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Newbie Capacitor delaying question...

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Kalym

New Member
I've been trying to understand how a capacitor works for introducing a time delay into a circuit.

I know that if you put a resistor in series with a cap the time delay is R x C.

What I don't understand is how you would arrange the components.

e.g. I want to delay a carry signal from one 4017 to another.



Would the above work? A is the carry out signal and b the clock of the next counter.

My understanding is that the current will not go through to B while the cap is charging. Once the cap is charged, the current can no longer go through to ground and will go through to B.
 

Optikon

New Member
For A to be a delayed version of B, move the resistor from the A leg to the B leg.

The idea is that the B voltage will charge through the resistor and cap thus causing the A voltage to see the delayed value(which is not tapped right off of the cap)
 

k7elp60

Active Member
Capacitor charge

You have the right idea about RC time constants. T=RC, where time in seconds is equal to resistance X capacitance. Where resistance is in ohms, and capacitance is in farads. Time is the time it takes the capacitor to charge to 63.2% of the applied voltage.

In your instance I think you want to delay the output of one 4017 before you trigger the next 4017. If this is right, the best way is to use a one-shot multivibrator with the delay time you want. That way the trigger will
have a sharp edge that the 4017 requires.
:D Ned
 

Kalym

New Member
I'm confused.

A is first counter, B is second counter.

I want B to be delayed when A has count to 10.

So I should put the transistor to B leg?
 

Sebi

Active Member
The circuit will work as delay, but the problem: output signal level increasing very slowly, and the next input not a schmitt trigger. Just connect a 40106 two section serial with signal for signal conditioning, and need an additional discharging transistor.
 

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Kalym

New Member
I'm still rather new to this. Can anyone explain how the above circuit works.

I don't understand how the Transistor fits in. I think I understand what you guys mean by the voltage rising slowly, and that having a Schmitt trigger will give a clearer voltage transition. I thought a 4017b already has an internal scmitt trigger?
 

Kalym

New Member
To start with I'm thinking about a 2 second delay.

I think I wanna put a pot to vary the delay.
 

daviddoria

New Member
i agree with the single shot 555 type thing. Have the output from the first chip (your 'A') turn on your 555 circuit, set the time delay in that circuit, then the output from the 555 put to the input of 'B'.
 
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