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how many ways to implement bjt?

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rohaan

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hey
i wanna do some thing with bjt ..
it could be light detctor or any thing..
actually i know only that bjt is for amplifying purpose..except this i wanna make some project..
so would any one of u knw bout it!!
sensing bjt circuit,,,or what it can be?
hope, u people help me out!!:rolleyes:
 
I guess you could make a dark detector and put it where the sun doesn't shine. It will detect the darkness, and turn on a light.
 
ok
so i have to put an led in the circuit..with LDR
actually i heard that to use relay with it..
so for what purpose i use relay ..?
there is no way to use bjt..??
 
rohaan said:
haiku??
:s
A 17-syllable poem, popular with our Japanese friends for whom it is a high art form.
 
rohaan said:
ok
so i have to put an led in the circuit..with LDR
actually i heard that to use relay with it..
so for what purpose i use relay ..?
there is no way to use bjt..??
You can use the bjt to boost the signal from the LDR, and you can use the bjt to turn on the relay. It can be used to make an astable multivibrator, or a OneShot, or a Flip-Flop.
 
what is to turn on the relay?
is it the part of flip flop or one shot..i guess not!
please can u explain :S
 
A relay has a coil. That coil is part of an electro magnet that is turned on when a current flows through it. The electromagnet will change the position of a set of mechanical contacts. A contact which is closed when there is no current in the coil is called "Normally Closed", A contact which is open when there is no current in the coil is called "Normally Open".

A bjt can be used as a switch, to allow current to flow through the coil when it is on, or to block it when it is off.
 
ok u mean it will just as a swtich..
but if i use bjt with LDR and relay..
so what it will do?
how it will act as a light detstor?
does i hv to put led in it? or LDR is enough
how can i know that it is working as light detctor..
 
You will use the current from the dark detector to turn on a bjt when it is illuminated. When the illumination goes away the bjt will turn off. When that 1st bjt turns off, a second one turns on and that will energize the relay coil. That is the basic dark detector, and you can put it where the sun doesn't shine to detect the dark.
 
Papabravo said:
You will use the current from the dark detector to turn on a bjt when it is illuminated. When the illumination goes away the bjt will turn off. When that 1st bjt turns off, a second one turns on and that will energize the relay coil. That is the basic dark detector, and you can put it where the sun doesn't shine to detect the dark.
:D sorry it struck me as funny.
 
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