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SMD LED based Emergency Lamp Circuit

The following post explains a simple circuit diagram of an automatic emergency lamp using 36 nos. SMD LEDs. The circuit has been presented in response to the following request sent by Mr.Ali Adnan.

Circuit Request for SMD Emergency Lamp

"Hi,How r u Bro?? I Hope you are enjoying Good and Healthy life. Bro I've 36 SMD LEDs(Side View Type), I Extracted them from my Broken Laptop's LED LCD screen. I tested them with multimeter and found all LEDs in working condition.

Now I want to make some useful from them like an emergency LED lite. I'll remove all 36 LEDs from strip and mount them on a PCB (will be Tough JoB Mounting SMD's) once you will design a circuit for me to drive them.

I don't know much about SMD LEDs so that's why I am bothering you. I googled for data sheet for that type of LEDs and I think I found right data sheet for this LED, please also compare the pictures of LEDs and data sheet.

I am attaching actual pictures of LEDs that I have and also attaching data sheet, please check and help me with a simple circuit with simple parts. and just for information I've not found the IC ZXSC310 (that you used in your 1 watt LED circuit) here in Lahore Pakistan ๐Ÿ™ and I am too sad for this.

Waiting for your Reply.

Best Regards,

Ali Adnan Khan"

"Hi Bro,

What kind of emergency light do you want to make? Automatic AC/Dc operated or just direct on battery?

The datasheet  and the pics are OK.

Best Regards,

"Hi, thanks for your reply bro. Automatic AC/DC operated with battery backup."

OK, here's an automatic ac/dc emergency light circuit using the proposed 36 SMD LED lights which is easy to build, cheap and yet reliable.


The Design of a an Automatic SMD based emergency lamp is shown below, as per the above request specification:

Parts List

All resistors are 1/4 watt, 5%,

R1 = 1M

R2 = 1K,

R3---R14 = 56 Ohms

C1 = 2uF/400V PP Capacitor

C2 = 100uF/ 25V

D1, D2 = 1N4007,

D3, D4 = 1N5402

T1 = TIP127

Z1 = 15V 1 watt zener diode

Battery = 12V/2AH

LEDs = SMD, 3V white, 20 mA


About the Author

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

67 thoughts on “SMD LED based Emergency Lamp Circuit”

  1. Howdy, Friend! Interested to Learn Circuit Designing? Let's Start Discussing below!
  2. hello sir,
    sir i want to use two 6v 1aH BATTERIES in series with the circuit,so what modification would be required.

    • connect the black line of the zener with the battery (+) terminal and the other side of the zener with the battery (-) side…use a 14V 1 watt zener

  3. How to fixed charging indicate led ?
    I used 2 12v 2 amps battery parallel how to modify circuit?
    This circuit support 6v 4.5 amps battery used?

    • Connect a resistor in series with D2, and connect an LED parallel to this resistor, as long as the battery charges this LED will glow and will gradually shut-off as the battery reaches full charge.

      the resistor value could be anywhere between 2 and 10 ohm….you will need to experiment the right value

      if possible connect a 47 ohm resistor in series with one of the LED lead for safeguarding it

  4. I am having transformer 12v 2Amps. i replaced it, the whole night it took, but Battery backup didnt increase.. The system works (when the AC is on, DC off). the transformer is also so Hot….

    • your battery could be internally damaged….put an ammeter in series with the battery and check how much current it is taking in…if it shows zero will indicate a faulty battery.

    • for quicker charging you will need to remove the transformerless supply stage consisting C1, R1, Z1, and replace it with a 12V 1amp AC/DC adapter input

  5. Sir

    Your circuit ideas are valuable and useful.So many people are taking advantage of it
    You are rendering a great service to the world.

    Best regards

    Best regards

  6. Sir can you provide me any schematic or give any idea about the 2 watt led blinker with strobe light.(i will use two 1 watt led in parallel)..
    The circuit should work in this manner…When we press the button the led will glow continuously and the second press will make the led to Blink. and finally the third press will turn off the led.
    I have seen similar feature in Cree led torch ..
    Sir please guide me…

    • Syed you can try the circuit that's shown in the following link with a few external modifications:


      Remove all the relays and connect the LEDs at the collector of the pin2 and pin4 transistors, use TIP122 for the transistors.
      Connect pin7 with pin15 through a 10k resistor instead of pin10 and remove the transistor stage at pin7 because we don't need it.

      Now make a 555 PWM circuit and integrate its pin3 VIA a DIODE 1N4007 to the base of pin4 transistor…diode anode to base, cathode to pin3 of 555.

      That's it your circuit is ready.

    • Kim, you can use 1N4007 diode for making the bridge or simply connect the transformer wires directly across the anode of D1 and ground in the circuit that's shown in the above article.

      remove C1, R1,Z1 these are not required.

  7. thank you very much sir.

    its like the AC is giving it power because you can notice the light flickering. im sorry sir but im new to transistors but I know that it can act as a switch.

    I can see that you changed the position of D3. we haven't tried that yet.

    I also measured the voltage across the base and emitter. when the AC is off, it has voltage and when it is on, the voltage is zero. but I connected it to D3 in the old diagram where it is directed to the LEDs. Is it wrong?

    • thanks Kim,

      yes I have made a slight change by putting D3 at the emitter of the transistor, just to make the results more accurate.

      By the way did you use a bridge rectifier for rectifying the transformer voltage to DC before applying to the circuit?? otherwise the LEDs won't shut off correctly.

      You can try changing the position of D3 as shown in the new diagram and check the results.

  8. we are using an 18 volt transformer with 750ma

    we love your work a lot and we think that it is amazing. but sir we are having a problem now. thank you very much for your help.

    • with 18V at the base of the transistor it should completely cut of….

      the transistor may not be OK, or some other issue could be there.

  9. Good day sir,

    May I ask if it is okey to put an 18V/750mA transformer instead of a transformer-less AC supply? and change D3-D4 to 1N4001 or 1N5401?

    Also, whenever I connect the AC supply, the LED are still giving light. What could be the possible problem?

    Your kind response wuold be greatly apprecieted. Thanks.

    • Good day Kim,

      yes a transformer power supply could also be used
      use 1N4007 for D1,D2, 1N5401 for D3/D4.

      if LEds are not shutting off at mains switch ON, indicates a faulty transistor or incorrectly connected transistor.

    • yes sir. we are already using those diodes on our circuit. On a tip127 transistor, is the base on the left most pin, collector on the middle pin and lastly emitter on the last pin?

      and we are using two 6volt batteries in series with 4aH each. whenever we connect the AC source, the led's just dims.

      and lastly, we are using a ready made led sheets with 3 SMD leds per sheet that is intended for cars. does these have to do with our problem?

      please sir, you've been a great help. thank you very much.

    • Kim, increase the value of R2 to 10K, or 22K, or 33k until the LED shuts off completely while mains is present.

      please remember that the base voltage (or the supply voltage from the transformer) to the transistor must be slightly higher than the battery voltage otherwise the LEDs will keep glowing even if R2 is increased to any level.

    • we already tried to increase to R2 to 10K but the transistor heats up and the leds wont light. the leds only light up when we use 1k resistor on R2.

      is it okey to remove the transformer?

      thank you very much sir ๐Ÿ™‚

    • measure the voltage across the base and emitter of the transistor with transformer supply ON, and also everything else connected.

      It should be around 0V to make the leds shutof.

      if not, check and make sure the rectified voltage from the transformer is higher than the battery voltage….
      if still it doesn't work, your transistor could be faulty.

      or you can opt for a NPN transistor design circuit as shown at the extreme end of this article:


  10. Sir iam using 12v 5amp bike battery with 40leds. Brightness is low. If I directly connect leds to battery brightness is good. I used 6.8ohms resistors R3-14. Please tel how can I modify circuit to get more brightness. Thanks.

  11. need a ckt to drive Chinese led torch (4 led in parallel with only one limiting resistor to the bank, operate on 4 v rechargeable battery) from a 12 v bike battery without any power loss. thanks

  12. hello dear sir,
    i want to make an automatic AC/DC led light switch with transformer less supply.
    when AC supply on the led,s should be on and when AC fails then it should be shift to battery back up .
    i want to run only 5 LED,s of 1 watt each.
    i shall be very thankfull to you for this.

    best regards.
    Sameer Ali

  13. You can try the following circuit….you may remove the three collector diodes, they won't be required:


    The LED resistors may be selected as 100 ohms.

  14. sir i want to know that why u used a R2 in parallel how supply voltage offs and blink led on battery through R2

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