Touch delay light circuit using time base circuit (2)

It is a touch delay light switch that adopts wire connection method and uses NFA.55 time base circuit
. It can directly replace ordinary mechanical switches without changing the original indoor wiring.
    The power supply of this circuit
is the same as that in Example 96, especially
whether the U light F is on or off
, the circuit can always output
a stable current voltage of fiV
to supply power to the base circuit NF,155
. Normally, NE5ji
is in a stable state, pin ③
inputs a low level,
fJ of the transistor VT1 is activated,
clamps at a level, VTI is turned off, and the lamp E does not light up. When the human hand touches the electrode sheet M, the human body leakage current
is injected into the base of the king tube VT2 through R, causing VT2 to quickly conduct, which is equivalent to
inputting a negative pulse to the trigger terminal ② pin of the NE555, and the time base circuit is busy, ③ The foot jumps to quotient level. Therefore, the gate potential of the thyristor VT1
is raised, VT1 obtains the trigger voltage and is blocked, and the lamp E is energized and emits light. At the same time, the charge stored in G
is quickly discharged through VTZ. After the person leaves M, VT2 returns to cut-off, and the 6V DC power supply passes through R;
power is supplied to G, causing the potential at both ends of f to continue to increase. When it rises to 2/3VDO, which is 1V, the time base circuit is reset, pin ③ returns
to low level, wri loses the trigger voltage, and when the alternating current crosses zero, it turns off and the lamp E goes out.
    The delay time of this circuit is divided by R. , C, the charging time constant is not only dependent on the cursor, but also related to the length of contact
. When the human hand touches for a longer period of time K, the G stored electricity can be fully discharged, so the time it takes to charge to 4V
will be longer, and the corresponding lamp will light up for a longer time. In addition, the load capacity of the circuit is also affected by the stability of the Pressure tube vs. dissipation
power constraints, so the power of bulb E should not be greater than 40W.