Re: helpppppppppppppppppppppppp!for design timer

From: petrus bitbyter (
Date: 07/28/04

Date: Wed, 28 Jul 2004 23:20:46 GMT

"yar" <> schreef in bericht
> I asked a question before and received answers which, although
> helpful
> to some extent, did not provide me with what I need to know. So, I
> decided to rephrase the question.
> HI'
> I am yar intellegence then I decide send my problem to solve it
> for me .I want to make a timer circuit to control 4point with this
> following specification :
> 1- point one connect for an adjustable time with(variable
> resistance)then point one disconect aand point two is connect
> 2- point two connect for an adjustable time with(variable
> resistance)then point two disconect and point three is connect
> 3- point three connect for an adjustable time with(variable
> resistance)then point three disconect and point four is connect
> 4- point four connect for an adjustable time with(variable
> resistance)then point four disconect and point one is connect another
> time
> note: my problem is how can make the first circuit (555) triger the
> next circuit
> IF there is aanother useful IC's to catch my goal then why not
> note :I try this circuit but it isnot worked
> right(
> and I this component for each 555
> pin1----gnd
> pin2----10k resistance&in4148diode&connect to the next 555 pin 3
> pin3----connect to a coil relay
> pin4----connect to pin8
> pin5----connect to 0.01 uf ceramic capacitor(the capacitor in between
> pin 5 &gnd)
> pin6----connect to 1000 uf&25volt electrolytic(polar)(the negative leg
> is connected to gnd)&39k ohm connected in between pin6 & pin7
> pin7----connect to 1 M ohm variable resistance in between pin 7&pin 8
> pin 8----connect to the vcc (the power supply is 12volt adapter)
> I want any help
> thank you YAR

Can't find your site and in a first impression the description of your
circuit does not look well. My firtst question is, what triggers the first
timer the first time? The moment the first timer has been triggered you can
always trigger the next one on the falling edge of its predecessor. The same
problem occurs when some disturbance resets the whole circuit. So you have
to provide a watchdog timer, a retriggerable monostable that preferably is
triggered by all four other timers. Once the triggering of this timer stops
due to lack of activity, it times out and the falling edge has to trigger
the first timer again. This watchdog timer has also to be triggered a first
time. This can be done by the power on reset. A more reliable approach is
using a slow astable. This can be reset by one or more of the four timers
all the time. When this resetting stops, the astable will produce u pulse
that can be used to trigger the first timer again.

I should not use 555s for this circuit but CMOS timers like the 4538.

petrus bitbyter

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