Multiple 555 timer question

[zalmaflash]

I want to know if I can trigger three 555 timers (one shot mode for all) from one trigger source on pin 2.
Timer A, timer B, and timer C to all start at the same time from one one second trigger push. They will then time out at different times (which I can set)

Yes, I know it will work in my experiment but that was a short time. I want this to work indefinitely (one or two triggers every hour or two) for a couple years.

To try to make it clearer - a motion detector is triggered. The aux. contacts close for a second or two and triggers all the 555's. Timer A stays on for 5 seconds, timer B stays on for 10 seconds, and timer C stays on for 47 seconds (all made up times and I do know how to set them) Each timer will operate an individual NPN. All timers will be mounted on the same small perf board.

Will this last without undue stress on any component?

The operating voltage is 6vdc or 9vdc and adding IN4148 diodes inline to each trigger is my next thought.

Thanks in advance for any and all input.

[budm]

Re: Multiple 555 timer question

There should not be any stress in the circuit as far as the triggering concerned, and yes, I would use the diode for each trigger line to isolate each timer trigger pin, the Cathode side will be grounded to trigger the timer.
The stressed parts will be the Output of the 555, it depends on how much load current will be, and what kind of load will be, inductive or resistive loads? Sink or Source the load?
Sounds like you are going to use the Output of the 555 to drive the Transistor, so that is light load.
I would also use non electrolytics cap for timer so you do not have to worry about the caps dry out and lose its capacitance.

[stj]

Re: Multiple 555 timer question

it would be cheaper to use an 8pin pic-chip

[zalmaflash]

Re: Multiple 555 timer question

Thanks guys for the input. I'll give it a shot (one).

[Longbow]

Re: Multiple 555 timer question

Your idea is not described in a way that encourages comments. It is clear that several 555's can be triggered at the same time, but how many depends upon your V+ and triggering source. Normally, logic triggering is set to be the shortest pulse that will achieve reliable triggering. A one-second trigger will cause you lots of headaches since it will interact with the other timers, as well as preventing proper operation of a timer that is set to less that one second. De-bouncing is always a good idea. Since I have never triggered multiple timers at once I can't say whether there will be any consequences from having them all hooked up to one driver - something tells me you will have to deal with the triggering source to isolate the individual 555's.

After all, one or more sections will be timing out whilst the others are still in the timing mode. Which brings up the question - you have described monostable operation. What do you want the timer to do after it cycles? How will all the timers in the design return to ready state? Must all the timers be in the ready mode before any of them can be triggered? You have some extra logic functions to perform.

A block diagram of your design, perhaps?