This IC provides two highly accurate 555 Timer circuits that are capable of producing both time delays or oscillation. It has two 555 timer circuits in a single 14 pin DIL package and can be operated in astable or monostable mode with external (RC) timing control.
The 555 timer is a simple circuit. By taking the trigger signal from high to low the flip-flop is set. This causes the output to go high and the discharge pin to be released from GND (0V). The releasing of the discharge pin from GND causes an external capacitor to begin charging. When the capacitor is charged the voltage across it increases. This results in the voltage on the threshold pin increasing. When this is high enough it will result in the flip-flop to resetting. This causes the output to go low and the discharge pin is also taken back to GND. This discharges the external capacitor ready for the next time the device is triggered.
Pin Out information:
| Pin. | Information. |
|---|---|
| V+ | Supply Voltage |
| GND | GND (0V) connection for supply voltage |
| Threshold | Active high input pin that is used to monitor the charging of the timing capacitor |
| Control Voltage | Used to adjust the threshold voltage if required. This should be left disconnected if the function is not required. A 0.01uF capacitor to GND can be used in electrically noisy circuits |
| Trigger | Active low trigger input that starts the timer. |
| Discharge | Output pin that is used to discharge the timing capacitor |
| Out | Timer output pin |
| Reset | Active low reset pin. Normally connected to V+ if the reset function is not required |
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