555 timer with a 4017

[Fred1]

Hello;
I'll start off with the parts I am using. A 555 timer and a 4017. I am trying to set up a string of chase lights . The circuit works but not the way I want. I need the lights to start running then to slow down to a stop. Can anyone help me with a circuit for the 555.
Fred.

 

[ericgibbs]

hi fred,
You say you want the led turn ON selection to slow down.

Need to know,
How fast at start and how long is the slowing down period before it stops.?
Does the slow rate have to linear?

EricG

 

[AllVol]

Thinking it through, the 555 emits a sink or source pulse on pin 3 at regular intervals as determined by the resistor-capacitor setup on pins 2, 6 and 7. The 4017 simply responds to this pulse by advancing one count until it reaches 10, then starts over. To gradually slow the count, you would have to systematically alter the duty cycle of the 555, lengthening the off space each pulse until it counts ten, then repeating for each cycle.

I can think of no way to do this with just a 555 and 4017, although some of the wiser may.

It could be easily done with a PIC, however. (OMG! I'm beginning to sound like THEM!

 

[Fred1]

555 with 4017

Hello;
Forget about the 4017. My problem is the 555. I need it to start pulsing to a high rate then slow down to a stop. I can adjust speed with potentiometer.
I am using the 4017 as a counter for the lights.
FRed.

 

[Hero999]

There seem to have been quite a few "555 with 4017" threads around recently, I wonder if a college has it as part of the course.

 

[Roff]

Hello;
Forget about the 4017. My problem is the 555. I need it to start pulsing to a high rate then slow down to a stop. I can adjust speed with potentiometer.
I am using the 4017 as a counter for the lights.
FRed.

Do you want it to do this only every time you turn it on, or do you want to be able to leave it on and restart the cycle with a switch or control signal?

 

[Fred1]

555 with 4017

Hello;
I am going to use a momentary switch.
Fred.

 

[TheSmuel]

Hi all,

Fred,
**broken link removed** might have what you want. Scroll down to "diminishing frequency astables". I adapted this to make an "electronic dice" that counted from 1 to 6 with diminishing speed until it stopped at a random number (although it seemed to stop at 3 rather often ).

Hope this helps,

Sam

 

[Roff]

Hello;
I am going to use a momentary switch.
Fred.

You also need to answer Eric's question.

 

[AllVol]

The easiest way to MANUALLY alter the duty cycle of a 555 is by attaching a pot between + rail and ground with the wiper to pin 5. Then, you can, with practice, slow the blink rate of the LEDs as the 4017 counts. You would need to start with a very slow count, using a high value timing cap and appropriate resistors on pins 6 and 7.

 

[Fred1]

555 with 4017

Hello;
Thanks to everyone for all this information. I have destroyed more then one chip trying to figure out the circuit. Who is Eric and what was the question.
Fred.

 

[Fred1]

555 with 4017

Hello;
I found Eric's ouestion.
Fred

 

[ericgibbs]

hi Fred,
Ti's I Eric.

How fast is the pulse generator running at the instant you have pushed the momentary switch, for example is it 1000hZ or 100hZ ??

What period of time from when you push the button does it reach the stop state ??

Does it matter if the slow down rate is linear with time or will an exponential rate do ?? [RC discharge/charge]

EricG

 

[Roff]

Hello;
I found Eric's ouestion.
Fred

That's very informative. Are you going to answer it?

 

[House0Fwax]

I think that this is the sort of thing Fred is after;
https://www.electro-tech-online.com/custompdfs/2007/02/3003.pdf
I posted this link for him in another thread ( before he started this one ).

 

[Roff]

I think that this is the sort of thing Fred is after;
https://www.electronic-kits-and-projects.com/kit-files/3000/3003.pdf
I posted this link for him in another thread ( before he started this one ).

I think I would add a resistor in series with the emitter of Q4, and swap R2 R1 and R2 to keep Q4 out of saturation. Otherwise, that's similar to what I had in mind.

 

[Fred1]

555 with 4017

Hello;
First Thanks House of wax. I took your advise tried this thread.
Eric: Sorry I did not answer your question. What I have been trying to do is when I push the momentary switch the 555 starts pulsing a speed where I can still see the count,(4017) then when I release the switch the 555 slows down to a stop.
Thanks guys your taking a lot of time with my problem.
Fred