A transistor is an electronic device which has three terminals and can be used as electronic switch and signal amplification.Here is an example of transistor as a switch which is designed by me.
AUTOMATIC STREET LIGHT
Automatic street light is the automatic switching device which glows at night automatically and turns off automatically at day. The following diagram shows the schematics of automatic street light.
PART LIST
Transistor -- BC547
light dependent resistor
resistors--330R, 1k
led
6/9 volt battery
EXPLANATION
The automatic street light functions as switch. To understand this let us view the following diagrams.
During day time, the the ldr or light dependent resistor has minimum resistance and a little current flows through it. it results the biasing of transistor bc547 and the current flows through it due to the sufficient charge carrier at base. so the potential drop across the transistor is zero and at that time light doesn't glow. so at day time light turns off.
during night time, the resistance of the ldr is very high so that the current doesn't flow through it and the transistor doesn't get base biasing. so the current doesn't flow through transistor bc547 and the voltage across it is maximum.so the current flows through led and the led glows. so at night the light glows.
click the link below to know about ldr
http://www.google.com.np/imgres?imgurl=http://tutorial.cytron.com.my/wp-content/uploads/2011/08/LDR1.jpg&imgrefurl=http://tutorial.cytron.com.my/2011/08/10/project-9-%25E2%2580%2593-analog-sensor-light-detection-using-ldr/&h=301&w=555&sz=16&tbnid=rncu010iSzWXsM:&tbnh=72&tbnw=133&zoom=1&usg=__HZucrbooALGMs_rbKLcvBoKVAqo=&docid=w7xVeq0pXp9kcM&sa=X&ei=QBEsUqbmHMuTrgfNy4CoDw&ved=0CDEQ9QEwAQ&dur=3209
In this way the automatic street light designed by me works. so please try it and enjoy the project.
if you have any question about this post you can ask to me by writing the comments or my mailing me on the email sangit.niroula@gmail.com.... thank you so much for watching....please like and share knowledge and technology.. ckick this link for bc 547 npn transistor information
PART LIST
Transistor -- BC547
light dependent resistor
resistors--330R, 1k
led
6/9 volt battery
EXPLANATION
The automatic street light functions as switch. To understand this let us view the following diagrams.
During day time, the the ldr or light dependent resistor has minimum resistance and a little current flows through it. it results the biasing of transistor bc547 and the current flows through it due to the sufficient charge carrier at base. so the potential drop across the transistor is zero and at that time light doesn't glow. so at day time light turns off.
during night time, the resistance of the ldr is very high so that the current doesn't flow through it and the transistor doesn't get base biasing. so the current doesn't flow through transistor bc547 and the voltage across it is maximum.so the current flows through led and the led glows. so at night the light glows.
click the link below to know about ldr
http://www.google.com.np/imgres?imgurl=http://tutorial.cytron.com.my/wp-content/uploads/2011/08/LDR1.jpg&imgrefurl=http://tutorial.cytron.com.my/2011/08/10/project-9-%25E2%2580%2593-analog-sensor-light-detection-using-ldr/&h=301&w=555&sz=16&tbnid=rncu010iSzWXsM:&tbnh=72&tbnw=133&zoom=1&usg=__HZucrbooALGMs_rbKLcvBoKVAqo=&docid=w7xVeq0pXp9kcM&sa=X&ei=QBEsUqbmHMuTrgfNy4CoDw&ved=0CDEQ9QEwAQ&dur=3209
In this way the automatic street light designed by me works. so please try it and enjoy the project.
if you have any question about this post you can ask to me by writing the comments or my mailing me on the email sangit.niroula@gmail.com.... thank you so much for watching....please like and share knowledge and technology.. ckick this link for bc 547 npn transistor information
