My Light Diagram

LEDs IN SERIES LEDs can be placed in series providing some features are taken into account. The main item to include is a current-limiting resistor. A LED and resistor is called a string. A string can have 1, 2, 3 or more LEDs. Three things must be observed: 1. MAXIMUM CURRENT through each string = 25mA. 2. The CHARACTERISTIC VOLTAGE-DROP must be known so the correct number of LEDs are used in any string. 3. A DROPPER RESISTOR must be included for each string. The following diagrams show examples of 1-string, 2-strings and 3-strings: LEDs IN PARALLEL LEDs CANNOT be placed in parallel - until you read this: LEDs "generate" or "possess" or "create" a voltage across them called the CHARACTERISTIC VOLTAGE-DROP  (when they are correctly placed in a circuit). This voltage is generated by the type of crystal and is different for each colour as well as the "quality" of the LED (such as high-bright, ultra high-bright etc). This characteris...

The circuit described here is a step-up converter to drive 20 LEDs, designed to be used as a home-made ceiling night light for a child’s bedroom. This kind of night light generally consists of a chain of Christmas tree lights with 20 bulbs each consuming 1 W, for a total power of 20 W. Here, in the interests of saving power and extending operating life, we update the idea with this simple circuit using LEDs.  Power can be obtained from an unregulated 12 V mains adaptor, as long as it can deliver at least about 330 mA.  The circuit uses a low-cost current-mode controller type UCC3800N, reconfigured into voltage mode to create a step-up converter with simple compensation. By changing the external components the circuit can easily be modified for other applications. To use a current-mode controller as a voltage-mode controller it is necessary to couple a sawtooth ramp (rising from 0 V to 0.9 V) to the CS (current sense) pin, since this pin is also an input to the internal PWM com...

The circuit in this Design Idea makes a voltmeter that reads to 0.99V. The idea uses a counter IC to drive two sets of four LEDs (Figure 1). Each of these two sets represents a BCD (binary-coded-decimal) value. With all of the LEDs off, the voltmeter reads 0V. With all of the LEDs on, the reading is 0.99V. Op amp IC1A generates a predictable voltage ramp. Figure 1 You use op amp IC1B as a comparator to compare the ramp to an input signal. The higher the input voltage, the longer the output pulse from IC1B is. You use this pulse to gate free-running oscillator IC2B. A potentiometer on this multivibrator circuit allows you to adjust the full-range count. The voltmeter has a maximum input of 1V and uses three dual-part packages. You make output counter IC3 work as a two-digit counter by strapping the enable pin of the IC3B part to the MSB (most-significant-bit) output of the IC3A part. A dual op amp is used to create the comparator function and the ramp generator. The design also uses a d...

Very simple, versatile modular design No limits to the number of modules used in the ring Circuit diagram using LEDs:                             Circuit diagram using Lamps: Parts: R1 1K5 1/4W Resistor R2 680R 1/4W Resistor (Optional, see text) C1 47µF 25V Electrolytic Capacitor D1 LED any type Q1 BC337 45V 800mA NPN Transistor P1 SPST Pushbutton LP1 Filament Lamp 12 or 24V (See text) Comments: The purpose of this circuit was to create a ring in which LEDs or Lamps illuminate sequentially. Its main feature is a high versatility: you can build a loop containing any number of LEDs or Lamps, as each illuminating device has its own small circuit. The diagrams show three-stage circuits for simplicity: you can add an unlimited number of stages (shown in dashed boxes), provided the last stage output was returned to the first stage input, as shown. P1 pushbutton p...

To get the maximum brightness and working life out of a high-power LED, it needs to be driven at the optimum specified current. Allowing the current to exceed the permitted value is to be avoided at all costs, since it will severely affect the life of the device. A power supply or a battery with a small current-limiting resistor is not really an ideal solution, since not only is energy wasted in heating the resistor, but, if a small value is chosen to minimise this wastage, small changes in the applied voltage will lead to large changes in the current that flows. It is well known that LEDs have a small dynamic resistance in the neighbourhood of their optimal operating point. We will there fore need more in the way of electronics than a simple series resistor to meet our requirements.   Circuit diagram: Efficient Current Source for High-power LEDs Circuit Diagram   The most direct way to provide a highly constant current in the face of relatively small changes in supply voltage i...

Description    This device was designed on request; to control the light intensity of four filament lamps (i.e. a ring illuminator) powered by two AA or AAA batteries, for close-up pictures with a digital camera. Obviously it can be used in other ways, at anyone's will.IC1 generates a 150Hz square wave having a variable duty-cycle. When the cursor of P1 is fully rotated towards D1, the output positive pulses appearing at pin 3 of IC1 are very narrow. Bulb LP1, driven by Q1, is off as the voltage across its leads is too low. When the cursor of P1 is rotated towards R2, the output pulses increase in width, reaching their maximum amplitude when the potentiometer is rotated fully clockwise. In this way the bulb reaches its full brightness. Circuit Diagram: Parts: P1 = 470K R1 = 10K R2 = 47K R3 = 1.5K C1 = 22nF-63V C2 = 100uF-25V D1 = 1N4148 D2 = 1N4148 Q1 = BD681 B1 = 2xAA cells in series IC1 = 7555 or TS555CN LP1 = 1.5V 200mA Bulb SW1 = SPST Switch  Notes:  LP1 can be o...

What do you think of building a simple LED tester, so you can test the integrity of the components before soldering directly to the PCB. It reduces the task of testing the meter components using the circuit with LED gives an indication about the good or bad condition of the component. Test Multiteste LEDs - Polarity - Continuity - Resistance Circuit When a component is placed in the circuit and establishes electrical continuity T1 receives base current through R1. When T1 conducts, the green LED turns on and off the red LED. This indicates that the component to be tested is good. If the component is bad, will not have electrical continuity and T1 remains off. In this state only the red LED light indicating that the component is bad.   Polarity Connect the red end of the positive range to the circuit board and to test the black edge point. Circuit board under test to be lit Green LED ON - positive feed. Green LED off and red LED - or no negative supply voltage. Continuity Connect bo...