It will definitely work - with a schmitt-trigger NAND gate (or inverter) and reasonable component values. 7400 however is no schmitt trigger. A respective component would be 74132 or CD4093. Only CD4093 or CD40106 will allow a supply voltage > 5V.
i followed all that & for now the circuit is on board before me but not working as per explanations
When you look at the datasheet for a Cmos logic IC like the CD4093 then you will see that its output current is low. Then its output current is used to light your LED instead of charging the timing capacitor.i applied CD4093 & ya its working but what i am observing here is the ON & OFF time are not same for the LED i connected at output pin 3 . .
No matter whats the value of capacitor & resistor but it always happen with output
When you look at the datasheet for a Cmos logic IC like the CD4093 then you will see that its output current is low. Then its output current is used to light your LED instead of charging the timing capacitor.
Simply use another gate in the CD4093 as a buffer that is driven by the oscillator then the buffer drives the LED.
The Schmitt trigger threshold voltages are not exactly symmetrical so the output of the oscillator will not be perfectly symmetrical but it will be close.
You NEVER leave a Cmos logic input open. It must be made high or low.
The CD4093 is a NAND gate (why didn't you look it up?) so if its second input is high then the oscillator runs but if the second input is low then the oscillator stops with its output high.
To turn the CD4093 oscillator off then make its second input a logic low which can be ground, the logic low output of another logic gate or inverter, the collector of a turned on NPN transistor or a resistor to ground.
The input of a Cmos Logic gate or inverter draws no current so the resistor to ground can have any value.
You're already using it as a Schmitt trigger. With one input held high, the other input and the output act as an inverting Shmitt trigger.
Of course it is automatic. It is already an astable oscillator.ya but thats an automatic type , i mean in astable mode . .
It does not need biasing. The second input is used to turn the oscillator on and off.i want actual biasing configuration so as to apply external input & all that
Of course it is automatic. It is already an astable oscillator.
It does not need biasing. The second input is used to turn the oscillator on and off.
What are you talking about? An SN7400 TTL gate package that will not work in this circuit? It does not have Schmitt trigger inputs.ya definitly , but as we do in schmitt trigger case ,
like an input, threshhold voltage setting etc & all that
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