March 1958 Popular Electronics
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. See all articles from
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
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 not used.
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 of viewers.
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
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.
- BRI-Mg.-CuS bridge rectifier, 5.2-volt output, 1.3 amp.
- Cla/Clb-20-20-μfd., 150-volt dual electrolytic capacitor,
not common negative (CornellDubilier EDL 2215SS) or two 20-μfd.
- 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
- 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.
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.
Finally, 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
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.
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 ratings.
The motor mounting sketch above gives details of installation
NIXIE" GAMES YOU CAN PLAY Bingo.
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.
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 board.
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."
The 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.
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.
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
Parts placement for the
underside of the Gamester chassis
is shown above.
Another piece 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
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.
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.
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.