Sorry, I didn't know about the thread on the other forum, so couldn't reply there. I didn't realise I needed to refer to it, to get the details, I assumed, they would be on this forum.
Now I've read it (other forum), I have a question.
Why not simply use a 1 second (timing amount adjustable, via switches), off the shelf timing relay (powering additional relay(s), if necessary, to meet the output specs) ?
E.g. for around £17 + VAT (if applicable), from RS. There are others they sell, and other suppliers. So, I am just giving an example.
https://uk.rs-online.com/web/p/timer-relays/1785021/Product datasheet:
https://docs.rs-online.com/e6ce/0900766b817142df.pdfIt seems it can be triggered by a switch, and will refuse to be started again, until it has seen the switch turn off, and then back on again. I.e. holding or shorting the switch, will not cause the 1 second to be exceeded, if I understand it correctly. It seems to have a basic +/- 0.5 % accuracy.
Function B: Single shot timer / delay off with trigger input
(leading edge) - as function “C” but the relay contacts energise and
timing commences on the immediate input to pin 5 (leading edge).
Also unlike function “C” if the trigger is still present after timing
has been completed this will not have any effect, in all circumstances
the trigger will need to be removed and reinstated for the function
to happen again. If the trigger input to pin 5 is present before the
connection of the supply to pins 2 & 10, when the supply is
connected the
I feel bad, because I came to the thread very late, and the design(s), have already taken place. But, as the thread on the other forum, seems to say. 555 timers, are not especially robust and reliable as such. As nice as designing a custom circuit might seem to be. There are all sorts of gotchas, with such circuits.
If you can just buy a ready made, (presumably) robustly/tested version, somewhat cheaply, and replacements are available. It perhaps deserves, some consideration.
But feel free to do what you think is best. It is your decision. Others seem to have put a lot of effort into this already, so I feel
If it was me. I'd be tempted to use it as a belt and braces type of unit, even if you still use your circuit. As it should mean that you don't exceed 1 second, even if the control circuitry tries to exceed the time limit.
tl;dr
I really like 555 timers. But, I've also had some bad experiences with them. They can trigger, possibly a bit too easily, and potentially be a bit haywire as regards the timings. I had a poorly suppressed DC motor, which basically turned a 555 timer, into a random number generator, rather than a precise timing unit, it was suppose to be.
It was a very long time ago, in my early hobby days.
But in fairness, 555 timers are basically reliable. But one needs to take care, if using them.
I haven't used timing relays like this (that I can remember). Maybe they have their own problems, I don't know.