need the design for this circuit and explanation

EDAboard.com Forum Index -> Electronic Elementary Questions -> need the design for this circuit and explanation

Author

Message

ziyadcomp

Joined: 16 Mar 2009
Posts: 1

16 Mar 2009 8:06 Help me pls.

Dear everyone
I need to analyze 2nd diagram (see the link in the bottom) for ic555 , i need the design for this circuit.
Why we use these values in the circuit (100k,10m,10u,,etc) not other values, I need to understand from where these values.
All I talking about 2nd diagram only.
Thanks.

http://www.talkingelectronics.com/projects/TouchSwitch/TouchSwitch-1.html

Google
AdSense
Google Adsense

16 Mar 2009 8:06 Ads

cameo_2007

Joined: 15 Mar 2007
Posts: 439
Helped: 17
Location: 13.04°N80.17°E

16 Mar 2009 9:57 Help me pls.

That is 555 configured as an astable multivibrator.
where, (refer: datasheet of 555)
T ( the charging time of C) is determined as 1.1RC
that means:
T = 1.1 * R * C
here R = 100K and C = 10u
so approximately , i guess they have set a time of 1sec,and thus arrived at those values of R and C.

And 10M,that is a pull up for trigger input.