Hello there,
As you know, the 555 timer in monostable configuration is triggered by a low going pulse edge which makes the output go high and stay high for a predetermined length of time. And as you probably also know, if the input pulse STAYS low, the output pulse never goes low again. That is, it wont only stay high for the predetermined time, it will stay high until the input pulse goes back to a high logic level. The ways to get around this are collectively called simply, "Input Lockout". Input lockout prevents the input from affecting the output pulse after the first low going edge starts the timer even if it stays low. A side effect is that it may also mean that the low going pulse can not affect it either if it goes low a second time within too short of a time period. This second effect would also be a benefit to this particular application which would not like to see multiple trigger pulses within some definite time period like 1 second or something like that.
There are different ways to do this, including the simplest which is a simple capacitor and resistor with the right time constant.
But i would like to see other ways of doing this too from your experiences or web searches. These might include circuits that link the output back to the input via a logic gate or two, etc., but not too very complicated. Maybe another 555 even.
All ideas will be appreciated.
Thanks and take care,
Al
As you know, the 555 timer in monostable configuration is triggered by a low going pulse edge which makes the output go high and stay high for a predetermined length of time. And as you probably also know, if the input pulse STAYS low, the output pulse never goes low again. That is, it wont only stay high for the predetermined time, it will stay high until the input pulse goes back to a high logic level. The ways to get around this are collectively called simply, "Input Lockout". Input lockout prevents the input from affecting the output pulse after the first low going edge starts the timer even if it stays low. A side effect is that it may also mean that the low going pulse can not affect it either if it goes low a second time within too short of a time period. This second effect would also be a benefit to this particular application which would not like to see multiple trigger pulses within some definite time period like 1 second or something like that.
There are different ways to do this, including the simplest which is a simple capacitor and resistor with the right time constant.
But i would like to see other ways of doing this too from your experiences or web searches. These might include circuits that link the output back to the input via a logic gate or two, etc., but not too very complicated. Maybe another 555 even.
All ideas will be appreciated.
Thanks and take care,
Al