The Electrical experimenter

May, 1917 THE ELECTRICAL EXPERIMENTER 39
UNIQUE INDICATOR SYSTEM
WHICH ANNOUNCES THE
ICEMAN AND GROCER.
A "stcp-savt-r" that's just what this device
is, for, when constructed, it will save
Mother or the housekeeper many a fruit-
Cfiming t/othing Jl/^omo^ic iif re/gffsf
The Women Folks INeed Not Run to the
Door for the Iceman and Grocer, When This
Apparatus Is Installed. T-he Tradesman
Turns the Switch Lever to the Proper
Number; the Kitchen Indicator Shows Who
Is Calling and the Cook Pushes the Button
Marked "Coming" or That Labeled "Nothing
To-day."
less trip to the door in response to the
ever-ringinR bell, because it enables her to
know xvho is calUng, whether the milkman,
baker, etc.. and signal to them if their goods
are needed or not— all witliout requiring any
more effort on her part than merely pushing
a button.
The tirst thing required is a wooden
frame or case, similar to that shown in
Figs. 1 and 2. Inside of the same are arranged
the indicator magnets and also the
magnets controlling the automatic switch
release (.'\ in Fig. 1). This latter may be
simply the armature and tapper rod of an
ordinary battery bell, bent as illustrated in
order "to allow the extremity to act as a
check pawl on the four-cam wheel, which
is centered on a shaft manipulated by the
switch handle. It will be seen that this
prevents the switch, when once set at the
point desired, from falling back to its
original position after jiressure has been
removed. The cam wheel, if not procurable
from old clock works, can be easily turned
out of wood by a jig saw or of brass in a
lathe. By the same methods any other
parts of tliis device may be constructed
when lack of simpler means prevents
otherwise. The carbon strip { another f ortn
of resistance may be used if tliis is not
handy) can be cut out from tlie carbon
electrode of an old battery cell and should
be placed on the inside of the box directlv
over the groove, by means of which the
switch makes contact with it. The partition
B, in Fig. 1. should have two holes for
the insertion of the core ends of the electromagnets
M' and M", which, on lieing actuated,
raise up one or the other gravity indicators.
Fig. 2. These latter are merely
short lengths of steel wire bent as shown,
.so as to allow them freedom of motion up-
wards. .\s can be seen one is lor the purpose
of signaling to the waiting tradesman
that the housekeeper 1.? comincj, while the
other performs an opposite function, as the
case may be.
I'ig. 3 sliows the indicator panel proper,
which includes simply a low resistance galvanometer
or ammeter, tw-o push buttons,
and a bell. If the reader cannot make such
an instruinent, he will find an admirable
one described in the August issue of the
"E. E." Of course, it is understood that
the scale card is not marked off in amperes
but instead into four divisions, numbered
froin one to four—each division representing
the title of such tradesmen as call inost
frequently. The front duor device is also
marked with corresponding numbers (see
Fig. 2) and a printed card like that shown
should be placed on it. It will be .neces-
sary to experiment for a while in order to
have these numbers correspond ; that is to
say, when the switch is turned to Crocer,
which is Xo. 1, the resistance traversed
must be such as to move the needle on the
indicator also to Xo. 1. Full electrical
connections are shown in Fig. 4.
Assuming that everything has been completed,
let us suppose the Milkman comes
and turns the switch to Xo. 4. Such action
allows more or less current to flow with
the result that, at the satnc time the bell is
rung, the indicator needle is turned also to
Xo. 4 and all tlie lady of the house need
do is to glance at the same to ascertain that
fact. If milk is not wanted, slie has only
to push the button designated Xolhing
To-day. The current set up actuates tlie
electro-magnet controlling the lower signal
and the latter is raised upwards, thus acquainting
the tradesman v/ith the fact that
his goods are not required. .Xt the same
time, it will be noticed by following out
the electrical diagram carefully, that the
armature of the switch return mechanism is
attracted upwards, thereby releasing the
check pawl and allowing the switch (which
has a coil spring exerting tension
to resume its original position.
upon it)
The device
is then ready for the next caller.
Contributed by JOHX T. DWYER.
[Editor's Note — IVc would sttggest the use
of a low resistance relay in place of the
vibrating bell, the local circuit of the relay
being connected to a bell and battery. This
permits the action of the IXDICATOR
system to be much more even and accurate.
This change in the layout is shozs.-n in supplemental
diagram Fig. 4.]
AN EXPERIMENTAL SPARK COIL.
I have just completed a small "spark
coil." of my own design, wliich embodies
a special feature of regulation. The full
strength of this coil, when the primary
is all the way within the secondary, is JS-
6 llll/ers^
paper "L=J.< endpiece
,I>M futie
i|»^
4?
T
Ifilxrenc
' Iff'
p/ece
'ricr/uie
'see
This Experimental Spark Coll Has a Removable
Primary Coll and Core. So That All
Sorts of Experiments Can Be Tried With It.
inch heavy spark, and »he miniinum
strength is "0," when the primary is drawn
all the way out.
The drawing explains all details. The
primary is made separate and complete
from the secondary with binding posts at-
@
HOOK-UP FOR STARTING UP TWO
MOTORS WITH ONE RHEOSTAT.
Kmergency niakmg necessary the use of
limited equipment for connecting up two
HJ horsepower direct current shunt field
motors, with one starting box, I made use
of the hook-up herewith reproduced to start
up each machine and connect it on the main
line.
The first step was to provide ample pro-
TPDT=Tr/pk pok ciouble /hrotv smfch
fl-r/ieostaf, /• JO omp. fuse, f'-ioo omp.fuse
S- shunf //e/d SS • j/torZ/og s>v/fc/7
DPST doud/epo/e s/ng/e r,')roir siv/fch ©
Useful Kink Utilizing One Starting Rheostat
for Starting Up Two Motors. After Each
Motor Has Been Accelerated in Turn, the
Proper Switch Is Closed. Throwing It Directly
on the Line.
tection against overloads and failure of
power, which was overcome by properly
fusing as per diagram.
With T.P.D.T. switch in neutral or
straight out position, connections to the motor
are broken. Throw main switch in,
then T.P.D.T. to either side to start respective
motor. Bring rheostat lever up
slowly to no-voltage release and lock : next
throw in respective shorting switch, when
handle on starter should drop, thus connecting
one motor on the line.
To start the second motor, throw T.P.-
D.T. switch to opposite side and start as
before, after which close the proper shorting
switch. Both motors now on the main
supply line; pull T.P.D.T. switch to neutral
position.
I have had entire success in running both
motors by this method for a period of
30 days, depending exclusively on the 30
ampere fuses for overloads and manually
opening the circuits in case of generator
shut-down or cutting off of the pow-er.
Contributed by RAY J. BUTTON.
tached. The secondary is W(iund upon a
spool, which also has binding posts attache
.
The primary unit comprises an iron
wire core 6 inches long ' by S inch diameter.
The primary winding is of two layers
Xo. 18 D.C.C. magnet wire. This is
covered w-ith several layers of waxed
paper. The primary terminals are mounted
on a fiber disc. 2 inches diameter, as
shown. The completed primary is soaked
in inolten paraffin wax. The secondary
coil consists of I'i lbs. Xo. 34 S.C.C. magnet
wire, wound in layers onto a wooden
or fiber spool, measuring 4 indies in length.
The starting or inner lead of the secondary
should be well insulated by passing
thru a glass or rubber tube outside the
spool or else by passing it thru a hole
drilled radially down thru the spool cheek.
Ibis one being made M-inch thick or more
for the purpose.
Contributed by CHAS. S. PORTER.