, Cobra007<mic...@xiac.com> wrote:
In short,
Take a look at Geert's clock here:http://www.dos4ever.com/geert/geert.html
Now, I do not know Geert but it seems to me he knows quite well what
he is doing. Check the HV power supply he uses for his clock and
estimate what the DC voltage will be.
...and he explicitly uses 400V cathode drivers (BF487), states the
safety issue and isolates the clock in a suitable box.
Just so you know for the future, Geert is the son of the sites author
(Ronald Dekker), who works for Philips as is extremely well known
here.
Or else, how about this
one?http://www.geocities.ws/podernixie/nixie/index-en.html
Simply a dangerous design. Should never be built.
Or, jee (although through a transformer), another
one:http://www.ledsales.com.au/kits/in14_clock_instructions.pdf
...who uses 300V cathode drivers (MPSA42).
I'm not sure what your beef is here - as has been stated by others,
generally nixies are driven by about 180-200VDC. All you've uncovered
in your examples are two good designs which use drivers with suitable
Vceo, and one dangerous design which has no isolation and overdrives
the cathode switches.
Look, If you want to drive your nixies from 500V, then use suitable
drivers. If, like probably 95% of the population you use about
180-200V to drive them, then 100V Vceo is fine. If you use 100V Vceo
drivers and 300V on the anodes, then frankly you deserve all you get -
this is the danger of the Internet...
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