In the process of testing amplifiers in my living room system, and just plain listening I find that no sooner have I sat down in the couch and the cat has made herself comfortable in my lap I have to get up and adjust the volume control on the Analog preamp across the room in the rack. My full range Ultor-X loudspeakers are very directional and it is impossible to guess the correct loudnesss setting of the volume control unless you are in the listening position. SO.....
I have finally bit the bullet as they say and acted upon a long time idea to employ a pair of selsyn motors, one to turn the volume control knob on the preamp, and the other in a control box on the coffee table to act as the new volume control knob.
For those of you not familiar with selsyn motors, they are instrumentation servo motors that can either act as a positional and torque transmitter or receiver. They have a 3-phase stator and a single phase armature and all you need to do to use them is apply 120 VAC, 60 Hz to the armatures wired in parallel and bridge wires between the three stator connections between the units. Note that some selsyns were made to operate at 400 Hz and these are not as easily employed by the DIY'er. When connected this way the turning of either shaft makes the other motor shaft follow the motion exactly. If the remote load is a step detented volume control the friction feel of the detents is actually conveyed through the system to the control selsyn shaft knob! These are way cool devices, and simple, no electronics.
The pair of Navy surplus selsyns I used are quite small and only have enough torque to turn a volume pot or tuner knob. They would not have enough power to crank a step by step vintage TV channel changer knob for example, although larger selsyn motors are available that could.
I have manufactured a 3 jaw claw, I'm likening it to the Terminator arm
which has a size range adjustment to accommodate various knob sizes making the remote control truly universal in application. Soft neoprene rubber tips grab the knob without scratching or damage. I have a picture here showing the guts of the robot head that will sit on a height adjustable microphone stand at the audio device to be controlled. This stuff fits inside a lathe machined hard maple case finished in piano black that is supported in a oilded black walnut yoke which is spring mounted to the mic stand.
For the control console I have manufactured a very substantial oiled black walnut pyramidical box with a single large knob on top with a polished brass panel. A 20 foot length of Belden 6 conductor shielded rubber cable runs from the control console to the robot head. An IEC power connector on the head accepts the power cord and two lamps indicate power on/off and torque. The Belden control cable is removable at the head with a Canon connector. On-off togle switch and line fuse are also located on the robot head.
I plan to power the remote control from the switched AC receptacle on the preamp that it is being used to control.
This invention is not quite in service yet as I am waiting for the finish on the robot head to harden before I can do final assembly.
This project represents an entire long week of shop time and I'm glad that is now over with. I am looking forward to the rest that the existence of this device will allow me in my senior years.
Universal remote control using WWII bomber technology
Cool!
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