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Automatic 40 Watt LED Solar Street Light Circuit

Automatic 40 Watt LED Solar Street Light Circuit

Today solar panels and PV cells have become very popular and in the near future we would possibly see everyone of us using it in some or the other way in our life. One important use of these devices has been in the field of street lighting.

The following article discusses one such interesting circuit which comprehensively explains the making of a smart 40 watt fully automatic solar street light circuit (designed by me).

The circuit which has been discussed here has most of the standard specifications included with it, the following data explains it more elaborately:

LED Lamp Specifications

  • Voltage: 12 volts (12V/26AH Battery)
  • Current Consumption: 3.2 Amps @12 volts,
  • Power Consumption: 39 watts by 39nos of 1 watt LEDs
  • Light Intensity: Approximately around 2000 lm(lumens)

Charger/Controller Specification

  • Input: 32 volts from a solar panel specified with around 32 volts open circuit voltage, and short circuit current of 5 to 7 Amps.
  • Output: Max. 14.3 volts, current limited to 4.4 Amps
  • Battery Full - Cut OFF at 14.3 volts (set by P2).
  • Low Battery - Cut OFF at 11.04 volts (set by P1).
  • Battery charged at C/5 rate with float voltage restricted to 13.4 volts after “battery full cut OFF”.
  • Automatic Day/Night Switching with LDR Sensor (set by selecting R10 appropriately).

In this first part of the article we will study the solar charger/controller stage and the corresponding over/low voltage cut-off circuit, and also the automatic day/night cut-off section.

prototype for 40 watt LED street light circuit
complete 40 watt LED street light circuit with charger, and darkness activated switch

Parts List

  • R1, R3,R4, R12 = 10k
  • R5 = 240 OHMS
  • P1,P2 =10K preset
  • P3 = 10k pot or preset
  • R10 = 470K,
  • R9= 2M2
  • R11 = 100K
  • R8=10 OHMS 2 WATT
  • T1----T4 = BC547
  • A1/A2 = 1/2 IC324
  • D1---D3,D6 = 1N4007
  • D4,D5 = 6AMP DIODES
  • IC2 = IC555
  • IC1 = LM338
  • RELAYS = 12V,400 OHMS, SPDT
  • BATTERY = 12V, 26AH

Solar Charger/Controller, High/Low Battery Cut OFF and Ambient Light Detector Circuit Stages:

CAUTION: A charge controller is a must for any street light system. You may find other designs on the internet without this feature, simply ignore them. Those can be dangerous for the battery!

Referring to the 40 watt street light circuit diagram above, the panel voltage is regulated and stabilized to the required 14.4 volts by the IC LM 338.

P3 is used for setting the output voltage to exactly 14.3 volts or somewhere near to it.

R6 and R7 forms the current limiting components and must be calculated appropriately as discussed in this solar panel voltage regulator circuit.

The stabilized voltage is next applied to the voltage/charge control  and the associated stages.

Two opamps A1 and A2 are wired with converse configurations, meaning the output of A1 becomes high when a predetermined over voltage value is detected, while the output of A2 goes high on detection of a predetermined low voltage threshold.

The above high and low voltage thresholds are appropriately set by the preset P2 and P1 respectively.

Transistors T1 and T2 respond accordingly to the above outputs from the opamps and activates the respective relay for controlling the charge levels of the connected battery with respect to the given parameters.

The relay connected to T1 specifically controls the overcharge limit of the battery.

The relay connected to T3 is responsible for holding the voltage to the LED lamp stage. As long as the battery voltage is above the low voltage threshold and as long as no ambient light is present around the system, this relay keeps the lamp switched ON, the LED module is instantly switched OFF in case the stipulated conditions are not fulfilled.

Circuit Operation

IC1 along with the associated parts forms the light detector circuit, its output goes high in the presence of ambient light and vice versa.

Assume it's day time and a partially discharged battery at 11.8V is connected to the relevant points, also assume the high voltage cut off to be set at 14.4V. On power switch ON (either from the solar panel or an external DC source), the battery starts charging via the N/C contacts of the relay.

Since it's day, the output of IC1 is high, which switches ON T3. The relay connected to T3 holds the battery voltage and inhibits it from reaching the LED module and the lamp remains switched OFF.

Once the battery gets fully charged, A1's output goes high switching ON T1 and the associated relay.

This disconnects the battery from the charging voltage.

The above situation latches ON with the help of the feedback voltage from the N/O contacts of the above relay to the base of T1.

The latch persists until the low voltage condition is reached, when T2 switches ON, grounding T1's base biasing and reverting the top relay into the charging mode.

This concludes our battery high/Low controller and the light sensor stages of the proposed 40 watt automatic solar street light system circuit.

The following discussion explains the making procedure of the PWM controlled LED module circuit.

The circuit shown below represents the LED lamp module consisting of 39 nos. 1 watt/350 mA high bright power LEDs.The whole array is made by connecting 13 number of series connections in parallel, consisting of 3 LEDs in each series.

How it Works

The above arrangement of LEDs is pretty standard in its configuration and does not focus much importance.

The actual crucial part of this circuit is the IC 555 section, which is configured in its typical astable multivibrator mode.

In this mode the output pin#3 of the IC generates definite PWM wave-forms which can be adjusted by setting the duty cycle of the IC appropriately.

The duty cycle of this configuration is adjusted by setting P1 as per ones preference.

Since the setting of P1 also decides the illumination level of the LEDs, should be done carefully to produce the most optimal results from the LEDs. P1 also becomes the dimming control of the LED module.

The inclusion of the PWM design here plays the key role as it drastically reduces the power consumption of the connected LEDs.

If the LED module would be connected directly to the battery without the IC 555 stage, the LEDs would have consumed the full specified 36 watts.

With the PWM driver in operation, the LED module now consumes about 1/3rd power only, that is around 12 watts yet extracts the maximum specified illumination from the LEDs.

This happens because, due to the fed PWM pulses the transistor T1 remains ON only for 1/3rd of the normal time period, switching the LEDs for the same shorter length of time, however due to persistence of vision, we find the LEDs to be ON all the time.

The high frequency of the astable makes the illumination very stable and no vibration can be detected even while our vision is in motion.

This module is integrated with the previously discussed solar controller board.

The positive and the negative of the shown circuit needs to be simply connected to the relevant points over the solar controller board.

This concludes the whole explanation of the proposed 40 watt automatic solar LED street lamp circuit project.

If you have any questions, you may express them through your comments.

UPDATE: The above theory of seeing high illumination with lower consumption due to persistence of vision is incorrect. So sadly this PWM controller only works as a brightness controller and nothing more!

Circuit diagram for the street light LED PWM controller

PWM LED street light controller

Parts List

  • R1 = 100K
  • P1 = 100K pot
  • C1 = 680pF
  • C2 = 0.01uF
  • R2 = 4K7
  • T1 = TIP122
  • R3----R14 = 10 Ohms, 2watt
  • LEDs = 1 watt, 350 mA, cool white
  • IC1 = IC555

In the final prototype the LEDs were mounted on special aluminum based heatsink type PCB, it is strongly recommended, without which the LED life would deteriorate.

Prototype Images

street light 20 watt from homemade circuits
Street light prototype by swagatam innovations
dazzling illumination 100000 lumens from 40 watt street light

Simplest Street Light Circuit

If you are newcomer and looking for a simple automatic street light system, then perhaps the following design will fulfill your need.

This simplest automatic street light circuit can be assembled quickly by newbie and installed for achieving the intended results.

Built around a light activated concept, the circuit can be used for automatically switching ON and switching OFF a roadway lamp or group of lamps in response to the varying ambient light levels.

The electrical unit once built can be used for switching OFF a lamp when dawn breaks and switching it ON when dusk sets in.

How it Works

The circuit can be used as an automatic day night operated light controller system or a simple light activated switch. Let’s try to understand the functioning of this useful circuit and how it is so simple to construct:

Referring to the circuit diagram we can see a very simple configuration consisting of just a couple transistors and a relay, which forms the basic control part of the circuit.

Of course we cannot forget about the LDR which is the prime sensing component of the circuit. The transistors are basically arranged such that they both complement each other oppositely, meaning when the left hand side transistor conducts, the right hand side transistor switches OFF and vice versa.

The left hand side transistor T1 is rigged as a voltage comparator using a resistive network. The resistor at the upper arm is the LDR and the lower arm resistor is the preset which is used to set the threshold values or levels. T2 is arranged as an inverter, and inverts the response received from T1.

How the LDR Works

Initially, assuming the light level is less, the LDR sustains a high resistance level across it, which does not allow enough current to reach the base of the transistor T1.

This allows the potential level at the collector to saturate T2 and consequently the relay remains activated in this condition.

When the light level increases and becomes sufficiently large on the LDR, its resistance level falls, this allows more current to pass through it which eventually reaches the base of T1.

How the Transistor Responds to LDR

The transistor T1 conducts, pulling its collector potential to ground. This inhibits the conduction of the transistor T2, switching OFF its collector load relay and the connected lamp.

Power Supply Details

The power supply is a standard transformer, bridge, capacitor network, which supplies a clean DC to the circuit for executing the proposed actions.

The whole circuit can be built over a small piece of vero board and the entire assembly along with the power supply may be housed inside a sturdy little plastic box.

How the LDR is Positioned

The LDR must be placed outside the box, meaning its sensing surface should be exposed toward the ambient area from where the light level is required to be sensed.

Care should be taken that the light from the lamps does not in any way reach the LDR, which may result in false switching and oscillations.

Automatic day and night lamp switch circuit using transistors and relay

Parts List

  • R1, R2, R3 = 2K2,
  • VR1 = 10K preset,
  • C1 = 100uF/25V,
  • C2 = 10uF/25V,
  • D1 ---- D6 = 1N4007
  • T1, T2 = BC547,
  • Relay = 12 volt, 400 Ohm, SPDT,
  • LDR = any type with 10K to 47K resistance at ambient light.
  • Transformer = 0-12V, 200mA

PCB Design

day night automatic lamp PCB

Using opamp IC 741

The above explained automatic darkness activated street lamp circuit can be also made using an opamp, as shown below:

darkness activated IC 741 automatic lamp circuit

Working Description

Here the IC 741 is designed as a comparator, wherein its non-inverting pin#3 is connected to a 10k preset or pot for creating a triggering reference at this pinout.

Pin#2 which is the inverting input of the IC is configured with a potential divider network made by a light dependent resistor or LDR and a 100K resistor.

The 10K preset is initially adjusted such that when the ambient light on the LDR reaches to the desired darkness threshold, the pin#6 goes high. This is done with some skill and patience by moving the preset slowly until pin#6 just goes high, which is identified by the switching ON of the connected relay and the illumination of the red LED.

This must be done by creating an artificial darkness threshold light level on the LDR inside a closed room and by using dim light for the purpose.

Once the preset is set, it may be sealed with some epoxy glue so that the adjustment remains fixed and unchanged.

After this the circuit may be enclosed inside a suitable box with a 12V adapter for powering the circuit, and the relay contacts wired with the desired road lamp.

Care must be taken to ensure that the lamp illumination never reaches the LDR, otherwise it may lead a continuous oscillations or flickering of the lamp as soon as it is triggered at twilight.


About the Author

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials. If you have any circuit related query, you may interact through comments, I'll be most happy to help!

174 thoughts on “Automatic 40 Watt LED Solar Street Light Circuit”

  1. The description looks so theoretical in my eyes . especially the circuit diagram. So compact, complex and confusing, not knowing where to begin from building a prototype on your own. Could you do a video with a step by step ; circuit by circuit until the end. I really want to do this.thank you.

    • It is a thoroughly tested project, and very easy to build. If you are totally new to electronics then I am afraid this project may not be for you. If you have any specific questions you can ask, I’ll clarify them concisely for you.

  2. hi Swagatam,
    can you provide a circuit to operate a led street light will using solar panels with batteries to charge it , 120 watt, and what the use of it? and what the cost , i need 250 pcs

  3. In the pwm led driver the 555 ic getting heated in normal operatig condition is that normal or is there any error in circuit design.

    • It is not normal, it will heat up only if voltage exceeds 15V or the output pin#3 is short circuited. Please check your IC connections. Pn#2 and 7 are not connected.

      • Sir, Thank you for quick reply. I my circuit i used 100ohm resistor instead of 4.7 K between pin3# of 555 ic and the tip122 transistor it merely act as a short and I didn’t connect pin2# and pin6# of the ic together now the ic is not heating any more also I can control the time period of pwm o/p. Thank for your patience and valuable time for aswering to my query even though I had made mistakes.

        • Thank you Thomas, connecting pin#2 and 6 is crucial and they must be connected together for this application. I think there could be some other issue with your design. At pin#3 please increase the value to 1K or any other higher value, 100 ohm is very low.

          • Thank you Sir , I corrected everything as you mentioned, now it was working fine without connecting trigger and discharge,ICcan’t work as pwm signal generator, Thank you for figuring out my mistakes within your working hours Have a great day ahead!.

  4. Sir only low voltage relay is triggering all the time as I adjust p1 and p2 nothing happens at the relay while providing 20 v dc at the solar point while batt not attached also by by varying p3 with in low and high cut out voltage, I used 200k preset for p1 and p2 insted of 10k is it a cause of the aforementioned problem.

    • Thomas, it means your A1 opamp has some problems. Initially keep the preset at ground level and with the full charge voltage (14V supply) input slowly adjust the A1 preset such that the (+) input pin of A1 just goes over the (-) input pin of A1. When this happens A1 output must go high.
      Please replace Z3, Z4 with LEDs which will help you to understand the switching actions of the opamps.
      200K is not recommended but still it should work

      • Thank for your attitude towards responding towards answer ing the query with in due course of time. I done a serious mistake in the circuit that I didn’t tied A 1 preset one arm to Vcc, now the comparator functioning Correctlly and I can able to set high and low voltage cut off. I replaced p1 and p2 with 10k as per design.

  5. What are the changes to be made in the circuit for a 12W LED solar street light system having dusk to dawn operation Sir? Please help me.

    • No changes will be required in the circuit, you just have to reduce the number of LED chains accordingly to achieve the required specs

  6. Hi, am Daniel from Kenya I purchasing a solar panel (mono)300w only to get disappointed. On a Sunny day the solar voltage goes upto around 36v open circuit and when connected to a battery, the voltage drops to that of the battery i.e if the battery has 11v it remains the same .please I need your advice,its rated open circuit voltage is 22.2V

    What is the function of z3 and d1, and why was resistor R12 placed between the transistor and diodes. I understand the voltage regulator circuit but having a challenge to understand the configuration of over voltage and under-voltage charging of the battery.

    • Good day Vivian, the zener is to block leakage voltage from the IC output. the series diode is placed to block the other external voltages from entering the IC output, which are meant for the transistor base.

      R12 is the base resistor for T2, a transistor cannot work without a base resistor.

    • to understand over voltage and under voltage functioning, you will have learn how the opamp works like a comparator….simply put, when the non-inverting (+) pin of an opamp is at higher potential than its inverting (-) pin, then its output goes high (equal to supply level) in the opposite case the output shows a zero voltage.

    • Matty, a 38AH will require a 5 amp current for at least 7 to 8 hours, for charging to some optimal level, so make sure your panel is able to generate 5 amps for 7 hours

  8. hello Sir,
    I am facing a hard time drawing the circuit using Proteus, it is not working accordingly as i simulate, i am finding it hard to trace the error that i am doing, Your circuit design is correct i am at fault, to which email may i sent it for your assistance.

  9. actually I don't remember how a much lumens a 36 LED would produce, however with around 320mA per LeD would enable maximum specified lumens from it

  10. hello, actually it is 3.5 amps for the whole 40 watt LED module, and not 1.2 amp, I have corrected the article now.

    current through each LED will be around 300mA, volts = 3.3V
    panel should be much higher than 40watt, around 50 watts

  11. Sir i have 74 watt solar panel, and 75AH battery. How to design a solar charge controller with LDR sensor and INDICATION LED of charging, discharging and low battery..

  12. The IC is used simply as a comparator here, only the pin#2 opamp is utilized while the pin#7 opamp is kept unused….pin#5 connection with pin#7 helps to provide some degree hysteresis to the triggering.

    • all components are 1/4 watt except R8.

      All reputed online stores are good, you can google "buy online electronic parts" for the list of main vendors.

  13. Hello sir,
    I want to make this project but with some modification.. I want solar panel to follow the direction of sun.. something like solar tracker… so can you please help me with the circuit diagram…. I would wait for your reply….

  14. Hello sir,
    I have one problem in my street light
    Panel 75w,20V
    Battery 75Ah , 12v

    O/p of controller to charge battery is 2.3volts
    O/p of panel is 20v
    Lamp is 15w 12v led

    Sometime operate and sometime don't opetate

    What can be reason

    • Hello Umesh, it would be difficult to understand the fault without a practical check up, but it appears that the unit is malfunctioning…

      yes you can connect the specified panel with the specified battery directly for the time being…it will still charge the battery, although not quickly.

  15. Hi sir, I spoke to you before about the strip board layout if you could help me with a strip board layout of this circuit i hope you remember and I would like to follow up to see if you have had a chance to make one for me. Thanks

  16. Dear Mr. Majumdar. I am interested in 15-34 watt LED street light project without battery at Haridwar, Uttrakhand
    Would like to be dealer for same.
    Also is there any solution for automatic invertor battery charger when the light goes off.
    Also it is seen that qhen the light is on the use of battery is nil. Can there be a design which when invertor battery is full it should cut mains and go on battery backup upto letus say 50% or it can be adjustable as per requirement. This way use of battery will be at maximum and electricity bill be reduced. Kindly reply if u feel it a good idea.

    • Dear Nauty,

      I already have the required battery charger design in my website, you can easily find the required from the "categories" list however the idea of having 50% supply from the battery during the mains presence will not do any good….because while the battery is supplying current to the load it is simultaneously acquiring it from the mains…so that would not help in saving mains power in any manner.

  17. I want to make Automatic 80 Watt LED Solar Street Light Circuit Project so can u plz tell me how many volts & amperes of solar panel is required…??? Should I double it compared to 40 watt…???? Please reply as soon as possible…. Please

  18. Dear sir, can you please provide more details on the LED lamp module. Orientation of the LEDs in that module. Are they connected in parallel or in series to each other. Also, what is the value of the current limiting resistors for each LED. Thanks

  19. Dear sir, can you please mention the specs for capacitor C1, Resistor R7, LDR and power wattage for the solar panel. Also min and max LED output power that this circuit can support. Thanks

    • Dear Gopal, C1 can be any small value capacitor between 1uF/25V and 10uF/25V

      Max LED power for a 26AH battery can be 40 watts for 6 hour continuous backup

  20. sir i wanna make project same as this in small scale plz help me . I wanna glow a LED with solar power. I have also sold 3v solar panel but my circuit is not completed due to non availability of components (0.47mH 4R9 and 10R)

    • sampath, it's clearly shown in the diagram, only N/C and the pole are used the N/O is unused for RL2…the coil is connected across the positive and the T3 collector

  21. Hello, i would like to build this circuit but was wondering if you have a stripboard layout for it because it will be easier to construct and instead of me spending time making one i thought to ask you..please help it will be really appreciated

    Thank You

    • It would be difficult for me due to time pressure and many pending assignments, I'll try though if I happen to get some free time…

  22. sir i have 12v 75ah battery
    i want to charge through solar panel please give me the circuit
    automatic night sensor with 4pin pl lamp 11w

  23. Hello Sir, the coil configuration of third relay(at extreme right side of the circuit diagram which is connected to LED lamp module) is no shown in the diagram.

    • Dipto, you can ignore this relay stage, it's not relevant to the twin battery charger design that you are presently building

  24. hello sir, instead of 40W LED module, what can i use in my minor project. I want simple or cheap device in this place or which can i use as street light.

  25. Ya I will take aluminium PCB to place LEDs as required. Pls. provide charge controller and LED driver with dusk to dawn operation that should be common PCB for many LED loads with little bit modifications. The LEDs I will connect in series mode only.
    Thank u very much…

  26. sir actually i m confused can u explain my question answer. without battery connect, When i apply 21 volt supply at solar panel point, at battery point voltage is 14.3 v by adjusting P3 ok. Next at this point adjust P2 for battery full cut out without disturbing setup. next again without disturbing setup adjust P3 to 11.3 v output of battery point now adjust p1 for low cutout.
    is this battery point open right that is no connect battery just open those point. so without load at battery point how we can adjust low & full cutout?

    • yes it should be without any battery connected, the variable inputs simulate the battery threshold levels and is used for setting the relevant presets.

  27. I assemble he circuit but i chk voltage at battery connector & D5 voltage is 14.4volt as in put from solar is 20.8 volt i adjust but thr is no changes in voltage. How to make cut off by adjusting P1 & P2 that means from which point 14.2 volt & 11.01 volt has to put?

    please help me….

    • don't connect the battery while setting up, I mentioned this in the previous comment also.

      initially use a 15 or 24V AC/DC adapter for supplying to the circuit, don't use solar panel

      without any battery adjust P3 to get 14.4V at the cathode of D5.

      Now adjust P2 so that the upper relay just activates, if it's already activated, adjust P2 to deactivate it and again adjust the same to activate it and seal P2.

      Now adjust P3 to reduce the voltage at D5 to 11.1V, and adjust P1 so that the upper relay just deactivates again, seal P1

      confirm the above actions by adjusting p3 back to 14.3V and 11.1V two three times.

    • Hi sir for long time i replied, actually i did not have variable voltage supply, now i assembled for the above circuit use. As you stated in above comment steps are as follow,
      1: disconnect battery supply at solar point 21-22volt dc using supply.
      2: adjust P3 to get 14.3 volt at battery point.( i do at this point)
      after that i rotate both preset but nothing happen with relay.
      3: adjust P3 to get 11.13 volt rotate P1 & P2 but nothing happen

      please guide me…

    • It means you might have done something wrong with the connections.
      Initially keep the collector of T2 disconnected from the base of T1.
      Now adjust P2 to activate the relay at 14.4V.
      Reconnect T2 collector to T2 base and apply 11V.
      Now adjust P1 to switch OFF the relay.

  28. I assemble the circuit i observe following:
    1: voltage at solar input 18.9 volt
    2: voltage at D5 is 13.02 volt
    3: Voltage at battery connection 13.02 volt
    is this ok? how to chk LED point? Actually i print the pcb at a time & assemble & chhk the circuit

    • voltage should be 14.3V after D5 without any battery connected, this must be adjusted with the help of P3.

      the LEDs will respond when P1 and P2 are set at their respective cut-of thresholds

  29. Can we use computer UPS with 12v/ 45AH battery as a INVERTER for home use?
    I have one UPS with inbuilt 7 AH battery i want to use above circuit to charge 45 AH battery and UPS as inverter. Can we do it?

    • UPS can be used as an inverter also.
      the above circuit can be used for charging a 45AH battery.

      45AH will produce 5 times more backup than 7AH

  30. thanks for reply.
    As you stated 2 comment what i do for all light grid in home in all room.
    and my first question can i use above circuit for home light system as charger & power supply.

    • yes it can be used, please provide all the details regarding your requirement? I'll try to figure out the procedures.

    • Ok i want use 1 watt LED that is in your next artilcle in three room. in which distance is 1st 12feet 2nd 20feet 3rd 30ft from Battery & charger point.
      1: so my question is there is loss due to distance?
      2: What is consumption of power take by LED light of 39 no of LED
      3:I want to use 20 watt*2 panel & 7 AH 2 batteri is it ok?

    • the distance will not cause much of a problem, since copper wire resistance will be hardly in milliohms for the mentioned distances.

      39 LEDs will consume 39 watts if each LED is 1 watt rated.

      7AH will last only for 4 to 5 hours if 20 watt is used with it.

  31. hi swagatam
    can i use this circuit for home light systems. there is some questions:
    1: There is no R6 & R2 right?
    2: As led 12v bulb light used as gives low light as length of wire increase what should we do for loss of power?
    3: What is max watt of panel & Ah of battery is used?

    • Hi Ashok,

      1.R6/R2 have been removed so it's not there in the present diagram.

      2.You can connect the Ac/DC adapter or the battery very close to the LED circuit and install them as one module over the desired location, this will solve the issue.

      3.It's not limited to any value, only the voltage of the two must not exceed above 24V.

    • R7 will depend on battery AH

      divide battery AH by 10, and place the result in the following formula:

      R7 = 0.6 divided by the above result

  32. I am using a 12volt, 10 watt solar panel, and a battery of 12 v nd led light of 12v, what are the values of resistors of r2,r6,r7, nd what should be the output of battery,…plz rply fast i need to attach only these 3 on pcb, ty

  33. We are using a 10 watt solar panel, 12volt battery, what are the resistor values, of r2, r6,r7…. We should use.., plz reply us fast,

  34. hi.
    there is some problem with this circuit. when i set A1 it works normally when i move voltage level up and down from P3. but when i adjust A2 for low cuttoff then although A1 changes its output indicated by empty and full led but relay doesnot deactivates. it seems as it creats some latching with relay of A2. again when i adjust A2 preset to zero value the A1 relay works properly. any suggestions???

    • Hi, the above design is absolutely correct, there could be some problem with your assembly or parts.

      Or the slight delay may be happening due to the zener diodes in series with the transistor bases, which is not a big issue.

      For exact confirmation you can replace these zeners with LEDs, and remove the existing LEDs across the opamp outputs.

  35. my ratings are 12v 5 watts solar pannel and battery is 12v 1.3 ah will this circuit can be made with this ratings? if not suggest me the appropriate ratings for low power (5-10 watts)

  36. I want to use this circuit as a college project but i need to finish it and put it in a reasonable cover and hence its a street light i was wondering if it will be possible to put the battery somewhere in the head of the street light

    Also is it possible to get a small solar panel that will give me the required 14.4V i need to charge the battery

    Thank you

    • The battery can be installed anywhere around the light box, but should be appropriately enclosed and protected from water and direct sunlight.

      The desired soar panel can be easily procured from your nearby electronic market.

  37. Hello Tanmoy,

    You can use the above circuit for your application with the following modifications:

    Remove the IC2 section entirely and connect the D6 anode with D5 cathode.

    That's all is required rest all will be as is, the circuit will start functioning as per your specifications.

  38. lm 338 was not available so i used lm7815 with transistor d1047 (connecting input of 7815 to collector, output to base)for current more than just 1 A(output from 7815). is this arrangement ok???
    secondly how much max current can bc547 can pass??? can i use d1047 in place of bc547 if bc547 cannot supply current upto 2.5 A? if yes then what other changes do i need to make.

  39. sir, 13.98v battery full, 11.04 low which is the pin aliment, 1m r10 focus light LDR 4.89v come change the relay. ldr set the PCB and near led so light distrupe?

    • adjust P3 to get 11v across D5 cathode and ground. then adjust P2 to activate the upper relay.

      then adjust P3 to increase voltage to 14V, then adjust P1 to deactivate the upper relay and activate the lower relay.

  40. sir circuit connection couplet, 555ic section not work , p1 p2 aliment confused , led relay not work help me what my mistake

    • apply 14V to the circuit adjust p1 such that the top relay just activates.

      Now reduce voltage to 11V and adjust P2 such that the above relay just deactivates.

  41. hi, i have a few questons.

    1. how many hours will the battery take to discharge completely if 40 LED's are used as in your circuit.
    2.Is R10 min LDR circuit a preset or fixed. if fixed can a preset be used and of what value???
    3. where are full/low battery and ambient light indicators are connected in schematic???

    • You can use the circuit shown in the above article, just remove the IC555 (green IC) from the design, and use the rest of the circuit for your application.

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