csdave
Member level 5
Hi all,
I need a TTL logic port (72LS02 or similar) to change state with a little delay with respect to its input. I don't need to control the delay with great precision, just make sure it's high enough (e.g. order of 0.1 sec)
what I thought of was connecting the output of the previous TTL circuit to an RC circuit, resistor in series then Capacitor between output of resistor and mass and output of resistor connected to input of my logic port.
This will cause the capacitor to charge or discharge through the resistor when the input port changes state. Clearly I need to make sure the charge current is low enough so I though 1Mohm 1uF for 1 sec and 1Mohm 0.1 uF for .1 sec.
The other thing to consider is to make sure that the output port doesn't bounce back and forth.
do I need schmidt trigger to make sure this does not happen? Or is the 7402 alone fine because the capacitor voltage is monotonic?
thanks!
Forgot to mention that I am assuming that the first gate will not change state before the capacitor has charged.
This is mostly academic (i.e. for me to understand)
I need a TTL logic port (72LS02 or similar) to change state with a little delay with respect to its input. I don't need to control the delay with great precision, just make sure it's high enough (e.g. order of 0.1 sec)
what I thought of was connecting the output of the previous TTL circuit to an RC circuit, resistor in series then Capacitor between output of resistor and mass and output of resistor connected to input of my logic port.
This will cause the capacitor to charge or discharge through the resistor when the input port changes state. Clearly I need to make sure the charge current is low enough so I though 1Mohm 1uF for 1 sec and 1Mohm 0.1 uF for .1 sec.
The other thing to consider is to make sure that the output port doesn't bounce back and forth.
do I need schmidt trigger to make sure this does not happen? Or is the 7402 alone fine because the capacitor voltage is monotonic?
thanks!
Forgot to mention that I am assuming that the first gate will not change state before the capacitor has charged.
This is mostly academic (i.e. for me to understand)
