Touch delay light switch circuit (1)

In use, as long as you touch the electric threshold plate M with your hand, the light E will be lit and the light will automatically go out
after a short period of time .     VD】, vs, (., C, form a 1H capacity step-down voltage stabilizing rectification line, (1 both ends can input the current voltage of 31V, the transistor VT1 and the thyristor WI2 form a delayed touch switch. Normally, VT1 is in the cut-off state, VL)2 has no trigger voltage output, the thyristor VT2 is turned off, and the light E does not light up. When a human hand touches the electrode sheet, the AC current induced by the human body is injected into the thyristor VT1 through the support The base of VT1 turns on, VIJ2 outputs positive H trigger current to turn on VT2, and the lamp E lights up. At the same time, (, is rapidly charged through VT1. When the human hand leaves the electrode sheet M, f. is still bearish. The door opening of VD2 l∞ and _T2 can therefore maintain the conduction of VT2, allowing the lamp to continue to shine. When (r) the charge is basically discharged, when the alternating current H is zero, VT2 is turned off , and the lamp E goes out and the lamp lights up . The length of time mainly depends on the values ​​​​of Ci and R: The larger the value, the longer the lighting time ; the shorter the J value. Using the old data, the delay time is about 9 (is. If you want to delay pregnancy In the meantime, increase the capacity of C, on the contrary, you can reduce (1.) or the value of R. It should be noted that the resistance of R, cannot be too large, otherwise the thyristor VT2 7 is easy to turn off. VT2 should be used CRiOli, 2N656j and other types of unidirectional thyristors with small trigger current (O. S-iA/40 (1V)), other component parameters are shown in the figure and there are no special requirements.