questions for the instructables make to learn youth contest :
what did you make?
-i made a light/dark sensor based on the LM741 opamp using parts from my local electronic store.
how did you make it?
- i got the idea from a video about making a dark /light sensor using arduino,so i decided to make an easier version of it.
where did you make it?
-i made it at my school and entered it for my science fair.
what did you learn?
- i learnt how a op amp works and how to use it and all the cool circuits you can do using it.
Step 1: COMPONENTS :
-4.7k resistor x1
-photo resistor x1
-180 ohm resistor(i did'nt put a picture for this)
-lm741 opamp ic
-l.e.d(any color) x1
-9v battery snap and
- a breadboard
Step 2: MAKING IT!
-insert the lm741 chip into the breadboard
-connect pin 4 to your negative rail of the breadboard(choose one side as your negative rail)
-connect pin 7 to the positive rail of your breadboard(choose the opposite side as your positive rail)
-connect a 100k resistor from pin 3 to negative rail of your breadboard
-connect another 100k resistor from pin 2 to negative rail of your bread board
-connect a 4.7 k resistor from positive rail of your breadboard to pin 3
-connect the photo resistor from pin 2 to positive rail of your breadboard
-insert the l.e.d into the breadboard (identify the positive(anode) and the cathode(negative) of the l.e.d)
-connect a 180 ohm resistor from pin 6 to positive of the l.e.d
-insert the red wire(positive) of the battery snap into your positive rail of the breadboard and the black wire(negative) to the negative rail of the breadboard.*
*note that the rails of the bread board do not run fully through the breadboard,they are split into 2 five pairs of 10 holes.