breathing circuit

[BioniC187]

Hey guys, has anyone made this circuit?
**broken link removed**
I have made it and i do not get the waveform that was to be expected.
Any other circuits similar to this that works?

 

[jpanhalt]

I am too tired to guess. What waveform do you get? Where did you measure it?

John

 

[Mikebits]

I am too tired to guess. What waveform do you get? Where did you measure it?

John

lol. I think he is looking for a ramp. When he said breathing circuit, I thought he meant it measured respiratory rate or something.

 

[BioniC187]

It's not a proper triangle wave form, i measured from the capacitor. I'm fiddling around with some stuff, will post feedback if i get a working circuit

 

[jpanhalt]

It will never be a proper triangle wave, because you are measuring the charging of a capacitor through a resistor. That is what the link shows.

What component values did you use? There are great 555 simulators on the Internet, as well as LT Spice. After all of these years, it is unlikely the 555 is not working properly. The most likely explanations are that you are getting exactly what you should be getting for the values you used, or you wired it up incorrectly. That is why seeing the waveform you are getting and knowing the component values you used is important.

John

 

[dougy83]

That circuit will be affected drastically by any changes in the transistor gain, and any change in temperature. If you want to use it, you'll probably have to stuff around selecting the appropriate value for R4.

You could always just drive the LED using a Sziklai pair connected to the capacitor (and don't forget the LED series resistor).

 

[audioguru]

Yes, I agree that the "amplifier transistor" is simply an on-off switch.
Also, you cannot fade-in and fade-out the brightness of an LED with a voltage triangle waveform. It must be a current triangle waveform instead.

 

[BioniC187]

Ok, so how can i convert a voltage triangle waveform to a current triangle waveform? Thanks for replies

 

[alec_t]

Here's one way
View attachment 66879

 

[BioniC187]

Hmmm, are there any other ways using pnp transistors? What you suggested seems bulkier than i anticipated , but thanks though

 

[audioguru]

Hmmm, are there any other ways using pnp transistors? What you suggested seems bulkier than i anticipated , but thanks though

The circuit can also use PNP transistors if it is wired correctly.

 

[alec_t]

Here's how you could do it with pnp transistors
View attachment 66908

 

[BioniC187]

Alright, i will look into it. thanks