Three Way Lamp Logic rev
2-26-05
One of the earliest circuits I put together was a lamp switch
from an old 1930's era floor lamp, two flashlight bulbs, and a battery.
These
little switches operated by rotating the knob and had three
wires on
them. They are still available today in hardware stores. On the
original
lamp the switch controlled 3 light bulbs. ( See 2-Bulbs
Page for that circuit - same switch )
Sample of switch
Most 3 way switches at that time had 3 wires ... Back, Blue, Red
This is what the head units of the lamps typically looked
like
The switch had four positions. Assuming the floor lamp used Qty. 3 - 60 Watt bulbs:
Position 1 |
all bulbs off |
0 watts |
no wires connected |
Position 2 |
Bulb #1 on |
60 watts |
black to red |
Position 3 |
Bulbs #2 + #3 on |
120 watts |
black to blue |
Position 4 |
Bulbs #1 + #2 + #3 on |
180 watts |
black to red & blue |
I wonder how many people back in the 1930's realized they were
operating a binary switch when they turned on their floor lamp at
night? :-)
Now change to 1.5v. flashlight bulbs, add a battery, and remove Bulb
#3 from the above circuit and you get a two bit binary counter:
Position 1 |
all bulbs off |
Binary 0 0 |
Position 2 |
Bulb #1 on |
Binary 0 1 |
Position 3 |
Bulb #2 on |
Binary 1
0 |
Position 4 |
Bulbs #1 + #2 on |
Binary 1
1 |
Of course as an eight year old I had no idea that this was a Binary
Counter but was fascinated by the pattern of the two bulbs going on and
off. By the time I was twelve I had learned what Binary was and used 3 of these
circuits to build a 6 bit binary counter.

So lets use the above circuit to count. Turn all 3 switches to
positions where all bulbs are off. Using Switch 1 as the count up incremental,
turn it one position to the right. Now Bulb 1 is on and bulbs 2,3,4,5,6
are all off. Rotate Switch 1 another turn to the right and Bulb 2 is on
and 1,3,4,5,6 are all off. Turn Switch 1 to the right again and Bulbs
1,2 are on with Bulbs 3,4,5,6 all off. (See Chart Below)
Now here is where it gets tricky. On the next count up, turn Switch 1
to the right, and all the bulbs are off. so the count went back to 0. So
you have to remember to carry one and rotate Switch 2 one turn to the
right whenever Bulbs 1,2 go from both on to both off.. So after turning
Switch 2 to the right Bulb 3 is on and Bulbs 1,2,4,5,6 are all off. You
have to do the carry each time thereafter when Bulbs 1and 2 go from both
on to both off. The same is true when both Bulbs 3 and 4 go from both on
to both off then the carry is made by rotating Switch 3 one turn to the
right.
(Below is sample of Chart -->> for
complete chart (Click Here)
I actually made this circuit automatic by attaching a round 1/8"
thick Masonite disk an inch or two in diameter to each of the 3 switches. A notch and pin system actuated
switches 2 & 3 so I only had to rotate Switch 1 to incrementally
count up. I installed a small clock motor that rotated Switch 1 and it
would endlessly count up through 64. It was supposed to be the
controller for my "Computer" that was to use Punch
Paper Tape to do the math calculations. OK, OK, yes I know, even if I
had gotten it all working it still would not have been a computer. But
give me a little credit, I did create a computer "Clock
Circuit" without even knowing it.
So you must be at least
mildly curious how a 12 year old could come up with this circuit. I had
always had the ability to memorize things. One day while being bored in
school (I often was), I was doodling on some math papers and realized
the binary math we were studying was exactly the same as the pattern of
lights I got from that early 3-way lamp switch circuit I had put together.
One on, the other on, both on, both off... or 01, 10, 11, 00. They were
exactly the same. So when I got home from school I put the circuit
together again and when I tested it found it was in fact exactly the
same. Later I bought two more switches and added the additional bulbs
and came up with the triple circuit version above. After that I
automated it with the Masonite disks and a little clock motor. It was
actually quite a revelation to me at the time and I frequently through
the years have gone back to the memory of creating that first Binary
Counter.
If I ever have time, someday I would like to re-create the
original automated device I built from Masonite Disks. I can't right now
remember how the notches in the disks were made or how big the pins that
actuated them were. But with a little trial and error I can probably
figure it out again.
Many years later I built the equivalent of this
circuit from IC's (Integrated Circuits) to use as a sequencer for a test
jig I built for Mason Electric (Glendale, Cal.) where I was employed as an Engineering
Technician. The jig was used to assemble EFSO's (Engine Fire Shut Off
Switches) for DeHavilland Aircraft. It was much more complicated but actually had LED's to show
the output of the binary count. The LED's light sequence was exactly the
same as my original 3-way switch and flashlight bulb design. Instead of
being turned by a Clock Motor as in my original design, the count was
triggered by a NE-555 oscillator circuit.
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by Juddley