Matt circuit

The 555 circuit below is a flashing bicycle light powered with four C,D or AA cells (6 volts). Two sets of 20 LEDs will alternately flash at approximately 4.7 cycles per second using RC values shown (4.7K for R1, 150K for R2 and a 1uF capacitor). Time intervals for the two lamps are about 107 milliseconds (T1, upper LEDs) and 104 milliseconds (T2 lower LEDs). Two transistors are used to provide additional current beyond the 200 mA limit of the 555 timer. A single LED is placed in series with the base of the PNP transistor so that the lower 20 LEDs turn off when the 555 output goes high during the T1 time interval. The high output level of the 555 timer is 1.7 volts less than the supply voltage. 40 LED Bicycle Light Circuit Diagram   Adding the LED increases the forward voltage required for the PNP transistor to about 2.7 volts so that the 1.7 volt difference from supply to the output is insufficient to turn on the transistor. Each LED is supplied with about 20mA of current...

This circuit uses low-voltage AC to drive a string of 50 or so bi-color LEDs (two LEDs connected in inverse parallel). Power to the LEDs is controlled by the Triac and the two optocouplers which have their photo-transistors effectively connected in inverse-parallel. Depending on which optocoupler is turned on, the Triac applies positive, negative or both half-cycles to the LEDs and so the colours can be red, green or in-between. Switch S1 is used to select the pulses from two oscillators which are formed by the NAND gates in IC1 (4011B). This provides a variety of LED flash patterns, depending on the setting of S1. Circuit diagram: Author: Matthew Peterson - Copyright: Silicon Chip Electronics

If you want to operate power LEDS with a truly constant current which significantly prolongs the lifetime of the lamp and avoid the power loss resulting from using a constant voltage supply with a series resistor, you need a suit-able constant current source. However, the only way to achieve really good efficiency is to use a switching regulator. Altogether, this means that you need a switching regulator designed to generate a constant current instead of a constant voltage. With this in mind, the author started working on the development of a LED pocket torch with especially high efficiency. Along with using high-capacity rechargeable batteries to maximise operating life, it’s worthwhile to be able to reduce the brightness, and therefore the operating current of the LEDs, when you don’t need full power. Accordingly, the author incorporated a dimming function in the design, based on operation in PWM mode in to reduce power losses to an absolute minimum. Power LED Driver Circuit Diagram ...

This Outdoor LED Solar Garden Lights project is a hobby circuit of an automatic garden light using a LDR and 6V/5W solar panel. During day time, the internal rechargeable 6 Volt SLA battery receives charging current from the connected solar panel through polarity protection diode D9 and current limiting resistor R10. If ambient light is normal, transistor T1 is reverse biased by IC1 (LM555). Here IC1 is wired as a medium current inverting line driver, switched by an encapsulated light detector (10mm LDR). Multi-turn trimpot P1 sets the detection sensitivity. When ambient light dims, transistor T1 turns on to drive the white LED string (D1-D8). Now this lamp load at the output of T1 energizes. Resistors R1-R8 limits the operating current of the LEDs. When the ambient light level restores, circuit returns to its idle state and light(s) switched off by the circuit. Circuit diagram: Outdoor Garden Solar Lights Circuit Diagram Assemble the Outdoor Solar Lights circuit on a general pur...

The article describes a very simple homemade emergency light circuit that can be used during power failures and outdoors where any other source of power might be unavailable. The circuit uses LEDs instead of incandescent lamp, thus making the unit very power efficient and brighter with its light output. Moreover, the circuit employs a very innovative concept especially devised by me which further enhances the economical feature of the unit. We know that LEDs require a certain fixed forward voltage drop to become illuminated and it is at this rating when the LED is at it’s best, that is voltages which is around its forward voltage drop facilitates the device to operate in the most efficient way. As this voltage is increased, the LED starts drawing more current, rather dissipating extra current by getting heated up itself and also through the resistor which also gets heated up in the process of limiting the extra current. If we could maintain a voltage around an LED near to its rated for...

Signals when an on-circuit battery is exhausted 5V to 12V operating voltage A Battery-status Indicator circuit can be useful, mainly to monitor portable Test-gear instruments and similar devices. LED D1 flashes to attire the user's attention, signaling that the circuit is running, so it will not be left on by mistake. The circuit generates about two LED flashes per second, but the mean current drawing will be about 200µA. Transistors Q1 and Q2 are wired as an uncommon complementary astable multivibrator: both are off 99% of the time, saturating only when the LED illuminates, thus contributing to keep very low current consumption.  Flashing-LED Battery-status Indicator Circuit Diagram The circuit will work with battery supply voltages in the 5 - 12V range and the LED flashing can be stopped at the desired battery voltage (comprised in the 4.8 - 9V value) by adjusting Trimmer R4. This range can be modified by changing R3 and/or R4 value slightly. When the battery voltage approaches...

This circuit (Fig. 1) simulates the old sand-glass timer. A total of 32 LEDs create the effect of sand grains passing from the upper half of sand-glass to its lower half. When the power is switched ‘on’, shift registers IC3 and IC4 are reset by the power-on-reset circuit formed by resistor R34 and capacitor C7. After a few seconds, the sand-glass action starts. IC CD4060B (IC2) is a 14-stage ripple binary counter with built-inoscillator. It generates clock pulses, which are fed to both the shift registers (IC3 and IC4). The clock frequency can be adjusted by preset VR1, while rotary switch S2 helps in selecting time periods. LED Sand-Glass Timer Circuit Diagram Time period options of 5, 10, and 20 minutes have been provided. Additional options are available on utilising outputs Q3 through Q9 of IC2. Switch S1 is an SPDT switch, which selects odd- or even-numbered set of LEDs. In other words, it selects which side of the sand-glass is up. Assuming S1 to be in position (a), every clock p...

The process mentioned below shows how we can convert the LEDs to the light sensors so that it can be used for many other purposes also. Read on to know more about this. As the Blinkenlight Shield has 20 of them, 20 pixel camera can be developed by it. After performing the experiment, it is recommended to reset the jumper setting to default. LED or Light Emitting diodes usually act as the photo diodes and are optimized to produce the light. LEDs can be used to make the light detectors that can be helpful in various conditions. The idea behind this is to reverse bias the diodes by turning the IO pins to output low so that the LEDs used will act as capacitors and will not be conducted. The current produced due to the LED is very small, and the photo current produced discharges the LED capacitors. After charging, the IO pins have to be switched to high Z so as to generate the light. The light produced and the current are directly proportional to each other. After the discharging o...

This simple LED torch is driven by a 2-transistor blocking oscillator which steps up the voltage from a 1.5V cell. It relies on the inherent current limiting of the 150µH choke to protect the white LED from over-drive. With a 9V zener diode in place of the white LED, it could also provide a 9V supply provided the current drain is modest. Circuit diagram: Author: Peter Goodwin Copyright: Silicon Chip Electronics

Description  The bi-directional sequencer uses a 4 bit binary up/down counter (CD4516) and two "1 of 8 line decoders" (74HC138 or 74HCT138) to generate the popular "Night Rider" display. A Schmitt Trigger oscillator provides the clock signal for the counter and the rate can be adjusted with the 500K pot. Two additional Schmitt Trigger inverters are used as a SET/RESET latch to control the counting direction (up or down). Be sure to use the 74HC14 and not the 74HCT14, the 74HCT14 may not work due to the low TTL input trigger level. When the highest count is reached (1111) the low output at pin 7 sets the latch so that the UP/DOWN input to the counter goes low and causes the counter to begin decrementing. When the lowest count is reached (0000) the latch is reset (high) so that the counter will begin incrementing on the next rising clock edge. The three lowest counter bits (Q0, Q1, Q2) are connected to both decoders in parallel and the highest bit Q3 is used to select...

This circuit provides a visual 9 second delay using 10 LEDs before closing a 12 volt relay. When the reset switch is closed, the 4017 decade counter will be reset to the 0 count which illuminates the LED driven from pin 3. The 555 timer output at pin 3 will be high and the voltage at pins 6 and 2 of the timer will be a little less than the lower trigger point, or about 3 volts. Circuit diagram :  Nine Second LED Timer and Relay Circuit Diagram When the switch is opened, the transistor in parallel with the timing capacitor (22uF) is shut off allowing the capacitor to begin charging and the 555 timer circuit to produce an approximate 1 second clock signal to the decade counter. The counter advances on each positive going change at pin 14 and is enabled with pin 13 terminated low. When the 9th count is reached, pin 11 and 13 will be high, stopping the counter and energizing the relay. Longer delay times can be obtained with a larger capacitor or larger resistor at pins 2 and 6 of the...

A very simple LED torch can be designed using the NSI45090JDT4G adjustable constant current regulator (CCR) designed by ON Semiconductor ,using extreme few external components. NSI45090JDT4G device is designed to provide a cost effective solution for regulating current in LEDs. This Constant current regulator is based on patent-pending Self-Biased Transistor (SBT) technology and regulates current over a wide voltage range. It is designed with a negative temperature coefficient to protect LEDs from thermal runaway at extreme voltages and currents. LED Torch Circuit Diagram The Radj pin allows Ireg(SS) to be adjusted to higher currents by attaching a resistor between Radj (Pin 3) and the Cathode (Pin 4). The Radj pin can also be left open (No Connect) if no adjustment is required.The maximum current that can be adjusted using this chip is around 160 mA , and the maximum input voltage is around 45 volts The D1 from the circuit shown here is used for reverse battery protection . Bellow you...

Now we're going to talk about the selection of LED strip lights for home decoration. You should pay attention to the following notes on how to select LED strip lights. Why LED strips are always recommended for home decoration? Because: 1. LED strip light is soft. It can curl like power wire. 2. It can be cut and connected. 3. The bulb and the circuit is completely encapsulated in a flexible plastic cover, which ensures a good insulation, waterproof, safe condition in use. 4. LED strips are weather resistance(-20-50 ℃). LED strip lighting for home decoration 5. It's not easy to break. Besides, it has a long life, up to 80,000 ~ 100,000 hours. 6. It's easy to make graphics, text and other shapes. 7. It has rich colors. The color effects include white, green, yellow, red, orange, warm white, red and blue, purple, or mixed colors. 8. Energy-saving and eco-friendly. Cold light, No radiation, no mercury elements, no harmful substances. 9. Easy installation. Widely used in home de...

This circuit shows how to use an ordinary LED as a light sensor. It makes use of the photovoltaic voltage developed across the LED when it is exposed to light. LEDs are cheaper than photodiodes and come with a built-in filter, which is useful when the application involves colour discrimination. The photo-voltage of a red LED (its bandgap voltage) is typically about 2V. The source impedance of this voltage is about 800MΩ in daylight, rising to infinity in darkness. A TL071 JFET input op amp is used to amplify and buffer this extremely high impedance signal. Circuit diagram: LED As A Light Sensor Circuit Diagram Resistor R1 ensures that the op amp "sees" a 0V input when the LED is in total darkness. To avoid undue loading of the signal, R1 would ideally be a 100MΩ or larger resistor but since such high values are rare and expensive I used a smaller value and increased the gain of the op amp to compensate for the voltage loss. To avoid the need for a second variable resistor to ...

This circuit senses AC audio voltage supplied to the car-radio loudspeakers and displays it as power using a LED bar graph, achieving at the same time an attractive visual effect. It is designed to cover common car-radio output power ranges, but can easily be modified to suit different needs. It is supplied from the 12 V car electrical system and is suitable for classical CC (Capacitor-coupled) as well as BTL (Bridge Tied Load) types of amplifier with no changes to the circuitry or connections at all. In fact, only the meaning of the LEDs changes — with BTL, the LED increments equal four times the CC value on the same load. CC-type amplifiers have the loudspeaker connected via a DC-decoupling capacitor at the output and ground (negative). BTL-type amplifiers, on the other hand, have the loudspeaker DC-coupled and ‘stretched’ between two equal, parallel, but phase-reversed outputs. Project image : Stereo LED Power (VU) Meter Image The result compared to ‘CC’ is twice the voltage sw...

The LM3410 IC is a constant current LED driver useful in either boost con-verter or SEPIC design applications. A SEPIC (Single Ended Primary Induct-ance Conver ter) design allows the power supply’s output voltage to be set above, below or equal to its input voltage. In this application the chip is configured as a boost-converter (i.e. the output voltage is greater than the input voltage).  LM3410 LED Driver Circuit Diagram The LM3410 is available in two fixed-frequency variants. Using either the 525 kHz or 1.6 MHz clock version it is possi-ble to build a ver y compact LED driver. The output stage can supply up to 2.8 A, allowing several high-power LED s to be driven from a rechargeable Lithium cell or several 1.5 V bat-teries. The chip also features a dimmer input giving simple PWM brightness control.Output current is defined by an external shunt resistor. To keep losses low the LM3410 uses an internal voltage reference of just 190 mV. Power dissipation in the shunt resistor i...

The concept for this small birthday present was to create a small heart shape with red LEDs and then to draw a heart shape underneath it on the PCB as a backdrop. Then a small processor was added to control the heart shape of LEDs for both fade and pattern control. The method of control that we use (PWM) allows us to save precious battery life, control the exact brightness of each specific LED and create this tiny but awesome project. [ ]