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Simple dream baby automatic sensor night light

My daughter is about 1 year old, normal to wake request milk. Several times a night.
So to turn on lighting up the night. Causing inconvenience And uneconomical.

We are thinking to buy a baby night light to replace normal lamp instead. By lower light than it to to reduce visual distractions. But enough to see the bottle. And able to breastfeed.

This method makes it more power efficient. Turn on the lamp for the night because If turn on use power of 20 watt, but this system consumes just 1 watt only.

I design Simple dream baby automatic sensor night light as Figure 1 since it cheap and easy to makes
This ideas circuit.
I see in amazon look at many baby night light and I like auto light ideas because it is convenient. It not need have switch on-off. The LEDs glow brightly just when in night or dark only.

How does it works

Simple baby automatic night light
Figure 1 is circuit diagram which I use 4 LED super bright as nigh light so saving. And use an old small DC adapter 9volts is power supply which it have high performance than transformerless power supply.

I use a photoresistor(LDR1) as light sensor he resistance of it will changes with light.

The current flow through to VR1-potentiometer and LDR1 that is set circuit in divider form.


In normally the more light to strike the photoresistor. It cause voltage drop across it is low voltage. So not have current flow to base of Q1.
Therefore Q1,Q2 not works. So LED go out.

Then, not light to LDR, cause voltage across them is high. It cause have current flow to R1-120K to base of Q1,Q2 so them is connected as darlington compound so high gain ratio. Thus the current through to LED1,LED2 to collector and emitter of Q2 to ground. The LED1,LED2 is glowing now.

How to build its

This is very simple project,I assemble parts and wiring on perforated board or Universal PCB board. And install them to universal box. As Figure 2.
Next I test it in bedroom,We can adjust the sensitivity of the circuit with VR1.

assemble parts and wiring on perforated board

Prototype of Simple baby automatic night light
Lastly I take it to really uses as video below.

Note:
1. This circuit not use R-limiting current because we use LED super bright that use voltage 3-4V in fully light.
And This supply voltage is 8.4volts approximately.
2. If you use AC adapter that not good filter, I alway insert a 100uF 25V electrolytic capacitor across +V and Ground to smooth noise or ac ripple voltage. But it not need if you use normal DC power supply regulator.

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This Post Has 8 Comments

  1. Where are the current limiting resistors in series with the LEDs?

  2. In schematic there are no capacitor but demo has capacitor so, where should i put capacitor in schematic?

  3. Hi,Mihai.
    I use LED super bright that use voltage 3-4V in fully light.
    And This supply voltage is 8.4volts approximately. So not need to use a limitting Resistor.

  4. Hi,Salim Khan

    I use a 100uF 25V electrolytic capacitor across +V and Ground to smooth noise or ac ripple voltage.

  5. Hi, Mr OHM 1970

    Thanks so much for feedback.

  6. can we use ordinary cellphone charger adapter?

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