Apart from the timing functions ,the two comparators of the 555 timer can be used independently for other applications.One example is a Schmitt Trigger shown here. The two comparator inputs (pin 2 & 6) are tied together and biased at 1/2 Vcc through a voltage divider R1 and R2.Since the threshold comparator wil trip at 2/3 Vcc and the trigger comparator will trip at 1/3Vcc,the bias provided by the resistors R1 & R2  are centered within the comparators trip limits.

By modifying the input time constant on the circuit,reducing the value of input capacitor (C1) to 0.001 uF so that the input pulse get differentiated,the arrangement can also be used either as a bistable device or to invert pulse wave forms.In the later case ,the fast time combination of C1 with R1 & R2 causes only the edges of the input pulse or rectangular waveform to be passed.These pulses set and reset the flip-flop and a high level inverted output is the result.


Circuit diagram with Parts list.




  • Assemble the circuit on a good quality PCB or common board.
  • The circuit can be powered from a 9V battery or 9V DC power supply.
  • The IC NE555 could be mounted on holder.


  1. lampu ledil

    LEDs are arguably essentially the most energy-efficient light source offered. Case in point, LEDs have developed upwards of 80 % energy savings within the traffic signal business. Having said that, within this application, the LEDs had two all-natural advantages: LEDs are monochromatic, so virtually all the light generated is utilised. In contrast, the white light generated by an incandescent bulb requires to transmit via a colored filter. Light outdoors of your frequency on the colored lens is wasted.

  2. harga lampu led

    LEDs are directional, so almost all the light generated was emitted towards the lens. In contrast, light from an incandescent bulb needed to be reflected toward the lens, resulting in loss of efficiency. Commercial and residential lighting applications stand to get similar, if not more, energy-savings by converting to LEDs. But, most applications are not as straight-forward as stuffing a Pc board with a bunch of directional red, amber or green LEDs. LED light fixtures and retrofit packages need to be created to distribute the directional light generated by the LED more than wide areas. Additionally, white LED technology, though continuously enhancing, does not yet have the optical colour and brightness that shoppers have grow to be accustomed to with incandescent lights. On the other hand, the energy savings might be important, for instance, in California the energy commission has adopted efficiency requirements for residential and commercial buildings. These requirements, Title 24, have accelerated improvement of LED illumination technologies.

  3. Hi,

    Thanks for the schematic and description. This may be what I need to eliminate ambiant noise on an infra-red transmission circuit!


  4. central led

    klo untuk lampu besar,setelah out put dari 555 di beri relai 12 v.bisa bos? caranya