Detector And Controller

Many applications require analog signals to be sensed and digital signals to be controlled. A way to detect these p

oints is by using a 555 timer in an unconventional configuration. This method will also add hysteresis to the circuit and guard against oscillation. The 555 supplies two comparators and a flip-flop eliminates the oscillation. Using this classic timer in the new configuration also reduces the component count. The circuit shows the 555"s trigger and threshold pins tied together. This enables the comparators to set and reset the flip-flop. Op amp U2 supplies both the trip-point setting and a way to adjust the hysteresis for on and off points. One application where this circuit would be useful is in a Nicad battery-charge controller.

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