Ne555 Timer with simple circuits
- 2. The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation, and oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as a flip-flop element.
- 3. It has been falsely hypothesized that the 555 got its name from the three 5 kΩ resistors used within. But Hans Camenzind has stated that the part number was arbitrary, thus it's just a coincidence they matched. The "NE" and "SE" letters of the original parts numbers (NE555 and SE555) were temperature designations for analog chips from Signetics, where "NE" was commercial temperature family and "SE" was military temperature family.
- 6. Pin 1 (Ground): Connects to the 0v power supply. Pin 2 (Trigger): Detects 1/3 of rail voltage to make output HIGH. Pin 2 has control over pin 6. If pin 2 is LOW, and pin 6 LOW, output goes and stays HIGH. If pin 6 HIGH, and pin 2 goes LOW, output goes LOW while pin 2 LOW.
- 7. Pin 3 (Output): (Pins 3 and 7 are "in phase.") Goes HIGH (about 2v less than rail) and LOW (about 0.5v less than 0v) and will deliver up to 200mA. Pin 4 (Reset): Internally connected HIGH via 100k. Must be taken below 0.8v to reset the chip.
- 8. Pin 5 (Control): A voltage applied to this pin will vary the timing of the RC network (quite considerably). Pin 6 (Threshold): Detects 2/3 of rail voltage to make output LOW only if pin 2 is HIGH. This pin has a very high impedance (about 10M) and will trigger with about 0.2uA.
- 9. Pin 7 (Discharge): Goes LOW when pin 6 detects 2/3 rail voltage but pin 2 must be HIGH. If pin 2 is HIGH, pin 6 can be HIGH or LOW and pin 7 remains LOW. Goes OPEN (HIGH) and stays HIGH when pin 2 detects 1/3 rail voltage (even as a LOW pulse) when pin 6 is LOW. Pin 8 (Supply): Connects to the positive power supply (Vs). This can be any voltage between 4.5V and 15V DC, but is commonly 5V DC when working with digital ICs.
- 10. The IC 555 has three operating modes: 1- Astable. 2- Monostable. 3- Bistable.
- 11. In astable mode, the 555 timer puts out a continuous stream of rectangular pulses having a specified frequency.
- 12. In monostable mode, the output pulse ends when the voltage on the capacitor equals 2⁄3 of the supply voltage. The output pulse width can be lengthened or shortened to the need of the specific application by adjusting the values of R and C.
- 13. In bistable mode, the 555 timer acts as a basic flip-flop. The trigger and reset inputs (pins 2 and 4 respectively on a 555) are held high via pull –up resistor while the threshold input (pin 6) is simply floating.
- 14. There are many applications of 555 timers Google it to find circuits