Technical Info about the Senster

The Electronic System

I have an almost complete collection of original schematics of the Senster's electronic circuits. I have scanned some of them and will post them here when I have managed to work out a sensible way of displaying them. In the meantime, I will describe how I think the Senster's output electronics worked (disclaimer - this is my own opinion, don't take it as gospel).
Main schematic (click for full size image 275K)

Input Circuts

I have not analysed these yet. They basically took the inputs from: the two pairs of microphones and the pair of radar units mounted on the head, and the potentiometers mounted on the structure which measured the positions of each of the joints.

Output Circuits

There were 8 hydraulic actuators in total (including the two in the head) and they were controlled in pairs, so, essentially there is one standard circuit repeated four times (see circuit above). This description is for one such circuit.

The output from the computer was latched as 16 data bits (the input could also be set via manual switches, presumably for testing). All 16 bits were also taken to light bulbs for debugging (see below). The 16 bits were split into two sets of 5 bits which represented the next required position for an actuator, thus each joint had 32 (2^5) discrete positions (very low resolution by today's standards). Each set of 5 bits went to a digital to analogue converter. The analogue value next went into a circuit called the predictor. This was a complicated arrangement of op-amps, which basically smoothed the transition from one position to another, following a spline-like curve. It is one of the critical parts of the Senster's control system because it made the movement look very natural. The output of the predictor went to a servo amplifier, which controlled the hydraulic valve for the actuator.

I wasn't quite truthful when I said that there were four identical circuits - two of them are slightly different. As well as having the same circuit as above, each has an extra function. 3 spare bits from the latch go to another digital to analogue converter and the output goes to a circuit called the acceleration splitter. Unfortunately, I don't have the schematic for this particular circuit. The outputs of the acceleration splitter go to the predictor units in the other circuits. It basically set the time by which all the joints had to reach the next set positions, so that they all arrived at the same time, to make the movement look natural. There were two separate acceleration splitters: one for the hydraulics which moved the microphones and another for the joints in the rest of the structure.

The Predictor circuit (click on it for a full sized image 72K)

The original designer of this circuit, Mr. Kessel of Philips, recently contacted me with a detailed description of this circuit, which I will eventually put here.

Lamp Drivers

There were four input registers and four output registers (all 16 bit) taken to indicator lights shown in the photo at the top of the Computer System (9 rows of 16 lights).

  1. Input register '3: radar input and register read-in by hand (the schematics I have do not include any of the radar system)
  2. Input register '6: Acoustic system. Handles the signals from the two pairs of microphones (bit assignments not clear, but may be: bits 1,2: acoustic input from vertical pair of microphones, bits 3,4: acoustic input from horizontal pair of microphones, bits 5-9: unkown, bits 10-11: function unkown, bits 12-16: from A/D converter after full wave rectifier from one microphone channel - must have been used to get volume of noise - the Senster would shy away if the noise got too high).
  3. Input register '11: vertical and horizontal positions of microphone and hydraulic jack 2 from potentiometers mounted on the structure (bit assignments not clear from schematic, 5 bits each channel)
  4. Input register '12: potentiometer inputs (bit assignment not clear from schematic)
  5. (unknown)
  6. Output register '21: Drives horizontal and vertical movement of microphones (bits 1-3: to acceleration splitter, bits 4-6 not used, bits 7-11 to D/A to control vertical hydraulic jack position, bits 12-16 to D/A to control horizontal hydraulic jack position)
  7. Output register '22: Drives hydraulic jacks 1 and 2 (bits 1,2: unknown, bits 3-5: to acceleration splitter, bit 6: unkown, bit 7-11 to D/A to control hydraulic jack 1, bits 12-16: to D/A to control hydraulic jack 2)
  8. Output register '60: Drives hydraulic jacks 3 and 4 (bits 1-6: unkown, bits 7-11: to D/A to control hydraulic jack 3, bits 12-16: to D/A to control hydraulic jack 4)
  9. Output register '30: Drives hydraulic jacks 5 and 6 (bits 1-6: unkown, bits 7-11: to D/A to control hydraulic jack 5, bits 12-16: to D/A to control hydraulic jack 6)

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