Circuit arrangement for the non-contacting control of a sanitary fitting

Claim 1

A circuit arrangement for non-contacting control of the water flow of a sanitary fitting which includes: (a) a sensor which contains a light source and a light receiver that can pick up the light reflected on a user and generate a signal whereby in a case of great sensitivity the water jet of the sanitary fitting is located in the detection range of the sensor; (b) an amplifier which amplifies the signal produced by said light receiver; (c) a comparator which compares the output signal of said amplifier with a certain threshold value and which produces an output signal if this threshold value is exceeded; (d) a pulse shaper having an output signal which changes from a first to a second value forming a first generally rising pulse edge when the output signal of said comparator appears, and which changes fropm said second value to said first value forming a second generally decaying pulse edge when the output signal of said comparator disappears with or without a time lag, (e) at least one solenoid valve which is controlled by the output signal of said pulse shaper and which releases the water flow as long as this output signal has its second value, (f) an edge discriminator which monitors the appearance of said first pulse edge and of said second pulse edge in the output signal of said pulse shaper; and (g) a device which is controlled by said edge discriminator and which reduces the sensitivity of the circuit arrangement upon the appearance of said first pulse edge of the output signal of said pulse shaper from a high to a low value and upon the appearance of said second pulse edge of said output signal of said pulse shaper returns the sensitivity from said low to said high value with or without a time lag.