Automatic LED Emergency Light-Modified Version

Hi All Readers of CircuitsToday,

As there is serious discussions going on about our previous Automatic LED Emergency Light Circuit using LM 317, Mr.Seetharaman has come up with a modified version of the same which answers many of the doubts raised in our Comments section.

Note: Mr.Seetharaman has developed a new version of Automatic LED emergency light. This one is more simple,more efficient and uses minimum components. Take a look: Simple Emergency Lamp Circuit

Here follows Seetharaman’s Description about the Modified Automatic LED Emergency Light using LM 317.

Dear John
Since there were lots of doubts from our readers on the LED emergency light, I have written a detailed letter to two of our readers. Of course few modifications are required, which I have indicated on the drawings and on calculations how I arrived at it.  I thought of enclosing it to you so that it can be kept in some library of our site for any ones reference. For each circuit we can have a similar detailed theory, may not be with all calculation, just general operation theory of each part of the circuit. You may think of it. As a first feed back I am sending this.  I have a feeling that most of the people would have made the mistake in base emitter of BD140, the lead out are against normal convention.

Automatic-LED-Emergency-Light-Modified

To understand the above circuit in a better way, it can be divided into two parts.

1. LED lamp circuit
2. The Battery charger circuit

LED Lamp circuit

1. All are white hi bright LEDs rated for 3Volt @ 25mA
2. The total current requirement is 12 X 25 = 300mA
3. This current has to flow through T2 – BD140 PNP transistor
4. The minimum current gain (hfe) of this transistor @ 500mA is 50
5. Hence the base current Ib requirement is Ic / hfe, 300 / 50 = 6mA
6. Base emitter drop of T2 at 500mA is 0.77 volt
7. With the fully charged battery at 6.9volt terminal voltage (for cycle operation use) the voltage available across the new bias resistance is (6.9 – 0.77)
8. Hence the bias resistance is = 6.13 / 6 = 1000ohms
9. As the battery drains the final terminal voltage will be 5.4volt
10. The bias resistance will be (5.4 – 0.77) /  6 = 770 ohms Hence a 680 ohms was preferred for bias resistance with drained battery also it will give enough brightness.
11. The very important information about BD140 is, as you view the pins, metal portion of the transistor facing down left is emitter centre collector and right is base. Most of the constructors make this mistake, relying on the convention that left base and right emitter. If you have made this mistake please correct it.

Once this portion is checked for reliable operation we will proceed to charger portion.

PCB’s for this project can be orders through PCBWay. We shall upload gerber files (made according to rules of PCBWay) shortly.

The Battery charger circuit

1. The battery requires a full terminal voltage of 6.9V at this point charger should cut off.
2. That is the voltage across the chain ZD1, R2 and T1 be should be 6.9 volt
3. T1 be voltage of 0.7 volt plus drop across R2 and zener voltage should be 6.9V
4. T1 be current = Ic / hfe
5. Ic is 1.25 / 180 = 7mA
6. Ibe = Ic / hfe of T1  i.e = 7 / 70 = 100uA
7. Drop across R2  =1.2 X .1 mA = 0.12volt
8. Hence Zener voltage = 6.9 – (0.7 + 0.12) = 6.08 the near by preferred zener voltage is 6.2 volt
9. Say the battery voltage at full charge will be 7 volt with 6.2 volt zener diode
10. To calculate R16 value for charging at 1 /10 th of the rated current of the battery 4.5AH / 10 = 450mAH
11. Transformer 9volt AC the voltage across C1 will be 9 X 1.414 = 12.6 volt
12. The drop across LM317 at 450mA current for good regulation is 3volt
13. The drop across protective diode D5 is 0.7 volt.
14. The  voltage available at cathode of D5 is 12.6 – (3+0.7) = 8.9volt
15. The battery after fair discharge will be at 6 volt
16. Hence R16 = (8.9 – 7) / 0.45 = 6 ohms
17. The nearby standard value for operation is 5 ohms.
18. At the end point of battery 5.4 volt the maximum charging current can be of (8.9 – 5.4) / 5 = 0.7 amps well within the higher charging limit of the battery.
19. With this circuit over night the battery will get charged fully.
20. Over charging is taken care and protected by T1

Hope with the above guide line you can make your light work successfully.

More Modification!!!

Automatic LED Emergency Light with Under Voltage Cut Off Protection:

Dear Readers,

Mr. Seetharaman has further modified this LED Emergency Light with an under voltage cut-off protection to protect battery from deep discharge. Once the battery terminal voltage falls below 5.7 volts the LEDs will be switched off. Take a look at the modified circuit shown below.

LED Emergency Light with Under Voltage Cut-Off Protection

To understand the above circuit in a better way, it can be divided into two parts.

    1. LED lamp circuit
    2. The Battery charger circuit

LED Lamp circuit

    1. All are white hi bright LEDs rated for 3Volt @ 25mA
    2. The total current requirement is 12 X 25 = 300mA
    3. This current has to flow through T2 – BD140 PNP transistor
    4. The minimum current gain (hfe) of this transistor @ 500mA is 50
    5. Hence the base current Ib requirement is Ic / hfe, 300 / 50 = 6mA
    6. Base emitter drop of T2 at 500mA is 0.77 volt
    7. With the fully charged battery at 6.9volt terminal voltage (for cycle operation use) the voltage available across the new bias resistance is (6.9 – 0.77)
    8. Hence the bias resistance is = 6.13 / 6 = 1000ohms
    9. As the battery drains the final terminal voltage will be 5.4volt
    10. The bias resistance will be (5.4 – 0.77) /  6 = 770 ohms Hence a 680 ohms was preferred for bias resistance with drained battery also it will give enough brightness.
    11. The very important information about BD140 is, as you view the pins, metal portion of the transistor facing down left is emitter centre collector and right is base. Most of the constructors make this mistake, relying on the convention that left base and right emitter. If you have made this mistake please correct it.

Once this portion is checked for reliable operation we will proceed to charger portion.

  1. The battery requires a full terminal voltage of 6.9V at this point charger should cut off.
  2. That is the voltage across the chain ZD1, R2 and T1 be should be 6.9 volt
  3. T1 be voltage of 0.7 volt plus drop across R2 and zener voltage should be 6.9V
  4. T1 be current = Ic / hfe
  5. Ic is 1.25 / 180 = 7mA
  6. Ibe = Ic / hfe of T1  i.e = 7 / 70 = 100uA
  7. Drop across R2  =1.2 X .1 mA = 0.12volt
  8. Hence Zener voltage = 6.9 – (0.7 + 0.12) = 6.08 the near by preferred zener voltage is 6.2 volt
  9. Say the battery voltage at full charge will be 7 volt with 6.2 volt zener diode
  10. To calculate R16 value for charging at 1 /10 th of the rated current of the battery 4.5AH / 10 = 450mAH
  11. Transformer 9volt AC the voltage across C1 will be 9 X 1.414 = 12.6 volt
  12. The drop across LM317 at 450mA current for good regulation is 3volt
  13. The drop across protective diode D5 is 0.7 volt.
  14. The  voltage available at cathode of D5 is 12.6 – (3+0.7) = 8.9volt
  15. The battery after fair discharge will be at 6 volt
  16. Hence R16 = (8.9 – 7) / 0.45 = 6 ohms
  17. The nearby standard value for operation is 5 ohms.
  18. At the end point of battery 5.4 volt the maximum charging current can be of (8.9 – 5.4) / 5 = 0.7 amps well within the higher charging limit of the battery.
  19. With this circuit over night the battery will get charged fully.
  20. Over charging is taken care and protected by T1

Hope with the above guide line you can make your light work successfully.

545 thoughts on “Automatic LED Emergency Light-Modified Version”

  1. Hi Pete you can use even a single LED (3.2Volt @ 150 to 300mA) if that illumination is sufficient. The full calculation and explanation is available in the project itself. I have divided the circuit into two parts and given full explanation
    1. LED lamp circuit
    2. The Battery charger circuit
    hope this is sufficient.

  2. sir,
    our group decided to choose this circuit for our project. i want to know if i deduct a resistor or a led in the LED lamp circuit, will it affect the turning on and of the circuit?
    i also want to know the full details about this project. if you are willing to help, please email me the whole details.
    thank you!

  3. sir,
    In my circuit without battery mains on condition all 12led’s glow.If mains off led’s also off.this circuit is correct or wrong? if wrong send me the changes or solution. awaiting yuor reply

  4. hello sir
    i will try 20k pot also but the volt didnot raise 6.6v across the battry terminal(w/o battery). which place the volt measures? battery connected terminal(w/o battery) or LM317 output terminal 2? pls reply me

    1. I am also facing same issue…. unable to fix. If I disconnect the disconnect voltage to base of transistor ..I can find 6.9 up to 9.5

  5. Hi Assem adjust the pot on output of 317 on open circuit (battery not connected)it should be around 6.9 to 7 volt. which is the correct requirement.
    Hi Syed increase the pot value to 10K and connect 11k or 12 in Parallel with it, this will take care. With mains LEDs will not glow only when supply fails it will glow from battery supply. 12 volt transformer can be used but you have to use a big heat sink for LM317 to keep it cool. The above circuit is automatic once power fails the LEDs will come on automatically.

  6. Hi Seetharaman.
    This is my second notice to my question.
    I found that the max. voltage I can reach at the output terminal of the LM317 is 7 volts. is this normal??
    Regards
    Assem

  7. sir,
    If main supply 230v failed,led-12nos on automatically. So pls tell me circuit modification.pls mail me my mail ID.

  8. Hello Sir,
    battery volt didnot raise 6.9v. i will adjust 4.7k, but volt adjusted maximum is 6.6v o
    nly.pls tell me solution of this problem

  9. sir, i have only 12v transformer and without battery. how can i test the circuit, if without battery circuit work or not (LED glow or not).Pls reply me

  10. Hi Seetharaman.
    This is a notice for my previous question.

    Please Notice that I did build the lower part of the circuit, the battery charger only. I left the LEDs and the T2 control transistor for a later stage.

    Thanks for your help
    Assem

  11. Hi Seetharaman.
    Thank you for this circuit. After building the circuit and at no load (battery or LEDs) to what voltage should we adjust the output terminal of the LM317 using VR1?
    Thanks/Regards.
    Assem

  12. i’m doing my engineering in mechanical…….. i’m doing one project….. in that i need a circuit to detect the oxygen level… which should be cost effictive. please sent that

  13. Hi Sankar this circuit is suited for LAG cells. not for nicad cells, as the requirement is constant current of 1/10 rating. you have to modify this circuit totally. you may have to look for our future projects on nicad rechargeable emergency lights. LAG batteries are cheaper, hence they are preferred for the projects than nicads, which are quite expensive.

  14. January 10, 2011 at 5:40 am
    Can the latest circuit of yours be used for 5 nos. 1.2 volts 2000 mAs. (in series this works out to 6 volts) Ni. Cadmium batteries. Can I give parellel connection (2 sets of the cells) so that the ampere is high?

    Please respond to this mail that I posted on Jan. 10th. My email id is: yesemve@yahoo.com or yesemve@gmail.com

  15. dear sir
    iam having 8mm 0.5watt 100ma leds can i use in this circuit or any change is requir and how many leds should i connect.

  16. Dear Seetharaman,

    Please send the PCB lay out of above circuit to my email id dsrini73@yahoo.com.

    Secondly, I want to connect 40 LEDs to this circuit, please suggest suitable transistor.

    Next, wanted to incorporate low battery indicator and please suggest where to connect the LED and resistor value.

  17. Dear Mr. Seetharaman,

    From your reply i hope that you are in Chennai. If you don’t have any objection, please give me your address.I wish to meet you personally, for some of my projects. You can send it to my e-mail id: yesemve@gmail.com / yesemve@yahoo.com.

    Thank you,

    Sankar.

  18. thank you boss for your kind reply. But ples help me with that automatic night light also.. Thanx to mr.Harry also

  19. ASWIN, in which country you live ? Website’s like digikey, mouser and farnell have options to search based on parameters.

  20. hi
    i would like to assemble this circuit., but for my unluck BD140 is not avail for me. ,i tried for 2N2905 also,but no hope. So ples help me, smbdy tell me sme transistors that can be replaced in place of BD140.ples help me. I also added a comment in the topic ”automatic night light with timer”, i will be greatfull to you if u help me.. Plezzz…..

    Thank you

  21. Sir,
    If I use 6Volt 5.5Ah Battery charging circuit are same??
    How many watt use for resistors??

  22. sir and other guys ,those of you who have completed this circuit, pls send me a diagram showing the naming of terminals of the bd140 and bc548 transistors…
    here is my mail:
    abhi.dav@gmail.com

  23. Hallo,
    Seetharaman, hope you are fine.

    First of all i would like to appriciate you for the work that you have done and for the support that you are providing to the readers individually. This is really really a good and a positive activity.

    I build this circuit about a month back. There are no issues. Worked so fine, I’m just willing to share my experience with other readers.
    Guys, I Could not get a transformer with 0-9v output at 500mA but got at 800mA, which is Working fine. No issues at all.
    Please be careful in identifying the pin connections of the bd140 and bc548. This is critical for the correct working of the circuit.
    I used an on/off slide switch in series with battery that i found was added by the author in modified version. A good addition in deed. I used a RED LED to indicate the charging the battry. Any value is suitable but it should be 2.7k Min. 6.8k Max.

    The beauty and the simplicity of this circuit is really somthing to admire.

    Thanks alot seetharaman.
    May you be happy always.

  24. Hi Seetharaman

    I want to dim the LED’s for interest sake. How do i connect a Pot in the circuit. DO i have to connect it to the base of transistor? Maybe a 1k pot could be used?

  25. Hi Seetaraman,

    i want to make this project, but with 80 pc leds and 6v, 5.5Ah sealed lead acid battery.
    And can i replace BD140 to a higher rating transistor for increasing the no of leds.
    so tell me the modification can i do or you can mail me with modification details with ckt dgm.

    E-MAIL ID:- sougata.kundu51@gmail.com

  26. Dear Sir,
    Please help me for selecting an appropriate battery in SIZE….6volt 4.5Ah is used in our old emergency kight naa? With me a 36 LED platform, but the casing is small…. please tell me the SMALL SIZE battery with this value or please tell me if there is any choice of two 3 volt battery combination with current value….

  27. Hi Roshan check the zener disconnect and try as i have indicated in my previous reply. now check both the circuits-LED glow circuit and charger circuit separately as indicated in the article. With mains if LEDs are glowing reduce R15 to 390 ohms.

  28. When i re soldered some connections, this is what happens:- i changed
    it to 10k potentiometer…but,still the charging voltage is below 6v…All
    the LEDS in the LED section glows when charging. When I disconnect the
    main supply, the leds in the LED section glows, but, it is very dim.

    when i connected the charging leads to the battery, and then connect
    it to the indicator LED, the indicator glows, and the LED section
    turns off. Otherwise, the leds in the LED section glows(which shows
    error).

    Why is this?

  29. Kindly check up your Zener diode ZD1. disconnect the diode one end and try adjusting the pot for 7.0volt now connect ZD1 if the voltage falls ZD1 is not rated for 5.1volt. measure the voltage across ZD1 if it is less replace with the correct one. You contact Mr. Ravi 9841394518 for your requirement of PCBs and LEDs.

  30. Hello sir,
    i changed it to 10k potentiometer…but,still the charging voltage is below 6v…All the LEDS in the LED section glows when charging. when i connected the charging leads to the battery, and then connect it to the indicator LED, the indicator glows, and the LED section turns off.
    Why is this?

  31. Thank you Seetharaman…But, even if the charging voltage is low, the led should have to glow theorethically. but, it is not glowing.

    similarly, the battery, when connected directly to the leds, they glow, but, in the circuit, it is not glowing. why

  32. I tried to increase the charging voltage by turning the pot, but, the maximum it increases is 4.69 volts…..an i forgot to mention, the preset pot i am using is 4K7

  33. Hi Roshan LA batteries require constant voltage for charging . for cycle use 6.9 volt is the limit recommended by battery manufacturers. hence without connecting battery you have to set the pot for 7volt if not getting increased change the pot to 10K. The LED will glow while charging, once battery is fully charged it will extinguish.

  34. Hello Seetharaman,as in your comment dated june 17,2010,related to a query about adjusting the pot, you said that we have to adjust the charging voltage to 6.9-7 volt. Is it that, only a charging voltage of 6.9v can charge the battery. The voltage at the wires that is to be connected to my battery is less than 4 volt. Do I need to increase this? Do i have to turn the pot to increase this voltage. I have a preset potentiometer. Please reply.

  35. Hello Seetharaman…I have dropped the work in making the basic automatic emergency light circuit, and have started the modifies automatic emergency light with under voltage cutoff protection.

    It is seen that there is a small led connected to the 4.7K preset variable resistor. What is the use of it? Does it glow when connected to the mains?

    After assembling the entire circuit, nothing happens. Neither the LED section glows, nor the small led near the variable resistor glow.

    How to know whether the circuit is working properly?

  36. Hi Crystopher This transformer is best suited you can use. 0.5 watt is ok, use 5% tolerance zener diodes., pcb details are available in my new emergency light project use it.

  37. Hi Crystopher This transformer is best suited you can use. 0.5 watt is ok, use 5% tolerance zener diodes., pcb detaols are available in my new emergency light project use it.

  38. I found a transformer thats 230vac-9vac and 670mA, is it fine or do I have to make changes?

  39. Hi Admin, could I use 0.5W resistors for the above circuit? And the zener used should be atleast 5% tolerance or less?
    Which is prefered?

    1. @ Roshan
      I used 5mm LEDs. Size doesn’t matter but you have to consider the current/ voltage ratings.

  40. Hi again sir,could you also send a PCB layout of the final modified circuit via email thanks

  41. Hi there sir,could you please add some calculations on how i obtain the correct size heatsink as i really want to use this for my project at school and if you could reply soonest it would be much appreciated 🙂

  42. Hi CW one BD140 can drive 12 LEDs of 25mA each. You add more BD140 in parallel and connect 12 LEDs for each BD140. Since the battery used is 4.5AH, for 5 hrs use you can use 3 BD140s and 36LEDs.

  43. Dear Sir,

    I have mailed you my address on “seethasub@hotmail.com” please send me the art work of the Automatic LED Emergency Light-Modified Version.

    Many thanks.
    Bhavesh.

  44. Yes it is ready if you can mail me i will reply with art work if you want ready made PCB it is also available in chennai. please inform your requirement.

  45. Hi! Seetharaman,

    How are you sir, can you please tell me if the PCB layout for this Automatic LED Emergency Light-Modified Version is ready, if yes then where can I see it.

    Regards.
    Bhavesh.

  46. Hi Figo your suggestion 1 is fine saving component and reliable but it will not take care of deep discharge circuit with T3. T3 circuit can be improved similar to our voltage sensitive relay by including a potentiometer so the required cut off voltage can be set (due to spread in voltage of zener diode – tolerance of the diode)
    https://circuitstoday.com/three-phase-auto-changer-circuit

  47. Hi Hotshot it is a good idea, there is an efficient version is under design in that we will try to incorporate your suggestion.

  48. In fact the emergency lighting should has an opto sensor circuit add in as power failure during day time with the emergency light turning on is just a waste. Battery will not last till night falls. Hope this can take into consideration. Thank you.

  49. Figo Chen - Shenzhen China

    Im glad seen so many reader send their comments on this circuit to make the circuit has been more perfects, but I still has some comments:

    1. Regarding the Transformer:
    The linear transformer is not good to to provide the stable voltage, when the input voltage drop to 180Vac in some conditions, then the tansformer output voltage will be reduced too, that will cause the LED light up @ 180VAC input.

    Suggestion:
    A: Connect base of T2 directly to output of LM317.
    B: Delete R17 AND r15, change discharger circuit, see below.

    2. For over discharger protection circuit:
    In current discharge protection circuit, the battery will not stop even the T3 is turns off, becoz the base of T2 alway stay at about -1.4V when AC input is cutoff.

    Suggestion:
    1. use a voltage comparator IC such as LM358 to do voltage detection on battery for overdischarge protection.
    or who can provide a simply circuit to us will be better.

  50. андрей

    Dear SHEETHARAMAN. Designed the lighting for your new circuit with a device from a deep discharge battery. Unfortunately just a device I have does not work. The rest of the scheme is quite rabotosposobna.Skazhite please, if you have solid evidence of efficiency is the device from a deep level in this scheme? Have you ever been repeated Ñ”tu scheme. I’m interested in is protecting against deep discharge batteries. If you can, marking the transistor BC548 from right to left on the conclusions. (In the datasheet information about labeling this transistor is different) Thanks.

  51. hi sir.
    presently am using 12volts 7ah battery for my system UPS, i want to change that to 12volts 40ah. will the ups work properly or is der any problem by doing such changes…
    please help me out………

    thanks……

  52. Hi! Seetharaman,
    Thank you for sharing!!
    I want to make this project, but with 100 led and 12v 7Ah lead acid battery, could you please mail me the circuit

    Thanks & Regards
    John

  53. dear sir, can u pls mail me about the first circuit on THIS page/link. i have to write a report on this circuit. sir if you cud please help me write the abstract it would be greatly appreciated. i dont know what is hapenning in this circuit.sir pls tell me how exactly this circuit works. can i use a 300mA step down transformer instead of a 500mA one? also is BC140 transistor equivalent to BD 140? sir do pls mail me your reply.thank you

  54. Hi Seetharaman, I have 12 v lead acid Battery and I would like to setup led light circuit.Kindly publish the circuit which can use 12 V battery as power source.

  55. Can the latest circuit of yours be used for 5 nos. 1.2 volts 2000 mAs. (in series this works out to 6 volts) Ni. Cadmium batteries. Can I give parellel connection (2 sets of the cells) so that the ampere is high?

  56. Hi! Sir,

    How are you, can you please tell me if the PCB layout is ready for Automatic LED Emergency Light-Modified Version, if yes then where can I see it.

    Regards.
    Bhavesh.

  57. Hi Amdani T1 will take care of that function automatically when the terminal voltage falls below the set voltage.

  58. Hi! Seetharaman,
    Thank you for sharing!!
    Is this circuit can begin charging automatically when battery is weak?

    Thanks & Regards
    amdani

  59. Hi Mint you are correct, it is not that it cannot be charged during day time. normally during 10pm to 6am wthese are not used hence it is normally said that it can be charged over night.

  60. Thanks for the circuit. You mentioned that the battery can be fully charged at night, then someone would use the light in the daytime? Rather it should charge in the day and and show light in the night. Anyway sometimes we also need light even in the day. Thanks again.

  61. Hi! Seetharaman,

    How are you Sir, can you please tell me if the PCB layout is ready for Automatic LED Emergency Light-Modified Version, if yes then where can I see it.

    Regards.
    Bhavesh.

  62. Hi Adnan your charger capacity is 5amps. your battery is 50AH(not only amps but also the current for how many hours). your charging current is 5amps hence it will take 10 hours to charge the battery. capacity of battery / charging current (50 / 5)

  63. Suppose if we have a battery charger which is giving 12v @ 5A and a car battery of 50A?
    what time will the battery take for full charge?plz tell me the calculation also??

  64. Suppose if we have a battery charger which is giving 12v @ 5A and a car battery of 50A?
    what time will the battery take for full charge?

  65. Hi Bhavesh this pot should be adjusted in such a way that the battery charging current is limitted to 1/10 of the battery capacity. in this case 450mA. If you cannot achieve it, reduce R16 to 2.2 ohms and adjust the pot for 450mA charging current (when the battery terminal voltage is around 6.0 volts). This will charge the battery over night to its rated capacity.

  66. Dear Mr. Seetharaman,

    Thank you very much for your previous reply, Please tell me if the VR1 setting is kept for full, max voltage, will the charging stop at 6.9 & start charging at 5.2 volt of the battery??? As I am keeping the VR1 on full for faster charging, as my circuit is charging only at about 250~300mA. with a transformer of 9V 500mA. Regards. Bhavesh.

  67. sir please explain these lines:
    5. Ic is 1.25 / 180 = 7mA
    6. Ibe = Ic / hfe of T1 i.e = 7 / 70 = 100uA
    7. Drop across R2 =1.2 X .1 mA = 0.12volt

    why ic is 1.25(volt)/180(ohm)???

  68. Sir!!
    Can any other alternative components can be replaced to reduce the cost of the circuit???PLzz sujjest me sir………

  69. Hi Bhavesh If you have a constant current source with a burden of say 30 volts you can use it. if not use a 30volt power pack use a 4.7 to 5.6 K resistance in series and feed it to zener diode. if you are getting say 0.7 volt across the diode you have reverse the leads. The drop across the diode is the voltage of the zener diode. choose the correcrf value zener and use it.

  70. Hi! Seetharaman, can you please tell me in details, how to give 5mA curent to check the zener??? Thank you for your earlier reply. Best Regards.

  71. Hi Murali you have to check the pot value increase it to 10K and try the voltage if it is not increasing to 10 volt your IC 317 is faulty or wrongly wired.
    reduce 560 ohms to 330 ohms or so it should solve your problem.(it can be any value between 220 to 330 ohms.

  72. Hi SeethaRaman,

    Can you please publish this circuit with a 12V 7AH battery. I tried the same with modification suggested by you earlier. But it is not working as expected. BD140 is not turning off LED’s when mains supply is available.

    Regards,
    Gururaj

  73. Hi Murali what is the open circuit voltage at positive lead to battery with pot VR1 is at maximum resistance value. what is the resistance value you are using for R15.
    Hi Adnan you can use the same circuit add 1no BD140 parallel to existing BD140. connect base to gether, connect collector together use 0.47 ohms with each transistor emitter and then connect it to battery positive through light on / off switch.

  74. i have a pcb of an old emergency light having 60 leds coonected in parrallel what transistor will i use to make automatic switching system like above light????

  75. sir iam not able to increase d battery voltsmore than 5.6 volts
    when power resume d led is not switching off it glows dim pls send me reply

    regards

  76. Hi Sindhu I am enclosing my earlier reply to Mr. Kumar on
    June 10, 2010 at 9:09 am
    Hi Kumar the PCB is getting ready will all improvements. once it is ready, will inform.
    For enclosure you can use any one of the old 2 tube enclosure with single 6volt 4AH battery. The appoximate cost with High Bright white 12 LEDs, new battery PCB will be around (you can use the transformer available in the old light) INR 500 to 600

  77. sir iam not able to increase d battery volts more than 5.6 volts.
    2. when power resumes it is not switching off d led glows dim

  78. Hi Bhavesh check zener diodes ZD1 & ZD2 for their correct voltage by feeding 5mA constant current through them. If they are different from the indicated value their tolerance are quite high try to use 5% or better. It has to stop charging at 6.9 volt plus minus tolerance of the diode. similarly switch off glowing LEDs at 5.7 volts.

  79. Hi! Seetharaman, I have assembled this circuit on a bread board, but it does not disconnect the battery at 5.1 Volts, also it does stop charging at 6.9 volts. Please sir tell me what I have to check, or change. Regards. Bhavesh.

  80. Rajesh Kumar Joshi

    Hi,

    I tried this circuit with 30 LED’s and it is working fine.
    Can we also have a full charge indicator (LED) in this circuit.

    Also, I am looking for a 12v lead acid automatic battery charger.It will be great if you can help me with your expertise.

    Thanks
    Rajesh

  81. Hi Ifan you see mains operated LED it is 230 volt 25LEDs
    “Mains Operated LED Circuit”. It is tested and proven circuit.

  82. sir, please send me the schematic for 24 led.
    i want only 220 V AC to 24 led.

    thanks and regards
    ifan angelo

  83. Hi Ravi the pot is required to set the max current for a flat battery.
    try by reducing R15 to any value between 220 and 330 ohms it should solve your problem.

  84. Hi Adnan you can rectify fix limitting resistance or surge protective device and use it.
    LEDs can work only on DC. If you use AC you have to take care of reverse voltage protection during negative half cycle.

  85. Sir the led section working very well but when power resumes the ckt not switching off and glowing dim,please suggest solution for me

  86. Hi Sindhu you use the normally closed contact of the remote control relay to suplly power to the emergency light once the supply is disconnected, the LEDs will come on automatically once the remote connects the power LEDs will go off and start charging the battery.
    The PCB is getting ready with alternate like 12volt 36LEds or 24 LEDs 6 volt 12 LEDs it will be ready soon i will send the lay out and the template soon
    hi mounica it requires lots of modification it is now available in my new pcb please wait.

  87. Hi! seetharaman,

    Can you give me the PCB layout of this circuit for 6V & 12V battery charging, with your new modified circuit. I will be very much thankful for the same. I tried it out on the bread board but could not get the required mA, I am getting only 45 to 50 mA, with 9V, 500 mA transformer. Rest all my circuit is working ok, my email add bslpei@dataone.in
    Regards.

  88. Thanqq for U’r answer sir !! But know i am in a conffusion that where i have to attach this receiver ckt in this emergency light .Can U help me sir???

  89. Hi Sindhu you can use the ultrasonic remote control appeared in these columns for your remote operation of LED lights
    the article appeared as “Ulhttps://circuitstoday.com/ultrasonic-switchtrasonic switch”

  90. Sir !
    Can i operate a remote controll for operating these LED’s.I did found any remote controll for operating LED’s in any website .Can U plz help me in doing this ???????plzz reply me….and also for my mail……

  91. Hi! seetharaman,

    Can you give me the PCB layout of this circuit for 6V & 12V battery charging, with your new modified circuit. I will be very much thankful for the same. I tried it out on the bread board but could not get the required mA, I am getting only 45 to 50 mA, with 9V, 500 mA transformer. Rest all my circuit is working ok.
    Regards.

  92. Sir Seetharaman,

    wat purpose of VR1 4.7K on the circuit.should it be always set at max?

    thanks in advance.

  93. Hi SeethaRaman,

    Can you please publish this circuit with a 12V 7AH battery. I tried the same with modification suggested by you earlier. But it is not working as expected. BD140 is not turning off LED’s when mains supply is available.

    Regards,
    Gururaj

  94. Hi Adnan it will become 12Volt 4.5 amp battery. batteries inseries will add up voltage. batteries in parellel will get their current added.

  95. if connect two 6v 4.5amp batteries in series will it becomes the 12v 9amp battery or the 12v 4.5amp?

  96. Hi Sindhu add one more BD140. that is connect both the bases together similarly connect both emitters together and to the collector of added BD 140’s connect the next 12 LEDs as per existing circuit. my email is seethasub@hotmail.com

  97. Sir,
    U said that the base and emitter terminals of BD140 should be shorted.R they can B shorted by connecting them to the existing switch in the above ckt???Is the 1st LED of next set can B connected(in ||el)to D 12th LED in the previous set??Sir can U give me U’r ID so that i can mail U the expected ckt 4 D 24 LED’s (OR) U only mail me the ckt 4 24LED’s.Plzzz sir reply me……

  98. Hi Sindhu add one more BD140 connect base and emitter torether. in its collector connect 12 LEDs as per existing circuit. now you can have 24 leds. fix heat sink for LM317 and BD 140s they should have electrical isolation to heat sink with insulated mounting kits.

  99. Sir,
    Here U used 12 LED’s if i want to use another set of 12LED’s i.e total 24LED’s .Then 4 than what modification should i have to do in the circuit????Where should i have to connect the heat sink for the circuit modified by U(As shown above)????PLzz reply me sir….

  100. what is the mcd of the 10mm led used in this model? what angle is needed to get good lighting? where can i ge 50mA 10mm buton leds?

  101. Hi Magnet the bias for the BD140 transistor is given through this transistor and zener, if voltage falls below the set level the zener will not conduct hence no bias for BD140 hence the LEDs will go off.
    Dear deepak you have to use one more BD140, emitter connected to existing BD140 and base to existing BD140 and collector to one more set of 12 LEDs. with 24 LEDs of 25mAs consumption each a total of 600mA is required a fully charged 4.5 AH battery will give illumination for 4.5 / 0.6 = 7 hours appoximately.

  102. Hi Patrick Vaz you have to use a good heat sink for regulator IC LM317 as it has to dissipate around 3 watts.

  103. Hi Admin,
    I Have a 0-12V transormer 500ma and the battery is 6v 4ah will any modification be required in the circuit, Pls respond.

  104. Hi Admin,
    I Have a 0-12V transormer 500ma and the battery is 6v 4ah will any modification be required in the circuit, pls reply.

  105. Hi,
    I Have a 0-12V transormer 500ma and the battery is 6v 4ah will any modification be required in the circuit, pls reply.

  106. Magnet Electronics

    Sir,
    Very nice circuit.Does the “under voltage cut-off protection section” really switches-off LEDs???!!!!

  107. Sir,i want to make this circuit with 24 led’s. please tell me what modifications are required for making this? tell me all changed resistors values. and also tell that,with lead acdid battery of 6v 4.5AH,how many hours it will give light? plz reply soon.

  108. Please mention that is there any kind of current limiting /current regulation also present in this circuit
    other than the limiting resistors R3 to R14. ?

    is there any role of T2 or T3 in likiting LEDs current?

    thanks

  109. Dear Gentlemen,
    A different topic didnt know where to address.
    I have couple of 500G hardisk, over the years, have collected movies,i want to play them directly to a TV or LCD, any circuit ideas, which can convert and play movies, directly on LCD,
    Thanks in advance

  110. sir is any resistor and driving transistor should be added? what about the cost of these leds?

  111. Hi Pradeep you can use 4LEDs in series in each loop. so 3 loops are sufficient. if you use high bright white button LEDs of 3volt 50mA current, 3 loops 150mA hence your batterywill give power to LEDs for minimum 20hrs.
    the charging circuit has to be modified fully. please refer to lion battery manufacturers recommondation.

  112. is reflector is needed for the leds? what type of reflectors can be used ? where can i get it?

  113. hai sir,
    thank you for your valuable info in this site . in the above circuit if i use 14.4 v,3.5Ah lithium ion battery what are all things i have to change in the above circuit? how many leds can it drive for long time?

  114. sir, please send me the 12v 3 or 5amp regulated power supply circuit for audio system if you have any.

    thanks and regards
    santhosh

  115. Hi Adnan you cannot compare a battery with an amplifier both are of different charecterestics. both the principles are different.

  116. if i give the more current to an amplifier it will draw only the required current but why the battery don’t do that???why the battery not draw only the required charging current?????????

  117. Hi Biman the circuit can be modified add a resistance of required value (r= 0.65 / currnt in amps – please donot exceed 1amp with this IC) between emitter of T1 and battery negative. disconnect R2 from ZD1 and connect it to battery negative. with this modification it will become a constant current charger.

  118. If the supply current is high amplifiers and others devices consumes there required current but why the battery doesn’t do this if the current is high

  119. Hi seetharaman, Thanks
    My problem is solved.
    But the battery cherger circuit here is a constant volt
    cgerger, I want a constant current cherger for the same
    please.

  120. If the supply current is high amplifiers and others devices consumes there required current but why the battery doesn’t do this if the current is high????

  121. if the supply current is high amplifiers and others devices consumes there required current but why the battery doesn’t do this if the currewnt is high????

  122. ZD2 is giving bias to bd140 through T3. if the battery voltage is low BD140 will not get the bias and the leds will not glow

  123. Hi Adnan for 4volt battery the cutoff voltage at full charge is 4.6 volts hence you require a 3.9 volts zener. and bd 140 to cut off the voltage is 3.5 volt hence the zener should be 2.7 volts.
    if you are using anyother circuit kindly send me that i will suggest you.

  124. no i have a fixed charger not the above one and i have a light having 4 volts battery and i want to add a switching system in that with 5v charger light not the above one

  125. Hi Adnan BD140 is for switching on th LEDs. if you want to cut off the LEDs at say 4.2 volt then use a 3.3 volt zener for ZD2

  126. Hi Seetharaman,
    I have made the circuit but not working.
    then I understand that biasing of BD140 is missing from the Battery. please Suggest me the Biasing.

    As per your circuit it is lighting when AC Power is ON.

  127. Hi Ankit if you use 12 leds of 25mA total current will be 300mA A ‘D’ size cell with 500mA hr rating will give illumination for an hour and half. (90mts)

  128. hello sir,suppose 4(1.5v *4=6v)non rechargeable battery is connected with 12led(25ma),then according to calculation for how much continuous hour will it switch on the led? thanx

  129. Hi Arun connct an electronic bleeper between battery positive and collector of Q1 through a 1N4007 diode(cathode toward positive of the battery), once the battery is fully charged Q1 will be turned on in turn the bleeper also will be on

  130. Hi..It would be helpful if you post a modified circuit for knowing the full charge of battery..

  131. Hi Xplod the battery charger circuit requires to be changed to constant current charger instead of constant voltage charger(suitable for lead acid battery only). the lighting circuit does not require any modification

  132. Hello sir, can i use the circuit with 6V/7Ah NiCd battery since its shown 6V 4,5Ah on the circuit? If not what modifications should be done?

  133. Hi Gururaj You can use 12 volt zener with one 1N4001 in series it will be 12+0.65 + 12.65 volts.
    1.8 K is correct.

  134. Hello Sir,

    Thanks for your reply. Please clarify few doubts.

    The Battery’s fully charged voltage is 13.5. So Can I use 13V zener with R2=1K? Calculation will be,

    Ib = Ic/hfe = 0.1
    Let R2 = 1K
    Vdrop accros R = 0.1V
    Voltage across the chain ZD1, R2 and T1 be should be 13.5

    ZD1 = 13.5-(0.7+0.1) = 12.7 or 13 (Only 13V zener is available in market).

    Also, according to calculation I had changed the baising resistor of BD140 to 1.8K instead of 560E. Is that ok or BD140 will never turn off?

    Regards,

    Gururaj

  135. Hi Gururaj
    R2 has to be 1K only it is there to protect the transistor hence reduce it to 1K.
    With 12 volt zener and 1K resistance charging will cut of at
    12.8 volt itself.
    Similarly LED cut off voltage will 10.8 volt with 10Volt Zener and R18 1K.

    Kindly check your R16 calculation

    After the above modification give a feedback.

  136. Hello Sir,

    I have modified the circuit to work with 12V, 7AH or 12V, 40AH car battery. But the circuit is not working as expected.

    The problem I am facing is that :

    1) The BD140 is not switching off even when the battery voltage drops to 11.8V.
    2) The charging is not stopping even at when battery voltage reaches 13.5V.

    Following are my modifications. Please verify the same and let me know what is my mistake.

    Fully Charged Bat 13.5
    Bat Drain Voltage 11.8
    Supply Voltage from transformer : 24V
    After Capacitor : 24*1.414 = 33.9V
    After drop across 317,D5 and R16 : 33.9-3.7 = 30.2

    1/10 of rated charging for
    7Ah = 0.7
    40Ah = 4.0

    R16 value for 7AH = (30.2-11.8)/0.7 = 13E @ 5W
    R16 value for 40AH = (30.2-11.8)/4 = 27E @ 5W

    BD140
    ———– mA/Ω A/KΩ

    Bais Voltage 0.77
    Ic = 300mA 300(for 12 LED of 25mA each)
    hef at 500mA 50
    Ib = Ic/hfe 6 0.006
    Bais Resistance (Ω) 2121 2.121
    Bais Res, Bat Drain (Ω) 1838 1.8 (Currently Used)

    T1 : BC148
    ————
    Bais Voltage 0.7
    Ic = 1.25V / 180E 7
    hef of BC 148 70
    Ib = Ic/hfe 0.1
    Let R2 be 10K
    Vdrop accros R = R*Ib 1V

    Voltage across the chain ZD1, R2 and T1 be should be 13.5
    i.e : 0.7 + Z + Rdrop = 13.5
    ZD1 = 13.5 – (0.7+1)
    ZD1 = 11.8V or (12V)

    Similarly
    ZD2 = 10V
    R18 = 10K

    Regards,
    Gururaj

  137. Seetharaman,V.S

    Dear Mouly
    It is called SPST switch (single pole single throw switch)
    In fact you can use any domestic electrical on / off switch.

  138. Very useful circuit Sir.What is that ON/OFF switch name in the market .Does it have any specification.Is that manual switch or automatic.Please reply me

  139. Hi Satu if you use a narrow beam LEDs you will have problem. I have used high bright white LEDs of 25mA rating. They are giving goor illumination similar to 7 watt emergency lamp, ofcourse not all around only 180 deg around 90deg brighter illumination. if you have narrow beam leds give an ofset between LEDs say around 15deg. This will help you to spread the light.

  140. Hello Sir, the second plan is a theoretically complete power cut off emergency led lighting. But led lights are light ray! While you tested it, did the led light spread throughout the room?

  141. Hi Kumar You dont require BD140. It is only required when you want LEDs to come on automatically during power failure. If you want it as an LED torch light/ lantern you can connect (if it is white hi bright) white LED through a resistance to battery. say the LED is rated for 50mA. then 6.9 – 3.2 / 0.05 is the resistance value. you can use 68 ohms in series with each LED. Any number of LEDs with 68 ohms in series with each LED can be connected in parellel. 12 is sufficient if you want an illumaination similar to 11 watts U type energy saver lamp, you use 24 LEDs.

  142. hello sir, thanx 4 ur response.due to unavailable of some components in the market, i want to divide the whole ckt into 2 parts i.e charging and led ckt.for charging i want to use a ckt of an old emergency lamp which charges 6v/4.5ah lead acid battery.and 4 the led ckt i want to use ur above mentioned ckt.i mean after charging i will disconnect battery from the ckt.it wont b automatic.so what changes i have to made in led ckt.?where the base of bd 140 will b connected.?is it possible to make such separate led ckt with or without using bd 140?

  143. Hi Kumar you can use 3 sets of 12LEDs with BD140 each with three switches.
    Normally LED will go open circuit hence no problem, it will not affect.
    For LM317 a cooling clip is a must, even it is 12 LEDs.

  144. hello sir, …1)suppose i connect 3 sets of 12 led with bd140 each.and 3 switches for the 3 set of leds,so as i can switch on any or all of them.is it possible? if 1 led blows then will it affect the others??
    2) whether heatsink will be required for lm 317??

  145. Hi Sanju without connecting battery measure the charging voltage and set it for 6.9 to 7 volt. After this adjustment connect the battery.

  146. Dear Sir;

    What is the procedure to adjust the pot.Kindly let me the same.Regards;/Sanjeev

  147. Hi Aji 2200uF can be used. Kindly assemble as per the above values indicated in the modified circuit.

  148. hi guys,,i tried to make this circuit.But there are many problems with my circuit.I have got 2200uF capacitor instead of 1000uF.Resistor with 16ohm resistance is not available to me…Is there any problems with these.Whether this problems affect my circuit
    Please reply..

  149. hiii seetharaman, thanx 4 the reply..plz let me know whenever pcb with improvement is ready.i really need it..thanx.

  150. Dear Mr.Seetharaman,
    I had gone through this.Thanks a lot. We want one Emergency Light manufacturing unit. Now small way. Can you pls help us giving the Kits/Boards.. We want LED Emergency Light or CFL Emergency Light to be run by Rechargable Sealed battery of 4.5 AmP or more or less which can give a three hours backup.. Pls mail my Email id..Waiting for your reply,Best.

  151. how can i use two bd14o how aill i connect them i want to increase 38 more leds
    so how much bd140 i will use?

  152. Hi Adnan the reply i have given on this on May 16th

    May 16, 2010 at 12:47 amHi Faraz Khan You can use 3 circuits of 12 leds driven by its own BD140. That is connect all the three BD140 emitters together. base through 680 ohms from each BD140 base to -ve rail. 12 Leds as above to each BD140 collector. this will enable all the three BD140 to share the current equally.

  153. Hi Kumar the PCB is getting ready will all improvements. once it is ready, will inform.
    For enclosure you can use any one of the old 2 tube enclosure with single 6volt 4AH battery. The appoximate cost with High Bright white 12 LEDs, new battery PCB will be around (you can use the transformer available in the old light) INR 500 to 600

  154. Hi Adnan 36 X 25mA 900mA a lot of current you require a very good heat sink for cooling BD140. I want the current to be distributed such that a small cooling clip will do.

  155. but sir my light is working on 36 leds on one bd140?
    what is the drawback of one bd140 on 36 leds?

  156. Hi Yofan yes you have to change the transformer also to 15volts secondary.
    Hi Prasanth you have to use 2 more BD140 circuits so that you can light upto 36 LEDs. Say each LED consumes 25mA then you require 900mA, Battery will last for 4hrs before requireing to recharge

  157. Hi Sir,
    it’s possible modified your charger from 6 volt batt to 12 volt batt with only replace the zener diode ?
    and also it’s fully automatic batt charger right ?
    thanks for advise

  158. hello SEETHARAMAN,thanx a lot 4 the modified ckt..i want to work on the above ckt..so to mount the above ckt, whether general pcb r availaible in the mkt or else what i have to do??hope u undrstand..question is regarding pcb.and what will be the approx cost for making this ckt in rs..thanx..

  159. Hi Sankar with a small modification, change of transformer and 3 LEDs in series we can have a circuit with improved efficiency. I will try to send one soon.

  160. At times of rainy season, current available time is less. So I want a modified circuit diagram of 12 volts. With less number of LEDs i can use the charger for a long time.

  161. Thanks a lot for this diagram. Can the same circuit be modified for a 12 volt battery circuit with different charging levels?

  162. plz give me the quick charger circuit for this light or tell me how to increase the current for quick charging?
    or mail me the circuit i shall be very thankful to you

  163. Hi Adnan you have to make a different charger circuit of the required capacity. Existing design is not meant for it.

  164. i have 4.5amp battery and the 30% of 4.5 is 1.35amp tell me that or modify the circuit that the existing power supply will give approx 1.2 or 1.3 amp?thanks

  165. Hiu Adnan you can fast charge the Lead acid gel cells with 30% of the rated current, say in 3 1/2 hours you can charge fully. Ensure the battery is not getting heated up warming up is normal.

  166. i want to charge the battery quickly tell me what will i do because it takes a long period for charhing so how i can charge the battery quickly?

  167. Hi Adnan Normally these small trasformers will have no load current of 8 to 10mA @ 230 Volt. So 2.3 watts of energy is always consumed even without load. These trasformers normally has a loss of around 15% at rated load. 9 X 0.5A that is 4.5 watts as the efficiency is 85% the primary requirement will be 4.5 / 0.85 = 5.3 watts. 5.3 + 2.3 = 7.6 watts will be the primary power requirement. All these calculations depends on the quality of the transformer. price is proportional to quality.

  168. how much power is consumed by the 9v 500mA transformer tell me the formula that i will able to calculate the watts consumed by transformer so i will calculate the electric bill?and also tell me the electric bill calculating formula Thanks

  169. Hi Adnan this was my earlier rely to one of our constructor

    May 15, 2010 at 8:51 am
    Hi Faraz Khan use an electronic sounder (phezo electric) in parallel with diode D5, +ve of the sounder to cathode and -ve to anode of D5. When the battery is getting charged the sounder supply is reversed (you get around -0.7volt). once the battery is fully charged T1 switches on the battery will supply sounder around 4 volt for it to sound. If dont want negative voltage of 0.7 across the sounder add a diode inseries with the sounder to block negative voltage.

  170. i hav e succesfully use this circuit but i want a modification when the battery is full charged an led indicator will glow so we can get n switch the power off so upload a circuit diagram with this modification i shall be very thankful

  171. Hi Prasanth, mail you mail ID to seethasub@hotmail.com i will send you the modified circuit with your requirement. i have already posted the modification required to ADMN, “circuitstoday”

  172. Hi seetharaman,Thanks for the reply.Can you please elaborate & send us the modified schematic.

  173. Hi Prasanth you can use a BC148 with a 5.1 volt zener similar to charge limitting circuit and its collector to be connected to the 560 ohms available at base of BD140 instead or returning it to common negative. When the battery terminal voltage falls below 5.7 volts the LEDs will be switched off.
    Hi Adnan As per the battery manufacturer’s recomondation maximum charge current cannot exceed 1.2 amps. and charging voltage canot be more that 6.9 volt for cycle use. Hence a 6.9 volt regulator with maximum current limit set at 1.2amp is a must. If these precautions are not taken, the life of the battery will get dramaticaly reduced. For cycle use over night charging(8 to 10 hr charge cycle) is strongly recommended. Each LED drawing 20 to 25mA 36 LEDs will consume 0.9 Amp Hr. The recommended batery can give an useful glow of 3 to 4 hrs per charge. If you want more duration you may have increase battery AH capacity and the charging circuit accordingly.

  174. hi I’ve successfully made this circuit with 36 leds and my light is working and it give 6hour(not continuous)
    but if i use 24 volts(12-12) transformer instead of 9volts can i replace the transformer and if i do this will the battery charged quickly?

  175. hello sir.how can i implement the under voltage cutoff for the
    LED Emergency Light Circuit,since battery get drained.

  176. Hi Tutul you can try 5volt instrument cooling fans, which are avilable for low price or you can get one from a old defective power pack. ( used for PC power supply cooling).

  177. Hi Digaonto you can use a standard 6volt DC fan with 9″ blade Connect -ve to battery negative and +ve through a switch to battery positive. These fans work normally for 3 hours with fully charged battery. The fan consumes around 1.25 amps.
    For operation during power as well emergency use, increase transformer rating to 2amps all rectifiers to 3amps ( eg. 1N5404) use the standard current increasing technique for LM317 with a PNP power transistor like 2N2955 and a resistance of 6.8 ohms. with this your fan can operate always. during emergency will operate for 3 hours.

  178. Hello Seetharaman,
    There is no doubt that it is really an excellent & efficient circuit for those countries like us where Load-shading is daily routine . I also want to add a motor to make fan in this circuit . Which volt’s motor will I use ? Will I use 6V or 9V motor ? And the motor will run also while the battery is charging too .

    So, From where and how will I connect the motor line . The motor will run in both time- while the battery is charging & in emergency(from battery) time . – Thanks

  179. Hi Michael if PMPO is your requirement as per your link then you can construct 60 watt RMS amplifier, in bridged configuration it will give you 240watts RMS. As per your link’s Sony’s specification it will be 5200 watts PMPO. You can use Sub woofer amplifier appeared earlier in ‘Circuits Today’ with modification and covert it to a full range amplifier, bridge and use it.
    You require 4 amplifiers to make a stereo system with the similar power supply with the current rating increased suitably.

  180. Dear Sir,i need the circuit diagram of a 5000W audio power amplifier using STK… IC families and another one using transistors.

  181. Hi Saad A fully charged battery can work in this circuit for 12 hours minimum for continuous illumination. 5.6volt is the end point voltage for lead acid gel cells. Hence you have to recharge the battery at this point. This is only a general guide line for a new battery. As the battery ages the characteristic will change.
    The LEDs will not glow during charging since R15 gives positive voltage to base of T2 it will cut off the current flow during charging. Once the power goes off the positive voltage goes and T2 gets forward biased and starts conduction to illuminate the LEDs. If there is still very illumination from the LED R15 can be reduced to 100 ohms. This problem I faced with amber LEDs.

  182. Dear Sir,

    It is very nice to view lot of electronic circuit which are useful to many students to learn the technology.

    It is to request you to send Synchro to Digital conversion circuit at the earliest.

    Thanks

    Kamesh

  183. hello sir.how can i calculate the remaining time of the battery?will the circuit glow while batery is charging?

  184. Hi a small correction is left out, the potentiometer to be changed to 4.7K or add 1K in series with the existing pot 2.2K. With 2.2K you will achieve only a maximum of 5 volt.

    1. sir,
      first time i appreciate ur great effort for design such wonderful circuit.since last two years its works well in my home in absenCe of me..let me ask some quisten sir.1-i would like to use power led of 1w-24NOS nos.what modification require?2-please let me know the maximum current can taken from bd140 transistor?3-if i increase transistor means parellel more BD140?4 -can i replace bd140 with 1061 or MJE 3055 transistor?AND WHAT MODIFICATION REQUIRE COLLECTOR EMITTER TERMINAL JUST REVERSE?EXPECTING UR EXPRESS RESPONSE.
      C.S.SISON
      ALWAHDA MALL
      ABUDHABI
      UAE-
      PHONE HOME-9747447168

      1. dear sir,

        i made this circuit. i have an issue output of battery charging point (without battery and zener disconnected) shows only 6.4 maximum after preset is adjusted full level volt i cant raise to 6.9 volt.when battery and zener connects it shows 5.12.battery not charging. please can you help me. what could be the issue.?

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