h2	MicroGrasp Robotic Arm by Powertran Cybernetics


p	from Will's auction:

p	This is an all-metal 1982 Powertran Cybernetic ‘MicroGrasp’ micro robotic arm controllable by the Sinclair ZX81. Included is the interface card, and manual containing construction notes with sample programs to get the robot to operate.

p	These were available as a kit with instructions published in Practical Electronics magazine or were available pre-built. This was bought pre-built for a University’s Electrical Engineering Department. The prebuilt price was £1750, and because of this I presume that not many were sold at the time and not many still in existence.

p	The Arm has five servo motors to control these movements: finger grippers, wrist, elbow, upper-arm, shoulder rotation. Each one of the operating motors have a potentiometer fitted at the end of their axel – this tells the robot when each arm joint has reached its desired position and then stops the motor. The interface card also has a series of pots using which the user calibrates each motors starting position and maximum turn (comprehensive instuctions in manual). The interface card fits into the back of the ZX81 and provides accommodation for addition of 16k expansion. The ZX81 is then programmed to make the arm carry out movements.