# helpppppppppppppppppppppppp!for design timer

Discussion in 'Electronic Basics' started by yar, Jul 28, 2004.

1. ### yarGuest

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(http://www.tarrypin.dail.pipex.com/images/555Timingchain-yar.gif)
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

2. ### petrus bitbyterGuest

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

3. ### Robert C MonsenGuest

I think a 555 is OK for this. Just trigger off of the falling edge of
the prior retriggerable monostable, which is simple to do with a cap,
resistor, and diode. Have a circle of these, with the timeout
controllable by a pot.

The first one can be started with a pushbutton to ground, which will
override the trigger input.

Another way would be to use an analog switch and a 4017 to switch in
different resistors on a single 555.

Regards,
Bob Monsen

4. ### John FieldsGuest

---
Four pots. If you use HC123's or 4538s's, then the coupling caps, the
resistors and the diodes go away (12 parts)
---
---
Yes, and the whole chain could be started with a POR, but there still
needs to be a supervisory circuit included to monitor whether the
thing has gotten stuck and either restart it or sound an alarm.
---
---
That's three chips instead of two, but you do save three timing caps.

Unfortunately, the OP didn't say anything about what the timing is
supposed to look like, so the optimum configuration is anybody's
guess.

5. ### yarGuest

I AM YAR THANK YOU FOR YOUR REPLAY THE MAX. TIME IS 4 MINUTE(240 SECOND)
BUT IDON'T KNOW THE CIRCUIT IF THIS IS NOT DIFFICULT PLEASE SEND ME THE CIRCUIT
OR HOW CAN DO IT

6. ### Terry PinnellGuest

Hope you constructed it with more attention to detail than you gave to
this post!

That's the outline I suggested for you on 14th June, in the thread you
originally started
Newsgroups: sci.electronics.design
Subject: Re: design 4 points timer
Date: Tue, 15 Jun 2004 15:09:51 +0100
Message-ID: <>

and the correct URL was
http://www.terrypin.dial.pipex.com/Images/555TimingChain-yar.gif

Do you have a friend or colleague (or some official, such as at a