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110/220V safety questions and a hamfest find
I have a pair of 30A contactors that I want to use in my 220V control
cabinet. The problem is that the power to the cabinet is going to be
from a 3-wire 220V outlet (2 hot and a ground), and the relay coils are
energized by 110V. I have been told that I should have a 4-wire circuit
if I wanted to use a single side of the 220V line to get 110V at any
appreciable current, but am I going to have problems if I just wire the
relays up so I use one hot side and the ground of the 220V to get the 110V
needed to energize the coils, or should I do something else. I see my
options as: 1. just use the relays, 2. buy a small 220V to 110V
transformer, 3. rewire the outlet to use a four-wire circuit, or 4. get
some new relays that have low voltage coils and start all over again.
Obviously, time and money are considerations, but safety is my number one
concern (my wife and kids would be mighty upset if I "disrupted" myself
one day).
Now for something to look out for at hamfests or book sales...
I bought a series of small paperback books at a hamfest yesterday that
look really neat, particularly for those neophytes out there who are
interested in learning more about vacuum tube coils and the like (like
me). The series is called "Electronic Circuit Action Series" and was
published by "Howard W. Sams and Co." back in the 60's. The books use
lots of color-coded diagrams and "non-mathematical, logical explanations
to discuss and explain the electron currents and their significance to the
overall circuit operation" for all sorts of things. The one book that
sold me was the one on oscillator circuits, which explains crystal,
hartley, colpitts, tuned-plate tuned-grid, electron coupled, phase shift,
and blocking oscillators, in addition to multivibrators and thyratron
sawtooth generators.
Other books in the series include "Detector and Rectifier Circuits",
"Transistor Circuits", "Amplifier Circuits", "TV Sync and Deflection
Circuits", and "TV Video and Sound Circuits".
This whole series of books (in it's original cardboard "case") set me back
the prodigious sum of $1 - yet another example of how if you're not going
to hamfests, you're really missing out on some Good Stuff.
Other hamfest purchases included five .1uF, 25kV Pyranol caps from GE
(anybody have a guess as to what these were originally used for (PFC,
etc...) and whether they might be paper, mylar, plastic, or ???), a bunch
of 1mW HeNe laser scanners, a box of 6 megohm HV resistors, a large spool
of 16 gauge insulated wire (not magnet wire), an xray control box (the
xray transformer is in Annapolis, I might go get it one of these days),
and some other miscellaneous junque.
Steve Roys.
(P.S. to R. Hull - I saw Dave S and Alex, but missed you at Gaithersburg.
Did you find anything interesting that I missed <grin>?).