Abstract: An orbital shaker apparatus which has a tray for cyclic motion is flexibly suspended from a frame which is flexibly suspended from a plurality of stationary supports. The flexible suspension constrains the tray to move only translationally along one axis with respect to the frame and constrains the frame to move only translationally along one axis perpendicular to the tray movement axis. A single chip microprocessor is used to scan, input store, display and control the speed, duration and control functions for the orbital motion. Embodied in the software of the microprocessor is a real-time closed loop speed control which monitors the actual speed of the orbital motion thru an interrupt facility by calculating the duration of pulses received from an optoelectric sensor. The measured pulse duration is digitally compared to the desired duration and a digital control signal is provided to drive a DC motor which is directly coupled to the drive shaft which imparts the motion.

Abstract: An orbital shaker apparatus which has a tray for cyclic motion is flexibly suspended from a frame which is flexibly suspended from a plurality of stationary supports. The flexible suspension constrains the tray to move only translationally along one axis with respect to the frame and constrains the frame to move only translationally along one axis perpendicular to the tray movement axis. A microprocessor is used for receiving operator input to set the speed and duration of the cyclic motion. Embodied in the microprocessor is a closed loop speed control which measures the actual speed of the cyclic movement with an interrupt routine which calculates the duration between the pulses of an optoelectric speed sensor. The actual speed is compared to the set speed and a digital "bang-bang" control signal is generated to regulate motor velocity from the difference between the two speeds.

Abstract: Apparatus for switching alternating current from a power source to a load for substantially all of one selected half-cycle, but not before at least one full cycle after the apparatus receives an operator command to switch the current, includes a mechanical switch for commanding the apparatus at an arbitrary time to switch the current. Electrical control devices produce a control output during a portion of the selected half-cycle. A second switch device, such as an SCR, responsive to the control output switches the current to the load during the selected half-cycle. The control output is turned off before the end of the half-cycle and is not produced again until the mechanical switch is released and provides another command to switch the current.