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Light Laser LED
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8051 / 8052
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Remote Control Toy
H Bridge Circuit
Interconnection & Timing
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4 Band Resistor
5 Band resistor
6 Band resistor
Light Laser LED Circuits
LED driver combines high speed, precision
The LED driver in Figure 1 illuminates retinal neurons in a biological experiment that has similar requirements. For a given LED at a given current, the intensity is stable, so switching a stable current is a simple and effective way to obtain the needed function. The circuit provides current pulses to the LED with rise and fall times lower than...
LED doubles as emitter and detector
Figure 1 shows the relative responsivity and emission spectra for an Infineon (www.infineon.com) SFH409 LED. This infrared GaAs LED has peak emission at 940 nm with a half-peak bandwidth of 50 nm. In detection mode, it peaks at 920 nm with a half-peak bandwidth of 55 nm. As Figure 1 shows, the wavelength of peak responsivity is shorter than the...
LED driver as fault monitor
Using just four transistors and six resistors, this circuit provides switchable, constant-current drive for an LED and indicates both open- and short-circuit fault conditions (Figure 1). And there`s a bonus, too. Control signal VCONT switches the LED on and off. When VCONT is high, Q1 and the LED are off. When VCONT is as low as 0V, Q1 turns on...
LED stepdown power supply
Below is a proof of concept circuit which needs improvement. The part values shown will run a high efficiency red LED with a Vf of 1.9V from only 2 nicads, right down to 2 volts. For a white LED you will need more batteries and you must increase the 1.0K resistor to a higher value. Current sensing at a mere 18mV over 1ohm makes this stepdown...
I don`t know why, but people like blinking lights. You see LED chasers everywhere, in TV shows (Knight Rider), movies, and store windows. This schematic is my version of a simple 10 LED chaser. There is no 555 timer used because at my local electronics store they are over $4 Cdn. Instead, an oscillator made up of two sections of a 4011 NAND gate...
LED dimmer uses only two lines
The circuit in Figure 1 provides 32 steps of brightness controlfrom 0 to 100%for a backlight or instrument panel, using just two general-purpose-microprocessor signals. In addition, the circuit requires little board space, because it uses only three SOT-23s and one µMax package. Although Figure 1 shows the circuit driving white LEDs, the load...
This circuit operates two LED strips in pulsing mode, i.e. one LED strip goes from off state, lights up gradually, then dims gradually, etc. while the other LED strip does the contrary. Each strip can be made up from 2 to 5 LEDs at 9V supply. The two Op-Amps contained into IC1 form a triangular wave generator. The rising and falling voltage...
LED driver provides software-controlled intensity
This design reconfigures the APD-bias IC, IC1, to allow its low-voltage DAC output to modulate the high-voltage, current-sense feedback via a high-voltage-output transconductance stage comprising Q2 and Q3. These two complementary transistors provide first-order temperature-compensation sufficient for the application. Vendors in recent years...
LED power supply
Efficiency can be increased by using a germanium transistor at the 33 ohm current sense resistor, and by using a proper torroid core in place of the crappy ferrite bead. Single AA cell powers two LEDs at constant current..
Heart of LEDs
For those who dont like microcontroller projects, pretend the micro is a dedicated LED driver IC that just happens to have been designed to control 30 LEDs in the shape of a Heart (what a stroke of luck!). And it wont be declared obsolete just after publication like a purpose designed IC might be! Using a PC parallel port to control external...
98 LEDs Fantastic Atom Expander
Here is the schematic, PC board pattern, and parts placement for a "Fantastic Atom Expander". This circuit produces an "exploding atom" effect using 98 LEDs. # The LEDs can be any colour but blue. For a very interesting effect, make one ring red, the next one green, the next one orange, then yellow, etc. # The transistors can be most any...
White LED Driver Features Internal Switch & Schottky Diode
The LT®3465 white LED driver is ideal for backlight circuits in small, battery-powered portable devices such as cellular phones, PDAs and digital cameras. The LT3465 includes important features such as automatic soft-start to prevent large inrush current, open LED protection and an integrated Schottky diode in a low profile (<1mm)...
White LED Driver Guarantees Matching LED Brightness
White LEDs are widely used in small LCD backlight applications for simplicity, high reliability and low cost. However, due to variations in the forward voltage drop of white LEDs, matching the brightness becomes a major design consideration for multiple LED applications. Since LED brightness is proportional to current rather than voltage,...
PWM controller drives LEDs from high-voltage lines
The circuit forces a current to build up in the L1 coil and the LEDs until the voltage developed across R3 reaches VFB/3.3V. At this point, power switch Q1 turns off, and the magnetizing current keeps circulating in the coil and LEDs, thanks to freewheeling diode D1. To maintain a "clean" current in the LEDs, L1 must be large enough to keep...
Rainbow LED indicates voltage with color
The circuit in Figure 1 comprises IC1, a Microchip PIC12F675 microcontroller driving IC2, a Kingbright AAF5060PBESEEVG "rainbow" indicator that contains three ultrabright LED chips (red, green, and blue) within one package. Modulating each LED`s duty cycle produces all of the perceivable colors of the visible spectrum, including white light....
Pocket LED Light
This is a pocket-sized LED flashlight operating with only one AAA battery. However, the super high luminosity LEDs(blue,green or white) require at least 3.5 volts of forward voltage. This flashlight is boosting input voltage up to operating voltage of a LED with simple DC-DC converter. Right image shows the circuit diagram for the LED light. It...
Power-supply IC drives multiple LEDs
The circuit in Figure 1 uses IC1, the integrated offline Viper22A switching regulator in a constant-current configuration to drive two to eight 1W LEDs. The circuit operates by monitoring the voltage drop across the sense resistor, R6, and uses this voltage as feedback to regulate the current through R6 and the LEDs. An operational amplifier in...
Processor`s PWM output controls LCD/LED driver
The circuit comprises simply the PWM source, capacitor C, and resistors RD and RW. For CMOS circuits, you calculate the open-circuit output voltage as VCONT=D½§VDD, where VCONT is the control circuit`s output voltage, D is the PWM duty cycle, and VDD is the logic-supply voltage. The control circuit`s output impedance is the sum of the...
Simplified white-LED flasher
The white-LED flasher in Figure 1 offers an alternative approach to a previously published idea (Reference 1). Targeting use in portable appliances and products powered by a single cell, this circuit flashes an LED to provide a highly visible warning signalfor example, to indicate power on, battery low, or another eye-catching visual signal....
Single cell lights any LED
The circuit in Figure 1 allows you to light any type of LED from a single cell whose voltage ranges from 1 to 1.5V. This range accommodates alkaline, carbon-zinc, NiCd, or NiMH single cells. The circuit`s principal application is in LED-based flashlights, such as a red LED in an astronomer`s flashlight, which doesn`t interfere with night vision....
White-LED driver touts high efficiency
Most products use multiple LEDs to provide adequate backlight for a display. Because the LED`s brightness depends on its forward current, these multiple diodes commonly connect in series to ensure that the same current flows through each of them. You need approximately 14V to forward-bias four series-connected LEDs, starting from the nominal...
Using white LEDs
The yellow LEDs are on a small PCB, which are easy to remove. On the PCB there is 3 yellow LEDs and 4 diodes. Pictures of the PCB can be seen here : Top-side - Bottom-side. The schematic is as follows : You now remove the 3 LEDs and the 3 normal diodes (the ones who are in series). I actually only removed the outer 2 as the remainder is...
Voltage-to-current converter drives white LEDs
You sometimes need to drive a white LED from one 1.5V battery. Unfortunately, the forward voltage of a white LED is 3 to 4V. So, you would need a dc/dc converter to drive the LED from one battery. Using the simple circuit in Figure 1, you can drive one white LED or two series-connected green LEDs, using only a few components. The circuit is a...
Two-LED Pilot Light
This circuit was designed on request and can be useful to those whishing to have, say, a red LED illuminated when an appliance is on and a green LED illuminated when the same appliance is off. Any mains operated appliance can be monitored by this circuit, provided a suitable mains switch, capable of withstanding the full load current, is used...
ULTRA-BRIGHT LED LAMP
This ultra-bright white LED lamp works on 230V AC with minimal power consumption. It can be used to illuminate VU meters, SWR meters, etc. Ultra-bright LEDs available in the market cost Rs 8 to 15. These LEDs emit a 1000-6000mCd bright white light like welding arc and work on 3 volts, 10 mA. Their maximum voltage is 3.6 volts and the...
White-LED driver backlights LCD and keypad
Figure 1 shows a method for driving all the LEDs with a single driver IC from Catalyst Semiconductor (www.catsemi.com), the CAT32. Power comes from a single lithium-ion battery cell. A FET switch can independently turn off the group of six LEDs. The shutdown input, , on the CAT32 turns off all the LEDs. LED brightness is a direct function of the...
White-LED driver provides 64-step dimming
The circuit of Figure 1 is designed for portable-power applications that require white LEDs with adjustable, logarithmic dimming levels. The circuit drives as many as four white LEDs from a 3.3V source and adjusts the total LED current from 1 to 106 mA in 64 steps of 1 dB each. The driver is a charge pump that mirrors the current ISET (sourced...
White LED Head Lamp
This is a practical white LED head mount lamp (flashlight). Recently many white LED flashlights appear on the market. However, most flashlights require three cells because they are regurating output current with only series resister. The odd number of cells except one is not good, and a margin between VLED and VBAT is too small, intensity of...
Single-port pin drives dual LED
Figure 1 illustrates one possible approach that uses external inverter IC1 to drive D1, a red/green bidirectional LED. A logic-high output on the port pin forces current through the green (upper) LED and pulls the inverter`s input high, which drives the inverter`s output low and sinks current from the green LED. A logic-low output on the port...
LED or Lamp Pulser
This circuit operates a LED in pulsing mode, i.e. the LED goes from off state, lights up gradually, then dims gradually, etc. This operation mode is obtained by a triangular wave generator formed by two op-amps contained in a very cheap 8 pin DIL case IC. Q1 ensures current buffering, in order to obtain a better load drive. R4 & C1 are the...
LED or Lamp Flasher
* Flashing frequency can be varied by changing R1 value in the 1M - 4M7 range. * This circuit is very efficient when driving a small 3.2V incandescent lamp. In this case omit the LED and R3, connecting the bulb across Q2 Collector and positive supply, further reducing parts counting. * Maximum current drawing of the bulb type used...
FET Controls 2nd LED Array in Switch-Mode LED Backlight
Maxim/Dallas > Designer`s Library > App Notes > DISPLAY DRIVERS Keywords: Single FET Controls 2nd LED Array in Switch-Mode LED Backlight Related Parts APP 1871: Feb 03, 2003 Download, PDF FormatDownload, PDF Format (29kB) APPLICATION NOTE 1871 Single FET Controls 2nd LED Array in Switch-Mode LED Backlight White-LED...
Light Sensing Circuits
Light Dimmer Circuits
Ultrasonic distance finder circuit
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is measured. There are three main categories of distance measurement methods in use: a) By...
Simple Metal detector circuit with CD4030
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to find something potentially valuable, hidden a few centimeters below the soil. So many...
Fully automatic watering circuit for flower pots
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This circuit comes as a solution to this problem. Depending on humidity of the pot at...
Simple deep searching metal detector circuit
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the circuit of this metal detector, it is possible to detect a metal coin in depth of 90 to...
Sub-Harmonic Bass Converter for Electric Guitars
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound, such as filtering or distortion. Instead, a frequency division system produces outputs...
Echo Depth Sounding Sonar for Boats
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the calibration of the rope. This arrangement still exists in some yachts. The big...
100W HiFi Audio Amplifier Circuit
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power supply must be symmetrical so that no electrolytic capacitors are needed at the outlet....
Plant-Pot Water Level Indicator Circuit
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower. The circuit of the device is shown in Figure 2. The water detection is made from the bottom...
Analogue Sound Preasure dB-Meter Circuit
The best human ear can capture sounds from 20Hz to 20KHz. These limits are known to be the broadest that can exist. Normally the normal limits range from 100Hz to about 13KHz and depend on the age and health of the individual. We for our measurements and to have a good accuracy we will get the limits of 20Hz to 20KHz. A sound to be heard does...
Digital Signal Integrity
Interconnection and Timing of Digital Circuits
CMOS Circuits Tutorial