The only electronic website that answers to every comment, and addresses all circuit related issues..

## LED Projects

This page presents a huge collection of LED related circuit links, meticulously designed and compiled by me.

Here we exclusively deal with the various LED driver circuits, consisting of articles explaining how to make LED drivers for high watt LEDs through SMPS concepts and also using capacitive power supplies. We also learn regarding the various safety related parameters essentially stipulated for these LEDs, this includes detailed instruction regarding how to make precise current control circuits and also regarding how to wire the LEDs correctly such that the SMPS and the LeDs become perfectly compatible with each other and render an optimal performance and maximum operating life span. The following link will take you to some most insteresting and useful LED related circuits, such as LED drivers, LED formulas, LED hobby circuits and many more.

LED Lamps
LED Drivers
LED Projects

1. Hey Swagatam , I am really fascinated by your simple circuits . I am requesting you to provide a LED circuit which dances with music for different frequencies . I want to light my PC table with many 3 LED strings of different colour for differnt frequencies of music and I power them with my 12 V wall adapter . Please help

1. Hi Kishore,

Thank you!

I'll try to post this circuit very soon in my blog, the title will be "simple spectrum analyzer circuit"

2. Super cool, will keep my eyes open for that. I have a question related to my cpectrum analyzer circuit that I will post or email.

3. Dear Sir,
My self Bhumit.
I am developing a power supply for LED Driver.
Input is 230V AC @ 50Hz.
Output should be 32V DC @ 2.8 Amp.

LEDs Per string is 9
Total strings in a light is 8
So total 72 LEDs.

LED has Forward Voltage of 3.3V each
And Forward current of 0.35A
Please guide me with this application.
Regards,
Bhumit

1. Dear Bhumit,

You will need an smps circuit for it and then add a current control circuit to it. You can buy a ready made 12V or 24V 2.5 amp smps and then modify the outer winding of its transformer for getting the intended 32V. Once you have done it, you can add a LM338 current limiter to its output for driving the LEDs.

4. hello sir Swagatam. my name is amir of Buenos Aires Argentina ... can you help me with a circuit that generates a pulse every 30 or 45 minutes to connect with CD4017 and changing LED lights in 30 to 45 minutes talves with IC555. thank you very much.
ATTE: Amir of Argentina

1. hello amir, you can use the circuit shown in the following post:

Use only the desired number of outputs from the IC 4017, and do not the diodes connect the LEDs directly via 1k resistors. also connect the pin15 to the pin immediately after the last selected output of IC 4017.

set the IC555 for generating the specified intervals.

5. Hi Swagatam

I am thinking if a transistor tester (without micro-controller) could be made which could give results as shown in the attached diagram.

https://dl.dropboxusercontent.com/u/20969135/Transistor%20Tester.gif

The colors of the LEDs corresponds to the colors of wires. The circuit should detect the C/B/E and light up the corresponding LEDs.

For a PNP the Green LED will be illuminated and for NPN the Yellow one.

The circuit should also detect if the transistor is Darlington, if yes the Red LED should light up.

A faulty transistor may be indicated with a combination of the existing LEDs or an additional LED may be used.

Shall be thankful to you if you could design a circuit for this.

1. Hi Abu Hafss,

It could be a very difficult configuration to design, I am not able to find any hint how to begin with it.

Do you yourself have any idea?

6. Hi Swagatam

I have seen micro-controller based transistor testers, which displays results on LCD.

I thought that there should be some similar transistor tester without micro controller. But could not find any circuit so I just started with the output based on LEDs. I knew, it could be really a challenge to make such a big circuit. So, being my USTAAD, I approached you first to have your valuable comments.

1. Hi Abu-Hafss,

The circuit links that you have provided are ordinary transistor testers, what we want is a lead identifier, meaning no matter in what position the transistor under test may be inserted, the relevant LEDs will instantly identify the collector, base and the emitter through the relevant colors.
For this we'll need three individual color LEDs on each terminal of the transistor socket, so that the above functioning can take place irrespective of how the transistor is being inserted....this looks like a challenge.

7. Hi Swagatam

I have checked the circuit for transistor pin identifier (based on Red/Green LEDs), it works. Meanwhile, I have also finished my design to connect with this circuit. However, I am stuck at the point of interface.

https://dl.dropboxusercontent.com/u/20969135/Interface.gif

My design begins with three NAND gates corresponding to each pair of LEDs. My idea is to sense if one or both LEDs of a pair are illuminated and feed it to the corresponding NAND gate. For this I used the configuration shown in yellow window. But the problem is that actually LEDs are blinking alternately at very high frequency (appearing that both are lit) and hence the output of the NAND gates are changing with the oscillation (in simulation). Do I need to incorporate a latch before each input or there can be some other better configuration?

1. Hi Abu-Hafss,

If it's a normal functioning and you are only interested to stabilize the output then probably a singe capacitor at the output of the NAND after a 1K resistor will do the job, otherwise you may have to find why the LEDs are oscillating and need to troubleshoot the cause.

2. Hi Swagatam

The circuit operates as per description shown in the website. When a transistor is connected to the three connectors:

- One LED of the pair corresponding to Base will be illuminated (If red, the transistor is NPN; if green, it is PNP)
- Both LEDs of the pair corresponding to Collector will be illuminated
- Both LEDs of the pair corresponding to Emitter will be illuminated
When the switch corresponding to the Base is opened
- the Base LED will go off
- One LED for Collector will be illuminated (Green or Red)
- One LED for Emitter will be illuminated (Red or Green)

LEDs of a pair are connected parallel with opposite polarity. When both are lit, actually they are blinking alternately at high frequency.

In yellow window, I have used pair of diodes across each LED. At the junction of diodes of each pair, I collected signal, filtered it with capacitor and fed to the input of NAND. The signals are changing their state with the LEDs, which means the inputs to the NAND are changing and hence the output is also changing.

My questions:
1) Is this correct approach to collect signal from the LEDs? Or do you have some more simpler one?
2) If my approach is correct, how to have constant (locked) signal from the fast blinking LEDs? A latch???

Lastly, as requested earlier, would you please recommend me some reliable ICs for latches and analog switches?

3. Hi Abu-Hafss,

I have already answered to your above questions. You can simply add a resistor or more precisely a diode at the output of the Nand gates (anode to gate output) and a capacitor across diode cathode and ground...the junction of capacitor and diode would give you a constant DC with no fluctuations.

As mentioned earlier you can try 4043 IC if you intend to use latches for the implementations.

4. ...or more simply add 33uf cap directly across the LED leads

5. Hi Swagatam

The output of the NAND depends upon the inputs. The fluctuations of the input has already been smoothed by the corresponding capacitors. My problem is that the inputs are changing their state LOW/HIGH at high frequency.

At instant when pin #1 is HIGH, pin#2 is LOW and hence the output is HIGH.
At instant when pin #2 is HIGH, pin#1 is LOW and hence the output is HIGH.
And in a simulation I noticed their is a brief gap after each cycle, when both pin#1 and pin#2 are LOW which makes the output LOW.

For this reason I am getting LOW/HIGH at the output. Whereas, my idea was to sense if one LED is on, the output of NAND should go HIGH and if both LEDs are on, the output should go LOW. Now, I think incorporating a latch before each input pin of NAND would do the job.

I have almost finished my design and it is working perfectly but, I am stuck at this input stage. I am really excited to make such a complex circuit and am very anxious to see it working after coupling it to the circuit made by 'redcircuit'.

Lastly, pardon me, you never replied about the ICs earlier. Thanks for recommending 4043 and how about IC for analog switches which I want to replace for transistors.

6. Hi Abu-Hafss,

I thought you wanted a constant DC at the output irrespective of the input fluctuation, that's why I recommended a diode and capacitor at the output of the NANDs, anyway if you think a latch would do the job you should go ahead with it....you can use single BT169 scrs also as latches.

In my previous comment I remember I had entered the figures 4043, but may be while searching for the datasheet I lost that comment and re-entered a new reply and forgot to add it back, that's why very strangely it's missing in the last reply.

We are also too much keen to see the results of your handwork...it would be an achievement for you if you could succeed with it, in fact you are almost done.
Best wishes to you.

I am sorry to say that my LED sensing set-up is not giving true results. So I need your help to detect if an LED is illuminated or not. After failure of various set-ups, the last thing I could think of is LDR circuit for each LED. Do you have a better idea?

9. Oh yes, another option is an opto coupler. If you have any other idea please share with me.

Thanks

1. For sensing a genuine illumination only, an opto-coupler could be the best choice, so you should try it according to me.

2. Hi Swagatam

Pleased to inform you, I have finished the basic design of my circuit. I have checked it, the simulation is giving perfect results.

Now, I am working on the darlington checking module. Can you give me some hint what a darlington has something unique which I can check for? I mean something which can be checked with a multimeter. Or, please spare some of your time to study the original circuit/description and then see if you can get some idea. I just want to show an LED indication that the transistor connect is darlington or not.

3. Hi Abu-Hafss,
That's great news! congrats to you.

Darlington pair has the property of extremely high current gain, meaning it can be used for switching relatively higher collector currents through minute base current triggers.

A high current load at the collector of a Darlington transistor can be switched ON with a trivial amount of current at the base.

10. nyc concept sir.

1. What is nyc? Do you mean "nice"?

Here is the job I have done so far.

1) https://dl.dropboxusercontent.com/u/20969135/Transistor%20Analyzer%20flow%20chart.gif
It is the flow-chart which is base of my circuit.

2) https://dl.dropboxusercontent.com/u/20969135/Transistor%20Analyzer%20-%20A.gif
This shows the modifications I made to the original circuit to collect the information about the illumination of each LED.

3) https://dl.dropboxusercontent.com/u/20969135/Transistor%20Analyzer%20-%20B.gif
Finally, this is the circuit which I have designed.

4) https://dl.dropboxusercontent.com/u/20969135/Transistor%20Analyzer.pdf
This is the description of the circuit.

You are kindly requested to check this circuit thoroughly. I shall appreciate if you could please suggest me refinements/improvements.

1. Hello Masterji,

The circuit is too elaborate and due to lack of time I am unable to look into all the details, but since you have been into this design for so many days I think you could conclude it by yourself without anybody's help and I am sure you would do it.

It's really commendable, seeing the level of designing effort and the simulations that you have presented.

If you permit me to put it in my blog, I would happily do it.

2. Hi Swagatam

I understand that it needs some time to check. Actually I just wanted to have some improvement/refinement tips.

You may put the circuit in the log. However, there is an important point which needs to be sorted first. As I have mentioned in my description, for an off LED the output is less than 1V (not exactly zero). My question is when the inputs to a NAND gate is 9V and 0.7V will the NAND assume the input LOW for 0.7V or HIGH? If it accept it as low then no change otherwise, I have to introduce a comparator for each output of opto-coupler.

3. Hi Abu-Hafss,

0.7v will be definitely taken as a "low" for any cmos gate

12. Perhaps you might need this revised picture, without DARLINGTON checking function. I haven't yet include the same in my design, I need some tips from you for that.

https://dl.dropboxusercontent.com/u/20969135/Transistor%20Analyzer.gif

1. hmmm.....looks great Abu-Hafss.

I think I have explained you regarding the basic characteristics of Darlington devices??

2. ....here's how a Darlington transistor could be configured as (TIP122 for example):

http://4.bp.blogspot.com/-LqHW4mlnOhw/UqGL5ydq3RI/AAAAAAAAF1w/ijb_tMSWWEE/s1600/TIP152%20darlington.jpg

3. I have seen the internal schematics of various darlingtons. The problem is that I cannot figure out what kind of checking module should be integrated with my circuit?

So I really need your guidance in this respect.

4. Actually I did not study your circuit much so can't really suggest how to integrate a Darlington measurement in your design, I'll see if i can present my own version of it.

Thank you masterji for appreciating me so much:)

5. Hi Swagatam

At least just spare some moments to study my flow chart, I am sure you will get the idea of my logic. Then you can get some hint. Or if you want to make your own version then please design it on the basis of the opto-coupler circuit otherwise, it might be difficult to integrate with my circuit.

6. Hi Abu-Hafss,

Presently I am getting 50 to 70 comments everyday,before i can finish it another 100 are ready.....that's why I am unable to look into your circuit, moreover the design is quite elaborate and has many parameters to be checked which can make it quite time consuming...i'll surely refer to it the moment this comment flood becomes a little lower.

Okay Sir, I understood. You spare hours to reply the comments, helping people like me. Simultaneously, you also look and work on new ideas.
That is really appreciable.

I shall be grateful for your contribution.

8. Mastermind Abu-Hafss,

Thanks very much, yes i'll do it very soon, BTW I have posted your car turn signal indicator circuit, did you see it?

9. Hi Abu-Hafss,

I have posted your transistor identifier circuit also, please see it here:

13. dear sir,
i am using 12v 60ah battery, i want 1watt dc to dc led driver circuit (use for down light color)

14. how can i calculate
1-how many led*s can be derived properly in series with provided voltage and current?
suppose i have 100VDC 2A source then how many led*s in series or paralell i can join this source for working equally with no voltage drop/burning,,
2-how many led*s can be derived properly in paralell with provided voltage and current?
mean what is formula ? and what specification are needed to calculation

1. you can take the help of the following article for understanding it:

15. Good Day Mr. Swagatam. I was just hoping if you had circuits that could drive around 100 superbright LEDS. iwould like to use them for solarpanel-based lighting system. we would use 1000 of these LEDS, series-parallel, to illuminate the study area in our school. THANK YOU!

1. Good day Blitz,
I would like to know the specifications of the input supply and the LEds, the wiring of the LEds would crucially depend on these parameters, so please let me know about these....I'll provide you with the required info once these are furnished.

16. This comment has been removed by the author.

17. Hi Swagatam.
You have a very good job here.

I would like build lights switch with driver for my car, between HID 2x35W and 2x8 (led diodes each 1W).
I wanna have to make ambient light sensitive circuit and working just with key in the ignition (key sense + 6V)
Thank you.

Do you mean the lights must adjust its brightness in response to ambient light conditions?
Lights should go darker during day and brighter during night...right?

2. Hi Swagatam.

I mean daily light LED on and darker condition and evening and night HID xennon lights on.
Switch between LED and XENNON is response to ambient light conditions.

I'll try to post the design soon in my blog, it may little time though.

18. Hi Swagatam.
Thank you very much for your time and good job.
I got that circuit and I will try to build it up.

19. dear sir do you have circuit to drive 20w single chip LED?

20. Aapni schematic gulor songe jodi paren tahole PCB layout gulokeo post korte paren. Tate ki hoy amar etching korte subidhe hoy. PLZZZZ POST THE PCB LAYOUT !!!!!!!

1. I'll consider your request and try to update the PCB layouts in the articles, if time permits.

21. Hai, I bought a 5W LED driver from market. On the top of the driver, it is labled as follows...
Model: 4-5 X 1W LED Driver
Input voltage: AC 85~277V
Output voltage: DC 6~18V
Output power: 4~5W
Can drive 4~5W LED lamp.
So If I connect 5 one watt LED in series means, it needs 5 watts. I.e the series needs 16.5v, 350mA.
And If I connect 4 one watt LED in series means, it needs 4 watts. I.e the series needs 13.2v, 350mA. But the output voltage from the driver is 18v. how the rest of the output volt wil get adjust?? or will the LEDs get fried due to over voltage?? Need clarifications... Thankyou..

1. Hi, you'll need to employ a current limiter stage and also a resistor with the LED string by doing some calculations as explained in the following article:

22. hi swagatam,
i want to make a LED display board with about 500 white LEDs 5 mm 1/2 watt.
non flickering and non moving.
can we use smps power supply of computer. if yes, then how to connect. please circuit diagram

1. Hi Navdeep, yes an smps would be the ideal way of powering the LEDs, but the resistors will need to be calculated appropriately as per the voltage rating used....

2. i want to use 3.3 volt led. please give circuit diagram of circuit of resistances.
how and which wires of computer smps to be connected.

3. i have no idea how to calculate resistance values.
please give a circuit diagram for 500 white leds 3.3 volts.
both on 220 volts and by using power supply. what rating of power supply should be used

23. am not from electronics field but have successfully made tubelight using your circuit. so want to make a bigger 10' * 3' LED board.

1. it would better to use a 12V, 2amp SMPS for reliable operation.

first make strings of three LEDs in series with a 100 ohm resistor.

Make 166 such strings having 3 leds and a a 100 ohm resistor on each string........ and then connect all the strings in parallel....connect the common parallel connected ends of the strings to the supply with correct polarity...your 500 led tube light is ready.

2. thank you so much boss.
I am using following LED with 100 ohm resistance on a string of 3 leds.
VF 3.2-3.4
WL 440 NM
BIN P3
IV 7000-9000 MCD
i hope these are correct leds

3. sir,
one more line is written on led packet:
Type: 8084UWC-0.75W/E30
Moonlight + led lamps.
can i use 12 volt 5 amps / 12 volt 10 amp smps for above leds for brighter illumination?

4. Navdeep, please provide the forward current specification of the LEDs, I have assumed it to be 20mA types....

the data you have supplied does not indicate the current of the LEDs.

24. forward current is not mentioned on packed.
so how to calculate amperes of power supply?

25. forward current is 20mA,
VF is 3.0 -3.4 volts
now if we make 166 strings connected in parallel, current becomes 3320 mA.
should o i use 12volt 2 amp / 12 volts 5 amp power supply.

1. yes that's right, then you must go for a 4amp or 5amp smps, a 9V/5amp transformer power supply will also do, after rectification it will produce around 13v

26. thank you swagatam for your kind and promt help.

27. please give a simple and durable, programmable circuit for 5 feet by 1 feet LED digital display

28. you can try the following circuit, P1 and P2 may set appropriately for fixing the ON/OFF delays of the timer and the load

29. dear sir,
how to make led driver(input 250v ac output 65v dc ) i used 5630 smd led (21 led X 4 lines) plz give me a circuit.

1. Dear Vijay,

You can try the following design:

30. hello swagatam,
i want to make a display board with red, green and blue leds. Approximately 350 each. and i want to use 12 volts rgb controller. please suggest how should i connect LEDs. I want to light red, green and blue leds separately and then in combinations. And how to make circuit. please also suggest which rgb controller should be used and how it should be connected.

1. hello Navdeep, I have no idea about it, it will entirely depend on the controller's output specs (V,I) and its sequence pattern.

31. dear swagatam,
can u suggest a simple circuit for 12 volt 3 amp each, red green blue, rgb controller. with primary colours only.
thanks.

this is the photo of circuit i got from internet. but am not able to understand how to make it
help please. please suggest a simple circuit using easily available components. for RGB controller

1. Dear Navdeep, please specify the sequencing pattern of the LEDs, meaning in what manner the RGB LEDs are supposed to light up in the sequence.

2. red first, then green , then blue, then red green togehter. or any order and any combination will do. i just need it for making a led display board. only wish is that leds should light in sequence and combinations.

3. you can try a 4017 and 555 chaser circuit....use transistor driver stage across the outputs of the 4017....this may be done through individual diodes on each pin and then base resistor for the transistors....the RGB LEDs will go across the collectors of the three transistor connected with the pin3,2,4, then pin1,7,10 may be terminated with diodes and their cathodes shorted and then from this short connect three more separate diodes and connect them with the transistors bases at the points where the previous diode cathodes are connected.
Next connect pin5,6,9 through separate diodes to the bases of the transistors as done in the above procedure.

You ca try other experimental combinations also by some trial and error.

4. You can do it in this way also

------>I-----^^^^--------transistor base 1
------>I-----^^^^--------transistor base 2
------>I-----^^^^--------transistor base 3

------>I-----|------>I-----^^^^--------transistor base 1
------>I-----|------>I-----^^^^--------transistor base 2
------>I-----|------>I-----^^^^--------transistor base 3

------>I-----^^^^--------transistor base 1
------>I-----^^^^--------transistor base 2
------>I-----^^^^--------transistor base 3

5. Dear swagatam,
I am not from electronics field. Am not able to understand it this way. please give a circuit diagram how to make connections.
thanks

6. Dear Navdeep, I'll try to post the design in this blog soon.

33. thanks swagatam, am waiting

34. I like to have a circuit once we clap twice in a fraction of seconds greenled must glow indicating as like good clap with short duration and if we clap twice with more duration ie from long distance red led must on indicating as failure to clap twice quick with less duration ...the title for this circuit is how fast u can clap -test your inertia plzz reply to this

1. I don't think this concept may have any useful application, if possible I'll try to put it out in my blog.

35. I would like to have a circuit to generate 7 colors of the rainbow using RGB cathode Leds. Need to use 7 LED's for 7 colors.

1. you can try the following circuits:

36. Hi Sea. Do U have a method of determining power requirements for leds which have been salvaged Or where the specs are unknown.
Thank U

1. Presently I do not have any such circuit, but I'll surely try to find it online...

37. Hi Swa. We have 10 spotlight leds 220v 10w. Each have their own drivers. What is your opinion on having DC supplied direct to them from a single source, opposed to multiple devices doing the AC DC conversion n supply. Thank U

1. Hi Mitchell, It's possible to use a single adequately rated DC source for driving all the LED modules together

38. Hello sir

I found RGB LED Driver circuit during browsing how can i used 1 Watts RGB LED with this circuit with same transition effect mention in circuit I uploaded google drive link

1. helo sandeep, connect the cathodes of your RGB LEDs together and terminate it to the ground, and next cnnect the individual anodes with the emitters of the transistors...

39. Dear Sir, kindly advise how to use a 12v input to turn OFF a circuit. Eg if a blinking LED circuit using 555 is running normally on a 12 v supply. Now when another 12 v input is applied, this circuit should switch off (and when this 2nd 12v is switched off, the earlier circuit should start functioning again). Thanks

1. Dear Ankit, you can do it in the following way:

Connect the pin4 of the 555 to the positive through a 10k resistor.

take a Bc547 transistor, connect its collector to pin4 of the 555 IC

connect the emitter of BC547 to ground, and now applying the external 12V to the base of this transistor via a 10K resistor will shut off the IC 555 functioning.

40. dear sir , i need a project design for led torch light . The torch light must have 4 modes. 1) red stable 2) green stable 3) red flashes 4) green flashes also suggest suitable charges for the circuit.

Thanks

bala

1. sir iam waiting

2. Dear Murali, you can make it in the following manner.

Make a IC 555 astable circuit with a 1 Hz frequency at pin3.

Take red and green LEDs, connect their cathodes to the negative line of the IC, connect 1K resistor individually to the anodes of each LED, now connect the ends of the resistors through a SPDT switch across pin3 and the positive in the following manner:

center lead of the SPDT switches separately connect with the ends of the 1K resistors.

the upper two leads of the switches are made common and connected with the positive line...and the lower two leads of the switches are also identically joined together and connected with pin3 of the IC.

3. thank you master. if u give circuit diagram that will be very helpful for me .

4. sorry, drawing a diagram will be difficult for me at the moment due to my busy schedule....

41. Dear Sir, Kindly advise on the following circuit
1. A 12V circuit is desired to be designed to light a 12V LED, such that it lights the LED in pulses (that is to say that the current to led is sent intermittently (say once every 1 minute roughly) and the current pulse stays for a brief duration (say 5 seconds roughly))
2. So, the LED lights repeatedly once every 1 min and stays on for roughly 5 sec each time.
3. It is also desirable that the above circuit starts working automatically when it is dark and stops when the atmosphere is lighted.
4. The above circuit is intended to be used in a parked car so that the LED keeps blinking in the rear when car is parked in dark and the cycle stops when it is day time.
5. Further, as expected, when the car is driven at night, its rear red lights will be on and the blinking LED will no longer be needed. So, it is desired that in some way a 12V +ve signal feeded to the circuit from rear red lights (when glowing) should stop the blinking cycle of the circuit.
Sir, it will be so kind of you to help on the above mentioned aspects of the circuit.
Thanks

1. Dear Ankit,

The design is possible, but please let me know the importance of this circuit, because I prefer publishing those posts which have some kind significance or value for the users and has a fresh concept...

2. Dear Sir, Thanks for replying. The significance is as follows...
Mostly at night the cars are parked by the roadsides due to shortage of space inside homes. Often it is very dark due to absence of street lights or lack of electricity supply. So sometimes pedestrians, cycles or rikshaws or few vehicles without headlight bump into the cars. An intermittently pulsing LED as requested above would mark the presence of car, at the same time without undue battery drainage. When there is surrounding light in daytime or when the car is being driven, this blinking light would not be needed, So an LDR may turn off the circuit and also during driving the 12V +ve supply from car rear light would in some way turn off the blinking led.
Kindly advise on the requested circuit.
Thanks

3. ok sir no problem . plan to this circuit for Train guard.

by bala

4. Thanks bala, if you have problems let me know, I'll help you out.

5. Dear Ankit, I'll try to design it soon and post it in this site.

Dear Bala, since your application is for train signalling then it's also a useful concept...so you can also expect to see your circuit published soon in this blog..

both gentlemen please keep in touch.

6. Thank you sir

7. Thanks Sir. Eagerly waiting for your circuit design...

8. Dear Ankit, it's published here:

42. dear sir,i live in hyderabad telangana and run a small hotel here. i want to fix myself led sign board named ANNAPOORNA MESS. in the local market sign board makers are charging 350 rupees for an inch on the board.so i decided to make on own.i happened to watch youe programs in the inter net.please provide me information about how to arrange led bulbs circuit design.each letter approx takes 500 to 600 leds according my knowledge.thanking yo sir.

1. dear nageshwara, I'll try to explain it to you through a new post soon...

43. Dear Sir, Thanks for so promptly designing the circuit. Kindly advise on the following
1. Kindly specify the pin no connections of IC 4093
2. Whether only 1 or 4 ICs are needed.
3. Connected to N1, one diode is shown in the diagram and it is written 1N4148 X 3Nos. So whether only 1 or 3 diodes are needed (and if three whether in series or parallel)
4. Connected to emitter of TIP122 is shown diode 1N5408. So if 5408 is not available can 4148 or any other diode be used or 5408 is very specific.
Thanks

1. Dear Ankit,

please check out the datasheet of the IC 4093, you will find 4 gates in one chip, each gate has two inputs, and one output....the two inputs of each gate are shorted, as shown in the diagram....you can use these gates in any order, and don't forget to connect the supply pins to the supply line of the circuit...

only one IC is needed.

there are 3 diodes in the vicinity, all need to be 1N4148.

1N5408 is like a truck, and 1N4148 is like a bicycle, so how can these be interchanged ??? any 3 amp rectifier diode can be used in its place

this circuit requires advanced knowledge of electronics, so please be cautioned before building this circuit.

44. Hallo sir,I am very grateful of your work. Sir I want to make a circuit,which available in the market like 1 or 1.5ft long led light stick and the led flow's from up to down ,like water flow's slowly down from up.so please sir help me out the circuit. Thanks

1. Hello Pintu, I can try to design it but let me know the local name of the unit.... so that I can get an appropriate title for the project

45. Sir,I finally found the name, the name is "rain tube led string" size 50cm on Internet I found another name hot meteor shower

1. that's great pintu, I'll try to upadte it soon after a few previous pending articles are published....keep in touch.

46. thanks sir, i am waiting

47. it's here:

48. sir can u help me to build a 25 led circuit operated in 50 hz mains(transformer less power supply)

49. sir kindly help me for making ac 220v rainfall led circuit.
please send the circuit diagram to my e-mail- paulsumit82@gmail.com.

1. you can try the second circuit from this link:

replace the buzzer with a LED having a series a 1k resistor

and power the circuit with a mobile charger adapter

50. Morning Sir,

Sir, I go through this LED blogs seeking to see a ballast circuit that can operate a 35watts fluoriscent lamp with 5 to 12v battery, but I couldn't find any.

I'am gratefull for all these helps, Sir.
Thank very much!

51. halo, sir.

can you give me some advice to design/create circuit related to turn on/off led. before that, sorry my english.

how to turn on/off led with 1 button. first push button to turn on, sencod push to turn off, and keep going. so its close loop circuit.

1. hello eantaru,

you can use a 4017 IC flip flop circuit for implementing the application.

52. SIR I WANT TO KNOW THAT WHAT MATERIALS I NEED FOR MAKING A 100 WATT LED

53. Dear Sir,

I have a 12v 10A SMPS which I want to power 12 X 3W LED down lights. Since the current here is very high please advise me on any circuits which will bring down the current and I do not burn out the LED's.

Also wanted to check if I can connect the LED's to 12V 120AH battery directly.

Best regards,

1. Dear Jagan, you can apply the following concept for the LEDs, and use the LEDs safely with the SMPS or the battery

2. my LED's are rated at 12V and 350mA and how do I connect them i.e., in Parallel or in series.

Best regards,

3. since your supply is 12V, therefore you will have to connect the LEDs in parallel.

use the recommended LM338 circuit in between the supply and the LED bank.

also use a resistor with each LED just to make it safer for the LEDs.

you can use the following LED calculator for calculating the resistors...put the supply voltage slightly higher than the LED voltage otherwise the calculator will not work.

4. There are 2 resistors and do I use the same resistor for both and what is the wattage I'm supposed to use.

5. connect the LED and the resistors as indicated article.

the formula for LM338 resistor calculation is given in that article itself

the LED resistors can be calculated by using the referred LED resistor calculator software

54. Sir,

As per my understanding the below mentioned link will help me connect the LED's to the Battery directly (http://www.homemade-circuits.com/2013/07/making-led-halogen-lamp-for-motorbike.html) which is quite clear.

But for connecting it through the SMPS I'm still not able to figure out how to calculate the value of the second resistor (R1 which is connected to the Vout of LM338)

55. Jagan, you can use the following software for finding the LED resistance.

keep the supply voltage slightly higher than the LED voltage

56. R1 formula is given in that article itself

R1 = 1.25/LED current

57. Sir... Circuit is working as intended. But I observed that the brightness of the LED increases when I add more resistance in parallel which is connected in series to the LED's.

1. Jagan, adding resistors in parallel will cause the effective resistance to decrease and allow more current in the LED, this could make the LED brighter but will ultimately damage the LED

58. Hello Swagat, its great to see your knowledge about Electronics and circuits. IT would be nice if you can also Build these Circuits and sell them through your website.

okay now to my query :)
I want a driver that i can use for 10 Led either in Parallel or series.
LEd - 10 wat 12 vol 1 AMP

Thanks and Regards

1. Thank you Asheesh, I'll surely consider your suggestion!!
for a 10nos of 12V/10 watt LEDs you can either procure a 120V/1amp adapter and connect the LeDs in series with its output or use a 12V/10amp adapter and connect the LeDs in parallel with its output.

for both the cases you will have to put a current control circuit in the middle.

59. Thanks Sir, so you mean i need a ciruct that should give exact amps as output?
Do you have any circuit that i can refer?
Thanks

1. Asheesh, you can add the following circuit in between the power supply output and the LED module for getting the required current control for the LEDs

the transistors will need to changed as per the voltage current rating of the adapter

61. Hello friend have fabulous projects on your website, I'm from Venezuela. And I wanted to know if I could do a project in the area of LED. To light a 100w Led power grid with AC 220/110 residential, without a LED driver and the same holds capacitive power supply. I hope to answer.!

1. thanks elvis, you can try the following concept, this will be more suitable for your specific application:

62. Hi I want to make 24w Ac powered LED Tube Light. Please give me a safe Circuit Diagram.

63. Good day prof. ever since I came across your blog, I've being additted to your blog. help me with a circuit design of a transformerless step down from 230VAC to 110VAC of current of 1Amp. thanks in advance

1. Thanks Elvis, the idea may not be possible without a transformer.

64. Want to make a growlight circuit using 10 leds each of full spectrum leds and cool white leds,basically want to make an array of them i.e mix 10 leds of full spectrum and 10 of cool white.I do have two power supplies of 12v,2A,so need to power white leds and full spectrum leds separately.How should I power them?Please provide circuit and schematic.
Thanks.

2. Oh sorry forgot to mention that :P
The full spectrum ones have:
Voltage:3.0-3.4 v
Current:700 mA

White led ones:
Voltage:3.0-3.2 v
Current:350 ma

Both leds are 3W rated.

3. you can make 3 strings of LEDs having 3 series LEDs on each string, do this for both warm and cool LEDs, that means you will have total 6 strings of LEDs.

use 3 ohm 2 watt resistors for each 700mA LED string
use 7 ohm 1watt resistors for each 300mA LED string
join all these string in parallel and apply 12V across their common ends

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65. Hi just found your website while searching for a low battery alarm and ive been reading your simple circuit design since. Just wondering if you can show me a simple circuit to light my front door to find my keys at night using a 3v supply it must have a push button to activate the led lights and will stay on for under a minute ( or can be adjusted to a desired time )and automatically switches off itself . Thank you so much n advance

you can replace the shown 12V input with 3V, if you are using a white LED then the series resistor with the LeD will not be required.

2. Hi your reply time is excellent mate, definitely will try this circuit. Whats the difference between bc557 and bc557b or are they the same thing. I'm making my list of components to buy. Can I change the value of the capacitor to a much higher capacity so i can add more LEDs for a brighter light or is it possible to this circuit? Thanks again

3. Hi I have tried your 1st circuit design and it works, i just need now to fix the light on the wall, thanks a lot for your help

4. Hi, I am glad it's working for you, you can also try the following improved version of the same

5. Hi the first design circuit that I've followed fits perfectly for my project due to its simplicity and minimal components used . I have incorporated this to a small lmagnetic LED lights which is powered only by two cell battery, it s been a brilliant weekend project which is very useful, thanks to you.
I have another question for you but not sure where to post it , it's about 240 v CFL bulb converting to
12 volts dc using some of its original internal components if possible . I have loads of CFL bulbs left after my house conversion to LED lights and I'm thinking of using them for 12 volts applications, I know i can just use an inverter to power them but inverter can drain the battery too during outdoor use. And if possible components can be all put back inside the cfl casing . Thanks again in advance

6. OK great, but the first circuit will give you a smaller range of delay than the second one.

for operating CFLs on 12V you can build a IC 555 based flyback converter and then use its output for powering a CFL

7. The 1st circuit gives me 2 minutes of light and dims slowly up to 5 minutes , i dont have a 2M2 resistor so I've used 2M instead. I don't have components to build a flyback never done that before i thought a simple change in existing cfl components will convert the lights to 12 volts .

8. OK will do.

as for the CFL, I don't think a simple change will allow you to use the CFL with a 12V supply...if you search online for a 555 flyback converter you will be able to find many related designs across many different websites.

9. I checked your ebay diagram, you can increase its sensitivity by using a Darlington paired transistor for Q1, use two BC547 and connect them in Darlington format in place of the existing Q1

10. Hi tried it just now, leds remains lit and it doesn't flash, anymore ideas or do you have other circuit that i can follow?

11. revert Q1 to its previous form, and try the Dralington for Q2....if still it doesn't work, then try increasing the value of the base capacitor...or tweak the value of the MIC resistor....the resistor and the capacitor decide the triggering level of Q1 in response to MIC's sound detection

66. i have a LED Driver circuit which is rated 12V 2 Amp. how to calculate no. of LEDs having different current rating and wattage which i connected to this driver circuit

1. your LED fwd voltage must match the 12V spec of the driver unit and LEd current must be within 2 amps....if the LED fwd voltage is less than 12V then you will have adjust it with a calculated resistor.....