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4098 Rising and Falling edge detection

Jagatha

Jan 2, 2017
3
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Jan 2, 2017
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Dear Members

I'm trying this 4098 edge detector for a small project and works fine getting two separate pulses ( with different duration) to sound and alarm. However the cct has a flaw that it puts both outputs same time when I connect the power. The data sheet mention on setting the reset pin to VSS during power on to inhibit the output and could somebody direct me on how to do it please?
here is the cct I use.. thanks in advance.
4098.png
 
Last edited:

Arouse1973

Adam
Dec 18, 2013
5,178
Joined
Dec 18, 2013
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5,178
Have a look for a power on reset IC or circuit. This can be a simple RC network followed by a Schmitt trigger logic gate.
Thanks
Adam.
 

Alec_t

Jul 7, 2015
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Jul 7, 2015
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3,587
What is the approximate supply voltage rise time at power-on? An R and a C with a time constant greater than that can be added across the supply (R to +, C to ground) with the reset pin connected to the R/C junction.
 

Jagatha

Jan 2, 2017
3
Joined
Jan 2, 2017
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Thank you for your valuable advice. A RC worked perfectly, The input was actually through a 74LS14 so I'm having enough resources there too. Arouse1973, and Alec_t thank you so much for your valuable guidance
 
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