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From: chuck on 23 May 2010 13:19
Thanks for the replys.
I am using the monostable configuration that is shown in the datasheet
(unsure of manufacture but I think its a universal configuration), it
uses two external caps between pin 5 and 6 and a resistor between pin
7 and 8. A falling edge is supposed to trigger a high output from the
555 timer but doesn't when the input to the 555 is taken across the
pull up resistor of the compartor.



From: chuck on 26 May 2010 19:11
On May 23, 11:19 am, chuck <chuckd87...(a)yahoo.com> wrote:
> Thanks for the replys.
> I am using the monostable configuration that is shown in the datasheet
> (unsure of manufacture but I think its a universal configuration), it
> uses two external caps between pin 5 and 6 and a resistor between pin
> 7 and 8. A falling edge is supposed to trigger a high output from the
> 555 timer but doesn't when the input to the 555 is taken across the
> pull up resistor of the compartor.

Actually, the 555 isn't triggered until the falling edge reaches 1/3
Vcc.
From: John Fields on 27 May 2010 09:10
On Wed, 26 May 2010 16:11:02 -0700 (PDT), chuck
<chuckd87106(a)gmail.com> wrote:

>On May 23, 11:19�am, chuck <chuckd87...(a)yahoo.com> wrote:
>> Thanks for the replys.
>> I am using the monostable configuration that is shown in the datasheet
>> (unsure of manufacture but I think its a universal configuration), it
>> uses two external caps between pin 5 and 6

---
That's wrong.

It uses one cap from pin 5 to ground and another from pin 6 to ground,
but the one on pin 5 you can pretty much get rid of.
---

>> and a resistor between pin
>> 7 and 8. A falling edge is supposed to trigger a high output from the
>> 555 timer but doesn't when the input to the 555 is taken across the
>> pull up resistor of the compartor.

---
It's not supposed to be taken across the pullup, it's supposed to be
taken from the end of the resistor connected to the output of the
comparator and cap-coupled to the 555 if the low-going output from the
comparator lasts longer than the 555 output pulse.
---


>Actually, the 555 isn't triggered until the falling edge reaches 1/3
>Vcc. ^
on pin 2
---
That's right.

JF
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