555 Timing Question

Archiver

Do I have to use an Electrolytic capacitor for the timing portion, or can I
use a Ceramic Disk capacitor ?

I am trying to generate a 40kHz signal. I am using the 555 Timer program by
Andrew Clarkson. It says that for a 40kHz
I should use a 7.2K for Ra and 177K for Rb with a 100pF capacitor.

Archiver

If your goal is to do IR object detection, you can do it without using the
555. FREQOUT generates enough harmonics to modulate an IR diode. Download
the IR LED document from this link:

http://www.parallaxinc.com/html_files/resources/wknd_specials.htm

If you're going send encoded data, then you should avoid ceramic discs in
your circuit. They are not very stable and will give you a lot of problems.
I'd use a mylar or better quality cap.

-- Jon Williams
-- Parallax


In a message dated 1/11/02 8:09:09 AM Central Standard Time,
bsmith@w... writes:


> Do I have to use an Electrolytic capacitor for the timing portion, or can I
> use a Ceramic Disk capacitor ?
>
> I am trying to generate a 40kHz signal. I am using the 555 Timer program by
> Andrew Clarkson. It says that for a 40kHz
>




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