Light Sensor Circuit

[shelladavis]

i finally understand thank you

[guruakagos]

lastly a straight forward question eh, i have a 3V-4.5V motor and a power source of 3-4.5V i need an ldr (or anything else that might work) in between this two, to cut the supply to the motor if there is too little light detected.

[guruakagos]

hey also, i'd like to ask why do i need the rest of the components? can't it just be a simple circuit, a power source connected to an LDR connected to and LED. when you cover the LDR the LED doesn't light and when the LDR is exposed to light the LED does? can that work?

[guruakagos]

and also is it still possible if my circuit runs on 3V? is there any changes i should make?

[justvisiblesilence]

@guruakagos It can still work with 6V. Any lower than that it may not work.

You can try using a "Photo transistor" instead of a light dependent resistor.

[guruakagos]

hey whats the name of the transistor again? ujt?

[justvisiblesilence]

@guruakagos It's called BJT (Bi-polar Junction Transistor)

[joshstube]

Thank You for your video & explanation.

I have had trouble with switching loads from the emitter side of the transistor. I can only get it to work if I connect the emitter to ground and sourcing the negative side of the load.

Also, If you switch the resistor/LDR won't it work in reverse (like a photo light outside)?

thanks for your demonstration

[strangerlover11]

Excellent video but you did't mentioned the measurement of LDR how many voltage

should be ? and if i use PNP transister rather than NPN than.........???

[kakulugiashthegreat]

dude i need a circuit which can light when it is dark and turn off after five mins help me please

[stegtenudlar]

Excellent!

[mooreno444]

very good. only i need , with night .

[kraudio7]

@mooreno444

To make it light at night, just place de LDR were the 22k resistor is, and place the 22k resistor where the LDR is.

[smellyfry]

i luv your singaporean accent! great tutorial. Well done.

[penixnet]

If the emitter and collector connections were reversed..would it make the circuit into a dark detector?

[man13preet]

yeah....may be...

once i made a light detec. with BC 547...with right polarity...means connection were right with collector and emitter....

so i decided it with 2n3906...i didnt knew its C B E pins...so as i connected, it didnt lit up...so when i put off the lights....it lit....

try .... thats the way... :-) :-) :-) :-) :-)

[hotsawse007]

@penixnet No it would be a dark matter detector. Haven't you seen the movie Angels and Demons?