Introduction: AUTOMATIC SOLAR POWERED NIGHT LIGHT
Hello friends
Thank you for your support for my previous project
Today I am going to make life hack "instructable" can save both money and time. This is the tutorial of “how to make an automatic solar powered night light”. This device can charge at daytime and work automatically at night
Step 1: Know Your Circuit
This device has three circuits. a switching circuit. a solar charging circuit with battery and a LED night light circuit
Step 2: The Switching Circuit
Switching circuit is most
important part in this system. to make the switching circuit you need
1) IRFZ44 MOFSET
2) 150K Ohm resistor (see the step 3 for more details)
3) 3 2pin PCB connecter
4) Wires
5) LDR
6) PCB BORD
Fig shows the circuit
I am using a long two core coated wire to connect the LDR to main circuit. it will help to avoid the unwanted lights from other light sores
Step 3: Calibration of the Circuit
This is the most important step
in the circuit designing. Calibration of the circuit helps to improve the sensitivity of the dark sensor
LDR is the important component of this circuit. it will act as the dark sensor. There are two methods to calibrate the LDR one pre calibration and other one is post calibration
In pre calibration we use a single resistor with pre calculated resistance. in post calibration we use a variable resistor and calibrate circuit at final stage
I am using pre calibration just because of its simplicity in India cost of a variable resistor are 5 to 10 times higher than a single resistor
For pre calibration you need to find the right resistor. For this first you need to find R max and R min of the LDR
Connect your LDR to multicenter and find the maximum resistance(R max) at day time. Repeat the step at night time and find out the minimum resistance(R min)
In my case R max is 600k and R min is 2k
To find the resistance we need I am using voltage divider equation
V out = V in x (R2/R1+R2)
V out = voltage to MOFSET Gate
V in = supply voltage (12V)
R1 = R min (2K or 2000 Ohm in my case)
R2 = R1 (I am using 150K or 150000 Ohm resistor)
12x (2000/2000+ 150000) = .150V
That means the MOFSET will stay off
Now test with R max .it is 600K or 600000 Ohm
12x (2000/2000+ 600000) = 9.5V
So the MOFSET is turn on and it switch on the light
Step 4: "Power, Light and Charging"
I am using a 12v 7Ah battery as
power source and a 12v 2W LED as light source. To charge the battery i am using 12v 6W solar panels. to reduce the cost i am using a DC to DC buck converter as charge controller. it can boost 12v to 14v and prevent reveres flow of voltage with a high capacity diode
You may wonder how this circuit work without any overcharge protection
After the one month test run i found out that these solar panels can’t fully charge the battery. Due to low current, battery needs 18 hours to fully charge the battery but sunlight is only available for 12 house max. in conclusion at the night time the switching circuit and LED light consume 10 to 12w of power from battery and at day time the solar panels refill the battery. Little bit tricky but its work!
Step 5: Fitting and Wiring
The fig shows the circuit of whole system
Step 6: The Moment of Truth
If everything is correct the circuit switch on the light at night and switch off and charge at the battery at day time. Just fix everything on a safe place and it work automatically
Step 7: Sum Ting More
if you want more powerful light just replace 12V LED with a 12V relay and connect that relay to ac power sources

Participated in the
Hack Your Day Contest

Participated in the
Full Spectrum Laser Contest 2016
25 Comments
Question 1 year ago on Introduction
I have never done anything like this before. My question is why will this solar box light the 2 led diodes that it’s connected to but when I connect a diode from out of the bag it will not light up? Please help.
Answer 1 year ago
can you please give me some more details
Reply 1 year ago
I’m trying to make a solar light for a garden ornament. I have the solar box but I can’t figure what LED to use and what wire I need to connect it all. Are the LED’s in the bag the wrong ones? See attached picture. Thank you
Question 3 years ago on Step 4
Hi i would like to inquire how the DC-DC power boost module is connected to the switching circuit?? is that considered as the charge controller? and can you provide me the total circuit diagram including the step 4?
3 years ago
Where is the step 4 pcb in the moment of truth video?
3 years ago on Step 2
IRFZ44 MOFSET sir what is this ?
4 years ago
Can you please add me in that group?
5 years ago
this circuit still need to connect to the ac power supply or from the solar panel
Reply 5 years ago
this circuit is designed for solar
5 years ago
What is the watts of Solar panel with charging an 7.8ah battery
Reply 5 years ago
you need a solar panel can produce more than 10w,i recommend 15w
5 years ago
how much does it cost
6 years ago
hii.vina
can u tell me what is the total cost of this solar project
6 years ago
How long can this LED light glow?
Reply 6 years ago
Full night,about 12 hours
6 years ago
Where do you Buy That???
Reply 6 years ago
WHAT?
6 years ago
that's just what i was looking for :)
Reply 6 years ago
thank you for your positive feedback :)
this is a cheap but effective night light circuit
6 years ago
Nice job