Ok, my use of 555s has gone on since I was a kid, but I think that I have never used Pin 5.
Is this some sort of conspiracy dreamt up by microcontroller uses to limit my useage!!!
I can only imagine the grandeur that could have been if we only knew of what this pin can do!!

 

The control pin can be used to shift the comparator reference voltages.

 

Back in the 1970s, electronic magazines had columns where people would show clever ways to use circuits.
In one of them, it showed how to use this pin to fine trim a multiple-delay mono stable.
Browsing for something else, I saw it a couple of weeks ago, but I can’t find it now.

 

Ok, my use of 555s has gone on since I was a kid, but I think that I have never used Pin 5.
Is this some sort of conspiracy dreamt up by microcontroller uses to limit my useage!!!
I can only imagine the grandeur that could have been if we only knew of what this pin can do!!

"We" can know of what this pin can do by reading the data sheet:

 

I use it to reduce the size of the timing cap needed, as well as some esoteric use I have with my "breathing" circuits.

 

I can only imagine the grandeur that could have been if we only knew of what this pin can do!!

Example of pin 5 (CV) using:
https://forum.allaboutcircuits.com/...it-not-working-in-proteus.186554/post-1733652

 

So it seems that it is more a way of "Tuning" its function??

 

Example of pin 5 (CV) using:
https://forum.allaboutcircuits.com/...it-not-working-in-proteus.186554/post-1733652
View attachment 359713

i HAVE NEVER GOTTEN SICH A CLEAN WAVE OUT OF A 555 (Caps Lk.)

 

I use it to reduce the size of the timing cap needed, as well as some esoteric use I have with my "breathing" circuits.

Now thats interesting, and useful

 

Never done this but I think it can vary the tone of an audio tone generator. By varying the voltage level on pin 5 you can shade the tone up or down. Don't know how much of a change it can bring but this is what I've been told before.

 

Never done this but I think it can vary the tone of an audio tone generator. By varying the voltage level on pin 5 you can shade the tone up or down. Don't know how much of a change it can bring but this is what I've been told before.

what does the "Tone" of a signal actually consist of changing?...amplitude?

 

Hello,

Have a look at the pages 13 and 14 of the attached datasheet for the use of pin5.

Bertus

 

Ok, so the spec sheet marks this as CONT, which in some cases can accept a frequency in, but it seems in other cases is tied to ground with a 0,01uf capacitor?

 

hi Kim,
Pin #5 Con is often used for adding some control of the frequency, by applying an external voltage, when not used it should be tied down with a 10n to 0v,
E

 

As Eric mentioned, it is good engineering practice, to bypass this pin with a cap when not used.
Although most people don’t follow good engineering practices.

 

what does the "Tone" of a signal actually consist of changing?...amplitude?

Pin #5 Con is often used for adding some control of the frequency, by applying an external voltage

Tone and volume are two different things. Changing the tone, as ericgibbs states in the quote, is for changing the frequency. Volume would equate to changing the amplitude not the tone.

 

Hello,

From page 25 of the application booklet shows you a "warble" circuit.

Bertus

 

Have you noticed that the minimum and maximum voltages for pin 5 are not shown on the datasheet? All it says is the voltage that will be present there if nothing else is connected.

 

Ok, so the spec sheet marks this as CONT, which in some cases can accept a frequency in, but it seems in other cases is tied to ground with a 0,01uf capacitor?

Look at the internal diagram of the 555:



The threshold voltage for the comparator is generated by a resistive voltage divider to Vcc/3.

If you apply a voltage to the control pin, the threshold voltage becomes Vcntl/2, giving you direct control over the threshold, which in turn gives you the ability to change the timing behavior of the circuit.

When you don't want to do this, you want the threshold voltage to be as stable as possible, but any noise on the power supply will appear (at one-third the value) at the threshold. By bypassing the control voltage pin to gnd, you stabilize the threshold voltage by shunting power supply noise currents through the cap.