Many Electronic circuit projects in simple ways of learning

Automatic led night light switch

This is the automatic night light circuit system with LED display, and from battery power. Because the house is not convenient plug So the charging system with a solar cell.

Moderately convenient to use.

At night, the LED lights up and LED daytime off and electricity from solar cell charged a 12-volts battery.

The guidelines circuit design

We need to have a Lamps automatically lit up when dark or night.

And the place that install them no AC electrical cable. So I use battery 12-volts as source which is neat for LED lamps.

We use LED 12-volts 1.5-watts as Figure 1 which use Low power consumption than general a lamps and have also long life.(20,000 hour up) But expensive price than them about 2 times.

The LED lamp 12-volts 1-5-watts
Figure 1 The LED lamp 12-volts 1.5-watts

But we must to have DC voltage source for charges that battery. Which we would to like use a solar cells, because easy to use in location that have sun light to convert as DC voltage between 17-volts to 22-volts at 10-watts per one units.

In Figure 2 is the solar cells that we use. I am get them from good my friend. Though very ancient, it still have many uses.

solar cells - 12V 20 wattts for source charger
Figure 2 the solar cells is used as source charger.

The requirements of circuit

In case of this automatic LED night light switch, we should save energy so I design this with main parts below:

1. LDR or photoresistor is used for sensor light-activated. It is cheap and easy to use.

2. A CMOS Digital-IC No.CD4069 is a inverter gate every useful and cheap.

Next, we come to design simplified night light sensor as Figure 3 We see on step by step better:
-Firstly,The 12-volts flowing through VR1-potentiometer to LDR1 and R1.

-Secondly, the LED1 will glow brightly when no light or like night state to strike photoresistors (LDR1). Which its resistance is higher-value so cause voltage drop across LDR1 and R1-resistor as high state or “1”.

-We will see that, R1 is connected with LDR1 in series to limit current through them not too much.

-Then An IC1a,IC1b,R2,R3 are assembled together as a buffer gate that similar the schmitt triggers form (we will see detail later).

-The output of IC1b pin 4 is logic high that voltage of 12-volts, cause LED1 glow and R4 reduce properly current for LED1.

Figure 3 A simple night light sensor circuit.

3. As “The requirements of circuit” we should add “third” is using the transistor instead a relay. Since the driver transistor use lower current than the relay.

You can see in Figure 4 Q1 and Q2 are connected in a darlington compound so have very many gain. Q2-TIP31 can use lower than 2A so use easily with 12-volts LED lamp 1.5 watts or 0.125A current.

IC1c and IC1d,IC1e,IC1f are mixed as buffer gate which also have current amplifiers. To increasing current up before to transistor dirver. We use IC1 fully six inverter packet.

Figure 4 buffer gate and driver transistor.

C1-220uF 25V electrolyte capacitor for filter smooth current and C1-0.1uF 50V – ceramic capacitor as spike remover of IC1-digital IC.

D4-diode-1N4007 is used to absorbs current spike from LED lamps to protects external transistor driver and buffer CMOS gate circuit.

Then, we see Figure 5 the perfect circuit. We add the solar cells charger circuit for a 12-volts 2.5Ah battery as power source of this circuit.
5-Automatic led night light switch circuit
Figure 5 the perfect circuit.

The battery is use long time for 2.5A/0.125A = 20 hour. Which normally we need to use it for 8 hour per night only. Therefore it can be used easily.

Since output voltage range of solar cell between 17V to 22V So we use LM7815 DC voltage regulation output to 15-volts. Or 1.5 time of voltage battery.

D1-1N4007-diode is used for protect voltage feedback from charger circuit.

Both capacitors C3,C5-470uF 35V are used to filter voltage to bset smooth. C4,C6 are filter noise.

LED3 for indicating voltage solar cells and R7 controlled current-limiting of LED3.

The solar charger circuit directly connects to the battery. And S1-Switch is used for turn ON-OFF the automatically LED night light switch circuit.
LED2 is used for show the power on and R6 for current-limiting.

LED1 indicated the circuit of light sensor section.

How to builds and test

This project we assemble parts on a perforated PCB and wiring to universal PCB board. as Figure 6 and test it as show on video belowe.
Assemble parts on perforated PCB
Figure 6 assemble parts on perforated PCB

Testing circuit.
the solar cells charger
Figure 7 the solar cells charger

Installed on the project real place
Figure 8 Installed on the project real place.

Figure 9 The automatically night light controller

front of solar cell charger box
Figure 10 Front of solar cell charger box.

Figure 11 Inside the solar charger box

Use the Corrugated Cable Conduit for wiring outdoor.
Figure 12 Use the Corrugated Cable Conduit for wiring outdoor successfully.


This project is easy but you should solar-cells at sunlight all day and use big size or high power than 10 watts up.
In first day it may not fully works you wait it come to third day it will good running.

A two weeks ago this project works so well everyone in my family like it very much I think it will have long life and save our money very much.

The component list

Q1: 2N3904, 45V 100mA NPN Transistor
Q2: TIP31, 30V 2A NPN transistor
IC1: CD4069___Six inverter CMOS
IC2: LM7815, 15-volts DC Regulator IC
LDR1: LDR or Photoresistor

C1: 220uF 35V
C3,C5: 470uF 35V

Ceramic Capacitor
C2,C4,C6: 0.1uF 50V
0.25W Resistors, tolerance: 5%
R1,R7: 1.5K
R2: 22K
R3: 220K
R5: 10K
R4,R6: 1K
VR1: 100K, Variable resistor or potentiometer
Perforated board
Box,wires,solar cells,LED lamp 12V,and others.

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This Post Has 7 Comments

  1. thanks for your help for am new in electronics

  2. I want to make a inverter of approx. 1000w.
    so pls. send a circuit diagram with component list.
    thanks with regards
    sunil pandey

  3. dist -junagadh .
    respacted sir ,i requarment led auto cut lamp ,so please help me this product ,(i purchase this products .)

    thanks ,i awayting your positive reaply.

  4. 1.can i use a 12v 5A power supply to replace the solar cell?
    2. Will it automatically charge the battery when its drain?

  5. Hello. You are doing great job here, congradulations.
    I don’t know much about circuits but I have a few questions on your “Automatic led night light switch” project.
    – At the beginning you mention C1 as 220uF 25V but on your parts list it is listed as 35V. ?
    – You are using an LDR circuit to detect darkness. Couldn’t you use the solar cell itself for this purpose. It would not produce electricity when it is dark and thus isn’t it a sort of light sensor?
    – how could we adopt this circuit for 6V battery and 6V LEDs?

  6. Thanks for doing this

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