Hi
I need to design a 30 second delayed counter circuit. The spec is after a output (0) is given this said circuit will count down 30 seconds and then turn a transistor on which in turn turns 4 reed switches on. The transistor / latch and reed switch part is all completed.
The problem i have is the delay
Firstly I choose a 555 timer only to discover the delay in monostable was the oppersite to what I need.
So then I decided to go astable, only to be completely baffled by setting the clock pulses to 1 sec intervals.. I tried to use and online calculator and have the following as R1 R2 & C
R1 = 2k
R2 = 72k
C = 10 microfarad
So in believing i had this sorted i went for a dual 4 bit binary counter. By linking these two together, I can get a count of 30 secs.
I have run this through the crap bit of ecad software and I get pulse of 500ma out of output of the timer but the counters do not work. I am using a program called multisim....
I have spent some serious hours on this now and quess i stupid..
Sorry for the long first post but can anyone help me
Cheeers
SI
I need to design a 30 second delayed counter circuit. The spec is after a output (0) is given this said circuit will count down 30 seconds and then turn a transistor on which in turn turns 4 reed switches on. The transistor / latch and reed switch part is all completed.
The problem i have is the delay
Firstly I choose a 555 timer only to discover the delay in monostable was the oppersite to what I need.
So then I decided to go astable, only to be completely baffled by setting the clock pulses to 1 sec intervals.. I tried to use and online calculator and have the following as R1 R2 & C
R1 = 2k
R2 = 72k
C = 10 microfarad
So in believing i had this sorted i went for a dual 4 bit binary counter. By linking these two together, I can get a count of 30 secs.
I have run this through the crap bit of ecad software and I get pulse of 500ma out of output of the timer but the counters do not work. I am using a program called multisim....
I have spent some serious hours on this now and quess i stupid..
Sorry for the long first post but can anyone help me
Cheeers
SI