Touch-type adjustable timing circuit (2)

It is a touch-type timing light composed of NE505 time base circuit . The timing time can be
continuously adjusted within 10 - 60m, n. When the timing time is reached, the light will turn off in vain. Within the specified time limit, it is also possible
to turn off the lights in advance through touch. This circuit is very suitable for table lamp timing control.
    The power supply of this machine is capacitor f1. Step
-down, VD1 rectification and vs voltage stabilization,
after power on, m
12V stable DC voltage can be output at both ends of C for
powering the whole machine. The NE550 time base circuit and
RP, R, and G form a typical
monostable trigger. Normally, the circuit
is in a stable state. Pin ③ outputs low
level, the thyristor VTH is turned off, and
the lamp E does not light up. When you need to turn on the light,
just touch the "on" electrode piece
h/ll, and the stray signal induced by the human body will be coupled through C; VD3 rectifier, the -k
series negative pulse signal can be obtained at the ② pin of the af base circuit. The NE505 is set to enter the transient state. The ③ pin outputs high-level VTH and can obtain
the forward trigger current through R to turn on the lamp E. When the lamp E is energized, it emits light. This is called 12V power supply which will pass through Rl, R. Charge to (2)
, when / T=ll (RP4-R.) C, the transient state ends, the circuit returns to the steady state, the ③ pin returns to low level,
VTH will lose the trigger current, and will turn off when the AC crosses zero. off, the light goes out, so the central potentiometer RP
can change the timing time of the circuit. If the timing time has not arrived and you want to turn off the light, just touch the "off" electrode
piece M2, and the miscellaneous i signal induced by the human body will pass through ￡ 1. Coupling, VD2 rectification, allows the forced reset terminal
④ of the time base circuit to receive a negative pulse signal to force the circuit to reset. The ③ and ⑦ pins jump to low} U level. VTH is turned off and
the light goes out. At the same time, ( The stored charge is quickly discharged through the ⑦ pin, which can be used to prepare for the next Jf light . In the figure
, the luminescent tubes I and F:D are the working indicator lights of this machine.