Discussion in "Project Doubts" started by    saxenanitesh    Mar 3, 2008.
Mon Mar 03 2008, 11:23 AM
can u please explain me the working of the ckt diagram exp the part of the
transmitter n reciever part it would be a great help
and is there any changes in the code of this project?? or any
problems in the ckt???
please sir this is really urgent
if u can help me out please....
Mon Mar 03 2008, 04:54 PM
re-post/duplicate ? :-|
Mon Mar 03 2008, 04:57 PM
no actually i posted on both
i just wanted to knw if possible if u can me with this project
n explain me the reciever side of the ckt please
Tue Mar 04 2008, 05:06 PM
ok i explain from room.gif
first the left side of AT89S52:
you see two sensors. sensors are connected in the following way on the entrance of door.
---> Entrance this way -->  --------
  S      S
  1      2

S1 is sensor 1 and S2 is sensor 2
555 timers gives high->low pulse whenever user crosses the sensor.

Now right side of AT89S52, you have 7-segments to show count and one bulb through relay. When user count in room is greater than 0 blub glows.. if users in room are 0 blub switches off.. hence controlling the room's light.

Now room1.gif
it just have two transmitter circuit which will be on the other side of door facing the receivers(sensors) on the other side of door.

I hope circuit is clear to you now.. is there anything else you want to know about?
 saxenaniteshgsriram187 like this.
Tags visitor counter room light controller projectcircuit explanation room light controller visitor
Tue Mar 04 2008, 05:21 PM
yes sir
i have another question...
y did we add 56k resistance n cap. to the reset pin?? and how did we arrive to those
wats the function of 555 in the room.gif n how did we arrive to those values??
as i calculated the t=0.24secs so y tat long???
Tue Mar 04 2008, 05:36 PM
i get tat when there a change.. in sensor it gives high to low pulse..
i m not able to understand how come we have chose 100K n 2.2uf
for the 555 to get t-0.24secs for pulse width to be given to the MC??
where did we get those values can u please help me with tat?? y 100k n 2.2uf
n y a period of 0.24secs as a pulse width???? tats where im little confused...
Tue Mar 04 2008, 05:43 PM
and y have we added
56K n 1uf cap with reset pin???
y is tat also??? its just not making sense to me..
so can u please me n the earlier thread... thanz you..
Wed Mar 05 2008, 06:06 PM
hello sir...
i just wanted to the y 555 is giving a 0.242 secs of low op in the ckit
and how did we arrive to tat value of 100K??? please sir can u reply me tat
asap if it would be really help.
2. the sensor gives a op of 5V whn it is not interrupted and CE cofig is used??
wats the use of tat CE config in this ckt for amplying?? whn the sensor is not
giving any output whn it is interrupted??
thank you
please sir hopefully u can answer my doubts...
thank you again..
Wed Mar 05 2008, 07:57 PM
read about 555 timer.. and see how the value of Resistors and caps are calculated.

whatever you mentioned in point 2 is correct...
when interrupted you will get low.
Thu Mar 06 2008, 02:14 AM
ok sir..
but i dont understand y its being used the 555 n amplifying CE ckt..
coz in the sensor datasheet they have put sensor directly to the
uC without the those two ckts!!!!
i knw how to get the resistor value...
but i dont understand y we have only chose 0.242 secs for a low pulse being
applied to the ckt...and finally the use of 555.. its not clear.. can u please
explain it to me... couldnt we have fun a lower time period of a low pulse than
we have calculated...

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