LED Berdaya Besar

LED (Light Emitting Diode) digunakan hampir pada sebagian besar perangkat elektronik seperti televisi, radio kaset, alat musik, alat kesehatan, perangkat pengujian, otomotif, dan lain-lain, sebagai lampu isyarat atau indikator.

LED mempunyai banyak keunggulan ketimbang lampu lainnya seperti: Mempunyai umur pakai yang sangat panjang, membutuhkan daya listrik yang sangat kecil (hemat energi), respon kerja yang sangat cepat dan baik.

Pada tahun 1999 Philips Lumileds Lighting Company menemukan LED yang diharapkan dapat menggantikan fungsi lampu yang biasa digunakan untuk penerangan. LED tersebut mengeluarkan cahaya yang sangat terang dengan warna putih. LED tersebut dinamakan LUXEON. Kantor R&D Lumileds berlokasi di San Jose dan Penang (Malaysia).

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Kehadiran LUXEON ini membuat berbagai peluang baru dalam aplikasi yang membutuhkan cahaya terang dengan ukuran yang kompak. Sudah dapat kita temukan yaitu pada Lampu Flash Handphone Camera, terlihat pada saat flash padam, akan terlihat berwarna kuning. Saat ini Philips sedang terus mengembangkan LUXEON untuk menggantikan lampu rumah tangga dan perkantoran. Bisa dibayangkan terangnya.

Saya sempat menemukan LUXEON yang berdaya 1 watt, bentuknya menempel pada Base berbentuk seperti bintang, atau sering disebut LUXEON Star, saat ini (10/2006) dijual dengan harga sekitar rp.75.000 per buahnya.

Baru-baru ini saya mendapatkan bingkisan dari sahabat saya, LUXEON dengan daya 3 watt, sering disebut sebagai LUXEON Emitter.

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Dikarenakan dayanya yang besar, LUXEON memerlukan pendingin (HeatSink) yang ditempelkan pada bagian belakang LED tersebut. Jika temperatur berlebihan, maka LED tersebut akan cepat mati/rusak.

Terlihat pada bagian bawah LUXEON Emitter terdapat plat besi sebagai penyalur panas untuk ditempelkan pada Pendingin (HeatSink).

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Sayang sekali, LUXEON membutuhkan masukan tegangan dan daya yang cukup kritis. Dibutuhkan tegangan masukan sebesar 3,2volt dan daya konstan sebesar maksimum hingga 350mA (untuk 1watt), 700mA (untuk 3watt).

Aplikasi yang hanya menggunakan resistor sebagai pembatas tegangan seperti LED pada umumnya tidak disarankan untuk LUXEON ini, ketika mendapatkan daya yang sangat besar, membuat LUXEON rusak.

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Foto di atas adalah aplikasi LUXEON dengan hanya menggunakan resistor, dan terbukti ketika dihubungkan dengan masukan arus yang terlalu besar membuat salah satu LUXEON mati seketika.

LUXEON DRIVERSaya teringat IC regulator yang dapat berfungsi ganda, sebagai Pengatur Tegangan juga bisa digunakan sebagai Pengarus Arus konstan, yaitu IC LM317.

IC ini cukup murah, berkisar Rp 2.000 – Rp 4.000,- dan beberapa komponen pendukung lainnya yang jumlahnya tidak lebih dari Rp 20.000,-

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Skemanya saya coba desain sebagai berikut:

Dengan Trimmer Potensiometer, dibantu Volt Meter, kita set hingga mempunyai tengangan output 3,2volt.Arus yang keluar dari rangkaian ini adalah 560mA.

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LUXEON Emitter saya rekatkan pada pendingin (Heatsink) bekas pendingin Prosesor komputer.

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Jadilah rangkaian uji coba ini sebagai berikut.

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Nah saatnya melihat cahaya LUXEON berdaya 3Watt ini..

Hasil yang saya cermati, cahaya sangat terang untuk sebuah led, bahkan bisa dikatakan cahayanya seperti penggunakan lampu neon putih.

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Sempat terpikir, bagus juga untuk menggantikan lampu kabin mobil, lampu belajar, dan lain-lain.Ternyata tidak sepanas yang dikira… Jadi Heatsink yang digunakan terlalu besar untuk LED tersebut. Walau tidak begitu panas, Tetap memerlukan Pendingin.

Membuat Charger Baterai dengan Arus Konstan

Dengan rangkaian ini, baterai akan diisi dengan arus konstan yang umumnya sepersepuluh dari kapasitas baterai ampere-jam. Misalnya baterai 60AH, maka baterai akan diisi dengan arus konstan 6 Amper.Rangkaian ini dibagi menjadi tiga bagian: sumber arus konstan, proteksi pengisian berlebih dan indikator tegangan baterai  terlalu rendah sebelum proses pengisian.

Rangkaian baterai charger arus konstan

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Charger baterai memiliki beberapa fitur berikut: Chaeger dapat mengisi 6V, baterai 9V dan 12V,

dengan cara mengubah nilai-nilai dioda zener ZD1 dan ZD2.

Arus konstan dapat diatur sesuai dengan kapasitas baterai dengan menggunakan potmeter dan multimeter secara seri dengan baterai.

Setelah baterai terisi penuh, akan mencapai tingkat tegangan tertentu (misalnya 13.5-14.2V untuk baterai 12V), memberikan indikasi dan pengisi baterai otomatis akan mati. Anda tidak perlu melepas baterai dari sirkuit.

Jika daya baterai habis di bawah batas, akan memberikan indikasi pemakaian baterai berlebih.

Arus bocor kurang dari 5 mA dan sebagian besar disebabkan zeners.

Sumber tegangan DC (VCC) bisa bervariasi berkisar dari 9V ke 24V.

Terdapat proteksi hubung singkat. 

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R2 dan T1 membatasi arus pengisian maksimal jika terjadi masalah atau terminal baterai hubung pendek. Untuk mengatur arus pengisian, setelah multimeter dihubungkan secara seri dengan baterai dan sumber, atur potmeter VR1 perlahan-lahan sampai arus pengisian yang diperlukan tercapai.

 Sesuaikan VR2 saat baterai terisi penuh (katakanlah, 13.5V untuk baterai 12V) sehingga VGS dari T5 diatur ke nol sehingga pengisian arus yang mengalir ke baterai berhenti. LED1 menyala untuk menunjukkan bahwa baterai telah terisi penuh. Saat LED1 menyala, internal LED dari optocoupler juga menyala dan transistor internal menjadi konduksi. Akibatnya, gerbang-sumber tegangan (VGS) dari MOSFET T5 menjadi nol dan pengisian berhenti.

Jika tegangan terminal baterai turun, misalkan 11V untuk baterai 12V, sesuaikan potmeter transistor VR3 sehingga T3 menjadi cut-off dan T4 menjadi konduksi. LED2 akan menyala untuk menunjukkan bahwa tegangan baterai rendah.

Nilai dari dioda zener ZD1 dan ZD2 akan sama untuk 6V, baterai 9V dan 12V. Pada tegangan yang lain, Anda perlu menyesuaikan nilai dari ZD1 dan ZD2. Untuk pengisian arus 1 mA sampai 1 A, tidak diperlukan pendingin untuk T5. Jika maksimum pengisian arus yang dibutuhkan adalah 5A, tambahkan LM236-5 dipasang seri dengan dioda D2, ubah nilai R11 sampai 1 kilo-ohm, ganti D1 dengan dua SB560 dipasang paralel dan menyediakan pendingin untuk T1 MOSFET. IRF540 dapat menangani hingga 50W.

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1 Watt LED Emergency Lamp Circuit Using Li-Ion BatteryPosted by Swagatam Majumdar

The DesignThe requested Li-Ion cell operated 1 watt LED emergency light circuit  may be easily built with the help of the below given schematic:

The voltage from the cell phone charger power supply is dropped to around 3.9V by adding diodes in the positive path of the supply. This should be confirmed with a DMM before connecting the cell. 

The voltage should be limited to around 4V so that the cell is never allowed to cros the over charge limit.

Although the above voltage will not allow the cell to get charged fully and optimally, it will ensure the cell doesn't get damaged due to over charge.

The PNP transistor is held reversed biased as long as mains AC stays active, while the Li-Ion cell is charged gradually charged.

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In case the mains AC fails, the transistor switches ON with the help of the 1K resistor and instantly illuminates the 1 watt LED connected across its collector and ground.

The above design can also be implemented using a transformerless power supply circuit. Let's the learn the complete design:

Before proceeding with the circuit details it should be noted that the following proposed design is not isolated from mains and therefore is extremely dangerous to touch, and it has not been verified practically. Build it only if you  personally feel sure about the design.

Moving on, the given 1 watt LED emergency light circuit using Li-Ion cell looks quite a straightforward design. Let's learn the functioning with the following points.

It's basically a regulated transformerless power supply circuit which can also be used  as a 1 watt LED driver circuit.

The present design perhaps becomes very reliable owing to the fact that the dangers normally associated with transformerless power supplies are effectively tackled here.

The 2uF capacitor along with the 4 in4007 diodes form a standard mains operated capacitive power supply stage.

The preceding stage which consists of the zener, the triac and the associated passive parts form a standard crowbar network.

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The main function of this crowbar network is to restrict the available voltage to precise levels set by the preset P1.

Here it should be set at around 4.5V, which becomes the charging voltage for the Li-ion cell. The final voltage that reaches the cell is around 3.9V due to the presence of the series diode 1N4007.

The transistor 8550 acts like a switch which activates only in the absence of power through the capacitive stage, meaning when AC mains is not present.

During the presence of mains power the transistor is held reverse biased due to the direct positive from the bridge network to the base of the transistor.

Since the charging voltage is restricted at 3.9V keeps the battery just under the full charge limit and therefore the danger of over charging it is never reached.

In the absence of mains power, the transistor conducts and connects the cell voltage with the attached 1 watt LED across the collector and ground of the transistor, the 1watt LED illuminates brightly....when mains power restores, the LED is switched OFF immediately.

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3 Watt, 5 Watt LED DC to DC Constant Current Driver CircuitPosted by Swagatam MajumdarThe following article provides a simple yet very decent solution for driving powerful LEDs rated at 3 watt or 5 watt. These LEDs are able to produce highly intense and powerful light outputs, however these are extremely vulnerable too with their operating parameter. Let's learn more how to operate these devices very safely  using a simple power supply.

We have seen quite many power supply and driver circuits in this blog using the IC LM338, that's because this particular device is so versatile with power regulation and control functions.

The same IC yet again takes the center stage in this application too. Here the IC LM338 has been configured in its standard mode and it perfectly executes the expected current as well as voltage regulations for driving a 3 watt or a 5 watt LED.

As shown in the circuit diagram below, in its standard mode the resistor 240 ohms is a regular placement, and the next resistor connected to it is the one which decides the voltage at the output of the IC. Here it has been calculated and set for producing around 3.3V at the output, which is the optimal voltage value for driving all types of white LEDs.

However the IC itself cannot control the current and normally would allow about 5 amp at the output.

We can see that the IC is associated with an additional active component which is the transistor connected to its ADJ pin.

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The transistor here is employed solely for controlling the current at the output to the specified limits.

The resistor across ground and base decides how much current would be allowed to the output.

As indicated in the diagram, 0.6 ohms will pass about 1 amp maximum current which becomes suitable for driving a 3 watt led safely, and if a 5 watt LED needs to be driven safely, this resistor must be replaced with a 0.3 Ohms, which will allow a maximum of 2 amps of current.

The input to the IC can be derived from a standard transformer bridge capacitor power supply or from a suitably rated battery supply.

In fact, the transistor and the associated base/emitter resistors are absolutely not required, because once the voltage is set to precise 3.3V, the current would automatically get adjusted as per the LEDs specs.

So the correct circuit should be as given below:

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How to Make a Simplest, Compact 1 Watt LED Driver Circuit at 220V/110V Mains VoltagePosted by hitman

White LEDs are the lighting solutions of the future, simply because these devices can be lit brightly at relatively negligible power consumption. As an example, 1 watt LEDs are getting very popular nowadays due to their mini size and intense point brightness outputs, and as usual these require just  a watt at 4 volts for generating dazzling illuminations.

In this article I will show you how to build a very simply 220 V or 110 V operated 1 watt LED driver circuit,that would cost you not more 1/2 a dollar, excluding the LED of course.

I have already discussed capacitive type of power supply in a couple posts, like in LED tube light circuit and in a transformerless power supply circuit, the present circuit also utilizes the same concept for driving the proposed 1 watt LED.

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In the circuit diagram we see a very simple capacitive power supply circuit for driving a 1 watt LED, which may be understood with the following points.

The 1uF/400V capacitor at the input forms the heart of the circuit and functions as the main current limiter component of the circuit. The current limiting function makes sure that the voltage applied to the LED never exceeds the required safe level.

However high voltage capacitors have one serious issue, these do not restrict or are not able to inhibit the initial switch ON mains power in rush, which can be fatal for any electronic circuit LEDs are no exceptions.

Adding a 56 Ohm resistor at the input helps to introduce some damage control measures, but still it alone cannot do the complete safeguarding of the involved electronics.

An MOV would certainly do, also what about a thermistor? Yep, a thermistor would also be a welcome proposition.

But these are relatively at the costlier side and we are discussing a cheap version for the proposed design, so we would want to exclude anything that would cross a dollar mark as far as the total cost goes.

So I thought of an innovative way of replacing an MOV with an ordinary, cheap alternative.

What is the function of an MOV? It's to sink the initial burst of high voltage/current to ground such that it is ground before reaching the LED in this case.

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Wouldn't a high voltage capacitor do the same function if connected across the LED itself. Yes it would surely operate the same way as an MOV.

The figure shows the insertion of another high voltage capacitor directly across the LED,  which sucks the instantaneous influx of voltage surge during power switch ON, it does this while charging up and thus sinks almost the entire initial voltage in rush making all the doubts associated with a capacitive type of power supply distinctly clear.

The end result as shown in the figure is a clean, safe, simple and a low cost 1 watt LED driver circuit, which can be built right at home by any eletronic hobbyist and used for personal pleasures and utility.

CAUTION: THE CIRCUIT SHOWN BELOW IS NOT ISOLATED FROM THE AC MAINS, THEREFORE IS EXTREMELY DANGEROUS TO TOUCH IN POWERED POSITION. 

In the above shown simple 1 watt led driver circuit, the two 4.7uF/250 capacitors along with the 10 ohm resistors form a kind of "speed breaker" in the circuit,

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this approach helps to arrest the initial switch ON surge inrush which in turn helps to safeguard the LED from getting damaged.

This feature can be replaced with an NTC which are popular for their surge suppressing features.

This enhanced way of tackling the initial surge inrush problem could be by connecting an NTC thermistor in series with the circuit or the load.

Please check out the following link for knowing how to incorporate an NTC thermister in the proposed 1 watt LED driver circuithttp://homemadecircuitsandschematics.blogspot.in/2013/02/using-ntc-resistor-as-surge-suppressor.html

DC to DC Double Cell Phone Charger CircuitPosted by hitman

I have already explained regarding a couple of DC to DC cell phone charging circuits, however all these are designed for charging a single cell phone. For

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charging more than one cell phone from an external DC source like an automobile battery, requires an elaborate circuit. A recent request from one of my follower Mr. Raja Gilse (via email), prompted me to design a circuit that is able to facilitate charging of many cell phones simultaneously, let's learn how to make the circuit.

Dear sir. Please tell me that what alterations should i do,  to charge two mobiles at a time from your "12V BATTERY OPERATED CELL PHONE CHARGER CIRCUIT". (from bright hub) I am using the circuit from last 8 months, it's fine. Please post that article in your new blog also.

Dear sir, i tried so many time to post this comment in your blog in the "simple dc to dc cell phone charger circuit" but in vain. Please answer here~Sir, i used another 10 ohm 2 watt resistor in parallel with the existing one, as i don’t have the higher watt resistor. It’s working fine. Thank you very much, i have one doubt,  earlier,  in bright hub in the same article you told to use 10 ohm resistor, but here it is 5 ohm which is suitable ?

I have another question out of this article; please guide me could I use three 1N4007 silicon diode instead of one 1N5408 silicon diode?My aim is to allow 3A current in only one direction. But i don’t have diode of 3A i.e. 1N5408. As 1N4007 is of 1 amps capacity could use three 1N4007 in parallel and like wise for 5A five 1N4007 in parallel, because i have number of 1N4007

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Use the circuit given below:

As you increase the limiting resistor value, the charging becomes slower, therefore a 5 Ohm resistor would charge the cell phone faster than a 10 Ohm, and so on.

I'll check the problem with the commenting in my blog...however other comments are coming normally as usual! Let's see. 

Thanks and Regards.Sir, please answer my question about diode asked in last e mail. . . Please. . .

Yes three diodes in parallel will do.Parts List R1 = 0.1 Ohms 2 watt,R2 = 2 Ohms 2 WattR3 = 3 Ohms 1 wattC1 = 100uF/25VC2 = 0.1 discT1 = BD140D1 = 1N5408IC1 = 7805

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The circuit of the double DC cell phone charger was successfully tried and built by Mr. Ajay Dussa over a home designed PCB, the following images of the PCB layout and the prototype were sent by Mr. Ajay.

4 to 5 Cell Phone Charger Circuit

The following circuit can be used for charging as many as 5 cell phones at a time. The circuit employs the versatile IC LM338 for producing the required power. The input is selected to be a 6V but can be as high as 24V.

A single cell phone can also be charged from this circuit.

The circuit was requested by Mr. Ram.

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How to Make a Simple DC to DC Cell Phone Charger CircuitPosted by hitmanIt is estimated that there are probably more cell phones in India than the number of toilets present here. Astonishing, but true. A cell phone charger is one mate of cell phone that cannot be ignored because a cell phone would become dead without a charger.

Normally a cell phone charger come as an integral part of a cell phone package and we use it in conjunction with our AC mains supply.

But what happens if your cell phone gasps for power in the middle of a journey, probably when you are driving or biking away on a middle of a highway?

A very simple yet reasonably effective DC to DC cell phone charger circuit is discussed in this article, which can be easily built at home even by a layman.

Though the proposed charger circuit won't charge your cell phone at the rate equal to a normal AC to DC charger, nevertheless it will complete the function without fail and won't betray you for sure.

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The circuit diagram can be understood with the following points:

We all know the general specs of a cell phone battery, it's around 3.7 volts and 800 mAH. It means the cell phone would require at around 4.5 volts for initiating the charging process. However a Li-Ion battery which is employed inside cell phones are pretty sensitive to bad voltages and may just blow off causing serious life and property issues. Keeping this in mind the cell phone internal circuitry is specifically dimensioned very strictly.

The parameters just won't permit any voltage which may be even slightly out of the range of the battery specifications. The use of the versatile IC 7805 in the circuit answers the above issue just perfectly, such that the charging voltage at its output becomes ideally suitable for charging the cell phone battery. A high wattage resistor connected at the output of the IC makes sure that the current to the cell phone stays well within the specified range, though this might have not been a problem anyway, the cell phone would just refuse to charge if the resistor was not included.

Pictorial DiagramYou can use this cell phone charger for charging you cell phone during emergencies when there's no mains AC outlets, the circuit may be powered from any 12 volt lead acid battery or similar DC power source.

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Parts ListR1 = 5 Ohm, 2 Watt,C1, C2 = 10uF/ 25V,D1 = 1N4007,IC1 = 7805, mounted on a heatsink,Battery, any 12 volt automobile battery

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