Automatic LED Night Light (Using 555 Timer)




Introduction: Automatic LED Night Light (Using 555 Timer)

About: Super student

Gently got power cut !
And you finding your torch in the DARK !!! Ohh...

No worry, here is the automatic dark detected led light.

Step 1: Parts You Need

* 1M resistor
* 1K resistor
* 10 resistor
* LDR (light dependant resistor)
* Red led (2ma)
* 1W white led
* BC338 transistor
* 555 timer IC
* DC socket

Note: Use dc socket according to your charger/adapter pin.

Step 2: Circuit Diagram

The circuit uses main IC called 555 timer ic as it basically used in ustable and monostable modes.

The circuit is very simple to build across IC 555

Red led is provided as a Standby indicator which makes you know LDR is detecting light.

And as the darkness in the room get increased above certain limit, red led shuts off and 1W led is swiched on by transistor.

Here I have used 1M ohm resistor. You can adjust this resistance from pin 2/6 of the ic to ground(-) in order to adjust sensitivity to darkness.Less the value of the resistor, more the sensitive in dark.

Step 3: Container Box

Make the container box to best fit this instructable in it.

Step 4: Done !!

Now you got the light which get on Automatically in the dark.



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    20 Discussions


    2 years ago

    plz give me detail explanation of this circuit

    1 reply

    This circuit reffers the resistance of ldr to toggle the output and using 555 timer ic , is quit rasy.

    u can make this using any flip-flop to !


    2 years ago

    great circuit, but I tried it and it didn't work.......

    1 reply

    since all LDRs have different resistances change the 1 meg resistor accordingly.


    3 years ago

    Could you plz share the full circuit diagram with those auto functioning switch

    2 replies

    Hey I uploaded diagram with auto switch.

    Just checkout !!



    But father and mother wont give money to do this

    1 reply

    2 years ago

    Hi, what do you call that switch?

    1 reply

    Three way switch .

    Just checkout the new diagram I uploaded !!

    Nice Project but having problem while making, Please Elaborate 1M ohm resister working and how we calculate the appropriate register value instead of 1M ohm

    1 reply

    By increasing value to 1M, you making it less sensitive to DARK.

    And reducing under 1M will make it more sensitive to DARK !!!

    bro can you provide the charger crcuit for the 4v battery

    2 replies

    Here is the charger that works very nice


    simply you can charge with any 6V adapter ,if 1A then for an hour.



    In one of your photos, the switch is marked "Auto - Off - ON" and right below it, you have written "Mode - On 70mA - Auto 170mA - Standby 2mA".

    You didn't mention how you wired it?

    Nor did you explain the current draw in each position - I'd rather think of numbers like "Off 0mA - Auto Standby ~0.5mA - Auto On 400mA" and I can only guess on the ON current, as you didn't show how you wired it.

    A 1W LED with a 3.6V drop, should never see above 278mA!

    It seems like you use a 4V (2 cell) lead acid battery, so it will be around 4.2V when fully charged and 3.8V when flat. The Auto On current will vary in this interval from around 200mA to 400mA (if the LED has got a 3.6V drop, higher if the LED drop is say 3.3V)

    You really ought to have, (at least) a current limiting resistor on the LED! As is, the current is determined by 3 variables; LED voltage drop, Supply Voltage and the current gain of the transistor. The LM555 really should have a higher voltage - 4V is stretching it.

    If you raise it to 5V (or more), you'll be able to use a simple current limiter (attached pic), that is relatively unaffected by varying voltage or the LED's voltage drop.

    1 reply

    I used 2 leds in ON mode which are actually connected in parallel with 10ohm resistor in series with it, to deliver 35ma current to each of the leds.
    I have not mentioned about it, because is i have added for my purpose (to manually ON/OFF leds at lower current drawn around 70ma)

    Here 1W led no need current limiting resistor.As the full charged battery have 4.2V on it and transistor drops 0.5V. So, 3.7V max is fine for this led.