The post discusses an interesting energy saving lighting circuit design which switches ON only when it is logically required thus helps to save electricity, and also increases the working life of the whole system.
Technical Specifications
Hello Swagatam,
Thanks for response, the details which you asked are as such ,
1. solar charger circuit to charge a lead acid battery.
2. my project demands that in a room if someone is present then LED's should be always on.
3. if the natural light is good then it should dim its light .
4. if nobody is there in room then after a delay of 1-2 min it should switch off.
5. provision to shut down during holidays.
All i need is my department room during college hour or after if needed should be lighted with using solar energy directly or through batteries.
I am really counting on you , I DON'T HAVE ANYONE WHO CAN TEACH ME THIS AND I GOOGLED IT LOT BUT ITS NOT WORKING OUT.
The Circuit Design
AS per the request the following energy saving intelligent light circuit consists of three separate stages, viz: the PIR sensor stage, the LED module stage, and the PWM light controller stage consisting of a couple of IC555.
Let's understand the the different stages with the following points:
The upper stage consisting of the PIR sensor module, and the associated circuit forms a standard passive infrared sensor stage.
In the presence of humans in the specified range, the sensor detects it and it's internal circuitry converts it to a potential difference so that it's fed to the base of the first NPN transistor.
The above trigger, activate both the transistors, which in turn switch ON the LEDs connected at the collector of the TIP127.
The above stage makes sure that the lights are ON only during the presence of humans in the vicinity, and are switched OFF when there's nobody around. C5 ensures the lights don't switch OFF immediately in the absence of humans rather after a few seconds of delay.
Using PWM
Next, we see two IC 555 stages which are configured as standard astable and PWM generator stages. C1 determines the frequency of the PWM, while the R1 resistor may be used for optimizing the correct response from the circuit.
The PWM output is fed to the base of TIP127 transistor. This means, when the PWM pulses consist wider pulses, keeps the transistor switched OFF for greater periods of time, and vice versa.
It implies, with wider PWMs, the LED would be weaker with their intensity, and vice versa.
We all know that the PWM output from a 555 IC (as configured in the right hand side section) depends on the voltage level applied at its control pin#5.
With higher voltages nearing the supply level makes the PWM output wider, while voltage nearing the zero mark makes the PWMs with minimum widths.
A potential divider stage made with the help of R16, R17 and VR2 accomplishes the above function such that the IC responds to the external ambient light conditions, and generates the required optimized PWMs for implementing the LED dimming functions.
R16 is actually an LDR which must receive ONLY the light from external source entering the room.
When the external light is bright, the LDR offers lower resistance thereby increasing the potential at pin#5 of the IC, This prompts the IC to generate wider PWMs making the LEDs grow dimmer.
During low ambient light levsl, the LDR offers higher resistance initiating the opposite results, that is, now the LEDs start getting brighter proportionately.
The 220K pot may be adjusted to get the best possible response from the IC 555 stage, as per individual preferences.
As per the request, the above circuit must be powered from a battery, charged from a solar charger controller circuit. I have explained many solar charger controller circuits in this blog, the LAST CIRCUIT given in the article may be used for the present application.
Anonymous says
Sir, my project is outdoor night lighting system.features are auto-switching using LDR, autodimming using PIR sensors and dual power source – solar and from power grid. The last feature means when the 12V battery , charged by solar during the day, goes undervoltage in late night, the power source will automatically switch to the AC Grid for continous operation. Can you help me with the last feature sir? Thank you. More power.
Swagatam says
Hi, please type "solar changeover" in the search box given at the top of the page, you will be able to find many options from which you can select the one which suits you the best.
Nelio Abreu says
Hi Swagatam.
I need to combile this circuit «Solar LED Lights with Charger» with this one. I know I have to remove the LED bank from the «Solar LED Lights with Charger» but what other changes do I have to do? I need this circuit to be intirely powered up by the battery that will be charged during day and supply power during night.
Thanks.
Keep up the good projects.
Nélio Abreu
Swagatam says
Hi Nelio,
you'll just have to remove the 40watt LEDs as shown in the following circuit:
https://homemade-circuits.com/2015/03/solar-led-lights-with-charger.html
and replace with the LED bank shown in the above article, and connect the output from the linked LM338 to the supply inputs of the above PIR circuit.
Meaning the "solar LED lights with charger" output now supplies the power to the PIR/555 circuit, while the LED bank is replaced with the 40 watt LEDs.
Nelio Abreu says
Hi,
2 more things….. what are the values of the LED bank resistors and with current configuration, how many LED's can I add to the circuit without changing transistor T2?
Thanks.
Nélio Abrue
Swagatam says
assuming these are 5mm LEDs 20mA, the resistors could be 100 ohms 1/4 each…you can add as many such strings in parallel as you may prefer depending on how much current input you may be wiling to use with the circuit
kkaranjia says
Dear Mr. Swagatam,
Can you please explain me the detailed working of the PWM stage including both 555ic as i could understand just some of it.
Swagatam says
Dear kkaranjia, it could be long a explanation, I'll give you brief one here:
The 555 network is a PWM generator circuit whose duty cycle could be altered by applying a proportionate magnitude of voltage at pin5 of IC2…..the LDR and the VR2 constitute a voltage divider network which become responsible for applying a varying voltage on the above pin in response to the ambient light condition which forces IC2 to generate the optimized amount of PWMs at the the base of T2 which in turn controls the LED illumination according to that proportion.
Mac Donald says
pls help me explain ur circuit well for me ..;i would like to use it as a project work ….pls help me …i am approaching the deadline for my project submission pls
Swagatam says
It's already explained in the article….
Raja Banerjee says
is it safe to connect a pnp tr to the o/p of 555?? as o/p Pin 3 of 555 does not rise high enough to turn off the transistor and also 555 book prevents us to connect a pnp buffer tr to the o/p of 555. thanks
Swagatam says
please show me the link which states this.
Swagatam says
I have seen your link, it's rubbish, no IC will produce full supply voltage output, nor will it produce 100% zero output, so in that case even an NPN device won't work correctly.
We have to take external measures to counter this problem, only eliminating PNP devices cannot be the solution.
Anonymous says
Hello Swagatam
i am also requesting you to help me with this following project: a combined control device for solar charged battery and automatic emergency light.
The minimum specifications are:
1.A controller should charge automatically a 7Ah lead acid battery from a photovoltaic panel until fully charged. The battery should not get overcharged.
2.There should be provision for automatic initiation of the charging mode when the emergency light is ‘on’ even if the battery is still not fully discharged.
3.The photovoltaic panels should be protected against reverse currents from the battery or the load.
4.There should be a linear, ten level battery output voltage monitor with a range between 10 and 15 volts.
5.The device should operate from 220 V, AC power source.
6.The primary circuit of the power transformer should be fuse protected.
7.Yellow LED should indicate “charging” mode of the controller.
8.Green LED should indicate “charged” mode of the controller.
9.Red LED should indicate “low battery” state, when the voltage of the battery is below 10.5V.
10.Green LED should indicate “power on” of the device.
11.Power switch for the device.
12.An emergency light controller should operate a relay driven emergency light for ambient luminance below 20 lux.
13.The device should have 220V output for supplying an emergency light with Pmax=100W
I would really appreciate it if you help me.
please email me at: masenajackson@gmail.com
Swagatam says
Hello Masena,
This circuit diagram will be quite elaborate and require a lot of time to draw, since I already have many pending requests with me, it might take sometime for your request to get published.
Rachit Kumar says
Hello,Swagatam… can you explain me that why we are using particularly BC547 and TIP127 what is the specification in terms of gain and beta amplification factor and what can we do if we need more current and voltage at LED bank input… also the PIR module is just the component or full commercial device available in market…. and what is the function of the capacitors used other than C1 and C5 please help..thanks in advance.
Swagatam says
Hello Rachit,
you mau use other similar transistors also, the values are not fixed.
For more current you can add another stage after TIP127 consisting of transistor 2N3055.
The PIR is a complete sensor module with casing and three pin-outs(+, -, and out)
C3 is for generating triangle waves, and remaining are for stabilizing pin#5 of IC555.
Unknown says
My model would be like this –
1. If people enter into a room, the counter should increase to one and and the circuit (or lets a say a fuse) should switch on, allowing the person to access the lights in the room.
2. As people come into the room, the counter should be incremented. Still the fuse should be on.
3. If people leave the room, counter should be decremented.
4. The circuit should be switched off when the counter becomes zero.
Purpose – If people leave the room without turning off the lights before leaving, the fuse goes off and the lights are off automatically.
Could you please help me on this.? Could you give the circuit diagram and specifications ? I am really counting on you , I DON'T HAVE ANYONE WHO CAN TEACH ME THIS AND I GOOGLED IT LOT BUT ITS NOT WORKING OUT
Swagatam says
I did not understand the "counter" concept, do you mean LEDs lighting up in sequence as people increase in the premise??
Unknown says
No. I want a display to show the count of the people.for example – if one person enter the room, the value of the counter should be one and the display should show 1 and the fuse should turn on, allowing the person to access the lights in the room. As people come into the room, the value of the counter should increase. Now the display should show 2,3 and so on. As people come out of the room, the counter should decrease and should be shown in the display. The fuse must go off when the counter becomes zero. Until then it should remain on.
Swagatam says
OK, got it, I will try to design it if it's feasible and update it here.
Unknown says
Thank you so much. U are really awesome. I'm waiting for your design.
Kindly let me know as soon as possible. It would help me a lot. I'm totally depending on you. Thanks in advance
Swagatam says
I'll try to do it soon….my internet connection is down since last 4 days, so it's getting difficult to keep things updated.
Unknown says
Hi Swagatam,
As i'm nearing my project deadline, I have this small project in mind.
Could you please help me on this?. Here is the description –
I just need a circuit that detects the number of person passing by a door or a path(preferably using PIR SB0061, as i already have it) and displays the number on a 7-segment display (0-9)!
I have this basic idea of how to go about it but not able to realise the circuit.
The output of pir sensor can be used a trigger to increment the count. So we need a counter attached to a 7-segment display to display the value.
Could you please help me on this. Please reply as soon as possible. I'm totally depending on you 🙂 Thanks in advance 🙂
Swagatam says
Hi Unknown,
I tried but found the up/down counter difficult to design, in your previous comment you mentioned that when the people leave, the counter should read backwards which would require a complex up/down counter and sensor arrangement for reading the entry as well as exit of the people which was difficult for me to design.
Another difficulty was the fuse part, I couldn't understand how it would determine the position of the lights in the room.
Unknown says
Is this circuit working ? i'm planning to work on this project, please let me know
Swagatam says
the concept looks perfect to me, but has not been tested and verified yet.
Rachit Kumar says
Thanks A lot Swagatam…
In short period i will post the hardware pics f the same circuit , i just had work to find a suitable charger circuit for the above as you already said you posted many circuits for the same. Thankyou so much… 🙂
Swagatam says
That's great Rachit, but please note that the above circuit has not been verified practically, and might require careful modifications for proper functioning…. a lot of tweaking in the design.
Rachit Kumar says
Hello Swagtam, am getting problem in respect to the above circuit.. In the output part, current and voltage are very low, current is .13amp and voltage 4.55v. So how can i light my led bank of 30 watt as you said.. but actually i need to light 80 watt led bank for proper illumination… and also i dont know any alternative of TIP127 transistor. suggest me the way out of this problem.
Swagatam says
Hello Rachit, can you show me your circuit, did you connect the PIR module?
Rachit Kumar says
Thanks Swagtam for your really helpful response, I just wanted to know that,
1. Output of 7805 ic is going to which component whic has terminal + and – "the green colour component.
2. +ve terminal of the circuit which is to be connected to the battery charge controller circuit is visible but where to connect the -ve termnial of the battery charger controller circuit to above corcuit.
3. what is the total wattage or number of LED's we can connect to this circuit. please sepicfy the details of the LED's.
Swagatam says
My pleasure Rachit!
The output from 7805 is going to the PIR module which is a "human presence sensor"
The common terminal which is running from the center pin of 7805 IC to C1, and is marked by (0) symbol near C1 is the negative terminal.
Wattage of the LEDs here can be upto 30 watts, however it can be increased by suitably increasing the rating of T2.