The following LED emergency light with battery over charge protection feature circuit was designed by me in response to the request sent by PP.
Main Features
The article describes an LED emergency light circuit with advanced features such as,
- over charge battery cut off,
- day time auto-disable,
- and need less to say that the circuit switches ON the LEDs automatically when AC mains fails and reverts to charging mode when power is restored.
- The good thing about this circuit is that it incorporates ordinary, cheap components which can be easily procured from the local market.
Circuit Description
Let's try to understand the circuit functioning with the help of the following points:
IC1 which is our very own IC555 has been set as a comparator. During day time, the light over LDR keeps the LDR resistance low such that the potential at pin #2 of the IC is kept well over 1/3Vcc. This situation ensures that the output of the IC at pin #3 stays at logic high.
The logic high at pin#3 of the IC keeps T1 switched ON, which consequently keeps T2 switched OFF.
With T2 switched OFF, the LED array remains inhibited from the ground connection and therefore the whole white LED array also stays shut off.
Another factor that keeps T1 switched ON and T2 switched OFF, is the voltage from the transformer power supply stage.
This function is implemented via the resistor R9. This also means that as long as mains AC is available, T2 is restricted from conducting and therefore the LEDs cannot light up.
Now suppose the mains power to the transformer fails, and assume that this happens during night or complete darkness, pin#3 of IC555 reverts to zero and also there's no voltage from the power supply, means T1 has absolutely no base bias and therefore has to switch OFF.
This instantly prompts T2 to switch ON and consequently the entire LED array also switches ON, providing the required emergency illumination to the surrounding.
MAKE SURE THAT THE LIGHT FROM THE LED DOES NOT FALL OVER THE LDR, WHICH MIGHT TRIGGER A RAPID UNDESIRABLE SWITCHING OF THE LEDS.
The battery charging section consists of T3, T4 and the associated parts. P1 is set such that it switches ON T3 when the battery voltage reaches just above 14 volts.
The moment this happens, T4 switches OFF, cutting of the negative supply to the battery and restricting any further charging of the battery.
Diode D2 ensures that the battery receives the negative supply during the charging process only through T4 and also provides a normal negative path to to T2 and the LED array when they conduct.
The left side LED indicates, mains power ON or presence of day light.
The LED at the right side indicates, battery is charging.
Parts List
R1 = 2M2
R2 = 1M
R3, R4, R5, R9, R6, R7, R8 = 4K7
ALL LED RESISTORS = 330 OHMS
D1, D2, D3 = 1N4007
D4----D7 = 1N5402
C1 = 1000uF/25V
C2 = 1uF/25V
T1, T3 = BC547
T4, T2 = BD139
Z1, Z2 = 3V/400mW
P1 = 10K PRESET
IC1 = IC 555
TRANSFORMER = 12V, CURRENT = 1/10 OF BATTERY AH
LEDS = WHITE 5mm, OR AS PER CHOICE.
BATTERY = 12V, AH = AS PER LED POWER AND BACK-UP REQUIREMENTS.
Using a Single PNP BJT
The above circuit can be much simplified by eliminating the IC555, and by using just a single PNP transistor instead of two NPN in the battery auto-battery cut of section.
P1 is used for adjusting the ambient light threshold at which the LEDs stop illuminating.
P2 is set such that at 14.6V (across the battery terminals) the base LED becomes very dim, hardly visible, and at 12.5V it's brightly lit.
Adding a Solar Panel
The above circuit can be also coupled with a solar panel for getting an automatic charging facility from both the sources that is from the panel during day time and from mains after the sun sets.
Parts List
R1,R2,R3, R4, R5 = 1K
P1 = 470K
P2 = 1K
C1 = 1000uF/25V
D1---D5 = 1N4007
T1 = BC547
T2 = 8050
T3 = TIP127
ALL LED RESISTORS = 330 OHMS
LEDS = WHITE, 5MM
LDR = ANY STANDARD TYPE
TRANSFORMER = 0-12/1AMP
salman says
is it possible to cuf off load (led panel) when battery get discharged at 10.5v
Swag says
if you add 3 LEDs in series instead of two, then this can be implemented automatically
Gelu Lacusta says
Supeeeeer!!!!!
e-tutor says
Hi
How to adjust the over charge cut off circuit for a 4v 1ah battery?plz help..
Alihan Güllü says
Hello Swagatam,
I built the 2nd circuit you gave and checked a couple of times to make sure everything is connected to each other well. I got some issues though. First of all, I would like to use a led strip (rated 12V – 4,8W per meter), but I don't know how much length I need yet. I also discarded the LDR section with the LDR, P1 and R1. A couple of times I tried, it worked as expected. Later on, it didn't work. Here are the issues:
1- While it was working fine, when A/C mains was cut off, it took some 7-8 seconds for the leds to light up 🙂
2- As you mentioned in the description and in some of the answers you gave, I adjusted P2 to get 14V from battery terminals and I got a dim red light, but when it went down to 12V the light got dimmer, almost not visible.
3- With the use of strip leds, I guess I fried T2 (S8550), because after a few tries turning A/C power on and off, the leds starting lighting up with the A/C power on turning off when the power goes off 🙂 Also, the transistor was pretty hot.
Swagatam says
Hello Alihan,
the issues which you have mentioned can never take place because there's no possibility of those happening.
there's no capacitor associated with the T1/T2 so the delay effect cannot happen.
I hope you have only removed the LDR, R1 and P1 in your circuit and kept rest as shown in the diagram with R2 connection intact with the base of T1?
T2 can only become hot if the LEDs current is much higher than its tolerance level.
The charging LED will become dim as the battery voltage reaches 14V and vice versa so that's fine.
when mains is present T1 will be triggered ON through R2, which will keep T2 switched OFF, keeping the LED bank switched OFF, so the LEDs can never light up when mains is present unless one of the transistors has gone faulty.
by the way this a very basic and crude design so you cannot expect high precision from it.
for a high precision you can probably refer to the following design.
https://homemade-circuits.com/2015/10/smart-emergency-lamp-circuit-with.html
Alihan Güllü says
Thanks for your reply, you've been pretty helpful..
The only direct connection between T1/T2 and the capacitor is the negative pole, which I guess not very important.
As I presumed, I had fried T2 and when I replaced it, it worked fine again. Then it got fried again as I forgotten to remove some part of led strip before plugging it back :))
I realize that it is a crude design, still it is important for me to start building something small and make it useful at home..I have seen the other project you have mentioned and I will surely have some questions for that one too 🙂
If I change T2 to a more powerful transistor, would I be able to use it with a load of 2-2,5A? Or I need to upgrade the whole circuit for that? For T2, I found BDX53C, which seems to be pretty powerful, still not sure if I can use it for the same purpose, or do you have another suggestion?
Thanks in advance..have a great week
Swagatam says
yes obviously T2 must be dimensioned as per the LED current otherwise it will keep blowing of.
Only T2 and R3 will need to be upgraded as per the load current rest will as is unless any other parameter such as battery is upgraded too.
R3 = Batt supply – LED operating voltage / LED operating current
mayu takuma says
Hi Sir. We want to make a request. Is it possible to add a feature on this circuit? We would like to add a fan in this circuit so we can use it when there is power failure. Thank you.
Swagatam says
Hi Mayu, you can connect the fan exactly where the LEDs/resistor network is connected that is across the positive of battery and the collector of T2
varun gopal says
Sir
Please reply me
I have 12v 12AH led acid battery. I need to charge it. Please tell me the spec of 12v transformer
Swagatam says
Varun, you can use a 0-12V 2amp transformer for it, connect a bridge-rectifier with a 6800uF/25V to getting the required 14V 1 amp charging output for the battery.
varun gopal says
Sir
I have 12v 12AH led acid battery. For this how much Amp transformer need for making charging circuit
Thank you
SPARROW'Z TECH says
Hi am Akhil
In the first circuit circuit using IC555,where should the earth sign indicated point be connected?
to the battery -ve or bridge circuit's -ve?
Swagatam says
Hi, it's already connected with the negative of the bridge rectifier….no need to connect it anywhere else.
Sandeep v menon says
what changes should be made to the circuit if a large number of LEDs (say White coloured,75 or more in number) should be included??
Swagatam says
battery, T2 and the transformer rating will need to be increased accordingly
glen mico Herrera says
Sir can i ask where is the positive and negative in solar panel . the positive side is connected in the diode right ?
Swagatam says
yes that's correct
Kanta says
Hi Swagatam..
I just constructed the second circuit using 6 volt battery, with 24 Led, single series with R combined 3 diodes. For the emergency light, it is functioning well. However, for the charging and cut off section, i set up the LED with the fully charged battery (6.9volt) by triming the pre set of TIP 127, to get very dim LED. When the battery discharged to 4.4 volt, the LED is still dim, then i detached the Battery and measure the collector voltage of TIP 127, the output is zero. I trimed the VR in such away to get the output of the collector to 8.5 volt, the LED became very brigth. I put on the battery and let it get charge. After the whole day, i still saw the LED bright. Then i detached the battery and measured the voltage of battery, it was 6.9 volt. i put on the battery again and trimmed down the LED until dim. After that, i detached the battery and measure the output of TIP 127, it was zero volt. Could you please advise me, what is my fault. I use 7.5 volt transformer of 1 amp and 6 volt 4.5AH batery.
Many thanks
Regards
Kanta
Swagatam says
Hi Kanta,
using a single transistor as a sensor can be very crude and produce less accurate results…still you can try attaching a 3V zener diode in series with the base of the transistor (cathode towards base) and check the results, or you can opt for the next design using two transistors.
FARHAN NASEEM says
DEAR SIR
i implemented your circiut with ic lm555 ,the current with leg 3 of ic is fllowing in every condition of LDR if we opened the leg 3 of ic the emergency light works fine plz help me to make LDR operational in this circiut
http://2.bp.blogspot.com/-eT2gHZxSr_A/UcEtp0coNDI/AAAAAAAAEhU/_9SJyCbGqWQ/s320/emergency+light+with+overcharge+cut+off.png
Swagatam says
Dear Farhan,
in the absence of light on the LDR, pin3 will stop producing a voltage…..so make sure the LDR is held in sufficient darkness for this to happen…..or reduce the value of R2 until pin3 becomes zero volts at the desired darkness level
FARHAN NASEEM says
dear sir i implemented your fiirst circiut with ic lm 555 i am having an issue emergency leds are not glowing becasue in every case current is flowing from leg 3 of ic if we opened leg 3 of ic the emergency light works fine plz help me and make circiut operational with LDR
image url is
http://2.bp.blogspot.com/-eT2gHZxSr_A/UcEtp0coNDI/AAAAAAAAEhU/_9SJyCbGqWQ/s320/emergency+light+with+overcharge+cut+off.png
lokesh lokesh says
Hi sir
I am so glad to see ur interest towards electronic circuitry ..
So eagerly waiting for circuit which will be having following (few or all) features
-Low Battery Cut-off
– Overloading protection
– Short Circuit protection
– Reverse current protection
– Reverse polarity protection
– Thunder protection
– Over discharge protection
– Auto battery shut-off at Low voltage detection
– Overcharge protection
– Auto charge stop/ High Volt Detection
– Battery capacity level display(SOC)
Making this circuit for underprivileged location as donation for poor via charity
So hope I can have one ckt diagram with some or all features mentioned above or lts link..
Looking for ur reply ..
With full excitement
Thank you
Regards
Lokesh
If successful I am in plan to put ur & website name on my device 🙂
As part of tribute to you sir
Email: Lokeshelectronic@gmail.com
Plz WhatsApp me sir if possible to
9986829004
Swagatam says
Thanks Lokesh,
I'll try to publish it soon…..please keep in touch.
Pritam Bhowmik says
it seems in the 1st ckt, no need of z1,z2.. whats the function?
Swagatam says
it delays the response…but it's not important.
eroll king salvador says
hello sir swagatam.
sir i want to create your wonderful circuit above but the problem is., i never have bc547 if i substitute this by 2n5551 what is the difference and what transistor that can be substitute in bd139 if i never have tip122.,., i wait for your answer sir.,., thanks.,.,
Swagatam says
hello eroll
although not very much suitable, 2N5551 can be used in place of BC547, for BD139 you can use any other equivalent rated to handle at least 2 amp at 30V
gogutu says
domnule;sunteti o comoara.as dori sa stiu cum pot modifica incarcatorul pentru o baterie de 12v/75A.pot folosi un triac in locul tranzistorului?multumesc.astept raspuns pe lacustagelu_68@yahoo.com sau gogutu68@gmail.com
Swagatam says
thanks gogutu, you mean want to adjust the voltage of the charger using transistor circuit instead of triac??
Muhammad Salahuddin says
hello Sir,
i build your second cct ,its working fine ,except the charging part…….. you are right single transistor cct is crude………could you please integrate the charging cutoff section in first cct in second one…………..I tried some thing …………kindly make necessary ammendments………..
i have sent u this modified cct at homemadecircuits@gmai.com ,please check and reply accordingly.
Thanks in advance for your kind response//
Swagatam says
Thanks Muhammad, I'll check it soon and update the diagram here……….
Hans says
Sir i have an emergency lamp at home which is not working, LEDs and battery are intact. I would like you to suggest me a circuit so that I can charge it from mains, Thanking you
Hans John D'cruz
hansdcruz@gmail.com
Swagatam says
Hans, please provide the battery current/voltage specs so that I can calculate the parameters…
Hans says
I guess the battery is 6V 2A there are no details reg the battery on it
Swagatam says
you can use a mobile charger for charging it with a 470 ohm 1 watt resistor in series with the positive line. The battery may need more than 2 days to get charged fully.
Hans says
Thank u swagatam
Tony Thomas says
Sir,
Please mention diode D1 connect which pin of ic 555
Swagatam says
pin3 of IC 555
Tony Thomas says
Sir,
i set first circuit.i want remove LDR and insert switch. how to change this ciruit pls help me.
Swagatam says
Tony, insert the switch in place of the LDR…
Tony Thomas says
thank u sir…
Sir i need a circuit for a good amplifier pls help me
Swagatam says
please provide complete specifications of your requirement, only then i would be able to suggest
Tony Thomas says
Sir i want 200-200 watts power amplifier including sub system pls give me the circuit. please provide power section also
Swagatam says
Tony, you can make two of the following circuits:
https://homemade-circuits.com/2012/04/how-to-make-simplest-100-watt-mosfet.html
the circuit can handle well over 200 watts if the input voltage is around 50V.
presently i do not have a subwoofer circuit in this blog, will try to include it soon.
Tony Thomas says
thank u sir
sir i want one emergency light circuit for using 500leds.please give a circuit
Swagatam says
i'll look for it and inform you soon…
Tony Thomas says
K sir Thanks
Shakir Abbas says
Sir,
p
Rahul Ravishob says
Hello Sir,
Firstly I would like to appreciate your effort !!! G
Now my question is …can I use a 6V battery instead of 12 V…I would like to avoid LDR….Is there any modification neeeded?
Swagatam says
Thanks Rahul!
Just remove P1, R1 and the LDR if don't want the dark activation section.
yes 6V can also be used, the LED series resistors will not be required with a 6V supply
Kishore Cp says
Hi Swagatam, GN,
Your circuit is awesome and Good. Could u plz clarify some doubt! Thanks in advance.
I am using 12v 7.5AH rechargable battery, i am planning to connect 6 1 Watt LED to the battery. Can this circuit be used or do i need to modify or add any resistance to the circuit.
Swagatam says
Thanks kishore, you can try the above circuits, but T2 will need to be changed to TIP122 for driving 6 watt LEDs safely. Use large heatsink for T2
azeez fatai says
which simulation software do you use sir, am using proteus and i have problem editing its transformer to give a desire voltage. so i'd appreciate if u can share me the one you think will help me the best or suggesting me the link to downloading it. moreso am new to designing but love to design
Swagatam says
simulators are like blind persons with a stick, do you want to depend on a blind man's judgement??
Therefore i never depend on simulators and have never used any, rather I design the circuits by simulating them in my mind…I know it may be difficult for a new hobbyist to follow this but it also may not be a wise idea to depend on something which itself is so unreliable.
the best way (although hard) is to develop knowledge and understanding regarding the various concepts and begin simulating them with the help of the acquired knowledge
arun kumar says
how to tansformerless in used first circuit modifying circuit digrams. how to remove LDR in modifying circuit
Swagatam says
replace the following circuit with the transformer:
https://homemade-circuits.com/2011/12/cheap-yet-useful-transformerless-power.html
Batharakala says
hello there sir, thanks for your hard working. its really useful here.
may i request an led indicator for battery level like low, med and full when charging and using battery power 🙂
thanks for your answer sir
Swagatam says
Thanks Batharakala, you can try the following circuit:
https://homemade-circuits.com/2013/06/3-step-dc-voltage-level-monitor.html
Arka Roy says
thank you sir…
but the 1st circuit is not working
Arka Roy says
what is the value of r9
Swagatam says
10K
dhanish says
please also tell me that can i use circuit in the link below with 12v, 7ah battery to connect the led bulb shown in the above link with rating(Power: 1W, Voltage: DC 3.0V~3.2V,Current: 300~350mA).If yes then how long it will give light with that battery else please suggest an efficient circuit.
This is the link
https://docs.google.com/file/d/0Bwgu3V_6cEZsUjZhM2k3dXlhUGs/edit
Swagatam says
yes can be used but the 317 will become very hot, use heatsink for it..
it may last for about 2 hours.
dhanish says
can i use the circuit in the link below with the above mentioned solar panel, battery and bulb
https://drive.google.com/file/d/0Bwgu3V_6cEZsaUp1ZUEtdmpMR2s/edit?usp=sharing
Swagatam says
yes…
dhanish says
Can i use the above mentioned 1w (8Nos) led in this circuit.Will it give max light.
Swagatam says
yes can be used.
dhanish says
Is it possible to show a charging led in this circuit.If yes pls tell me how to?
Swagatam says
it's already there at the base of the transistor.
dhanish says
https://drive.google.com/file/d/0Bwgu3V_6cEZsZGZ6Y3R2WVRmSFk/edit?usp=sharing
i am using this circuit to charge 12v 7ah battery with the above mentioned solar panel.but its not charging is there any prblm in this circuit.if you have any better circuit to charge with solar panel pls give me.
Swagatam says
check the output voltage without connecting the battery, it should be set to 14V, and the solar panel must be able to produce 1amp current minimum.
dhanish says
my panel is only producing a max of 430 mA is there any circuit to charge the 12v 7ah sla battery with this panel.
Swagatam says
430mA will not charge 7AH batt…change the panel with a 1 or a 2amp variant
dhanish says
I dont want to use ldr can i used a switch instead of that.
Swagatam says
yes surely, remove the T1/T2 stage entirely.
dhanish says
Friend i am little bit confused thats why im asking to many questions dont feel irritated.please tell me that if i want to connect the 1w led direclty to 12 7ah battery then how many can be connected to the battery so that i will get a back up of 6-8hrs
Swagatam says
friend, make strings of 3 leds in series with a 6 ohm 1 watt resistor.
make 2 such strings and connect them in parallel (join their positive/negative ends together)
and connect the network to the battery.
2 strings in parallel having 3 leds in each string gives 3×2 = 6 leds
this would approximately run for 7 to 8 hours.
dhanish says
sir pls reply,
in the above comment you said to remove t1 t2 stage,then should i have to remove r1,r2,r3,p1 with that.
if yes then where i have to connect the led +ve and -ve.
I want to charge my 12v 7ah battery with this circuit pls tell me how.
Swagatam says
….please repeat your exact requirement pointwise.
dhanish says
Can you give me the circuit to connect LM317.
can i connect 12v 7ah battery?
can i use the given led bulb( 1w or 3w) in the link below in this circuit?
https://docs.google.com/file/d/0Bwgu3V_6cEZsdlZSRDM4QVJEcms/edit?pli=1
Swagatam says
if it's a 1watt led you can connect it directly with the 12V battery through a 40 ohm 1 watt series resistor
dhanish says
how many 1w led bulb can be connected to 12v, 7ah battery (pls give the resistor value also) which give max brightness and backup hrs.
Swagatam says
i am answering this for the second time, pls don't repeat your questions.
connect 3 leds in series with 6 ohm 1 watt resistor
make two such strings and connect their common ends with the battery
backup will be upto 3 to 4 hours
dhanish says
when i measure the voltage and current of solar panel with multimeter i got 19.2 approx 20v and
current within .5A.
I dnt know the rating of that bulb
Swagatam says
the solar panel can be used with the above circuit but after stepping down through a LM317 voltage regulator.
the OSRAM bulb tat you have mentioned is a fluorescent tube so it cannot be used directly with the above circuit.
dhanish says
also i have a 10w solar panel is it sufficient to use with this circuit
Swagatam says
please provide its V and I ratings
dhanish says
hi
my battery is 12v and 7amp,so is there any problem. And i have Osram Dulux S/E 7W 4 Pin CFL – 827 so is it possible to connect that in this circuit.
Swagatam says
hi how does the lamp work, please provide it's voltage and current specs for correct analysis.
aquarius says
Sir, I want to build the second circuit (without 555), but want to additionally incorporate a small solar panel for charging battery (first priority solar charging, second priority mains). Will be obliged if you please suggest a modification in circuit. safdar
Swagatam says
aquaris, it can be done by a simple modification, i'll try to update it as soon as i get some free time.
aquarius says
I'm very delighted and thankful for your prompt response. I will look forward that u have time to advise a good circuit. To elaborate requirement further, the battery should normally be charged by solar panel, and if not sufficient, like cloudy days, it should auto switch to charging from mains till battery is fully charged (of course with overcharge protection). Thanks once again.
Swagatam says
Thanks, I have updated the diagram please check it out.
aquarius says
Many thanks for the goodness. You are genius. I will build this circuit for my home and give u feedback soon.
Swagatam says
You are welcome
mujahid bhutta says
sir can I use same circuit for using 12v 7w led and battery of 12v 2.5Ah and how much time transformer needs to charge battery of 2.5 ah fully
mujahid bhutta says
sir can I use same circuit for using 12v 7w led and battery of 12v 2.5Ah and how much time transformer needs to charge battery of 2.5 ah fully
Swagatam says
12V/2.5 ah will not support the led for very long, may be only for 30 minutes.
lead acid battery needs 10 hours to get charged correctly.
achilles hector says
Good day sir!
I have some questions.
1.Can I replace the 12-0-12v 1A transformer with 15-0-15v 1A transformer then just use voltage regulator like LM7812 to regulate to 12v? Doesn't it affect the current?
Swagatam says
7812 will not produce or allow more than 1amp at its output, irrespective of input current or voltage
Anonymous says
How to calculate their values?
Swagatam says
please check out this article
https://homemade-circuits.com/2011/12/how-to-wire-led-lights-easy-clues.html
Anonymous says
what is the use of connecting so many resistor in series with the leds, cant we connect a single resistor in series with high watt and how to calculate the led resistor.
Swagatam says
the resistors distribute current equal among the LEDs creating uniform brightness and optimal response.
Anonymous says
Hello Dada,
Cant We Connect A single Resistance in Series instead of So many resistors in parallel and in Series with leds.
And I have Send You a circuit Diagram in facebook Messages please reply.
Tanmoy Singha Mahapatra
Swagatam says
Hello Tanmoy,
Using single resistor will make the LED brightness weaker and nonuniform.
Anonymous says
Please Check the facebook wallpost fast today iam going to buy the components.
Tanmoy
Abhishek Das says
what about using a photo-transistor for the circuit ??
i found one circuit on net but the problem is that i cant find the photo-transistor in market
is their any other option for a "dark detecting circuit" which can operate in 4v dc batt.
Swagatam says
LDRs are cheaper and easier to configure, they also work with all voltages.
Abhishek Das says
for lower voltages how LDR's can be configured
ie which transistor should i use???
waiting for ur reply…………
Abhishek Das says
🙂 thanks
how to control back flow(reverse flow)when charging any battery from a multi voltage adapter when the main fails
Swagatam says
you can add a diode with the positive line ssuch that current only passes from the adapter to the battery and not in the reverse direction.
Abhishek Das says
i made the circuit it works
But the fully charged 9v battery gets discharged
is it because of the transformer
what is the solution for that?
for charging a 9v battery which zener diode do i need 9v or 12v zener
Swagatam says
If you are referring to the first circuit, you may increase R6 to 10K, this will control the issue.
Abhishek Das says
give me u email id
i need help in some circuits which i want to send so that u can help me
secondly i need some modification in the circuit in which the charging stops automatically when the battery is fully charged
all for 9v battery
Abhishek Das says
instead of leds if i use two 1 watt leds do i need to attach resistors (5 ohms 1/4 watt)
im using 9v battary
is their any changes in the circuit (resistors)
im using multi voltage adaptor instead of transformer ( 0-9v)
Swagatam says
your 9V battery should be rated at at least 4AH….
make two parallel strings having 1 watt leds and connect 20 ohm 1 watt resistors with each led string.
also replace T2 with TIP122
Gopal Malviya says
hello abhishek sir
i gopal malviya from m.p. and i have just started by cfl repair and making
business but i dont have any good reasonable electronics parts supplier so please suggest me parts supplier vendor contact detail with your reference
Thanks for kind support
Gopal Malviya
Abhishek Das says
hi
sir i want some modification in the circuit
i want to built it for 9v dc.
what all modification will i have to make
plz reply 🙂
Swagatam says
use a 0-9v transformer and make all the LED resistors to 5 ohms, 1/4 watt
Abhishek Das says
what about the zener diode is its value will be same or a 9v zener
instead of bd139 if i use bd140 what wil be the difference
Swagatam says
The zener diodes are actually not required, you can remove them and connect the emitters directly to ground.
BD140 will not work as its a PNP transistor.
udara kapuduwa says
Sir,
can I use 12V car battery for this
Swagatam says
yes…..
imran wani says
bro I need only over charge cut off circuit with blinking led……….??
രജീഷ് പാലവിള says
Waiting for your reply Sir
രജീഷ് പാലവിള says
battery is 12V/7.5AH Lead acid sealed battery .Transformer is 15-0-15V/1Amp.
Swagatam says
disconnect the 7812 ground link and connect through 4nos 1n4007 diodes, do the connections as shown in the following article, connect the 2.2k resistor also as shown, ignore the rest of the components.
https://homemade-circuits.com/2012/11/high-current-transistor-tip36-datasheet.html
രജീഷ് പാലവിള says
Dear Sir,
the same problem exciting(ie,charging is too slow!).Remind you that i constructed your second circuit ,with 15-0-15v/1A transformer connected through 7812 regulater.Is there need any change for speed charging ?Now it is very very slow !
Swagatam says
what is your transformer amp, and battery AH?
Swagatam says
provide me the battery AH, and voltage…..
if it's 12V, you will have to remove the 7812 IC and give direct supply to the battery.
രജീഷ് പാലവിള says
Ok will check it..thank you for your support
രജീഷ് പാലവിള says
Dear Sir,
I make the second circuit ,it work well.Thank you.
One point noticed that charging is very slow .At the time when i connected the circuits to battery ,battery voltage is 10.81v .After 3 hours it slightly increase but not exceed 11.I check overall connection again and again ,it found correct .Is charging need more time ??
Swagatam says
You can use the preset to adjust the charging rate, tweak the adjustment as per preference, but do not make it too fast otherwise the battery may get damaged.
രജീഷ് പാലവിള says
If i make first circuit(ic 555),transistor BD 139 is capable to handle more than 50 LED's?? Can I use TIP 122 instead of BD 139 in same circuit arrangement ???
Swagatam says
make the second circuit, it's much easier. yes tip122 may be used.
രജീഷ് പാലവിള says
Thank you Sir
രജീഷ് പാലവിള says
Dear Sir,
i wish to make one of this above circuit. Presently a 15-0-15v/1Amp transformer and 12V 7.5 AH battery in my hand .In your specification the value of transformer is 12-0-12 V.Can i use 15-0-15V transformer instead of 12V in this circuit??Waiting for your immediate reply .Thank you Sir
Swagatam says
Dear രജീഷ് പാലവിള
You may use your transformer, use one 0-15V tap.
But you will have to reduce the voltage to 12V with the help of IC 7812 if you are using the IC 555
Anonymous says
Hi Swagatam,
I was wondering if I am able to connect the output from a boost converter @24V/0.4A to replace the transformer? Could you advice me how to go about changing the config?
Swagatam says
24V would be quite high for the above circuit, it should be around 15V.
Anonymous says
Hi! thanks for your reply… I was wondering if I used a linear reg of maybe 12v from the output of the boost converter, and use components that are higher voltage rated would do the trick?
Swagatam says
yes, then it would be OK!
Sanchay Chakraborty says
Hi Swagatam,
Today I got success with your 2nd circuit, thanks for your continues support for trouble shooting and advise.
Swagatam says
you are welcome!!
Jose says
Hi, Swagatam,
could u plz modified this circuit for me i need the 12v 7ah battery charger with over charge protection using 12v 1A transformer
Swagatam says
Hi Jose,
the above charger circuit section will not give accurate results……
Anonymous says
Hi Swagatam…!
I want 40 LEDs Light… Circuit also same for this..???
Swagatam says
Yes it will be the same…
Sanchay Chakraborty says
Hi,
Thanks for your help,
I have done as you told. But now white LEDs are not illuminating in any situation, the T3 led is glowing both in battery and main power on condition.
need help for troubleshooting.
Swagatam says
OK, it's probably due to the battery voltage that's passing through the emitter of T3 to the base of T1…..add a blocking diode after C1, so that the positive from transformer passes through this diode to the charging section consisting of P2, T3 etc….but the battery voltage gets blocked by this diode.
Sanchay Chakraborty says
Hi,
I have prepared the 2nd circuit, and there is some issue kindly help..
All white LEDs are glowing in the situation when the main on and the T3 LED is glowing but T1 LED is not glowing. And even no changes found when I switched off the main AC power, with battery power.
Swagatam says
Hi,
Remove the red LED at emitter of T1, connect the emitter directly to ground.
imron says
I'm going to build the 2nd circuit using 6v 4.5Ah lead acid battery. What should I modify in the circuit? should I change the LED resistors with another value?
Swagatam says
Yes the second circuit also has a over charge protection using the TIP127 transistor.
For 6V battery you can make the LED resistor to 10 Ohms 1/4 watt.
imron says
is the 2nd circuit (without IC555) also for battery over-charged protection?
Sanchay Chakraborty says
Thanks for your suggestion,
And now I am doing with the 2nd circuit and will update you accordingly.
Swagatam says
OK!
Sanchay Chakraborty says
Thanks Swagatam,
Can I use zenor 3.3v/250mW for Z1 and Z2 instead of 3v/400mW. And need to use heat sink for BD139?
Swagatam says
Actually zener diodes are not required, you can connect the emitters of the transistors directly to ground.
Sanchay Chakraborty says
Hi Swagatam,
I am going to make this project but I did not find the DIODE 1N5402, any alternative will be. Or can I use 1N5408.
Kindly suggest.
Swagatam says
Hi Sanchay,
Yes 1N5408 will work in place of 5402
bju says
Hi Swagatham,
It would be very helpful if you please elaborate bit more on the procedure on adjusting the value of preset P2. and what are changes i have to make in the circuit if LDR is replaced with a switch so that light dependency is removed in it's working.
Biju
Swagatam says
Hi Biju,
T3 and the associated parts form a very crude type of automatic charger circuit, you just have to adjust P2 such that the LED becomes very dim at about 14.5 to 15V which is the full charge level of a 12V battery.
You will have to remove LDR, R1, P1 for making the circuit not respond to light. An an/off switch may be connected in between LED positive and the battery positive.
bju says
Thank you. Wish you a very happy New Year.
Swagatam says
Wish you the same!!
dhanish says
Sir I finally decided to make your circuit, i need your help during my assembling if any error arises. sir please answer each question.
Please reply as early as possible.
some doubts are
1) In the 2nd circuit does it have overcharge protection?If yes can you just elaborate please?
2) Sir please specify the rating of solar panel (max current and max voltage) in 3rd circuit?And how to show a charging indication for solar panel?
3) Sir i know you said that my solar panel(17.5-19v and 500mA) not capable of charging this battery eventhough if i am connecting that solar panel, can i connect it as shown in your circuit?
Swagatam says
1) it will stop overcharging if the preset is correctly adjusted, but it's a crude circuit.
2) solar panel should be 15V/2amp for 7ah batery, the base led will indicate charging state of he batt.
3) yes can be done
dhanish says
sir i made the circuit but i have problem with the preset.pls help me to how to adjust it.
when i started adjusting a spark is coming from the 1k preset. so i stopped adjusting is that due to any wiring mistake .
please reply fast sir.
dhanish says
sir now its ok.
sir how long it take to charge the battery current charge is 12.68v?
sir how can i check my circuit that everything is working well?when i checked the output given to battery terminal without connecting battery it shows 13.00v and 400mA and the t3 base led lights up is it correct?
dhanish says
sir now ok your 2nd circuit is working but 3rd circuit i have problem.i want to use switch instead of ldr so i didnt use ldr,r1,p1.
and i didnt connected the white leds and the remaining circuit is completed without giving solar panel input.And when i give transformer input it gives only 400mA output without connecting battery terminals.
Swagatam says
dhanish, adjust it to get 14.5V and the LED should glow dimly at this voltage.
after this setting this done, you can connect the discharged battery which should force the voltage to drop to the level of the battery and render a higher brightness on the LED, as the battery charges the LED brightness will reduce and at full charge of 14.4V the LED will glow very dimly.
another point is, your panel voltage must be first regulated to 15V and then applied to the circuit.
use an LM317 circuit for this.
dhanish says
sir some doubts again
1)for connecting p2 preset there are 3pins two pins give fixed resistance,two pins give variable resistance, i connected the variable pin to r4 resistance, is it correct?
2)As you said i adjusted the voltage level to 14.5 without connecting battery but the t3 base led is not that dim.And when i connected the battery which have a voltage level of 12.6v the base led again becomes dim.Is that any problem in my wiring ,but i made the circuit 2nd time pls help me sir?
3)but with all these i connected battery it charges to13.06v and stops further charging.the base led is glowing still the battery voltage not increasing.why?
Swagatam says
dhanish, the center lead or the slider lead of the preset must go to R4.
The LED will become dim only if the supply voltage is 15V or equal to the battery full charge level.
Are you supplying 14 to 15V to the circuit? If not pls do it.
A single transistor charger is always very crude so you canot get accurate resuts from it….if you want better results make the first circuit using two transistors, it will be more responsive.
and if you are looking for even better and satisfactory results you can try the following design which is by far the most reliable of the designs.
https://homemade-circuits.com/2013/02/make-this-automatic-10-watt-to-1000.html
ra66ju99 says
Hi Swagatam,
I am really honored for your timely help. Thanks a lot. Surely I will start assembling this circuit and send you the photos of it.
Regards
Nagaraj
Swagatam says
Good Luck to you.
ra66ju99 says
Hi Swagatam,
The circuit, https://homemade-circuits.com/2012/10/automatic-40-watt-led-solar-street.html is exactly to my needs. But can you modify to fit in the above circuit and without relay ( in case if you can do it sooner than designing a new one).
Regards
Nagaraj
Swagatam says
Hi Nagaraj,
You can try the circuit shown in the following link:
https://homemade-circuits.com/2012/11/making-40-watt-led-emergency-tubelight.html
ra66ju99 says
Hi Swagatam,
What i meant was to have both the protection in a single circuit. Since there were two to three circuits, i wanted your help in integrating them into a single circuit.
Regards
Nagaraj
Swagatam says
Hi Nagaraj,
I'll update the required circuit here very soon, because it might be difficult to explain it through words….
Regards.
ra66ju99 says
Hi Swagatam,
Thanks for your prompt reply. But again i am confused after going through your above comment to incorporate another circuit in the above link. Actually after going through the comment section there, i found that you have replied to one Mr. Ajay's query and have suggested another circuit (https://homemade-circuits.com/2011/12/high-current-10-to-20-amp-automatic.html)for more efficient working of the auto cutoff from low battery voltage. Actually I wanted this one only to be incorporated. Can I incorporate the above circuit for my requirement and how do i integrate it in the above circuit so that i can have my battery safe by protecting from over draining and from over charging.
Regards
Nagaraj
Swagatam says
Hi Nagaraj,
But it has no low battery cut off arrangement….will it do?
ra66ju99 says
Hi Swagatam,
Sorry to disturb you often. For the above circuit, I also need the battery to be protected from draining too much. can you help me in this aspect.
Regards
Nagaraj
Swagatam says
You may incorporate the circuit given in the following link, use the second circuit:
https://homemade-circuits.com/2011/12/how-to-make-simple-low-battery-voltage.html
ra66ju99 says
Hi Swagatam,
One more help from your end for me to start building the above circuit. In one of your article "How to Make an Efficient LED Emergency Light Circuit", you have mentioned as "If we could maintain a voltage around an LED near to its rated forward voltage, we could use it more efficiently. That’s exactly what I have tried to fix in the circuit." Can you help me in achieving the same principle in the above circuit.
Regards
Nagaraj
Swagatam says
Hi Nagaraj,
It won't be required actually, the resistors will take care of the voltage for the LEDs.
In the other emergency light circuit, the voltage input was 6V so it was easy creating the required ideal voltage, but here it will be slightly difficult, so the above circuit is quite OK.
V.Pugazhenthiran, Development officer, lic of India says
Hi Swagatam,
I build the second circuit. But not working properly. Led's are illuminating in Battery. But When i give supply to charge the battery through transformer. The Illuminating Led's are not switching off. Where i gone wrong i dont know. I tried this circuit with 14 Led's. If this make any difference in circuit. Also 8050 Transistor getting heated. Please guide sir.
Swagatam says
Hi Pugazhenthrian,
Have you connected D5,R2? If you have connected them correctly there's no way the LEDs can illuminate with power supply ON.
With 14 LEDs (two in series with 330 Ohms) the current would be just 140mA, 8050 should not become hot…
However you can replace the 8050 with TIP122 if you wish. With TIP122 you would be able to handle even 100 leds.
V.Pugazhenthiran, Development officer, lic of India says
Yes connected D5 & R2 and given supply. Still Led's are glowing. Where i gone wrong i dont know. Pls guide me.
Swagatam says
Is the red LED at T1s emitter glowing under the situations??
It must glow, if it doesn't means T1 is not OK or connected wrongly.
And if it's glowing means T2 is faulty or wrongly connected.
V.Pugazhenthiran, Development officer, lic of India says
T1's red LED not glowing. But i checked transistor, its good. I also checked T2 its also good. But same problem. Where i gone wrong i dont know.
Swagatam says
Short circuit T1s emitter/collector points with a wire, this should illuminate the red LED and switch OFF the white LEDs. If this does not happen then either the red led is faulty or wrongly connected………….or just remove the red LED and connect T1s emitter directly to ground.
V.Pugazhenthiran, Development officer, lic of India says
Sir,
Before publishing circuit, please cross check the circuit, and if possible you built it and see. Not a single circuit worked for me. Sorry to say this sir. After purchasing components and building the circuit, if it does'nt work, its a waste of money and time for me. So dont mistake me sir. Its my humble request.
Swagatam says
Hi Pugazhenthrian,
It's my humble request to you to get my circuits verified from any expert electronic engineer, because I cannot discuss the details with you or anybody who may be new in the field.
Unless you understand the circuit functioning by yourself you won't be able to make it correctly, no matter how much help you get online.
Also please read the disclaimer at the left hand side section of the page.
Regards
Suresh KUMAR S says
Dear Swagatham,
please publish a simple circuit to convert an ordinary 3 dry cell torch to LED torch
Swagatam says
DearSuresh Kumar,
Please refer to the following article:
https://homemade-circuits.com/2012/05/how-to-make-led-flashlight-circuit.html
ra66ju99 says
Hi Swagatam,
Thanks for your reply. Here I need to have some more refinement before starting to build this circuit.
Firstly, I intend to have 100 LEDs in the above mentioned circuit. So do i have to modify the circuit in any way.
Secondly, should the transformer be 2A.
Regards
Nagaraj
Swagatam says
Hi Nagaraj,
You will have to dimension the transistor T2 so that it is able to handle the 100 leds safely…. probably a TIP122 would do nicely.
Also the battery has to be rated at 7.5ah minimum.
For charging the above battery a 1 amp transformer would be enough, no need of using a 2 amp transformer.
Regards.
Anonymous says
Hi Swagatam,
May i know which one is more efficient
Led or CFL
Swagatam says
Lightwise CFL is more efficient, lifewise LED.
V.Pugazhenthiran, Development officer, lic of India says
Hi Swagatham,
Can I use 3v White LED for this circuit. 12 LED's used in this circuit, that means 36volts (3vx12) needed. How it works in 12v battery. Please reply. Also confirm T1 & T3 is BC 547 and T2 & T4 is BD139.
Swagatam says
Hi Pughazhenthiran,
yes you can use 3V white LEs.
In the above circuit 24 LEDs are used, two in each series, so 2×3.3 = 6.6v that's well below 12V….the strings are connected in parallel so voltage does add up, rather current does.
Yes the transistors are correct.
V.Pugazhenthiran, Development officer, lic of India says
Sir I hv tried this circuit. But ic555 circuit is not working. Where i gone wrong i dont know. LED's burning at day time also. If power is on LED's getting switch off. Once again check the circuit. Please guide me. Thanks
V.Pugazhenthiran, Development officer, lic of India says
Sir, I tried this circuit, but ic 555 related components not working. T1 emitter and T2 emitter are connected in this circuit. R1 is 2.2 mega ohms and R2 is 1 mega ohms. T1 Collecter and T2 Base are connected. Pls confirm. I think there is some mistake in circuit. Thanks.
Swagatam says
Short the LDR points and check whether the LEDs are getting switched OFF or not. If it does, means your LDR is not proper, select one which produces a resistance of around 50K at ambient light and infinite resistance in the absence of light.
Swagatam says
The circuit is OK, no technical mistakes are there.
V.Pugazhenthiran, Development officer, lic of India says
Thanks sir for your quick reply. Let me try and respond to you.
V.Pugazhenthiran, Development officer, lic of India says
Hi Swagatam,
Your circuit not working. I tried in many ways. Just verify once again about ur circuit. Thnks.
Swagatam says
Hi V.Pugazhenthrian,
Disconnect T2/R9 from T2 and check the 555 section separately by powering it with the battery or adapter.
Short circuiting the LDR points should make the output high and vice versa.
network advise says
hi swagatham
thank you very much
network advise says
hi sir this is srinu
i want to make 24hrs leds on with battery backup. how can modify this circuit
thanks
Swagatam says
Hi Srinu,
For that to happen, you will have to remove the entire 555 IC circuit along with T1, T2, D3, R9 and connect the resistor common point of the LEDs directly to the negative of the battery.
Anonymous says
hi swagatam,iam mohamed from egypt ,very nice circuit,and nice explanation ,but kindly can tell me what is the jop of the 2 zener diodes , and how the circiut feel that the battery became 14v thanks
Swagatam says
Hi Mohamed,
Thanks! actually the zeners have no role and they can be removed. The preset at the base of T3 is set such that it conducts at 14v(battery fully charged), when T3 conducts, T4 switches off, which cuts of power to the battery, and the charging stops.
Anonymous says
Hello!! Can I ask how many watts are the resistors?
Swagatam says
all are 1/4 watt rated….
Senkor Sintaloi says
Hi, This a nice circuit you have developed. In our region we the power supply unstable hence surges and spikes. I would like to know if it is possible to add an MOV before the transformer input for surge protection?
regards
Swagatam says
Hi,
Transformers are resistant to normal surges and voltage ups/downs, so an MOV wouldn't be required actually.
Anonymous says
hello sir
i want to make tractor battery charger so please suggest me
how to make good charger for truck ,tractor charger
ranju
Anonymous says
sir… we are currently using your guide for our project in logic that needs logic gates therefore we need to change the TTL parts to an IC… we also would like to make it a standard emergency light which means were gonna need an HD light shud i say… thank you for ur suggestions and help sir deeply appreciated it
Swagatam says
Thanks very much,
As mentioned above, opamps would be more suitable instead of logic CMOS ICs for this application.
Anonymous says
Sir, about the part list, there is no T2 but there's T5… Can you please clarify it. Thanks!
Swagatam says
Thanks, now it has been corrected….
Anonymous says
Sir, since transistor are at TTL, can we replace it with ICs?
If yes, what IC for the T1,T3 and for T2,T4?
Thank you!
Swagatam says
Transistors are more suitable here as they are also able to handle high currents here, yet a IC741 can be used for replacing the stages, however the output would still need to be buffered by transistors.
Anonymous says
Sir!
I want to design a circuit for charging 4v SLA .7AH battery using 555 timer IC for over n under charge protection.As around 70mA charging current suffice i want to use capacitive power supply.Pls could u design this type of charging circuit.I am looking forword 4 ur urgent respose.thanks alot
Swagatam says
70 mA will not be enough….700mA will be required, so a capacitive power supply will not work.
Anonymous says
Sir!
I didn't understand. How will be required 700mA for this circuit.COuld u pls explain little bit. I have no more electronics khowledge.THankx 4 ur attention
Swagatam says
if you want to trickle charge the battery for many days or even for months then a 70 ma will do, but for charging a 7.5 ah in one day you will require 700ma current.
capacitive power supply will produce dangerous current in the circuit, that's another bad thing about it.
anyway you can check out this circuit:
https://homemade-circuits.com/2011/12/automatic-white-led-emergency-light.html
Anonymous says
Sir!
I have mini sla battery 700mA capacity with 4.5V terminal voltage.I want circuit as per mentioned in post dated 7th Sep'12. Thankx.
Swagatam says
I'll try to design it and inform you when it's done.
Anonymous says
Thnkx 4 ur attention.I will be periodically checking ur response.Regards
madura pradeep says
hi!
How to modify this circuit to 6v battery charging unit?
Swagatam says
Replace the battery and the transformer with 6 volt rated ones, and connect only one LED in each channel. That's all.
Gopal Malviya says
hello sir
i gopal malviya from m.p. and i have just started my cfl repairing and making business but i don't have any good electronic parts supplier
so sir please suggest me any parts supplier with your reference
i'll thankfull for your
Thanks for Your Kind Support
Gopal Malviya
wapcrppr says
Hello Sir, What value is the Variable resistor set to? Thank you.
Swagatam says
"P1 is set such that it switches ON T3 when the battery voltage reaches just above 14 volts. The moment this happens, T4 switches OFF, cutting of the negative supply to the battery and restricting any further charging of the battery."
wapcrppr says
Thank you very much sir for the reply. This is a wonderful site and you do great work. I hope you stay around for a very long time.
Swagatam says
My Pleasure….
alvin says
what is meant by P1 = 10K PRESET
Swagatam says
It is a variable resistor whose resistance can be varies from 0 to max, here it's 0 to 10k max.
pp says
…Can both the Zener Diodes 3V/400mW would be replaced with IC 7805???
Regards,
Swagatam says
Yes you can use a 7805 in place of the zeners….
pp says
…Sir,
What are those type of LEDs which are called 1Wtt, 2Wtt and so on..???
If these types of LEDs can be used in this particular circuit, how many of it will require…for more Bright and compactness.
Please share the information..
Regards,
Swagatam says
Higher wattage LEDs can be used here, however they will consume power and discharge the battery faster, you can involve as many leds as you like, but they must be connected in the shown format only….more leds would mean more powerful battery to be incorporated.
So, LEds will depend on your personal choice, you may find the right numbers and type through some practical trial and error……
pp says
Sir..it's really Surprising greatly!!!
You reply so fast…actually I thought it might take a weeks time to develop the circuit…which I requested.
R5 Value is NOT mention and If I am Not wrong C2 should be of 1000mfd 25v and C1 of 1mfd 25V.
Does IC555 needs a Heatsink.
Would you like to suggest any good quality LDR.
Can I use the Flat, which I guess 8mm, LEDs which comes fitted with Recharable Hand Torches.
In my JunkBox I've some Zener Diode, How do I check the Value.
…will it work in one go??? He..He..He..
Regards,
Swagatam says
Thanks PP,
R5 is now mentioned in the parts list.
C1 and C2 are also there in the parts list, yes the values are correct.
555 will not require any heatsink.
Select an LDR which gives below 100K resistance in the presence of ambient light.
Any type of LEDs may be used, will depend on your personal choice.
Zener value is not so critical as long as it's below 9V.
Adnaan February says
Hi Sir
i am really interested in this circuit, please advise if you have a sketch of the circuit on a breadboard
Adnaan February says
Hi Please advise if you have this circuit on breadboard, if so, a pic will be much appreciated.
mani says
Sri. Majumdar,
You say that the IC555 in your first emergency light ckt. can be dropped and have given the modified ckt. without the use of IC555. Does the second ckt.retain all functions of the first ckt?
svs
Krishan Chauhan says
sir which software your using for designing the circuit???
Krishan Chauhan says
please tell me