[Prev][Next][Index][Thread]
Re: Remote Tuned Primary (RTP) ideas...
> The first is a way to adjust gap timing remotely. This one is pretty
> simple. Just a DC gear motor attached to a lead screw to rotate the
motor
> on my rotary sync gap. There is a nut on the handle so when the screw
Or a gear head motor with rotary output to turn the entire motor..
>
> 1. Is mineral oil the best thing to use for insulation? Or is there some
> other substance (like silicone oil) that is really better?
Mineral oil (like Shell Diala) is probably your best bet, it's cheap works
well, and isn't too hygroscopic. Silicones are nice because they are very
hydrophobic, but, impossible to clean off if it gets somewhere it shouldn't
be, and really, really expensive.
Unless you want to use Askarel (PCB) <joke>... actually PCB's are very nice
(non flammable), but those darned contaminants are a problem.
>
> 2. There is one serious problem I have found. Most small relays have
> little isolation distance between the switch elements and the coil. An
arc
> to the coil will probably blow up the control electronics (fiber optics
> prevents such a thing from blowing the operator ;-)). Some small "safety
> relays" have a large distance between the coil and the switches that
should
> work good. They are usually pricey but they have cheap cousins.
However,
> perhaps someone knows of a perfect relay for such a use?? Big power
> contactors would be great but they are really too big for such a use.
Make your own HV relays.. You aren't concerned about operating speed, or
even life (typical spec for a commercial relay might be 1,000,000
operations, you'd be luck if you got to 10,000), and you can tinker. A
solenoid driving a dielectric rod to move a piece of copper pipe or strap
to bridge the stationary contacts. You can also set the moving contact up
as a lever, so that at the contacts there is a lot of throw, from the 1/8
to 1/4" you'll get from the solenoid. You can also use a gear motor to
drive a big home made rotary switch or a knife switch.
Another approach I use a LOT in switching HV is to use air power. Small
air cylinders with a few inch stroke are about $5. You can get pneumatic
toggle switches, solenoid valves, relays, etc. A small air compressor
(like for airbrushing) and a reservoir will provide air for lots and lots
of operations (we're talking less than a cubic inch per actuation. A .5 CFM
compressor is very small and cheap (<$30 surplus) and produces 860 cubic
inches in a minute). The nice thing is that you can use cheap 1/8"
polyethylene tubing to actuate the cylinders. Cheaper than fiber optics.
Bimba and Clippard are big brands in this area. The fittings can eat you
alive, cost wise, though, so a bit of planning and scrounging can save a
bunch. C&H Sales isn't the cheapest outfit, but they DO have a catalog at
least. Check the prices against new, first, particularly for fittings.
(why get used fittings for $.50, when you can get new ones for $.75).
For your fiber optic digital link, you might want to consider using one of
the many parallel to serial to parallel chip sets (from TI for instance)
that are designed to send a bunch of parallel bits to somewhere else. The
chip is essentially an autoloading UART. The fiber receivers and
transmitters for the 1000 micron plastic fiber are cheap, but not that
cheap, especially when you start wanting to send 10 or 15 lines. Another
alternative is a PIC microprocessor or Basic Stamp at each end. A couple
of hours programming, and you could have a nice remote telemetry and
control mechanism. A more costly (but still <$100) approach would be to
use those parallel printer to serial interface boxes.
Finally, I built a HV isolated system using fiber optics and surplus PC's
with some cheap fiber optic network cards. I got lucky and found some
DC/DC converters to make a 12V to PC power supply. Timing wasn't all that
hot (because I didn't want to screw with network drivers, etc., so I just
wrote a DOS program that looked for a file on the "server")
>
>
> Cheers,
>