Microcontroller based automatic door obstruction detector

Claim 1

Motor control apparatus for an automatic door, comprising: motor means having a drive shaft for mechanical linkage to a door for moving the door along a travel path between opened and closed positions, said motor means having a control input for receiving a motor control signal for controlling the velocity and direction of rotation of said drive shaft; shaft signal means associated with said drive shaft for producing shaft signals indicative of rotational velocity and direction of rotation of said drive shaft; motor control means having an input and an output connected to the control input of said motor means, said motor control means producing a motor control signal at its output in response to a signal at its input; processor means having an input coupled for receiving the shaft signals and an output connected to the input of said motor control means, said processor means including means for measuring the shaft velocity and determining the direction of shaft rotation from the shaft signals and for comparing the measured shaft velocity with a predetermined minimum shaft velocity limit, said processor means producing a signal at its output for causing the motor control means to reverse the direction of rotation of said drive shaft when the measured rotational velocity of said drive shaft falls below the predetermined minimum shaft velocity limit.