Light Detector, No Microprocessors, Just Simple Electronics :)
Intro: Light Detector, No Microprocessors, Just Simple Electronics :)
I will show you two circuits, one turns an LED off when theres no light, and the other turns an LED on when theres no light.
for the first one you will need:
-R1(LDR) 10K
-R2 (1.2K) colour code: brown, red, red.
-R3(10 ohms) colour code: brown black black.
-T1 almost any low voltage NPN transistor will do.
-L1 LED i used a red one.
-potenciometer(optional)
-jump wires
-breadboard
-2 1.5 volt bateries and pack for them
for the second one you will need:
-R1 (LDR) 10K
-R4 (10K) colour code: brown, black, orange.
-R3(100 0hms) colour code: brown, black, black.
-T1 any low voltage NPN transistor
-L1 LED i used a red one.
-potenciometer(optional)
-jump wires
-breadboard
-2 1.5 volt bateries and pack for them
it cost me under 1€ to make this, everything was salvadged from old radios, etc...
exept the LDR, but you can easiy get one from those light switch thingies at the dollar shop, or from the internet very cheap... add some more stuff if you get it from the net though... you dont wanna pay 10 cents for the part and 8 dollars for shipping =|
for the first one you will need:
-R1(LDR) 10K
-R2 (1.2K) colour code: brown, red, red.
-R3(10 ohms) colour code: brown black black.
-T1 almost any low voltage NPN transistor will do.
-L1 LED i used a red one.
-potenciometer(optional)
-jump wires
-breadboard
-2 1.5 volt bateries and pack for them
for the second one you will need:
-R1 (LDR) 10K
-R4 (10K) colour code: brown, black, orange.
-R3(100 0hms) colour code: brown, black, black.
-T1 any low voltage NPN transistor
-L1 LED i used a red one.
-potenciometer(optional)
-jump wires
-breadboard
-2 1.5 volt bateries and pack for them
it cost me under 1€ to make this, everything was salvadged from old radios, etc...
exept the LDR, but you can easiy get one from those light switch thingies at the dollar shop, or from the internet very cheap... add some more stuff if you get it from the net though... you dont wanna pay 10 cents for the part and 8 dollars for shipping =|
STEP 1: Turn LED Off When Theres No Light
the 1.2 K resistor goes in the middle pin of the transistor and to - on battery
dont forget the round part of the transistor is facing you!
DONT FORGET THE POLARITIES OF THE LED!!!
dont forget the round part of the transistor is facing you!
DONT FORGET THE POLARITIES OF THE LED!!!
STEP 2: Turn LED on Whe Theres No Light
it's basically the same circuit but the LDR now goes to - and the R4(10K resistor) goes to plus.
all you have to do is this small change and the whole purpose of the circuit changes!
dont forget the round part of the transistor is facing you!
DONT FORGET THE POLARITIES OF THE LED!!!
if you have any doubts/problems plz tell me.
all you have to do is this small change and the whole purpose of the circuit changes!
dont forget the round part of the transistor is facing you!
DONT FORGET THE POLARITIES OF THE LED!!!
if you have any doubts/problems plz tell me.
STEP 3: Apendix
Now i'm going to try to explain what some parts do.
on the first circuit the 1.2K resistor controls the sensitivity, go ahead change it! if it's 10K you will need total darkness to turn the LED off, so change it betwen 1K and 10K less than 1K will be way sensitive and wont work, and over 10K you will need something darker than total darkness, wich i dont think exists, maybe outer space :P
the second circuit the 10K resistor also controls the sensitivity, if you put 150K you will need total darkness to turn the LED on, so go ahed change it aswell! but only betwen 1K and 150K.
If it doesnt work:
check the polarities of the LED, and see if the transistor is the right way in, if the LED doesnt go on, on the first circuit, dont be sad, that circuit is tuned so it works in my room, just grab a potenciometer and tune it the way you want to, then with a multimeter read the resistance of the pot, and put the closest resistor you can find to that resuslt, thats how i got 1.2K and 10K
best of luck!
Now a video of what you should expect:
on the first circuit the 1.2K resistor controls the sensitivity, go ahead change it! if it's 10K you will need total darkness to turn the LED off, so change it betwen 1K and 10K less than 1K will be way sensitive and wont work, and over 10K you will need something darker than total darkness, wich i dont think exists, maybe outer space :P
the second circuit the 10K resistor also controls the sensitivity, if you put 150K you will need total darkness to turn the LED on, so go ahed change it aswell! but only betwen 1K and 150K.
If it doesnt work:
check the polarities of the LED, and see if the transistor is the right way in, if the LED doesnt go on, on the first circuit, dont be sad, that circuit is tuned so it works in my room, just grab a potenciometer and tune it the way you want to, then with a multimeter read the resistance of the pot, and put the closest resistor you can find to that resuslt, thats how i got 1.2K and 10K
best of luck!
Now a video of what you should expect:
62 Comments
Sports_Nut_ 9 years ago
awesomevicky 9 years ago
jamesricedesign 11 years ago
rohanbansal 11 years ago
McBlaise 15 years ago
amando96 15 years ago
http://s498.photobucket.com/albums/rr346/AmandoAbreu/?action=view¤t=100_2562.jpg
http://s498.photobucket.com/albums/rr346/AmandoAbreu/?action=view¤t=100_2574.jpg
i only have one motor yet though xD
but yea if its a small motor, its fine, if you want to use bigger rmotor, you'll have to put another transistor
wooohhhoooo9 12 years ago
jules15 14 years ago
robot1398 13 years ago
cool project
imakethings 13 years ago
imakethings 13 years ago
ARJOON 13 years ago
souichi 13 years ago
akhile1996 14 years ago
akhile1996 14 years ago
cybertron 14 years ago
In the first circuit...
Turn LED off when there's no light!
If i use 5VDC for the power supply do i need to change the resistor on the base of the transistor if so, at what value. Also the led resistor needs to change to compensate for the leds current. BUT i have that covered.
Does any other components need to change at 5VDC. This will be tested in a circuit to detect, very bright light.
Reply would be appreciated.
amando96 14 years ago
try using a potenciometer, to find the resistance you need for the light you want to detect.
cybertron 14 years ago
as stated, Got this covered.. Thanks for pointing that out.
So you're saying to use a potentiometer at the base of the transistor for base current to find the resistance i need for the light i need to detect.
How will that deterrmine the resistance of the light I'm detecting.
And what vulue would the pot need to be 1k, 5k. 20k. or Higher.
So the LDR dose not need to be replaced. i just need too lower the base current.
Reply Thanks.
DRM_MX 14 years ago
amando96 14 years ago