This solar LED light trap circuit for insects can be used to attract insects at night and keep them engaged with the light source. This distraction created by the LED light will keep the insects from flying towards the crops and save the crops from these harmful pests.
The circuit design was requested by Mr. Verma, as explained below:
The device turns on LED light automatically at dusk for 2-4 hours and attracts harmful insects in a crop field.
- The device has a small 3W solar panel for charging battery.
- This charges a 1500 – 1800 mAh battery during the day.
- At dusk, device lights up a LED strip of 1-3 W, using the battery power.
- The light remains on for 2 hours or 3 hours or 4 hours (selectable through a microswitch) and then switches off.
Device should not overcharge the battery, nor allow it to be depleted below a certain level to extend battery life.
Device should have a switch to manually turn the lights on and off.
The device should use low cost components since I need to deploy many of these devices.
The device should be essentially weather proof as it will be deployed in open field.
The following figure shows the complete circuit diagram of our solar LED light insect trap circuit with timer.
- All Resistors are 1/4 watt 5% CFR
- R1, R2 = 120 Ohms
- R3 = 1k
- R4, R6 = 4.7k
- R5, R11 = 10k
- R7, R8, R10 = 100k
- R9 = 2.2 Meg
- R12 = 1k
- P1 = 4.7k preset
- P1 = 1 Meg preset or pot
- C1 = Capacitor 2uF/25V non-polar
- D1, D2 = 1N5402 Diodes
- D3 = 1N4148
- Z1 = 6.9V 1 watt zener diode
- T1 = TIP32 Transistor
- T2, T3, T4, T5 = BC547 Transistors
- T6 = TIP122 Transistor
- LED = 3 watt LED strip
- IC1 = IC LM317
- IC2 = IC 4060
- Battery = 7.4V 2000 mAh Li-Ion
- Solar Panel = 12V 1 A solar panel
Referring to the above diagram, the working of the solar LED insect trap circuit stages can be understood with the following points:
Solar Regulator and Battery Charger
D1 is connected to the solar panel positive line, which safeguards the circuit from an accidental solar panel polarity reversal.
IC1 which is an IC LM317 is configured as a solar panel voltage regulator. It provides a constant regulated DC output for charging the battery.
The preset P1 is adjusted so that the output across the battery is just below the full charge level of the battery, which ensures that the battery is never over charged.
The battery recommended for this project should be a 7.4V 2000 mAh Li-ion Battery.
For a 7.4V Li-Ion battery the full charge level will be around 8.4V. Therefore P1 can be adjusted to generate around 8.2V across the battery terminals.
Alternatively, the P1 preset can be simply replaced with a calculated fixed resistor which enables the voltage across the battery to be precisely 8.2V.
The full charge level is intentionally kept a shade lower to ensure that the battery never gets over charged.
Low Battery Monitor and Cut-off
Transistor T1 along with transistor T2 and zener diode Z1 forms the low battery monitor and cut-off stage.
As long as the battery voltage is higher than the zener Z1 value, T2 remains conductive which allows T1 also to remain conductive.
This allows T1 to supply the power to the rest of the circuit connected on its collector side.
In an event if the battery voltage drops below the critical level or below the Z1 value, Z1 turns OFF and cuts off the base supply to T2.
T2 now stops conducting which in turn cuts off T1 conduction.
Once T1 is switched OFF, the entire circuit is turned OFF preventing any further depletion or over discharge of the battery.
Darkness Detector Circuit
T3 and T4 form the darkness detector for our insect light trap circuit. Until night sets in or as long as the solar panel voltage is above 0.6 V, T3 remains conductive causing T4 to remain switched OFF.
While T4 is switched off it keeps the timer IC 4060 disabled.
The Timer Circuit
The timer section is constructed around the IC2 which is a standard 4060 timer oscillator IC.
As long as transistor T4 stays switched off (until darkness) pin#12 of IC2 is held high via R8.
Once it is sufficiently dark and the solar panel is not producing any voltage, T3 turns OFF, and T4 turn ON.
With T4 switch ON, pin#12 of IC2 is grounded which activates the IC2 and its internal clock starts counting.
The output pin#3 of IC2 stays at logic 0 while the IC counts, during this period transistor T5 stays turned OFF causing T6 to switch ON. T6 now turns ON the LED lamp.
That means, when darkness sets in, the timer IC2 is activated, and while it counts, the LED remains switched ON.
The LED lamp now starts attracting the wild insects which are harmful for the field crops.
The LED lamp keeps the insects busy and buzzing around it, and thus prevents them from moving towards the crops.
After a few hours (as per the setting of P2) the IC2 time elapses and its pin#3 goes high causing T5 to switch ON. As soon as T5 switches ON, T6 is switched OFF, which in turn switches OFF the LED lamp.
The IC2 latches in this mode via diode D3 until the next morning when T4 is turned OFF causing IC2 to reset in its previous form.
Why the Timer Stage is Unnecessary
From the above discussion it seems the IC2 timer stage is unnecessary and redundant.
Because, we already have the low battery cut off stage, which ensures that the battery cannot be discharged below a certain low battery level.
This means the LED is going to shut off anyhow after a predetermined period when the battery voltage drops below the set low voltage threshold.
This concludes our article on a simple solar LED light trap circuit for insects which will hopefully be useful for protecting the field crops from these harmful pests.
Do let me know if you find anything missing in the design, or suggest a possible improvement in the design. Please feel free to comment through the below given comment box.