March 1958 Popular Electronics
of Contents]People old and young enjoy waxing nostalgic about and learning some of the history of early electronics.
Popular Electronics was published from October 1954 through April 1985. All copyrights are hereby acknowledged.
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tubes were used for numeric - and sometimes alpha - displays back in
the days before LEDs and LCDs. They were more light bulbs than tubes,
but were encapsulated in evacuated glass shells like vacuum tubes and
had round, multi-pin bases like tubes. Separate filaments were provided
for each character. There were two basic varieties: characters that
displayed through the top of the tube, and characters that displayed
through the side of the tube. Nixie tubes are popular with builders
of retro equipment, and a lot of products are available for sale that
incorporate them; e.g., clocks,
, calendars, games, and much more. Electronic test equipment
and medical instruments were big users of Nixie tubes. I remember a
couple of the signal generators we used on the MPN-14 radar has Nixie
tube displays. Supposedly the name "Nixie" derived from "NIX I", an
abbreviation of "Numeric Indicator eXperimental No. 1," as designated
by the Burroughs
sometime around 1955. The
HB-106 Nixie tubes
for this project can be purchased on eBay.
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Play Games with Nixie Tubes
by Harvey Pollack
Nixie Gamester installed in its grey aluminum cabinet. Activating
button is in the center of the front panel.
Completed motor and wiper assembly.
Large gear with wiper wire in place. Small pulley and shaft are
Commutators after etching. The copper is entirely removed between
segments. leaving ten 36° wedges of copper. Note bare 1/2" strip
You can throw away the whirling number wheels, the tumbling golf balls
in the squirrel cage, and the gallopin' dominoes! It's, much more fun
to play Bingo, Roulette, Put-and-Take, Quizzo, boy-girl parlor games,
and a host of other games - electronically! By merely pressing a button,
you can display a pair of randomly selected numbers for all kinds of
numerical games in shining neon lights visible up to 20 feet away.
This simple form of digital presentation is made possible by
a modern little electron tube called a "Nixie." Although specifically
designed for computer panel read-out systems, the Nixie can be used
in any device where any digit from 0 to 9 is to be displayed to a group
By using two Nixies, a pair of tiny electric motors,
two printed-circuit commutator boards, and a suitable power source,
you can make up a game machine that will put new life in the dullest
party, spark community and church affairs, and even help the youngsters
in the house practice their arithmetic; All you do is push the button.
Whirling motors flash the Nixie numbers inside the tubes too fast for
the eye to follow. When the button is released, the motors come to rest,
leaving two glowing numbers for everyone to see. CONSTRUCTION
Numerical selection is accomplished by a wiper installed on
the motor gear. As the armature rotates, the wiper arm contacts successively
ten copper segments separated by etched grooves on a printed-circuit
board which serves as a commutator. Prepare the Commutators.
Using a fine-toothed hacksaw blade, cut a single piece of 2" x 4 1/2"
XXXP copper laminate board exactly in half. Make up a little cardboard
wedge having an angle of exactly 36° with the help of a protractor.
Using the wedge as a template, divide the laminate into ten equal segments
of 36° each, and score the copper lightly with a sharp-pointed tool
to mark the divisions.
Lay strips of 1/32" resist tape over
the score lines and press their adhesive sides firmly down on the copper.
Carefully paint the liquid resist over the entire board, leaving about
1/2" of copper exposed along the bottom as shown in photo above. Repeat
this procedure with the second copper plate and set both pieces aside
to dry for about a half hour. PARTS LIST
- BRI-Mg.-CuS bridge rectifier, 5.2-volt output, 1.3 amp. (Mallory
- Cla/Clb-20-20-μfd., 150-volt dual electrolytic capacitor, not
common negative (CornellDubilier EDL 2215SS) or two 20-μfd. units
- M1, M2-3-6 volt d.c, motor (Mighty Midget, Lafayette F253)
- NE1, NE2-Type 6844 neon Nixie numerical indicator tube (HB-106-Burroughs
Corp., Electronic Tube Div., Plainfield, N. J. $10 each)
- PC1, PC2-Printed-circuit etched commutator - one 2" x 4 1/2"
section of copper laminate XXXP cut in two equal parts (Lafayette
- R1, R2-100,000-ohm, 1/2-watt resistor
- SO1, S02-13-pin Nixie socket (HSK-112-Burroughs Corp., $1.50
- S1-S.p.s.t. push-button switch
- SR1, SR2-130-volt, 65-ma. selenium rectifier
- T1-Power transformer, pri. 117 volts, sec. 125 volts @ 15 ma,
6.3 volts @ 0.6 amp. (Stancor PS-8415)
- 1 - 7 3/8" x 6 3/4" perforated Bakelite sheet,
cut down to 5 1/4" x 5 1/4" (Lafayette MS-306)
- 2 - 2" x 2 1/4" x 3/4" wood blocks
- 2 - 1/4" x 1" x 2" pieces of plywood
- 1 - 8" x 6" x 3 1/2" aluminum case (Bud CU 2109)
- 1 - 3-oz. bottle of liquid etchant (Lafayette PE-3)
- 1 - Bottle of liquid resist (Lafayette PRL)
- 1 - 1/32"-wide roll of resist tape (Lafayette PRT-1
- Misc. a.c. line cord and plug, solder, wire, etc.
After this interval, remove the resist tape and immerse the plates in
the etchant bath, leaving them in long enough to remove all the copper
in the clear grooves between segments and the strip along the bottom.
When the etching is complete, rinse the boards in clear running water
and then brush a little paint remover over them. You'll find that the
liquid resist is softened enough in a minute or two so that it can be
wiped off with a cloth.
The "Gamester" circuit incorporates a voltage
doubler circuit to permit use of an inexpensive power transformer (TI)
as a high voltage supply. The transformer's filament winding powers
the miniature motors.
wash the plates in soap and water and dry them thoroughly. Drill a very
fine hole in each segment as close to the outer edge of the wedge as
you can work. Tinned hookup wire will be passed through each of the
holes for wiring to the Nixie sockets as described later.
HOW IT WORKS
Nixies. The Nixie 6844 is
a gas-filled, cold-cathode numerical indicator tube having a common
anode. Each of the numbers is a separate cathode which glows when
a potential is applied between it and the common anode. Each tube
contains a suppressor screen to minimize darkening of the viewing
dome so that long life may be anticipated.
Anode Power Supply.
A voltage doubler arrangement is utilized to obtain approximately
250 volts for operating the Nixies. Transformer T1has a double purpose:
(1) it isolates the entire assembly from the a.c. line, thereby
eliminating the possibility of electrical shock from the metal case
to other grounded conductors; (2) it provides about six volts of
a.c. which is rectified and used as motor drive power. Series dropping
resistors R1 and R2 limit the current through the Nixies to a safe
value. Before applying power, be sure that these resistors are in
the circuit and that voltage cannot reach the tubes any other way
but through R1 and R2.
Motor-Drive Supply. Six volts a.c,
is taken from the low-voltage secondary of the transformer and rectified
in the Mg-CuS bridge rectifier (BR1). This provides about four volts
of d.c., which is more than adequate to run the motors within their
The motor mounting sketch above gives details of installation technique.
NIXIE" GAMES YOU CAN PLAY
This game is played in
the usual manner. The players are issued numbered cards on which
the numbers are crossed out as the Nixie Gamester reads them out.
When all the numbers in any horizontal, vertical, or diagonal row
are crossed out, the player calls out "Bingo" and is a winner. Unlike
other readout methods, the Nixie numerals are clearly visible to
all players. Roulette.
A good system
to use for this game is the addition of numerals. For instance,
if the Nixies show a 3 and a 6, then the winning number is 9. For
double zero (00) or a double blankout, all points go to the bank.
A large piece of oaktag divided into 18 squares makes a good roulette
etc. Any game played with dice or a spinning pointer is a natural
for the Nixie Gamester. Make up your own house rules as to whether
the digits are added or subtracted. Put-and-Take.
For those who remember this game, the advantage of the Nixie Gamester
over the old flat-sided top will be apparent immediately. Call the
left Nixie digit "put" and the right one "take." The game is played
with chips, marbles, picture cards, etc. A pot is started by each
player contributing ten items. Then each player takes his turn "putting"
and "taking" as the numerals dictate. A double zero or double blankout
means "take all." Party Games.
Nixie Gamester provides a new twist on the ancient games of "Spin
the Bottle" and "Post Office." If there are ten couples at the party,
each girl and boy are assigned a number (left-hand Nixie for the
girls, right for the boys). A tantalizing spin of the motors, and
a girl and boy are paired at random to go out and look at the stars.
Should there be fewer than ten couples, certain lucky ones may be
assigned two numbers, thus doubling their opportunities to have
a chance at some social astronomy. In this game, a single or double
blankout has no significance. Quizzo.
The group is divided into two teams. As the Nixie Gamester calls
out the digits, the "left" team and "right" team must answer questions
numbered according to the readout. Other variations of this idea
are easy to dream up so that the party can be kept under full steam.
Loosen the setscrew on the large gear
and slip it off its shaft. This will free the pulley and pulley shaft,
which should then be removed altogether. While you have the large gear
handy, drill and tap a hole to take a 4-36 brass screw about 1/4" away
from the toothed circumference. The wiper arm is made of thin wire (about
#28) folded into a hairpin shape at the end and looped under the screw
head. Spring wire is best for this, and phosphor-bronze or steel will
do fine. The model illustrated has Nichrome, which happened to be available.
Mount the motor on the two pieces of wood which serve as base
blocks. Note that the motor is screwed to a small piece of plywood which
raises it enough to permit the gear to spin clear of the larger block.
Using short wood screws, fasten the commutator board to the side of
the base block so that the clear center of the segments is directly
opposite the motor shaft. Thus, as the wiper spins, it will rotate in
a circle having the center of the commutator as its center of rotation.
Parts placement for the underside
of the Gamester chassis
is shown above.
of the same spring wire serves as the contactor which rides on the back
of the gear as the motor turns. It is held in place by another wood
screw as shown and its pressure is adjusted so that it doesn't slow
down the motor. It's a good idea, too, to connect the 100,000-ohm resistor
at this time, holding it in place with a solder lug at each end. The
resistors act as protective devices tor the Nixies and must not be omitted.
Power Supply Assembly.
The Nixie Gamester
is a.c.-operated. One low-cost transformer supplies the anode power
for the numerals and the low voltage for the motors. A full-wave voltage
doubler consisting of SR1, SR2, and the dual capacitor C1a/C1b comprise
the anode power supply, while an inexpensive magnesium-copper sulfide
bridge rectifier without filtering takes care of the motor drive.
All parts, except the push button and the Nixie sockets,
are mounted on a sheet of perforated Bakelite. Wiring is completed outside
the case and the finished assembly secured to the case by a long machine
screw and brass spacer in each corner. Wiring
After you punch two 1" holes where the Nixies
are to go, fasten the little glow tubes and their sockets in place with
a 1 1/4" machine screw through each socket-flange hole. (The diameter
of the Nixie is 1.080" so it cannot slip through the hole). In this
way, only the face of each tube will be visible through the hole and
the display will be much more effective.
Be sure to mount
the sockets with pins 1 and 8 in a vertical line, pin 8 nearest the
top of the panel. Pass a very short length (about 1/4") of the stripped
end of hookup wire through each of the small holes in the commutator
segments and solder to the copper faces carefully. Don't use too much
heat. Trim the ends of the wire off after the solder has cooled.
The actual wiring should be done in a random fashion. Don't connect
segment 1 to the socket lug for display number 1, segment 2 for number
2, etc. The numbers should follow each other haphazardly so that it
will be impossible to force the motors to stop at any given place. Note
that no connection is made to either pin 1 or pin 8 on the socket and
that the common anode connection is pin 2. TESTING
To be sure that your Gamester will play a fair game, run
through the following tests:
(1) Wiper contact. With power
on, slowly rotate each gear by hand and observe the corresponding Nixie.
Only one number should glow for each contact of the wiper on a given
segment of the copper. If one or more numbers do not appear, bend the
wiper so that it makes firmer contact. If more than one number is displayed
for any single contact, it means that there is a bridge of copper between
segments that was not etched away. A bridge like this can be picked
off with a sharp point and the insulating groove cleared.
(2) Contactor. While each gear is manually rotated, observe the rear
contactor to be certain that it maintains electrical touch with the
rear face of the gear throughout the entire rotation.
(3) Motor spin. Motors should start instantly when the power is applied
and should spin at high speed. If they don't do this, reduce wiper and
contactor pressure by bending the wires back very slightly.
(4) Blankouts. The small contact surface of the wiper permits it to
come to rest occasionally between segments. When this happens, the corresponding
Nixie will not glow. Chances of both wipers blanking out on the same
spin are very remote. You should, however, run through a number of spins
watching for this kind of thing. If it happens too often, the wiper
is catching on the edge of one of the segments as a result of excessive
wiper pressure. A single blankout provides a one-digit readout and is
desirable for most games in which the numerical sequence wanted runs
from zero to 99 with no numbers missing.