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Touch Sensitive LED

Below is the simplest circuit you can get. We can use any NPN. Connect the 220 ohm resistor, LED and transistor as shown in the figure below. Touch the top point with two fingers of one hand and the lower point with fingers of the other hand nad squeeze. When you squeeze harder, …

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LED Flasher Using Transistor

This simple LED flasher circuit will turn ON and OFF two LED alternatively. The first LED will turn ON when the second LED is OFF for some period, then the first led will turn OFF and the second LED will turn OFF. This cycle will be repeated as long as the battery is connected to …

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High-Brightness LED-Driver

This is a high-brightness LED-driver circuit. To provide a constant-voltage output we usually use DC/DC regulators. But constant-current output is the one that is needed in LED application. To provide a constant-current output, we can use this circuit. Here is the schematic diagram of high-brightness LED-driver circuit : This circuit uses …

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Manual Adjustable LED Driver

In many electronics-level adjustments such as LED drivers for LCD panel backlight controls, we can use AD5228. A manually adjustable LED driver is shown on figure below. The voltage across the white LED D1 is set by the AD5228 for the brightness control. A typical white LED with Vf of 3.5 V requires …

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Single Cell LED Flashlight

This is Single Cell LED Flashlight circuit. This circuit uses white LED that has best power-efficiency combination at about 20mA and requires abut 3.3V. Each Led in this circuit draws power about 66mW. This circuit uses seven LEDs. This circuit very useful for a tiny pocket flashlight because the whole array of leds run at …

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Voltmeter With LED For Car Battery

Below is a comparator circuit which is can measure with step of 1 volt, the voltage of car battery. The indication of voltage is done by comparison of  battery voltage with the reference set by D1. This voltage is applied  to the inverting inputs of amplifiers with to compare the battery voltage. We can regulate …

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