Trigger Pulse for IC555 using Inverted Square Pulse

[AnalogKid]

Attached is a circuit that does everything you have described, and uses a 555. Notice that there is no buffer stage. That is because nothing that you have described requires one.

ak

 

[Arouse1973]

Attached is a circuit that does everything you have described, and uses a 555. Notice that there is no buffer stage. That is because nothing that you have described requires one.

akView attachment 20846

Traitor, I trusted you

 

[AnalogKid]

Just poking the bear...

 

[Varun Dua]

1. A CD4093 is an IC. An LMC555 is an IC. Why is one allowed and the other not allowed?

IC555 because it has a stable circuitry with not too much to worry out.. plus my company head doesn't want me to use many IC's but work with transistors only

After the bridge rectifier, is there a filter capacitor to smooth the fullwave rectified AC into a DC voltage? Then what, a zener diode and an optocoupler, or something more precise like an analog comparator

Yup a voltage comparator using op-amps with low output impedance

What is the output stage of the voltage sensor? If it is a reasonably low impedance like an opamp or even an optocoupler, then one output can drive two circuits like the FET-A gate and a delay circuit. Why do you think you need a buffer section? From your descriptions, it looks like the voltage sensor output could drive FET-A directly, and it's negative edge could trigger a 555, so I without more information I don't see a need for a buffer, and without more information I can't design one anyway.

I tried it once earlier but couldn't succeed hence I was thinking of having a buffer stage. Some IC that would help achieve it?

Attached is a circuit that does everything you have described, and uses a 555. Notice that there is no buffer stage. That is because nothing that you have described requires one.

ak

Oh just saw this.. thanks a lot! But I think the buffer would be required..

By the way what does Capacitor C1 signify? Seeing something like this for the first time

 

[AnalogKid]

C1 is the power supply decoupling capacitor for the 555 IC. In my library the power pins are not shown on common parts.

The circuit in post #41 requires that the sensor circuit output be able to source and sink less than 1.5 mA. If it can sink 1.5 mA with an output voltage less than 1.0 V then it will work.

The circuit can be done with all discrete transistors. However, because of the long time delay it will take more than the minimum of 4. An extra stage is needed for hysteresis so the output waveforms to the FETs have rapid rise and fall times.

ak

 

[Varun Dua]

Alright got it.. thanks a lot! But you sure about the buffer section right?

 

[AnalogKid]

If the voltage sensor output is a low impedance that swings below 0.4 V in its low state, then Q1 is the buffer stage. If the low output is closer to 1 V, add a 1N914 or 1N4148 diode in series with the Q1 base.

ak

 

[Varun Dua]

Ohk and lastly, which is more feasible to implement - 1 resistor and 3 capacitor (connected to a rotary switch) or 1 capacitor and 3 resistors (connected to the rotart switch) considering lossesthat might occur in charging/discharging of capacitor?