| | | Multi-Channel Bend Sensor®-to-Digital Interface: Sampling Cycle (any Bend Sensor® channel): The microcontroller switches to a specific Bend Sensor® channel, toggling it high, while all other Bend Sensor® channels are toggled low. The RESET channel is toggled high, a counter starts and the capacitor C1 charges, with its charging rate controlled by the resistance ofthe Bend Sensor® (t~RC). When the capacitor reaches the high digital threshold ofthe INPUT channel, the counter shuts off, the RESET toggles low, and the capacitor discharges. The number of "counts" it takes from the toggling of the RESET high to the toggling of the INPUT high is proportional to the resistance ofthe Bend Sensor® device. The resistors RMIN and RMAx are used to set a minimum and maximum "counts" and therefore the range ofthe "counts". They are also used periodically to re-calibrate the reference. A sampling cycle for RMIN is run, the number of "counts" is stored and used as a new zero. Similarly, a sampling cycle for RMAX is run and the value is stored as the maximum ofthe range (after subtracting the RMIN value). Successive Bend Sensor® samplings are normalized to the new zero. The full range is "zoned" by dividing the normalized maximum "counts" by the number of desired zones. This will delineate the window size or width of each zone. Continual sampling is done to record changes in Bend Sensor® resistance due to changes in deflection. Each Bend Sensor® device is selected sequentially. | | |