The servo motor can be programmed somewhat to control peak speed and accel / decel profiles. There is a lever on the back case of the motor which sets the speed demand. At first the lever was relocated onto the table where the client could operate it directly to allow the client to use it by hand.
The servo motor’s own lever is connected to the motor controller by 3 wires, +5V, “Demand” and GND. It was found that stationary “Demand” was 1.7V when stationary, a higher value was the set value for speed.
The lever was then replaced by an mbed LPC1768 programmable controller and within the button box. In addition a reflective light sensor was added, in a 3D printed housing, picking up a black mark on the flywheel. A potentiometer was fitted to the box with a 3D printed knob.
The Red button will apply a gently rising speed to the machine to the set point of the pot, then run until the button is pressed again. The machine will stop as close to the light mark as it can (needle down).
The green button will move to the mark (single stitch, stopping needle down).
Both buttons delay for a set period before motion to allow the user to return both hands to the work.
This has proven to be very controllable and we look forward to making more adjustments as time allows.
Our client has a powerful sewing machine at his command and the quality of his work has much improved. The single stitch function, in particular, allows him to control the detailing of the glove.