Discussion in "Project Doubts" started by    saxenanitesh    Mar 3, 2008.
Thu Mar 06 2008, 10:15 am
The transistor is used more as an inverter......you need a low at the 555 reset pin when the output of the sensor is high and vice-versa.
The 555 is configured as a monostable and in a monostable the output duration(here 0.242s) should be greater than input pulse(provided by the visitor interrupting the sensor).Surely you would want to give atleast 0.24 seconds for a person to pass through .... do consider a fat guy walking past at a leisurely pace
Thu Mar 06 2008, 02:45 pm
oh ok fine..so the transistor is used as an inverter n the time 0.24secs is just fixed by us.. oh ok thanz alot.. it makes the things more clear...
but the the reset pin of 555 is connected to the VCC=5v... which is high..
i think u meant the trigger pin from with the transistor is connected?? i thought the 555 gives a high to low pulse??? or is it other way around low to high pulse???? being given to the uC can u explain me tat part also!!!!! please thanz you.. just little bit into the dark
abt tat part!!! thank you for explaining me tat much...
Thu Mar 06 2008, 02:56 pm
i just wanna make everything clear...
whn there is no interruption the sensor gives a high output..
the inverter inverts the o/p from a high to low o/p n supplys it to the 555..
555 gives a low o/p also which doesnt give any o/p to the uC..
am i correct so far?? for the working???
whn there is a interruption sensor sends a low o/p which is converted
into high o/p from the transistor n the 555 gives a high o/p to the uC and
it detects it as port 1 is needs 1 to act a input and increments the counter n
turns on the lights?? tats how the project works??? correct!!!
Thu Mar 06 2008, 05:12 pm
sorry to disturb again..
i implemented the ckt.. there is a slight problem in the code..
as soon as the first sensor the entry sensor is interruppted the lights are on tats ok
whn the uC checks for the first sensor again it switches off it doesnt check the
second sensor only..
its just first sensor interrupts the lights on n whn it senses the sensor1 o/p is high
it just offs the light.. again...
Thu Mar 06 2008, 07:51 pm
you have to cross both the sensors while entering and while exit not just one.. ok?
Thu Mar 06 2008, 08:02 pm
oh ok..
so how does it work then.. if we cross both sensors then
how does it knw whn it shld turn on? n turn off??
is it confusing!!!!!!

how does it work whn its suppose 2 turn off the lights??????
so we cross both the sensors n the light turns on tats it..
but how it suppose 2 knw whn light is suppose 2 turn off??
i thought the first sensor sensors senses the light to be turned on
n the second sensors senses whn the people leave n turns off the lights!!!
so yah.. wats the thing... can u explain it to me.. please...

is there any specific specf. tat the first sensor or second sensor has 2 be crossed or it can be any order??????

[ Edited Thu Mar 06 2008, 09:26 pm ]
Thu Mar 06 2008, 09:33 pm
well i think you are confusing yourself and not getting the real thing.

I tell you.. as i explained earlier, sensors are connected at the door stacked one after the other.. from the entrance side sensor 1 comes and then sensor 2.

So when you enter inside the room, you cross first sensor and then second sensor.. and room visitor count is incremented by 1. when you come out of room.. you cross sensor 2 and then sensor 1 and count is decremented by 1.

If the count is greater than 0, then light is on... and if count is 0 then light is off. This is how room lights are controlled automatically. and thats the main purpose of this project.

PS: Please do not make multiple posts.. you can click on edit icon to edit your post and add anything you want in your post
 saxenaniteshanuban like this.
Thu Mar 06 2008, 10:09 pm
oh ok thanz alot..
sorry.. i wont do it again!!!1
thanks alot u have helped me alot with all my doubts.. just one last questions
wat the use of 33e (33 ohms right??) in the transmitter side???
rest of my doubts are cleared thank alot.. really u have been really helpful...
Thu Mar 06 2008, 11:22 pm

whn there is no interruption the sensor gives a high output..
the inverter inverts the o/p from a high to low o/p n supplys it to the 555..
555 gives a low o/p also which doesnt give any o/p to the uC..
am i correct so far?? for the working???

More confusion.....when the sensor is interrupted it's output is high(it's a TSOP I presume).The transistor inverts it to a low and so the trigger i/p of 555 gets a hi to low pulse which is needed for the monostable to fire.It then outputs a pulse of 0.24s.
With no interruption the sensor's o/p is low hence 555's trigger is high so it doesn't fire.
Get it?
Thu Mar 06 2008, 11:48 pm
ok sure thanz.. alot.. so i was thinking it the other way around...
1. alrgiht.. and both the sensors have 2 crossed in order to turn on or off the list
at the same time!!!
2. n wats the use of 33ohms on the transmitter side??

Get Social


Powered by e107 Forum System



Sun Jun 16 2024, 09:44 pm
Sun Jun 16 2024, 03:05 pm
Sun Jun 16 2024, 04:23 am
Sat Jun 15 2024, 09:17 pm
Sat Jun 15 2024, 02:18 pm
Fri Jun 14 2024, 03:16 pm
Fri Jun 14 2024, 11:56 am
Thu Jun 13 2024, 06:00 pm