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Implementing the logic

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Gaussx123

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Here is a logic to operate a relay by using the change in pulsewidth. The pulsewidth of my input signal changes from 1 ms to 2 ms when I operate the switch. Whenever I keep it at 2ms posn., it should be on etc..

I have got the logic but the circuit I built is not working. Can someone give a detailed ckt. for the logic I have attached.

Thanks
 

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Here is a logic to operate a relay by using the change in pulsewidth. The pulsewidth of my input signal changes from 1 ms to 2 ms when I operate the switch. Whenever I keep it at 2ms posn., it should be on etc..

I have got the logic but the circuit I built is not working. Can someone give a detailed ckt. for the logic I have attached.

Thanks
hi,
This looks familiar.

Which part of the circuit have you actually built, also component values.?

How is it NOT working.?
 
My receiver o/p has 3 leads - +V, GND and signal. I connected the signal lead to the resistor (7MΩ) connected to the capacitor (100µF). Then I have used IC7414 for schmitt trigger inverter. I have connected its o/p to IC 4081 AND gate. The other i/p for the AND gate is the signal lead itself. I have given o/p of the AND gate to the clock of HEF 4013 (pin 3), the signal lead itself to pin 5 and and took the o/p from pin 1.

Pin 14s of all ICs are connected to the 4.8V +Vcc and pin 7s to the ground leads from the receiver.
 
My receiver o/p has 3 leads - +V, GND and signal. I connected the signal lead to the resistor (7MΩ) connected to the capacitor (100µF). Then I have used IC7414 for schmitt trigger inverter. I have connected its o/p to IC 4081 AND gate. The other i/p for the AND gate is the signal lead itself. I have given o/p of the AND gate to the clock of HEF 4013 (pin 3), the signal lead itself to pin 5 and and took the o/p from pin 1.

Pin 14s of all ICs are connected to the 4.8V +Vcc and pin 7s to the ground leads from the receiver.

If I follow your text, this is what you have.
[ a drawing is much easier to follow than a text description:)]

What time constant for the R/C are you expecting.?

t = C * R
 

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  • esp02 Sep. 29.gif
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AFAIK, you can't make a oneshot whose output pulse is wider than the input pulse using that type of circuit. You can do it with a CMOS 555.
 

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  • pulse width discriminator.PNG
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sorry.. I had made a mistake..I now used 100µF and 15Ω which results in a T of 1.5ms. My T1 and T2 are 1ms and 2ms. But now the output is a constant 5.2V which is not what I was expecting. The inputs of the AND gate are (as measured with the DMM) are 4.85V and 0.5-0.75V. The output of the gate is a constant 0. What is going wrong? Should I use some amplifier?
 
I don't have to use my Prof's idea itself guys.. I just want something which is working. I am pretty new to electronics. BTW I had made a small error by setting 1/RC as T.
 
I don't have to use my Prof's idea itself guys.. I just want something which is working. I am pretty new to electronics. BTW I had made a small error by setting 1/RC as T.
As I said before, your current approach won't work, because the 1ms input pulse is shorter than the 1.5ms pulse you are trying to create. Eric's approach from the other thread should work, but he should have used the /Q output instead of the Q output. See below.
 

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  • pulse width discrim.PNG
    pulse width discrim.PNG
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sorry.. I had made a mistake..I now used 100µF and 15Ω which results in a T of 1.5ms. My T1 and T2 are 1ms and 2ms. But now the output is a constant 5.2V which is not what I was expecting. The inputs of the AND gate are (as measured with the DMM) are 4.85V and 0.5-0.75V. The output of the gate is a constant 0. What is going wrong? Should I use some amplifier?

hi,
Using a 15R and 100uF puts a heavy load on the driving circuit.

A 74HC14 CMOS device would allow 15K/100nF caps
 
I am confused with your circuit i.e should I use the monostable circuit i.e using the IC555 as well as the flip flop you have drawn or should the blue arrow i.e the o/p from 12 go to the clock of the other flip flop (3) and what is the diode mentioned there? Will a normal LED work?
 
I am confused with your circuit i.e should I use the monostable circuit i.e using the IC555 as well as the flip flop you have drawn or should the blue arrow i.e the o/p from 12 go to the clock of the other flip flop (3) and what is the diode mentioned there? Will a normal LED work?

hi,
You did ask me this question before..:)

Tell me how you are driving the input to the circuit and I will redraw the circuit in order to clarify it.

EDIT:

Look at this image.
 

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