How to Make an Automatic Solar-Powered Street Light

Make an Automatic Solar-Powered Street Light: This instructable describes the design of an easy-to-make smart solar-powered street light.

DIY solar light projects provide a cheap and effective method for powerhouses using energy from the sun. Thus, it makes sense to create a street light system that uses solar energy to charge a battery during the day and then uses this battery to light up the street at night. And you may create your own!

This system will be managed by an electronic circuit, with the LED bulb automatically turning on at night and off during the day. To protect the battery from over-discharge, we will also incorporate a battery protection circuit.

What to Expect

There are five primary components needed for this system:

  1. Solar panel: as a light sensor and for charging the battery throughout the day.
  2. Battery: for storing the circuit and bulb and powering current.
  3. LED DC bulb: For lighting at night.
  4. Wires: according to the schematic design, for interconnection.
  5. Electronic circuit: To automatically control and switch the LED bulb, as well as for battery protection.

Using Solar Power to Charge a Battery

We selected a small 10W solar panel for charging the battery, but you may pick a larger one based on your power needs and budget. It can deliver 0.62 A of short-circuit current at peak brightness and charge a 12V battery. Its physical size is around 12″ by 9″.

solar panel

A 12 V DC battery with a 4 Ah current capacity was employed. The solar panels generate current throughout the day, which is used to charge the battery. With a full charge, the battery may have a maximum open circuit voltage of 13.7 volts, and it has to be recharged when the voltage decreases to 11 volts DC.

A Zener diode, which is soldered on Veroboard and houses the electronic circuit, is used to charge the battery by connecting the red wire of the solar panel (positive polarity) to the positive terminal of the battery.

The positive terminal of the Zener diode is connected to the solar panel, while the negative terminal is connected to the anode terminal of the battery by cables. When the circuit uses the solar panel voltage to turn on the light in the dark, the zener diode offers isolation between the battery and solar panel voltage. The battery's negative terminal is directly connected to the black wire (negative polarity).

The amount of current generated by the solar panel to charge the battery depends on the brightness of the sun. The battery provides current to an LED bulb. Using sensor data, an electronic circuit regulates the bulb (solar panel voltage). As indicated in the schematics, connect the positive terminal, or cathode, of the LED bulb to the positive terminal of the battery.

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Building the Electronic Circuit

The electronic circuit consists of two parts. One is meant to control the LED light, while the other is meant to prevent and control battery depletion.

Schematics of the Automatic Solar Street Light

The figure below shows the entire schematic for linking this system together. Create the electronic circuit for automated switching and battery drain protection on Veroboard.

schematics of automatic solar street light

What You'll Need

The following tools and components will be required for the electronic circuit: You can get them from online stores like DigikeyMouser, or Ali Express.

  • 2 x LM393 Voltage comparator IC
  • 1 x LM7809 9 VDC voltage regulator IC
  • 1 x ULN2003 Darlington pair transistors IC
  • 1 x Veroboard (for connecting circuit elements through soldering)
  • Soldering iron & soldering wire
  • Resistors (in Ohms) 1K, 10K, 36K, 53K, 100K, 280K (Or equivalent parallel/series combination of these values)
  • Digital Multimeter (for voltage and current measurement)
  • Zener diode (between the red wire of the solar panel and battery + terminal)
  • Wires
  • Screw terminal Block connectors (for connecting wires to solar panel, battery, and LED bulb)
tools and components

Controlling the LED Bulb

Use the solar panel voltage as a sensor to direct the circuit so that the LED turns on in the dark and off during the day. A Zener diode is used to separate the solar panel and battery. The zener diode is reverse-biased in the dark when there is no sunlight to illuminate the solar panel, to provide a large output voltage. In the daytime, the solar voltage will be greater than the battery voltage for charging.

A comparator is used in this circuit to compare the voltages from the solar panel and the battery. It provides the signal for switching off the light when it is higher (during the day). It serves as a signal to switch on the light when it is lower. With the aid of ULN2003 Darlington pair transistors, this logic is used to control the LED light. The comparator output is used as input by ULN2003. It permits the collector current to flow via C (Pins 10–16) to switch on the light if it receives the signal for “on” at input pins (1–7) of the ULN2003 (i.e., from comparator output pin 1).

Solder all of the circuit components on Veroboard to form the circuit. On the LM393 comparator, the Schmitt trigger (positive feedback at the comparator) is implemented to prevent bugs.

Preventing Over-Discharge

If the weather is cloudy or foggy, it is possible that the battery may not charge throughout the day, resulting in significant battery discharge for multiple nights in a row. This may cause the battery to discharge to the point that its chemical balance is upset, making it useless for future use.

Another comparator circuit employing the LM393 IC is shown in the schematics to prevent over-discharge of the battery by comparing the discharge voltage to a stable reference voltage. The LM7809 voltage regulator, which takes battery voltage (i.e., 11 to 14 VDC) as input and outputs a constant 9 V, is used for battery voltage regulation.

Use the comparator as a Schmitt trigger to make sure the battery doesn't discharge past the deep discharge threshold, which is 11 V. The Schmitt trigger will output a logic low when the battery voltage falls below 11 volts, which will turn off the switching circuit. A complete recharging of the battery to 13.2 volts is necessary to reactivate the switching circuit.

You can work out your own voltages (instead of 11 V for low battery level and 13.2 V for charged battery level) by selecting the suitable mix of resistors (though that's more in-depth than we're going to get into for now). Solder the circuit elements on the Vero board together to create the battery protection circuit.

Finally, connect the battery, light, and solar panel as shown in the schematic after making the automated switching and battery drain protection circuits on Veroboard.

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Testing Your Solar-Powered Street Light System

Place the solar panel in the sun to test the system's performance. When the solar panel is exposed to sunlight, you will see that the LED bulb is “off“. At the solar panel output and battery connections, measure the voltage using a digital multimeter. You will discover that the solar panel voltage is greater than the battery voltage. Use the digital multimeter to measure the current going into the battery to see whether it is charging in the sunshine.

battery charging under sunlight

The LED solar bulb turns on when you cover the solar panel in the next step with a thick covering to block out sunlight. When you measure the voltage of the solar panel, you'll see that it's not enough to charge the battery. The LED bulb will then use the current from the battery to generate light, so measure the current going from the battery to it.

cover solar panel to test bulb

Here is a short video demonstration of this testing:

Light Up the Night With Solar Light

This do-it-yourself project teaches you how to construct a small electronic assembly for creating an automatic solar-powered street light that uses clean, renewable solar energy. To guarantee that the solar panel charges the battery enough to keep the bulb on all night, choose the right specifications for the solar panel, battery, and bulb. This will maximize resource utilization.

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