## Wednesday, September 4, 2019

### Laptop Charger To Recharge Vehicle Battery

Laptop chargers can be used to recharge car and motorcycle batteries by adjusting the charger output voltage. So that the battery will not over voltage or overcharged and the charger is not damaged.

Also read the detailed explanation of the process to recharge the battery.

The following video shows when the circuit is tested on a car battery with a capacity of 36 amperes hour), usually it is called 40AH.

CAUTION: Before charging the battery, check the battery water level first. And keep the battery cap loose in it's hole for better gas ventilation. Overcharging can blow up the battery. The maximum charging voltage for dry cell battery is around 13.8 volts, while for wet cell battery is around 14.4 volts, please refer to your battery specifications to prevent overcharging.

The maximum current needed by the battery when charging is about 10 percent of the battery capacity. So for a 36 amperes hour battery, the maximum charging current is 3.6 amperes.

The laptop charger has an output voltage of 19 volts and a maximum current of 3.95 amperes, as the following photo shows. So it has just enough current to charge a 36 ampere hour battery.

This simple circuit regulates the laptop charger voltage to match the battery charging voltage and current. The output of this voltage regulator can be adjusted by connecting some diodes in series.

Components list:
Tr = 2N3055 power transistor with heatsink
IC = LM7815 voltage regulator
C1 = C2 = condenser 22 mf 25 v
D1 = D2 = diode 1N4007
R = 22 kilo ohms resistor

The above circuit will reduce the voltage of 19 volts from the laptop charger to 15 volts with the help of IC LM7815. Furthermore, the IC supplies current to the base of the transistor 2N3055 through several series diodes.

Theoretically, a single diode will drop voltage by 0.6 volts. So for two diodes, the 15 volts IC output will be reduced to around 13.8 volts, before entering the transistor base. Those diodes can be jumpered to adjust the output voltage.

In the transistor, voltage will drop again about 0.6 volts. So the transistor output will be around 13.2 volts.

Condenser and resistor function as voltage stabilizer. Without this component a digital voltmeter will show a higher no-load voltage, which can be confusing.

two diodes = 13.6 volts
one diode = 14.03 volts
no diode = 14.50 volts

The photo below shows the arrangement of the circuit components on a matrix board.

The video shows that the battery condition is still quite good, it looks blue in the battery indicator. As shown by the yellow arrow in the following photo.

But the battery voltage is quite low at 12.55 volts. By using a jumper cable, the charging current can be adjusted by selecting the number of diodes connected. The test results on the charging current fot that car battery are:
two diodes = 0.4 amperes
one diode = 1.7 amperes
no diode = 2.6 amperes

I prefer to use the lowest output voltage, because I don't want the laptop charger to be overloaded. The charger is still being used to charge the laptop battery. And the 2N3055 power transistor can overheat, if it produces a higher output voltage. Even if a larger charging current is needed, a circuit with one diode is usually enough for a 36 amperes hour car battery.

Based on the 2N3055 transistor datasheet, it is capable of carrying collector currents (Ic) up to 15 amperes continuous, and a maximum power of 115 watts. From the test result it can be concluded that the transistor is still within safe limits. If you really need to make a car battery charger from a laptop adapter with a larger current, then the heatsink must be bigger.

If it is applied as a simple motorbike battery charger, the circuit as seen in the video is sufficient, easy and inexpensive. IC LM7815 is theoretically capable for carrying current up to 1 ampere. So to charge a small battery such as a 5AH motorbike battery, where the charging current is around 0.5 amperes, there is no need for a power transistor. But it needs to be ensured the IC capacity, because the specification can differ depending on the manufacturer. If this IC is hot, it needs to be cooled by heatsink.

Diodes arranged in series can also reduce the voltage to match the battery voltage, without the need for an IC and power transistor. But the diode has a small current limit, less than 1 ampere. If you use a lot of large current diodes arranged in series, usually the cost is more expensive than using an IC as a voltage regulator and power transistor.

The charging current will decrease as the battery voltage rises. If the battery voltage is the same as the charging voltage, the charging current will be very small. So to prevent overloading on the circuit, charging can be done in stages. The initial stage uses two diodes, then the number of diodes is reduced gradually until the battery reaches its maximum voltage.

There is another simple and popular circuit that uses incandescent lamp around 5 to 21 watts 12 volts, the size of the lamp is depended to the size of the battery. The lamp is connected in series to battery to limit the charging current, when using a laptop battery charger as a vehicle battery charger. But on this circuit, charging will not stop even though the battery is full. Because the charging voltage is much higher. So that the battery can be overcharged, and the charger can also be damaged.

## Tuesday, August 6, 2019

### Cas Laptop Untuk Cas Aki Mobil

Charger laptop dapat digunakan untuk mencas atau setrum aki mobil dan sepeda motor dengan menyesuiakan tegangannya. Agar aki tidak kelebihan tegangan (overcharged) dan charger tidak rusak.

Baca juga penjelasan detail tentang proses isi-ulang atau cas aki.

Video berikut memperlihatkan saat rangkaian ditest pada aki mobil berkapasitas 36 ampere jam (Ampere Hour), biasanya namanya digenapkan ke atas menjadi 40AH.

PERHATIAN: sebelum cas aki, check level air aki terlebih dulu. Dan tutup aki tetap dibiarkan longgar di lubangnya selama aki dicas agar ventilasi gas lebih baik. Cas berlebihan dapat meledakkan aki. Tegangan cas maximum untuk aki sel kering sekitar 13.8 volt, sedangkan untuk aki basah sekitar 14.4 volt, harap berpatokan pada spesifikasi aki anda untuk mencegah cas berlebihan (overcharged).

Arus maximal yang dibutuhkan aki saat pengisian adalah  sekitar 10 persen dari kapasitas aki. Jadi untuk aki 36 ampere jam, arus maximal cas adalah 3.6 ampere.

Charger laptop yang digunakan mempunyai tegangan 19 volt dan arus maximal 3.95 ampere, sebagaimana foto berikut. Sehingga cukup kuat untuk mengisi aki berkapasitas 36 ampere jam.

Rangkaian sederhana ini mengatur tegangan charger laptop agar sesuai dengan tegangan dan arus cas aki. Output dari regulator tegangan ini dapat disetel dengan menyambung serie dioda-dioda.

Tr = transistor daya 2N3055 dengan heatsink
IC = regulator tegangan LM7815
C1 = C2 = kondensor 22 mf 25 v
D1 = D2 = dioda 1N4007
R = resistor 22 kilo ohms

Rangkaian di atas akan menurunkan tegangan 19 volt dari charger laptop menjadi 15 volt dengan bantuan IC LM7815. Selanjutnya IC tersebut mensuplai ke basis transistor 2N3055 melalui beberapa dioda.

Secara teoritis, arus yang melalui satu buah dioda akan turun tegangannya sebesar 0,6 volt. Maka jika melalui dua buah dioda tegangan dari IC yang sebesar 15 volt akan berkurang menjadi sekitar 13,8 volt, sebelum memasuki basis transistor. Dioda-dioda tersebut dapat dijumper untuk menyetel tegangan keluaran.

Pada transistor tegangan akan turun lagi sebesar 0,6 volt, maka keluaran dari transistor akan menjadi sekitar 13,2 volt.

Kondensor dan resistor berfungsi sebagai perata tegangan. Tanpa komponen ini voltmeter digital akan menunjukkan tegangan tanpa beban yang lebih tinggi, sehingga dapat membingungkan.

Tegangan tanpa beban yang terukur adalah:
dua dioda = 13,6 volt
satu dioda = 14,03 volt
tanpa dioda =  14,50 volt

Foto di bawah memperlihatkan susunan rangkaian pada papan matrix.

Pada video terlihat kondisi aki yang masih cukup baik, terlihat warna biru pada indikator aki mobil. Sebagaimana ditunjukkan panah kuning di foto berikut.

Tapi tegangan aki sudah cukup rendah yaitu 12,55 volt. Arus pengisian bisa diatur dengan memilih jumlah dioda yang tersambung, dengan menggunakan kabel jumper. Hasil test pada arus pengisian aki.mobil ini adalah:

dua dioda = 0,4 ampere
satu dioda = 1,7 ampere
tanpa dioda =  2,6 ampere

Saya lebih suka menggunakan tegangan output yang paling rendah, karena saya tidak mau charger laptop kelebihan beban. Charger tersebut masih digunakan untuk mengisi baterai laptop. Dan transistor daya 2N3055 bisa kepanasan, jika menggunakan tegangan output yang lebih tinggi. Jikapun dibutuhkan arus pengisian yang lebih besar, maka rangkaian dengan satu dioda biasanya sudah cukup untuk aki mobil 36 ampere jam.

Berdasarkan datasheet transistor 2N3055 mampu mengalirkan arus kolektor (Ic) sampai 15 ampere kontinyu, dan daya maximum 115 watt. Jika dilihat dari data test maka transistor masih dalam batas aman. Jika memang perlu membuat cas aki mobil dari adaptor laptop dengan arus lebih besar, maka pendingin (heatsink) harus diperbesar.

Jika diterapkan sebagai charger aki motor sederhana, rangkaian sebagai mana terlihat pada video sudah cukup memadai, mudah dan murah. IC LM7815 secara teoritis mampu mengalirkan arus sampai 1 ampere. Maka untuk mengisi aki kecil seperti aki motor 5AH, dimana arus pengisian sekitar 0.5 ampere, maka tidak lagi diperlukan transistor daya. Tapi perlu dipastikan dulu kemampuan IC yang dipakai, karena spesifikasi bisa berbeda tergantung pabrikan. IC ini jika panas maka perlu diberi pendingin (heatsink).

Dioda yang dirangkai serie dapat juga menurunkan tegangan hingga sesuai dengan tegangan cas aki, tanpa perlu IC dan power transistor. Tapi dioda mempunyai batas arus yang kecil, kurang dari 1 ampere. Jika menggunakan banyak dioda arus besar yang disusun serie, biasanya biayanya jadi lebih mahal dibanding menggunakan IC sebagai penyesuai tegangan dan power transistor.

Arus pengisian akan mengecil seiring naiknya tegangan aki.mobil ini. Jika tegangan aki sudah sama dengan tegangan charger maka arus pengisian akan sangat kecil. Maka untuk mencegah pembebanan berlebihan pada sirkuit, dapat dilakukan pengisian bertahap. Tahap awal menggunakan dua dioda, selanjutnya jumlah dioda dikurangi bertahap sampai aki mencapai tegangan maximalnya.

Ada sirkuit lain yang sederhana dan populer yang menggunakan lampu pijar sekitar 5 sampai 21 watt 12 volt, ukuran lampu disesuaikan dengan besarnya aki. Lampu disambung serie untuk membatasi arus pengisian, saat menggunakan pengisi baterai laptop sebagai pengisi aki kendaraan. Namun pada sirkuit ini, pengisian tidak akan berhenti meskipun aki sudah penuh, karena tegangan charger jauh lebih tinggi. Sehingga aki bisa overcharged, dan charger juga bisa rusak.

## Sunday, July 28, 2019

### Scenery Of LRT Rawamangun Kelapa Gading Public Trial

This video shows the scenery viewed from inside the Jakarta LRT (Light Rail Transit) during a public trial.

The stations that are traveled are: North Boulevard, South Boulevard, Pulomas, Equestrian, Velodrome. Then from the Velodrome station in Rawamangun go back again to North Boulevard at Kelapa Gading. The length of this route is around 5.8 km.

The following photo shows the card during a public trial.

View of the Bella Terra building.

The photo below is taken when the LRT train crossed the Perintis Kemerdekaan road.

Below is scenery of three buildings with unique architecture, they are like buildings in Korea, on the way to Kayu Putih Raya.

## Saturday, June 29, 2019

### Pemandangan Saat Menjajal LRT Rawamangun Kelapa Gading

Video ini memperlihatkan pemandangan dari dalam LRT Jakarta (Light Rail Transit) saat uji coba publik.

Stasiun yang dilalui adalah: Boulevard Utara, Boulevard Selatan, Pulomas, Equestrian, Velodrome. Kemudian dari stasiun Velodrome di Rawamangun kembali lagi ke Boulevard Utara di Kelapa Gading. Panjang rute ini sekitar 5,8 km.

Foto berikut memperlihatkan kartu saat uji coba publik.

Pemandangan gedung Bella Terra

Foto di bawah adalah saat kereta LRT melintas di atas jalan Perintis Kemerdekaan.

Saat melalui tiga gedung dengan arsitektur unik, mirip gedung di Korea, di atas jalan Kayu Putih Raya.

## Tuesday, June 4, 2019

### Hippopotamus Attraction At Gelanggang Samudra Ancol

This attraction is part of the Aneka Satwa show at the Gelanggang Samudra Ancol, Jakarta. Starting with the action of 2 beavers who are good at playing basketball, selling meatballs, riding bicycle. Followed by a sun bear who is smart at catching hula hoop, drive a car. Ended with the appearance of a 1-ton hippo named Ratna accompanied by Javanese music. The hippo is fed vegetables and fruit while showing its mouth open very wide.

In the photo below the fat and cute hippo looks like a very big puppy.

## Tuesday, May 14, 2019

### Atraksi Satwa Kuda Nil di Gelanggang Samudra Ancol

Atraksi ini adalah bagian dari pertunjukan Aneka Satwa di Gelanggang Samudra Ancol. Dimulai dengan aksi 2 ekor berang-berang yang pintar main basket, jualan bakso, naik sepeda. Diikuti dengan beruang madu yang pintar menangkap hula hup, kendarai mobil. Diakhiri dengan penampilan kuda nil seberat 1 ton bernama Ratna yang diiringi musik Jawa. Kuda nil diberi makan sayur dan buah sambil menunjukkan mulutnya yang terbuka sangat lebar.

Pada foto di bawah kuda nil yang gemuk dan lucu tampak seperti anak anjing tapi berukuran sangat besar.

## Thursday, April 18, 2019

### MRT Jakarta Beautiful Views on Flyover

The following YouTube video records the beautiful scenery of Jakarta during a public trial of Mass Rapid Transit (MRT) or also called Integrated Moda Raya.

In this first phase the MRT route that has been operating is from Lebak Bulus to the Indonesian Hotel Roundabout and vice versa, as shown below.

The underground route (subway) is illustrated in red, of course there are no scenery to see there, only the scenery inside each station. The subway stations are: Bunderan Hotel Indonesia, Dukuh Atas, Setiabudi, Bendungan Hilir, Istora, Senayan.

Flyover route is marked in blue. On this route there are many beautiful sights that are worth recording. The flyover stations are: Sisingamangaraja, Blok M, Blok A, Haji Nawi, Cipete Raya, Fatmawati, Lebak Bulus.

I start riding at Bendungan Hilir station and get off at the Hotel Indonesia roundabout. From the Hotel Indonesia roundabout ride again to Lebak Bulus, this is the farthest distance and it takes about 30 minutes with a distance of about 15 kilometers. From Lebak Bulus, I ride again to Sisingamangaraja.

As quoted from Jakartamrt, carriage or train in rail transport industry is called rolling stock. It has dimensions of 20 meters in length, 2.9 meters in width, and 3.9 meters in height. With a dominant color of blue and metallic gray, the carriages are made of stainless steel with an empty weight per train reaching 31 to 35 tons, made by Nippon Sharyo, Japan

The inside of the train is shown in the photo below. The train has a maximum carrying capacity of 332 people. In this phase 1, PT MRT Jakarta provides 16 trains. One series consists of six trains, the carrying capacity of one series reaches 1,950 people.

It is estimated to be able to carry more than 174 thousand people per day. Headway or time between vehicles is five minutes during rush hour, and about ten minutes outside rush hour.

The following photo shows when the train is above the TB Simatupang highway, the train is heading to Fatmawati station from Blok M. BPJS Cilandak employment office is located right under the Fatmawati station, the address is: Jl. R.A.Kartini No.18. Starting in 2018, the employment claim is processed online only, the employee then goes to the BPJS office according to the online queue schedule to complete the document. With the MRT, it will be easier to come to the BPJS office. Fatmawati station is also close to the bus stop for the Soetta-Cinere Airport Bus route, before the gas station.

The photo below is a scenere or railway depot at Lebak Bulus. Lebak Bulus station is close to Transmart Lebak Bulus (Carrefour), and Grand Mercure Simatupang hotel (Mercure Lebak Bulus).

During public trials (Uji Coba Publik), MRT tickets can be purchased at Bukalapak.com, and it is free to ride. The following photo shows the mark on passenger during a public trial.

When fully operational, the ticket can be purchased at the Ticket Office and at the Automatic Ticketing Machine (Ticket Vending Machine) as shown below.

Also read Cinere Bellevue bus to Soekarno Hatta airport (Soetta), via: Pangkalan Jati, Pondok Labu, One Bellpark, Fatmawati, Jakarta Outer Ring Road (JORR).

The photo below shows Transjakarta route 1E Pondok Labu - Blok M being parked at the DDN (Departemen Dalam Negeri) Pondok Labu park.

TransJakarta Blok M-Ciledug bus corridor 13 via elevated roads specifically for TransJakarta buses.

## Tuesday, March 19, 2019

### MRT Jakarta Indahnya Pemandangan Di Flyover

Video YouTube berikut ini merekam cantiknya pemandangan Jakarta saat uji coba publik Mass Rapid Transit (MRT) atau disebut juga Moda Raya Terpadu.

Pada fase pertama ini rute MRT yang sudah beroperasi adalah dari Lebak Bulus menuju Bunderan Hotel Indonesia dan sebaliknya, sebagaimana gambar di bawah.

Jalur bawah tanah (subway) tergambar dengan warna merah, tentu saja tidak banyak pemandangan di situ, hanya pemandangan di dalam setiap stasiun. Stasiunnya: Bunderan Hotel Indonesia, Dukuh Atas, Setiabudi, Bendungan Hilir, Istora, Senayan.

Jalur layang (flyover) ditandai dengan warna biru. Di jalur ini banyak pemandangan cantik yang layak direkam. Stasiunnya: Sisingamangaraja, Blok M, Blok A, Haji Nawi, Cipete Raya, Fatmawati, Lebak Bulus.

Saya naik dari stasiun Bendungan Hilir dan turun di Bunderan Hotel Indonesia. Dari Bunderan HI naik lagi menuju Lebak Bulus, ini adalah jarak terjauh dan ditempuh sekitar 30 menit dengan jarak sekitar 15 kilometer. Dari Lebak Bulus naik lagi menuju ke Sisingamangaraja.

Sebagaimana dikutip dari jakartamrt,  gerbong atau kereta dengan istilah perkeretaapiannya disebut rolling stock, memiliki dimensi panjang 20 meter, lebar 2,9 meter, dan tinggi 3,9 meter. Dengan warna dominan biru dan abu-abu metalik, gerbong terbuat dari bahan baja antikarat (stainless steel) dengan berat kosong per satu kereta mencapai 31 hingga 35 ton, dibuat oleh Nippon Sharyo, Jepang

Bagian dalam kereta terlihat pada foto di bawah. Kereta memiliki kapasitas angkut maksimum 332 orang. Di fase 1, PT MRT Jakarta menyediakan 16 rangkaian kereta. Satu rangkaian terdiri dari enam kereta, maka kapasitas angkut satu rangkaian mencapai 1.950 orang.

Estimasi akan dapat mengangkut lebih dari 174 ribu orang per harinya. Headway atau rentang waktu antarkereta lima menit pada jam sibuk, dan sekitar sepuluh menit di luar jam sibuk.

Foto berikut saat kereta berada di atas jalan TB. Simatupang menuju stasiun Fatmawati dari arah Blok M. Di bawah stasiun Fatmawati terletak kantor BPJS Ketenagakerjaan (Badan Penyelenggara Jaminan Sosial, Jamsostek) Cilandak, beralamat: Jl. R.A.Kartini No.18. Mulai tahun 2018 cara klaim bpjs ketenagakerjaan online, baru kemudian karyawan mendatangi kantor BPJS sesuai jadwal antrian yang didapat secara online tersebut untuk melengkapi dokumen. Dengan adanya MRT maka akan lebih mudah untuk datang ke kantor BPJS. Stasiun Fatmawati juga dekat dengan bus stop rute bandara Soetta-Cinere Airport Bus, sebelum pompa bensin.

Foto di bawah adalah pemandangan suasana tempat parkir kereta atau depo di Lebak Bulus. Stasiun Lebak Bulus dekat dengan Transmart Lebak Bulus (Carrefour), dan hotel Grand Mercure Simatupang (Mercure Lebak Bulus).

Pada saat uji coba publik, ticket MRT dapat dibeli di Bukalapak.com, dan harganya gratis. Foto berikut terlihat tanda pada penumpang saat uji coba publik.

Jika sudah beroperasi ticket dapat dibeli di Loket (Ticket Office) dan di Mesin Ticket Otomatis (Ticket Vending Machine) sebagaimana foto di bawah.

Baca juga bus Cinere Bellevue ke bandara Soekarno Hatta (Soetta), lewat: Pangkalan Jati, Pondok Labu, One Bellpark, Fatmawati, Jakarta Outer Ring Road (JORR).

Foto di bawah tampak Transjakarta rute 1E Pondok Labu - Blok M sedang parkir di taman DDN (Departemen Dalam Negeri) Pondok Labu.

Bus TransJakarta Blok M-Ciledug koridor 13 melalui jalan layang khusus bus TransJakarta.

Baca juga uji coba publik Light Rail Transit RLT Jakarta Kelapa Gading - Rawamangun.

## Friday, March 1, 2019

### Joule Thief With Fluorescent Ballast And Relay

Fluorescent lamp ballast or neon lamp ballast should not be thrown away because they can be used to make a joule thief. Joule thief is a simple and inexpensive circuit to increase the voltage by oscillation. It is usually used for small loads. Joule thief can be interpreted as an energy thief. This circuit is also known by other names such as blocking oscillator, joule ringer, vampire torch. The output of this circuit is high voltage reaching around 200 volts with direct current (dc). Usually it is using power transistor as switch to connect and disconnect current, and transformer with primary and secondary winding.

In this circuit there is no transformer with two windings (primary and secondary), only one winding. And it is using relay to replace power transistor. The photo below shows the arrangement of parts for this circuit. The LED lamp will be connected to those two pins of the capacitor. Because the circuit is very simple, it can be assembled without a printed circuit board (PCB) or matrix board.

Below is schematic diagram of this joule thief.

Ballasts (B) it was used for fluorescent lamp with a current capacity of 0.33 amperes and a voltage of 220 volts with a power of 15 watts.

Relay (R) with rated voltage of 5 volts, in the video the relay has 8 pins, but a 5 pins relay can do also. It functions as a circuit breaker to stop current from ballast to negative. Tested with 12 volt relay but it turns out that the power produced is lower than to the 5 volts relay. This is because the 5 volts relay draws a larger current so that the magnetic field in the coil is stronger too. Therefore the output power is also greater.

Capacitors (C) is 100 nano farads, with a voltage above 220 volts. It is collecting voltage spikes that arise when the relay cut off the current. If the current is cut off, the magnetic field in the ballast and relay coil collapses and induces high voltage in ballast coil and relay coil. This high voltage is connected in series to the supply voltage and capacitor. So that the capacitor accumulates high voltage induction plus the voltage from the supply (battery voltage).

Diode (D) 1N4007 prevents the high voltage charge in capacitor to turn back towards the ballast.

The following YouTube video shows when the circuit was tested.

If this circuit is supplied by two 9 volts batteries arranged in series, so that it has a voltage of 18 volts, it can turn on a 220 volt Philips LED lamp with 4 watts of power.

The Philips LED voltage (output) is around 56 volts with a current of 2.25 mA, so the output power or LED lamp power is 0.126 watts. Whereas the actual voltage is measured at about 17 volts with a current of 12.5 mA, so the input power is 0.213 watts, then the efficiency is around 59%. This efficiency is quite good for a very simple circuit.

Please note that not all LED bulb can be turned on by low voltage. LED bulb that cannot use dimmers, cannot work at low voltage. It is usually written as non-dimmable.

If supplied with one 9 volts battery, it is enough to turn on 40 LEDs arranged in series brightly.

For a 5 mm diameter LEDs load arranged in series, the input voltage is 9.6 volts, with an input current of 14.8 mA, so the input power is 0.142 watts. The output voltage of the LEDs series circuit is 88.4 volts with a current of 0.65 mA, so the output power is 0.057 watts. Then the efficiency is the output power divided by the input power, and the the result is 40%. This efficiency is low because the load is too small. While the power absorbed by the circuit is about the same when the circuit is given a greater load, the Philips LED bulb.

## Thursday, February 21, 2019

### Joule Thief Dengan Relai Dan Neon Ballast

Ballast bekas lampu neon atau trafo neon jangan dibuang karena bisa dimanfaatkan untuk membuat joule thief. Joule thief adalah rangkaian sederhana dan murah untuk menaikkan tegangan dengan cara osilasi. Biasanya digunakan untuk beban kecil. Joule thief dapat diartikan sebagai pencuri energi. Sirkuit ini juga dikenal dengan nama lain seperti blocking oscillator, joule ringer, vampire torch. Biasanya menggunakan power transistor sebagai saklar yang menyambung dan memutus arus, dan trafo dengan lilitan primer dan sekunder.

Pada rangkaian ini tidak ada trafo dengan dua lilitan (primer dan sekunder), hanya satu lilitan saja. Dan menggunakan relai menggantikan power transistor. Output dari rangkaian ini adalah tegangan tinggi mencapai sekitar 200 volt dengan arus searah (direct current, dc).

Ballast (B) bekas lampu neon dengan kapasitas arus 0.33 ampere dan tegangan 220 volt dengan daya 15 watt.

Relai (R) dengan tegangan 5 volt, pada video adalah relai dengan 8 kaki, tapi relai 5 kaki juga bisa, berfungsi sebagai pemutus arus dari ballast ke negatif. Dicoba dengan relai 12 volt tapi ternyata daya yang dihasilkan kalah dibanding dengan relai 5 volt. Hal ini karena relai 5 volt menarik arus yang lebih besar sehingga medan magnet pada koilnya lebih kuat juga, maka daya output yang dihasilkan juga lebih besar.

Kapasitor (C) senilai 100 nano farad, dengan tegangan di atas 220 volt, mengumpulkan tegangan tinggi (voltage spike) yang timbul saat relai memutus arus. Jika arus terputus, medan magnet pada ballast dan koil relai runtuh dan menginduksi tegangan tinggi pada kumparan ballast dan koil relai. Tegangan tinggi ini terhubung serie dengan tegangan suplai dan kapasitor. Sehingga pada kapasitor terkumpul tegangan tinggi hasil induksi ditambah tegangan dari suplai (baterai).

Dioda (D) 1N4007 mencegah tegangan tinggi muatan kapasitor berbalik arah kembali menuju ballast.

Foto di bawah memperlihatkan susunan rangkaian. Lampu LED akan disambung pada ke dua kaki kapasitor. Karena rangkaian sangat sederhana, maka bisa dirakit tanpa papan PCB (Printed Circuit Board) maupun papan matrix.

Video YouTube berikut memperlihatkan saat rangkaian ditest.

Rangkaian ini jika disuplai dengan dua buah baterai 9 volt yang tersusun serie sehingga bertegangan 18 volt, mampu menyalakan lampu Philips LED 220 volt dengan daya 4 watt.

Tegangan pada lampu LED Philips (output) sekitar 56 volt dengan arus 2,25 mA, sehingga daya output atau daya lampu LED adalah 0,126 watt. Sedangkan pada input terukur tegangan aktual sekitar 17 volt dengan arus 12,5 mA, sehingga daya input adalah 0,213 watt, maka effisiensi sekitar 59%. Effisiensi tersebut cukup baik untuk rangkaian yang sangat sederhana.

Harap diperhatikan bahwa tidak semua lampu LED yang bisa menyala dengan tegangan rendah. Lampu LED yang tidak bisa menggunakan dimmer (peredup), tidak bisa bekerja pada tegangan rendah. Biasanya tertulis sebagai non-dimmable.

Jika disuplai dengan satu buah baterai 9 volt, maka cukup untuk menyalakan 40 buah LED tersusun serie dengan terang.

Untuk beban LED diameter 5 mm yang dirangkai serie, tegangan input adalah 9,6 volt, dengan arus input 14,8 mA, sehingga daya input adalah 0,142 watt. Pada output tegangan rangkaian serie LED adalah 88,4 volt dengan arus 0,65 mA, sehingga daya output adalah 0,057 watt. Maka effisiennya adalah daya output dibagi daya input hasilnya 40%. Effisiensi ini rendah karena beban yang terlalu kecil. Sedangkan daya yang diserap rangkaian lebih kurang sama saat rangkaian diberi beban yang lebih besar yaitu bohlam LED Philips.

## Tuesday, January 22, 2019

### LEDs Series Connection For 9 Volts, 12 Volts, 220 Volts

Light-emitting diode (LED) is a semiconductor light source that emits light when a current passes through it. This article explain about LED light design made of a number of 5 mm diameter LEDs with series connection. In the schematic above, if 20 mA forward current flow from the anode (A, positive) to the cathode (C, negative), the forward voltage (V) will emerge on the LED pins as below:

That LED forward voltage data of various light colors is quoted from kithub.cc. Specifications can be different depending on the LED manufacturer. The average forward voltage can be considered at least 1.8 volts, with a safe maximal value is 3.3 volts. While the maximum reverse voltage is usually 5 volts. LED forward voltage is also often referred to as LED voltage drop.

The YouTube video above shows a series of LEDs when tested with various voltage levels.

The video shows that one LED can be turned on with a 3 volts CR2032 coin battery.

With a 9 volts Eveready battery, they are 3 LEDs arranged in series. Seen on video and photo above that the rightmost LED is not connected to the battery. And the brightest one is white LED.

By using a 12 volt adapter, the number of LEDs arranged in series is 4 pieces. Seen in the photo above that all four LEDs are on. The multi tester display shows about 11.46 volts. This series circuit can be applied to 12 volts LED light for motorbike and car. Because vehicle electric system voltage can raise up to 14.4 volts, so 5 LEDs in series will be more durable to compromise that voltage raise.

For 220 volts voltage like the above photo, the number of LEDs that are needed as below:

220/3 = 73.33 pieces

Rounded up to make it safer to 74 LEDs, and they can be connected directly to 220 VAC without transformer.

But the video only uses 40 LEDs. Then there must be a resistor to limit the current supplied to those series LEDs. For 5 mm diameter LEDs, the maximum allowable current is around 20 milliamperes.

As shown in the schematic above, there are only 2 LEDs in series to represent 40 pieces. To find the resistor value, you can use the formula as below:

R = (VT - VL) / i

R = resistor value

VT = total voltage = supply voltage

VL = LEDs in series circuit voltage = number of LEDs multiplied by LED voltage

i = LED current

The supply voltage (VT) is 220 volts.

The LED circuit voltage (VL) is 40 x 3 = 120 volts.

The LED current (i) is 20 mA = 0.020 amperes maximum

So the resistor value (R) = (220 - 120) / 0.020 = 5,000 ohms = 5 kilo ohms

But in the video the circuit is using 22 kilo ohms, because of safety considerations. And also, if the current is too big, the LED light is too bright so it can dazzle the camera.

As it is a series circuit, the current through the resistor equals the current through all LEDs. For 22 kilo ohms resistor, the current calculation as below:

i = VR / R = 100 / 22,000 = 0.0045 amperes = 4.5 miliamperes

And the resistor power is = P = V x i = 100 x 0.0045 = 0.45 watts

So using a 1 watt resistor is quite safe, it will not hot. If the resistor value is reduced to make brighter LED light, then the resistor power must be increased so that it does not overheat.

For alternating current, only half wave current is used to power the LED. The other half wave is stopped by LEDs. That is why the LED light in video looks like vibrating when the circuit is connected to a 220 VAC grid.

WARNING: do not touch the circuit when it is connected to a high voltage grid.