>I do not see R5 as being able to enable or disable the second stage timer.OK, I am obviously missing something here with the reference to R5. The circuit in post #11 reflects using two 555 timers. The first, on the left is configured as a "One Shot" where when the start button is pressed and released the first 555 on the left will have its output on pin 3 swing high and it will remain high for the duration of its R*C timing network. The original poster wants to use this high out from the one shot to enable the second timer. The second timer is another 555 configured for an astable mode. The idea here seems to be to have a pair of LEDs on its output alternately blink while it is active or enabled.
The free running frequency of the second stage, the 555 running astable is determined by:
Now would that be correct? That is how I see things working. So what is this thing with R5? The only thing R5 does is increase the On Time of the output pulse. I do not see R5 as being able to enable or disable the second stage timer. What am I missing with this R5 part of the discussion?
- Increasing C1 will increase the cycle time (and hence, reduce the frequency).
- Increasing R5 will increase Time High, but will leave Time Low unaffected.
- Increasing R4 will increase Time High, increase time low and decrease the duty cycle (down to a minimum of 50%)
Ah, so you are saying to ground R5 to disable the second timer. Place the junction of R5 and R4 at ground. Thank you as now I understand what you are suggesting.>I do not see R5 as being able to enable or disable the second stage timer.
If R5 connected to GND then the second 555 will stop and that is the first 555 want to do.
Left me thinking move it to where? Now I understand what you are suggesting.You should move R5 not the reset pin.
What I knew the methods to control a 555 astable to stop generate the pulse as :Ah, so you are saying to ground R5 to disable the second timer. Place the junction of R5 and R4 at ground. Thank you as now I understand what you are suggesting.
Left me thinking move it to where? Now I understand what you are suggesting.
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by Jake Hertz