Seleno, The Electric Dog
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[edit] Introduction
Seleno, the Electric Dog was designed by John Hays Hammond Jr., and Benjamin Franklin Miessner and constructed by the latter to prove and demonstrate an orientation mechanism that was the basis of self directed weapon systems like the dirigible torpedo.
[edit] How the Circuit Works
The chassis has two front wheels, one of which is powered by the drive motor. A third wheel connected to a solenoid controlled "rudder" is used to steer the bot. The control circuit uses two selenium photocells, four relays, five separate batteries, a drive motor and two solenoids.
The two selenium photocells are probably used in the photoconductive mode much like LDRs. Each photocell is in series with a battery and a sensitive relay. When the light level on either of the cells is high enough, the corresponding relay pulls in and the normally open relay contact closes. This contact connects the larger "pony relay" coil to a battery and changes over two pair of contacts, one normally open (NO) pair, and one normally closed (NC) pair. The isolation between these pony relay contacts is not obvious but the schematic shows a dark line of insulating material that connects the two contact arms mechanically but that separates them electrically.
When either pony relay NO contact closes, it connects the drive motor to the main battery and the bot moves forward. The corresponding NC contact opens and isolates the solenoid on that side of the bot.
If only one photocell is active, then the other solenoid is powered via the closed NC contact of the other pony relay on the dark side of the bot. This causes the rudder to swing towards the light and the bot turns.
When both photocells and both pony relays are active then both NO contacts are open and both solenoids are isolated. Drag will cause the rudder to straighten out and the bot moves straight forward towards the light.
When the light on both photocells is low the bot stops. The photo showing the robot demo indicates a flashlight is used as a "photonic leash" for this early "robopooch".
In case anyone is interested in duplicating seleno, it is still possible to get selenium photocells, which are about 2% efficient and put out 0.4V at a few ma.
[edit] Pictures and Schematic of Seleno, the Electric Dog
[edit] Related Patents
SYSTEM OF RADIODIRECTIVE CONTROL - Patent #1467154
SYSTEM OF RADIODIRECTIVE CONTROL - Patent #1387850
[edit] External References
Radiodynamics, By Benjamin Franklin Miessner (PDF file) - Chapter XXIV {24} (which begins on page 189 and continues through page 199) contains a description of the "orientation mechanism" that is the heart of Seleno, the Electric Dog. The entire book can be downloaded as a PDF file.
David Buckley's, History Making Robots: Electric Dog - 1912
Cordeschi, R., The Discovery of the Artificial: Behavior, Mind and Machines Before and Beyond Cybernetics, Kluwer, Dordrecht, 2002, Chap. 1.
