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.
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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.
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.
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.
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.
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.
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 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
C2,C4,C6: 0.1uF 50V
0.25W Resistors, tolerance: 5%
VR1: 100K, Variable resistor or potentiometer
Box,wires,solar cells,LED lamp 12V,and others.
More related below:
- Daylight sensor switch circuit.
- Automatic Battery Charger 6V-12V with Relay cut off by LM324
- Make solar aa battery charger by TL497
- Solar battery charger with overcharge protection
- Light switch using JK-Flip-Flop
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