Howdy All,
I have a simple running led circuit using a 555ic and a 4017ic.
The trigger is currently using a 50k variable resistor to control the trigger timing.

What I am trying to make it do is vary the led timing, so that the led's timing gets faster and then slower, continuously, when power is applied.
Is there a way to use the out signal of the 555 to charge a capacitor in part of the timing control? can the control input be changed? or can i bolt on some extra circuit part to achieve what I'm after?
Thanks for your help.

 

How fast do you want the frequency to vary?
Should this variation be synchronized to the LED sequence?
A triangle-wave generator could be used to vary the 555 frequency.

 

Welcome to AAC!

You could use another 555 to drive the control input of the existing timer:

If you're not picky about linearity, you can use the capacitor voltage of the second timer as the modulator:


Circuits from NatSemi datasheet.

 

How fast do you want the frequency to vary?
Should this variation be synchronized to the LED sequence?
A triangle-wave generator could be used to vary the 555 frequency.

Cheer, Only running slow.
2hz to 15hz

 

Cheer, Only running slow.
2hz to 15hz

So it doesn't need to be related to the LED sequence frequency?

 

The present frequency is 11.8~65 Hz?
R2 = 47K/15 Hz
R2 = 350K/2 Hz
R2 = VR500K in paralle with 750K and in series with 47K

555 Online calculator.
The online calculator of two resistors in parallel .

 

Cheers for the calc, Scott.
Yup that is the total hz range but to the eye becomes irrelevant up near 65. and the eventual outcome is visual.

The 555 out (pin 3) drives the rate of change in pin 14 of the 4017. So as the frequency of the 555 output changes the led's appear to speed up and slow down in their flow (across the 10 led's). Rate of timing or acceleration/deceleration timing needs only be a duty time of 10secs.

 

Yup that is the total hz range but to the eye becomes irrelevant up near 65. and the eventual outcome is visual.

For 10 LEDs then the 15 Hz should be up to 150 Hz, why is 65 Hz?

Rate of timing or acceleration/deceleration timing needs only be a duty time of 10secs.

2Hz is 0.5 seconds, one of 10 seconds is 1 second why they are different?

What is the real range that you want?

 

Here's another way to vary the timing. I haven't shown the LEDs and their respective current-limiting resistors (which would be connected as in post #1).

 

For 10 LEDs then the 15 Hz should be up to 150 Hz, why is 65 Hz?


2Hz is 0.5 seconds, one of 10 seconds is 1 second why they are different?

What is the real range that you want?

Scott you are awesome at picking short comings lol.
Original config as you noted is 11 to 65 hz this is going to be changed to 2 to 15hz, thanks again for the calculations.
This figure represents the actual driving pulses ie turning on and off 1 to 10 of the 4017. this is going to be good at max of 15hz.

The 10 second is a line in the sand, it is not critical and may have to be recalculated to best suit, this would be the duty cycle of going from 2hz to 15hz and back to 2hz.

The effect, needed is to have an array of ten led's, that turn on in sequence ie running flow, during multiple cycles of the flow the rate is to speed up and slow down.
As said this is purely visual just for the hand on willy factor.

 

Scott you are awesome at picking short comings lol.
Original config as you noted is 11 to 65 hz this is going to be changed to 2 to 15hz, thanks again for the calculations.
This figure represents the actual driving pulses ie turning on and off 1 to 10 of the 4017. this is going to be good at max of 15hz.

The 10 second is a line in the sand, it is not critical and may have to be recalculated to best suit, this would be the duty cycle of going from 2hz to 15hz and back to 2hz.

The effect, needed is to have an array of ten led's, that turn on in sequence ie running flow, during multiple cycles of the flow the rate is to speed up and slow down.
As said this is purely visual just for the hand on willy factor.

If you want to make the flashing speed can be speed up and down automatically then there is an easy way that you can try and that is:
NE555 Astable Multivibrator → RC Integrator → NE555 V to F(Voltage Controlled Oscillator (VCO)) → CD 4017 → R x10,LED x10