Circuits using a 74c14:
An oscillator is created by placing a
resistor from output to input and a capacitor from input to 0v.
The output will be a square-wave and and the mark (high) will be equal
to the space (low).
In figure C the output is output is low for a short period
of time as the two resistors R1 and R2 are discharging the capacitor. If
R2 is a very low value compared with R1 we can get the low duration to
be 10% or less, of the HIGH.
When the push-button is pressed, the input of the first gate goes LOW and the output goes HIGH. The high from the diode prevents the capacitor discharging and the output of the oscillator remains LOW.
To turn the oscillator on and off, we can add the following TOGGLE circuit:
The Touch Plates can be replaced with a switch and
To extend the action of a push button, a pulse-extender circuit can be added:
To produce a pulse of constant length, (no matter how long the button is pressed), the following circuit is needed:
2 MINUTE TIMER
The relay is energized for a short time, 2 minutes after the push-button is pressed. The push-button produces a brief LOW on pin 1, no matter how long it is pushed and this produces a pulse of constant length via the three components between pin 2 and 3.
This pulse is long enough to fully discharge the 100u timing electrolytic on pin 5.
The 100k and electrolytic between pins 6 and 9 are designed to produce a brief pulse to energize the relay.
Here is another very similar circuit. Use either the active HIGH or Active LOW switch and if the Active LOW switch is used, do not connect the parts or gate between pins 1 and 2 to the rest of the circuit.
The 74c14 can be used for lots of different circuits. In the following design, the output produces 3mS pulses every second. The circuit is adjustable to a wide range of requirements.
The next design interfaces a "Normally Open" and "Normally Closed" switch to a delay circuit.
The feedback diode from the output prevents the inputs re-triggering the timer (during the delay period) the so that a device such as a motor, globe or voice chip can be activated for a set period of time.
TOGGLE TWO ITEMS
This circuit will turn on the first relay for a
short period of time when the push button is momentarily pressed