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3 Way Lamp Logic

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.


= Bulb Off

= Bulb On


(Below is sample of Chart -->> for complete chart (Click Here)

  Bulb 6 - Bulb 5 Bulb 4 - Bulb 3 Bulb 2 - Bulb1   Switch 3
Switch 2
 Switch 1
  1 1 1
  1 1 2
  1 1 3
  1 1 4
  1 2 1
  1 2 2
   For Complete Chart  (Click Here)
  1 4 1
  1 4 2
  1 4 3
  1 4 4
  2 1 1
  2 1 2
  For Complete Chart  (Click Here)
  2 4 4
  3 1 1
  3 1 2
 For Complete Chart  (Click Here)

  4 4 2
  4 4 3
  4 4 4
  1 1 1
 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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Watch for my future page on clothespin memory :-)



Created by Juddley