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Help me trigger a pulse from a rising edge of an input signal

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heryrg

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Yet again i have a problem. :)
I need to trigger a pulse from a rising edge of a input signal. My input will go from 0 to about 2v. When the input changes from 0v to 2v i want to send a pulse of 1.3v or greater. The input will not go to 0 for longer then the impulse.

I've been playing around with 555 timer but with no luck. I built the attached circuit but no luck. Is there another way or is the attached circuit right ??
 

Re: Rising Edge Trigger

hi
no problem in ur circuit but there is some notice.
ur circuit work from 3v to 15v if u work under 4.5v u must use cmos type 555
like icm7555.
u must add rb resistore to base of transistor to limit ib.
and trigger signal must have fast rise edge to active trigger circuit at pin2
of 555
 

Re: Rising Edge Trigger

nashwan said:
hi
no problem in ur circuit but there is some notice.
ur circuit work from 3v to 15v if u work under 4.5v u must use cmos type 555
like icm7555.
u must add rb resistore to base of transistor to limit ib.
and trigger signal must have fast rise edge to active trigger circuit at pin2
of 555
Click to expand...

I'm using the LMC555CN timer and the 2n2222 and im still having some difficulty. I'm using the dual power supplies to test the circuit, so the rising edge is as fast as i can turn the voltage knob.

I looked at the picture you provided, in the output you send a pulse of 0v right?
I need to send a short pulse of about 1.5 or higher pulse.
 

Re: Rising Edge Trigger

hi
i understand here u want to add dc components to ur output pulse abt 1.5v
i mean here shift zero level of output pulse.

or want to control the vp of ur output pulse.
 

Rising Edge Trigger

I want to send a short pulse of about 1.5V or higher to an H-bridge to drive a solenoid. The pulse would be sent as a result of a rising edge of my signal.
 

Re: Rising Edge Trigger

wat the time for pulse width u need?
and abt to get 1.5v in the output u can ad pot to get value from zero
to vcc but value of pot depend of rin of next stage
 

Rising Edge Trigger

Is there any reason why a simple C-R high pass network
would not do the job? Maybe with a low voltage Schmitt
inverter if you need to square it up. Or a

Depending on how well controlled the input and the
output, seems like it could be quite simple.
 

    H

    heryrg

    Points: 2
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Re: Rising Edge Trigger

dick_freebird said:
Is there any reason why a simple C-R high pass network
would not do the job? Maybe with a low voltage Schmitt
inverter if you need to square it up. Or a

Depending on how well controlled the input and the
output, seems like it could be quite simple.
Click to expand...

I've tried that but what i did was wrong and didn't work. Is the attached circuit something similar to what you're thinking of?

I think the attached circuit might actually work, although the caps will be leaking some current correct?

I have a stupid question, the triangle in the photo is that a diode or an op amp??:D
 

Re: Rising Edge Trigger

The triangle is a generic logic buffer (3-15V means your
options are limited to B-series "CD4000" though). Or
discrete circuitry. How about this?
 

Re: Rising Edge Trigger

hi
see that circuit
 

Rising Edge Trigger

Thank you guys for all the help and the circuits, really helpful.

I tested the circuit i attached earlier, the RC integration. I put a diode instead of the logic buffer and it worked.
 

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