Showing posts with label to. Show all posts
Showing posts with label to. Show all posts
Thursday, December 26, 2013
LDR Based 12V White LED Driver for up to 30 LEDs
While we have now published quite a few LED driver circuits, to date we have not published a design to drive a bunch of high-brightness white LEDs. Such a circuit is now quite desirable as the price of white LEDs has fallen and you can have a handful for not a lot of dollars. However, white LEDs do present a problem because they need a higher drive voltage than monochromatic types such as red, green, orange etc.
Instead of around 1.8V to 2V or thereabouts, they normally require more than 3V to produce their rated brightness. In fact, if you are driving a bunch of them you need to drive them all at constant current otherwise their individual brightness tends to vary markedly. However, if you only have a 12V supply available, you can only put two or maybe three LEDs in series together with a constant current source and this leads to poor efficiency.
The approach in this circuit is to boost the 12V supply to something around 21V and this means that we can have groups of five LEDs, each in series with their own current source transistors. The result is a single PC board with the drive circuitry and 30 white LEDs. It can be used for lighting in caravans and recreational vehicles, emergency lighting or whatever application you can think of. Current drain is around 190mA at 12V.
Now let’s have a look at the circuit of Fig.1. It uses just one IC (a 4093 quad NAND Schmitt trigger gate package), a few transistors and diodes, 30 white LEDs and not much else. So where is the familiar boost converter circuit? Answer: there isn’t one or least not one with an inductor switched by a Mosfet. Instead, there is a charge pump inverter, comprising IC1c, transistors Q2 & Q3, Schottky diodes D1 & D2 and a few capacitors. It works as follows:
IC1c is connected as an inverter oscillator and its running frequency of about 30kHz is determined mainly by the 6.8kΩ resistor between pins 8 & 10 together with the 4.7nF capacitor at pin 8. This produces a rectangular waveform (not quite square but pretty close) at pin 10 to drive complementary switching transistors Q2 & Q3.
The waveform at their commoned emitters drives a diode pump consisting of two 100μF capacitors and Schottky diodes D1 & D2. The waveform generated by the circuit can be seen in the scope photo of Fig.2.
Oscillator IC1c is controlled by an RS (Reset/Set) flipflop comprising the two NAND gates IC1a & IC1b and this is controlled by pushbutton switches S1 and S2. Normally, this has its pin 4 low and pins 1 & 6 are pulled high via 470kΩ resistors. Momentarily closing S1 (ON) pulls pin 6 low, causing the flipflop to change state so that pin 4 now goes high to enable IC1c which now oscillates at 30kHz.
The 30kHz waveform produced by transistors Q2 & Q3 drives the diode pump referred to earlier and this develops about 21V to drive the LED columns. Each column of five white LEDs is driven by its own current source transistor which has a 33Ω emitter resistor. The bases of all six current source transistors (Q4-Q9) are driven from pin 4 of IC1b via a 6.8kΩ resistor and clamped to a maximum of +1.2V by diodes D3 & D4.
Subtract the 0.6V between the base and emitter of each transistor and you are left with 0.6V across each 33Ω resistor, thus setting the LED drive current to 18mA. Switching the circuit off is accomplished by pushing the OFF switch, S2. This momentarily pulls pin 1 low to toggle the RS flipflop, thus causing pin 4 to go low. This disables IC1c, Q2 & Q3 and also turns off the current source transistors.
Note that there is an interesting wrinkle to this drive circuit, because there is no On/Off switch. This means that the current source transistors must be turned off otherwise they would continue to draw current from the 12V supply even when the circuit is nominally off. The current path may not be obvious but it is via the boost circuit’s diodes, D1 & D2.
As well as using the pushbutton switches S1 & S2 to turn the circuit on and off, there is also a facility to automatically turn the circuit on and off depending on ambient light levels. Links L1 & L2 can be used to provide Auto On and Auto Off respectively and these features can be used separately or together.
An LDR (light dependent resistor) is used to monitor the ambient light level. When light falls upon it, it pulls the base of Q1 low, causing pins 12 & 11 of IC1d to go low and its pin 11 to go high. When darkness falls (or the room lights go out), the process is reversed. Depending on whether you have one or both links connected, you can use the pushbuttons to turn the circuit on and off and have it turn on and/off automatically as well.
Q1 also drives a red high brightness LED (LED1) at very low current, via a 470kΩ resistor. This is a bit of a gimmick but it does have the benefit of showing that this part of the circuit is working, if you have to trouble-shoot it.
Pins 1 & 2, 5 & 6 and 8 & 9 of IC1 on the circuit are all swapped. The PC board overlay diagram is correct.
Continue Reading[..]
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| 30 White LEDs Driver Circuit Diagram |
Instead of around 1.8V to 2V or thereabouts, they normally require more than 3V to produce their rated brightness. In fact, if you are driving a bunch of them you need to drive them all at constant current otherwise their individual brightness tends to vary markedly. However, if you only have a 12V supply available, you can only put two or maybe three LEDs in series together with a constant current source and this leads to poor efficiency.
The approach in this circuit is to boost the 12V supply to something around 21V and this means that we can have groups of five LEDs, each in series with their own current source transistors. The result is a single PC board with the drive circuitry and 30 white LEDs. It can be used for lighting in caravans and recreational vehicles, emergency lighting or whatever application you can think of. Current drain is around 190mA at 12V.
Circuit description
Now let’s have a look at the circuit of Fig.1. It uses just one IC (a 4093 quad NAND Schmitt trigger gate package), a few transistors and diodes, 30 white LEDs and not much else. So where is the familiar boost converter circuit? Answer: there isn’t one or least not one with an inductor switched by a Mosfet. Instead, there is a charge pump inverter, comprising IC1c, transistors Q2 & Q3, Schottky diodes D1 & D2 and a few capacitors. It works as follows:
IC1c is connected as an inverter oscillator and its running frequency of about 30kHz is determined mainly by the 6.8kΩ resistor between pins 8 & 10 together with the 4.7nF capacitor at pin 8. This produces a rectangular waveform (not quite square but pretty close) at pin 10 to drive complementary switching transistors Q2 & Q3.
The waveform at their commoned emitters drives a diode pump consisting of two 100μF capacitors and Schottky diodes D1 & D2. The waveform generated by the circuit can be seen in the scope photo of Fig.2.
RS flipflop
Oscillator IC1c is controlled by an RS (Reset/Set) flipflop comprising the two NAND gates IC1a & IC1b and this is controlled by pushbutton switches S1 and S2. Normally, this has its pin 4 low and pins 1 & 6 are pulled high via 470kΩ resistors. Momentarily closing S1 (ON) pulls pin 6 low, causing the flipflop to change state so that pin 4 now goes high to enable IC1c which now oscillates at 30kHz.
The 30kHz waveform produced by transistors Q2 & Q3 drives the diode pump referred to earlier and this develops about 21V to drive the LED columns. Each column of five white LEDs is driven by its own current source transistor which has a 33Ω emitter resistor. The bases of all six current source transistors (Q4-Q9) are driven from pin 4 of IC1b via a 6.8kΩ resistor and clamped to a maximum of +1.2V by diodes D3 & D4.
Subtract the 0.6V between the base and emitter of each transistor and you are left with 0.6V across each 33Ω resistor, thus setting the LED drive current to 18mA. Switching the circuit off is accomplished by pushing the OFF switch, S2. This momentarily pulls pin 1 low to toggle the RS flipflop, thus causing pin 4 to go low. This disables IC1c, Q2 & Q3 and also turns off the current source transistors.
Note that there is an interesting wrinkle to this drive circuit, because there is no On/Off switch. This means that the current source transistors must be turned off otherwise they would continue to draw current from the 12V supply even when the circuit is nominally off. The current path may not be obvious but it is via the boost circuit’s diodes, D1 & D2.
Auto on/off
As well as using the pushbutton switches S1 & S2 to turn the circuit on and off, there is also a facility to automatically turn the circuit on and off depending on ambient light levels. Links L1 & L2 can be used to provide Auto On and Auto Off respectively and these features can be used separately or together.
An LDR (light dependent resistor) is used to monitor the ambient light level. When light falls upon it, it pulls the base of Q1 low, causing pins 12 & 11 of IC1d to go low and its pin 11 to go high. When darkness falls (or the room lights go out), the process is reversed. Depending on whether you have one or both links connected, you can use the pushbuttons to turn the circuit on and off and have it turn on and/off automatically as well.
Q1 also drives a red high brightness LED (LED1) at very low current, via a 470kΩ resistor. This is a bit of a gimmick but it does have the benefit of showing that this part of the circuit is working, if you have to trouble-shoot it.
Note:
Pins 1 & 2, 5 & 6 and 8 & 9 of IC1 on the circuit are all swapped. The PC board overlay diagram is correct.
Thursday, December 19, 2013
The expert group is making every effort to enhance the design of the Cell Phone Jammers system
The expert group is making every effort to enhance the design of the Cell Phone Jammers system.
The standard test signal I1: is GsM modulated carrier signal, and its structure in accordance with the GSM signal burst (burst, as burst or short burst. Below) structure, but its all modulation bits (including the burst of part of the training sequence) are directly random or pseudo-random data stream. (5) The standard test signal I2: a standard GSM modulation signal, but with the C1 signal is different from the unexpected part of the training sequence of the standard GSM training sequence, but the burst of data bits (including bits 58 and 59) are random or pseudo-random data stream. Using the same standard RF cable and adapters, including adapters, including the requirements of the GSM bands between the channel loss is less than 0.5dB, loss of value of the difference is less than 0.2dB; DCS frequency band between the loss of each channel is less than 1dB, loss value difference is less than 0.3dB, with characteristic impedance adapter should be within 50 ± 5 ohms. The table will contain the result of quantity computation of Cell Phone Jammers .I use the above principles and interface technology to develop a project: Highway display guidance system. Installed on the highway in front of the LED display shows real-time road vehicle traffic situation and weather and climate conditions, advise and guide the driver, the correct driver. The use of the system to some extent, eliminate a lot of traffic hazards, thereby safeguarding the smooth flow of road safety and peoples lives and property. The system consists of the control center and several display screen. Control center in real time the latest information sent to the display. Building control center communication link with the display terminal, the traditional method of laying fiber optic cable with the cable or the realization, or build a private wireless network allowing wireless. Because of the special nature of the highway, the control center and the distance between the display terminal is usually very far, two programs must invest a lot of money and huge construction effort.
Typically, short message service SMS-based wireless data transmission monitoring and control system for a point to multipoint wireless two-way data communication and remote control system, shown in Figure 1. System control center or command center for data, from computer networks, databases, electronic map and GSM communication interface. The main control center complete the information and data transceiver and finishing: on the one hand, to receive various control points to upload information and data, and put them in the appropriate database and distributed to the appropriate monitoring computer in order to achieve the various monitoring points monitoring and management; another aspect, a computer control center monitors the response issued by the various monitoring points of the control information, and to the information issued to the corresponding control points to achieve the point of monitoring equipment for control purposes.
Continue Reading[..]
The standard test signal I1: is GsM modulated carrier signal, and its structure in accordance with the GSM signal burst (burst, as burst or short burst. Below) structure, but its all modulation bits (including the burst of part of the training sequence) are directly random or pseudo-random data stream. (5) The standard test signal I2: a standard GSM modulation signal, but with the C1 signal is different from the unexpected part of the training sequence of the standard GSM training sequence, but the burst of data bits (including bits 58 and 59) are random or pseudo-random data stream. Using the same standard RF cable and adapters, including adapters, including the requirements of the GSM bands between the channel loss is less than 0.5dB, loss of value of the difference is less than 0.2dB; DCS frequency band between the loss of each channel is less than 1dB, loss value difference is less than 0.3dB, with characteristic impedance adapter should be within 50 ± 5 ohms. The table will contain the result of quantity computation of Cell Phone Jammers .I use the above principles and interface technology to develop a project: Highway display guidance system. Installed on the highway in front of the LED display shows real-time road vehicle traffic situation and weather and climate conditions, advise and guide the driver, the correct driver. The use of the system to some extent, eliminate a lot of traffic hazards, thereby safeguarding the smooth flow of road safety and peoples lives and property. The system consists of the control center and several display screen. Control center in real time the latest information sent to the display. Building control center communication link with the display terminal, the traditional method of laying fiber optic cable with the cable or the realization, or build a private wireless network allowing wireless. Because of the special nature of the highway, the control center and the distance between the display terminal is usually very far, two programs must invest a lot of money and huge construction effort.
Typically, short message service SMS-based wireless data transmission monitoring and control system for a point to multipoint wireless two-way data communication and remote control system, shown in Figure 1. System control center or command center for data, from computer networks, databases, electronic map and GSM communication interface. The main control center complete the information and data transceiver and finishing: on the one hand, to receive various control points to upload information and data, and put them in the appropriate database and distributed to the appropriate monitoring computer in order to achieve the various monitoring points monitoring and management; another aspect, a computer control center monitors the response issued by the various monitoring points of the control information, and to the information issued to the corresponding control points to achieve the point of monitoring equipment for control purposes.
Sunday, May 5, 2013
Build a Converter VGA to BNC Adapter
There are monitors which only have three BNC inputs and which use composite synchronization (‘sync on green’). This circuit has been designed with these types of monitor in mind. As can be seen, the circuit has been kept very simple, but it still gives a reasonable performance. The principle of operation is very straightforward. The RGB signals from the VGA connector are fed to three BNC connectors via AC-coupling capacitors. These have been added to stop any direct current from entering the VGA card. A pull-up resistor on the green output provides a DC offset, while a transistor (a BS170 MOSFET) can switch this output to ground. It is possible to get synchronisation problems when the display is extremely bright, with a maximum green component.
In this case the value of R2 should be reduced a little, but this has the side effect that the brightness noticeably decreases and the load on the graphics card increases. To keep the colour balance the same, the resistors for the other two colors (R1 en R3) have to be changed to the same value as R2. An EXOR gate from IC1 (74HC86) combines the separate V-sync and H-sync signals into a composite sync signal. Since the sync in DOS-modes is often inverted compared to the modes commonly used by Windows, the output of IC1a is inverted by IC1b. JP1 can then by used to select the correct operating mode. This jumper can be replaced by a small two-way switch, if required.
In this case the value of R2 should be reduced a little, but this has the side effect that the brightness noticeably decreases and the load on the graphics card increases. To keep the colour balance the same, the resistors for the other two colors (R1 en R3) have to be changed to the same value as R2. An EXOR gate from IC1 (74HC86) combines the separate V-sync and H-sync signals into a composite sync signal. Since the sync in DOS-modes is often inverted compared to the modes commonly used by Windows, the output of IC1a is inverted by IC1b. JP1 can then by used to select the correct operating mode. This jumper can be replaced by a small two-way switch, if required.
VGA to BNC adapter PCB layout
This switch should be mounted directly onto the PCB, as any connecting wires will cause a lot of interference. The PCB has been kept as compact as possible, so the circuit can be mounted in a small metal (earthed!) enclosure. With a monitor connected the current consumption will be in the region of 30 mA. A 78L05 voltage regulator provides a stable 5 V, making it possible to use any type of mains adapter, as long as it supplies at least 9 V. Diode D2 provides protection against a reverse polarity. LED D1 indicates when the supply is present. The circuit should be powered up before connecting it to an active VGA output, as otherwise the sync signals will feed the circuit via the internal protection diodes of IC1, which can be noticed by a dimly lit LED. This is something best avoided.
Resistors:
R1,R2,R3 = 470Ω
R4 = 100Ω
R5 = 3kΩ3
Capacitors:
C1,C3,C5 = 47µF 25V radial
C2,C4,C6,C7,C10 = 100nF ceramic
C8 = 4µF7 63V radial
C9 = 100µF 25V radial
Semiconductors:
D1 = LED, high-efficiency
D2 = 1N4002
T1 = BS170
IC1 = 74HC86
IC2 = 78L05
T1 = BS170
IC1 = 74HC86
IC2 = 78L05
Miscellaneous:
JP1 = 3-way pinheader with jumper
K1 = 15-way VGA socket (female), PCB mount (angled pins)
K2,K3,K4 = BNC socket (female), PCB mount, 75Ω
Monday, April 8, 2013
How to Create 1000 Watt Power Amplifier
Power amplifier has up to 1000 Watt power, this circuit made one channel only so if you want to create a stereo in it must be made one again, actually this is more suitable power amplifier in use for Sound System or outdoor, so if only in use for the house I think is less suitable.
Maybe youve seen or even have an active speaker and there is written 1500 watts PMPO (Peak Music Power Output), make no mistake this is different from Power Amplifier Active Speaker, I often dismantle such Active Speaker in it only a power with power no more than 150 watts by using the transformer 2-3 Ampere. PMPO is not a real power which is issued by the Power Amplifier, but counting all the speakers that there is, for example: if there are 5 pieces of speakers on each channel and each speaker has a power of 10 W then it is 100 W PMPO.
Maybe youve seen or even have an active speaker and there is written 1500 watts PMPO (Peak Music Power Output), make no mistake this is different from Power Amplifier Active Speaker, I often dismantle such Active Speaker in it only a power with power no more than 150 watts by using the transformer 2-3 Ampere. PMPO is not a real power which is issued by the Power Amplifier, but counting all the speakers that there is, for example: if there are 5 pieces of speakers on each channel and each speaker has a power of 10 W then it is 100 W PMPO.
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| 1000W Power Amplifier schematics |
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| Part List 1000W amplifier |
While this 1000 Watt Power Amplifier minimal use transformer 20 Ampere. And the output of Power Amplifier DC voltage contains approximately 63 volts, with currents and voltages of this magnitude, this 1000 Watt Power Amplifier will not hesitate hesitate to destroy your woofer speakers to connect. To overcome that then before the speaker on connects to 1000 Watt Power Amplifier must be in pairs Speaker Protector.
Actually if you want to create a Power Amplifier with great power does not have to make a Power Amplifier with great power. Example: you want to create a Power Amplifier with 10 000 Watt power. You do not have to assemble a Power Amplifier with power of 10,000 watts, but you assemble the power Power Amplifier Small but many, such as you assemble the Power Amplifier with 1000 Watts of power for as many as 10 pieces, it will produce 10 000 Watt Power Amplifier helpless.
Circuit uses power transistors pair of 5 x 5 x 2SA1216 and 2SC2922 and 2SC1583 use a differential amplifier that actually contains 2 pieces of transistors that are in containers together. Why use such built-in amplifier differental tujuanya so identical / similar, could have uses 2 separate transistors but can result in amplifier so it is not symmetrical.
Tips combining speaker.
To get the speakers with great power combining techniques can be used in parallel series, combining each group of speakers should sepaker they will have the same impedance, the same type (Woofer, Mid Range or tweeter) and the same power. Number of merging these speakers should consists of 4 , 9, 16 ff, see picture
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| Speaker wiring |
Example: The number of speakers have 4 pieces each of its 200 Watt power generated will be a speaker at = 200 x 4 = 800 Watt. If there are 9 speakers 200 W then the result = 9 x 200 W = 1800 Watt.
Saturday, March 23, 2013
230 Volt AC To Inverter Switching Circuit Diagram
Before three weeks i am introduced inverter circuit diagram but the circuit not included ac to inverter switching part so today i introducing a 230 Volt Ac to inverer switching circuit diagram .
Circuit showing a inverter switching . Here i have used bc 558 ,BC 548 and a relay for making this circuit . 230 volt connected to the base of the transistor Q1.When the power is ON positive volt coming to the base of the transistor so the relay circuit is open and load working in 230 V AC .When the power is OFF ground voltage coming to the base of the transistor so the Base of the Q2 is positive there for the relay circuit closed and load working in inverter input .Part list and applications are showing below.
Part List
| Component No: | Value | Usage |
| R1 | 100KΩ | Emitter Load |
| R2 | 10K Ω | Base Biasing |
| R3 | 180KΩ | Current Limiting |
| Q1 | BC558 | Switching |
| Q2 | BC548 | Switching |
| D1 | IN4007 | Relay Balancing |
| RL1 | 12 V | Inverter Switching |
Applications
* Inverter Switching
* AC Switching
Tuesday, March 19, 2013
How to Make 1 A Constant Current LED Driver Circuit
The article explains a simple circuit using the IC MBI6651 from MACROBLOCK. The IC has been specifically designed for operating high power LEDs safely by providing a constant current output. The circuit includes very few external components and therefore becomes very easy to assemble at home.
About the IC MBI6651
The IC MBI6651 is a high efficiency, step down DC to DC converter chip capable of driving high power LEDs at a safe 1 Amp constant current.
The IC requires just four passive external components for making it functional.
The output current of the IC can be externally set by selecting the appropriate resistor value.
The IC also features a PWM controlled dimming control of the connected LEDs.
Some of the other outstanding features of this IC includes UVLO meaning under voltage lockout, over temperature shut down, LED open circuit protection and LED short circuit protection, all these ensure complete safety to the IC from wrongly configured output loads.
Typical Application of this device are:
Automotive decoration and illumination
LED flood lights using high intensity, high power LED.
The IC also can be used as a constant current source in particular circuit applications.
Setting the output Current
The output current of the IC is fixed through an external resistor Rsen. The output current Iout and the adjustment resistor Rsen has the following relation:
Given Vsen=0.1V
Rsen=(Vsen/Iout)=(0.1V/Iout)
Where Rsen is the value of the external resistor. This resistor is connected across the pin outs SEN and Vsen of the IC.
The optimum current with Rsen 0.1 Ohms is 1000 mA or 1 Amp.
Optimizing External Component Selection
Inductor: Two issues specify the inductor type, the switching frequency and the ripple current. The involved calculation can be written as:
L1>{Vin - Vout - Vsen - (Rds(on) * Iout)} * D/fsw * delta.IL
where, Rds(on) is the on-resistance of the ICs internal MOSFET. The value is typically around 0.45 at 12V
D is the duty cycle of the IC, given as D = Vout/Vin
fsw is the switching frequency of the IC
While designing the inductor for the given circuit, along with the inductance the saturation current must also be taken into account,because these are two basic factors which typically affects the overall performance of the circuit.
The rule of thumb, the saturation current of the inductor should be selected 1.5 times greater than the LED current.
Moreover, selecting high values for the inductance provides better line and load regulation.
Refer circuit diagram
Selecting the Schottky diode
The diode D1 shown in the circuit diagram basically acts as the flywheel diode for nullifying the inductor back emf during the periods when the LED is switched OFF.
The diode must be selected with the following couple of important characteristics:
It should have a low forward voltage rating and maximum possible reverse voltage tolerance.
Selecting the capacitor
The general rule is always to select a capacitor value with a voltage tolerance 1.5 times higher than the supply voltage.
Preferably, a tantalum capacitor should be selected because these have high capacitance and low ESR characteristics.
The proposed circuit of 1 Amp constant current LED driver circuit is given below:
The basic operating parameters are given below:
Pin Out Specs:
About the IC MBI6651
The IC MBI6651 is a high efficiency, step down DC to DC converter chip capable of driving high power LEDs at a safe 1 Amp constant current.
The IC requires just four passive external components for making it functional.
The output current of the IC can be externally set by selecting the appropriate resistor value.
The IC also features a PWM controlled dimming control of the connected LEDs.
Some of the other outstanding features of this IC includes UVLO meaning under voltage lockout, over temperature shut down, LED open circuit protection and LED short circuit protection, all these ensure complete safety to the IC from wrongly configured output loads.
Typical Application of this device are:
Automotive decoration and illumination
LED flood lights using high intensity, high power LED.
The IC also can be used as a constant current source in particular circuit applications.
Setting the output Current
The output current of the IC is fixed through an external resistor Rsen. The output current Iout and the adjustment resistor Rsen has the following relation:
Given Vsen=0.1V
Rsen=(Vsen/Iout)=(0.1V/Iout)
Where Rsen is the value of the external resistor. This resistor is connected across the pin outs SEN and Vsen of the IC.
The optimum current with Rsen 0.1 Ohms is 1000 mA or 1 Amp.
Optimizing External Component Selection
Inductor: Two issues specify the inductor type, the switching frequency and the ripple current. The involved calculation can be written as:
L1>{Vin - Vout - Vsen - (Rds(on) * Iout)} * D/fsw * delta.IL
where, Rds(on) is the on-resistance of the ICs internal MOSFET. The value is typically around 0.45 at 12V
D is the duty cycle of the IC, given as D = Vout/Vin
fsw is the switching frequency of the IC
While designing the inductor for the given circuit, along with the inductance the saturation current must also be taken into account,because these are two basic factors which typically affects the overall performance of the circuit.
The rule of thumb, the saturation current of the inductor should be selected 1.5 times greater than the LED current.
Moreover, selecting high values for the inductance provides better line and load regulation.
Refer circuit diagram
Selecting the Schottky diode
The diode D1 shown in the circuit diagram basically acts as the flywheel diode for nullifying the inductor back emf during the periods when the LED is switched OFF.
The diode must be selected with the following couple of important characteristics:
It should have a low forward voltage rating and maximum possible reverse voltage tolerance.
Selecting the capacitor
The general rule is always to select a capacitor value with a voltage tolerance 1.5 times higher than the supply voltage.
Preferably, a tantalum capacitor should be selected because these have high capacitance and low ESR characteristics.
The proposed circuit of 1 Amp constant current LED driver circuit is given below:
The basic operating parameters are given below:
Pin Out Specs:
Courtesy: http://www.ledlabs.ru/pdf/macroblock/mbi6651.pdf
Wednesday, March 6, 2013
How to Make Any Light a Strobe Light Using Just Two Transistors
If you feel strobe lights very interesting but are disappointed by the fact that these wonderful light effects can be produced only through complex xenon tube then probably you are quite mistaken. It is very much possible to make any light a strobe light if you are equipped with a proper driving circuit capable of handling different lighting devices to generate the desired strobe light effect. The present article shows how a circuit as basic as a multivibrator may be modified in different ways and made compatible with ordinary bulbs, lasers, LEDs to produce spectacular light pulses.
A strobe light may be used for warning, scientific analysis or as an entertainment device, whatever may be the application the effects are simply dazzling. In fact it is possible to make any light a strobe light through a proper driving circuit. Explained with Circuit Schematics.
Introduction
A light when made to blink or flash indeed looks pretty eye-catching and that’s the reason why they are used in number of places as a warning device or for decorations. However a strobe light in particular may also be considered a flashing light yet is uniquely different from ordinary light flashers. Unlike them in a strobe light the ON/OFF pattern is so optimized that it produces sharp dazzling pulsed flashes of light. There’s no doubt why they are mostly used in conjunction with fast music to enhance a party mood. Nowadays green lasers are being popularly used as a strobing device in party halls and gatherings and have become hot favorite among the new generation. Whether it’s LEDs, lasers or an ordinary filament bulb, all can be made to flash or rather strobe using an electronic circuit capable of producing the required pulsed switching in the connected lighting element. Here we will see how we can make any light a strobe light using a simple electronic circuit.
The following section will acquaint you with the circuit details. Let’s go through it.
Pulsating any Light to Produce Strobing Effect
Through one of my previous articles we came across a nice little circuit able to produce interesting strobe effects over a few of the connected LEDs. But this circuit is only suitable for driving low power LEDs and thus cannot be applied to illuminate big areas and premises. The proposed circuit allows you to drive not only LEDs but also powerful lighting agents like incandescent bulbs, lasers, CFLs etc.
The first diagram shows the most basic form of a multivibrator circuit using transistors as the main active components. The connected LEDs can be made to strobe by suitably adjusting the two potentiometers VR1 and VR2.
The above circuit forms the base for all the following circuits through some suitable modifications and additions.
For example if you want to illuminate and pulsate a small torch bulb using it, you would just need to do the simple modifications as shown in the second diagram. Here by adding a PNP power transistor and triggering it through the collector of T2, a torch bulb is easily made to strobe. Off course, optimum effect is achieved only through proper adjustment of the two Pots.
As already discussed already in the previous section, green laser pointers are pretty popular nowadays; the diagram illustrated shows a simple method of converting the above circuit into a pulsating green laser pointer strobe light. Here, T3 and T4 form a typical current controlled transistor configuration – a must when vulnerable lasers are involved. The selection of R6 can be critical and will decide the current limiting threshold for a safe operating of the laser. A wrong calculation may instantly roast your costly laser bulb. The following formula may be used for calculating R6:
U = 0.6/Ilaser,
Where U = Operating voltage of the laser and the circuit.
I (laser) = Maximum safe operating current of the laser device.
The next diagram shows how an AC mains lamp may be used as a strobing light source using the above circuit. Here a triac forms the main switching component receiving the required gate pulses from T2’s collector.
Thus we see that through the above circuit designs it becomes very easy to make any light a strobe light simply by doing the relevant modifications.
Parts List
R1, R4, R5 = 680 Ohms,
R2, R3 = 10K
VR1, VR2 = 100K pot
T1, T2 = BC547,
T3, T4 = BC557
C1, C2 = 10uF/25V
Triac = BT136
LEDs = as per choice
Parts List
R1, R4, R5 = 680 Ohms,
R2, R3 = 10K
VR1, VR2 = 100K pot
T1, T2 = BC547,
T3, T4 = BC557
C1, C2 = 10uF/25V
Triac = BT136
LEDs = as per choice
Saturday, March 2, 2013
How to Make a Cheap LED Name Plate with Illuminated Back Light
LEDs are no doubt gaining popularity by leaps and bounds and probably most of the illuminated decorative articles today incorporate LED as the light source. These devices are relatively cheap, extremely bright and outstandingly efficient with their operations.
Digital displays today also incorporate LED technology and we all know how impressive they look with the involved digits distinctly visible with an illuminated back light.
The back illumination especially gives a fuller look and helps to highlight the display in a better way.
However these displays can be pretty expensive and require microcontroller ICs for producing the involved illuminations. A new hobbyist may find it difficult to grasp and make such displays at home.
Using LEDs in series for designing alphanumerical displays consisting of the desired names and numbers looks good but these dont produce the effects which is generally obtained from a back illuminated displays.
A cheap way of making a back illuminated display or a name plate having the desired alphabets is explained here, lets see how we can implement the whole concept very cheaply.
For making the proposed back illuminated name plate circuit design we will basically require the following very few of the components.
Four high bright LEDs, color will depend on the user preference, I used blue LEDs in my prototype because my party wanted blue back light illumination for his displays.
A rectangular plastic lens, made up of acrylic material.
PCB as shown in the figure.
Positive film of the desired name or, a screen printed film with the name portion kept transparent while the rest of the area painted black and opaque.
150 Ohm resistor, 1 no.
Refer circuit diagram
How to Make the Display.
Connect the LEDs and the resistor as shown in the figure below such that the LEDs focus the light across the length of the rectangular PCB.
Cut the acrylic lens such that it perfectly fits in between the LEDs, make notches or grooves at the lens ends for making a snug fitting with the LEDs.
Now scratch one of the surfaces of the acrylic lens with a polish paper or an emery paper, such that it becomes rough and grainy on that surface and almost opaque for a clear vision, this operation is the secret behind producing a perfect and uniform back light.
Place a white paper cut to size on the PCB such that the light from the LEDs floods the white paper across the length.
Next place the lens in the center of the LED, over the PCB and the above white paper with its roughened surface on the top side.
Next place the positive film of the name display over the above lens.
Switch ON power to the LEDs, wow! your name plate is glowing bright with an illuminated back-light thats uniformly lit across the whole displayed name.
Put insulation tape over the side ends of the unit such that light does not escape from these areas.
Enclose the whole unit inside a suitable rectangular box for displaying it in the preferred location.
PCB, LED and the Lens Set Up
Positive placed over the lens for the final illuminated get-up:
Now some glimpses of the actual prototype:
First, the PCB/LED design:
Completed Prototype, Switched ON:
In Dark:
Digital displays today also incorporate LED technology and we all know how impressive they look with the involved digits distinctly visible with an illuminated back light.
The back illumination especially gives a fuller look and helps to highlight the display in a better way.
However these displays can be pretty expensive and require microcontroller ICs for producing the involved illuminations. A new hobbyist may find it difficult to grasp and make such displays at home.
Using LEDs in series for designing alphanumerical displays consisting of the desired names and numbers looks good but these dont produce the effects which is generally obtained from a back illuminated displays.
A cheap way of making a back illuminated display or a name plate having the desired alphabets is explained here, lets see how we can implement the whole concept very cheaply.
For making the proposed back illuminated name plate circuit design we will basically require the following very few of the components.
Four high bright LEDs, color will depend on the user preference, I used blue LEDs in my prototype because my party wanted blue back light illumination for his displays.
A rectangular plastic lens, made up of acrylic material.
PCB as shown in the figure.
Positive film of the desired name or, a screen printed film with the name portion kept transparent while the rest of the area painted black and opaque.
150 Ohm resistor, 1 no.
Refer circuit diagram
How to Make the Display.
Connect the LEDs and the resistor as shown in the figure below such that the LEDs focus the light across the length of the rectangular PCB.
Cut the acrylic lens such that it perfectly fits in between the LEDs, make notches or grooves at the lens ends for making a snug fitting with the LEDs.
Now scratch one of the surfaces of the acrylic lens with a polish paper or an emery paper, such that it becomes rough and grainy on that surface and almost opaque for a clear vision, this operation is the secret behind producing a perfect and uniform back light.
Place a white paper cut to size on the PCB such that the light from the LEDs floods the white paper across the length.
Next place the lens in the center of the LED, over the PCB and the above white paper with its roughened surface on the top side.
Next place the positive film of the name display over the above lens.
Switch ON power to the LEDs, wow! your name plate is glowing bright with an illuminated back-light thats uniformly lit across the whole displayed name.
Put insulation tape over the side ends of the unit such that light does not escape from these areas.
Enclose the whole unit inside a suitable rectangular box for displaying it in the preferred location.
PCB, LED and the Lens Set Up
Lens Placed over the PCB
Example film positive of a particular display name:
Positive placed over the lens for the final illuminated get-up:
Now some glimpses of the actual prototype:
First, the PCB/LED design:
Completed Prototype, Switched ON:
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