Tag Archives: BC547

Geiger Counter Uses Cockroft-Walton Multiplier

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The recent tsunami in Japan and the on-going calamity with the Fukushima nuclear power plant has apparently greatly increased sales of radiation meters, not only in Japan but elsewhere around the world. This device will allow an estimation of the level of radioactivity, being sensitive enough for background radiation monitoring… Read more »

Simple Preamplifier for Microphones & Tape Heads

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This circuit consists of a single transistor as amplifier and it gives a nice amplification to weakest and unipolar signals for feeding to a real amplifier. The center of this circuit is a BC547 OR BC548 transistor and the rest of the circuit is few resistors, and capacitors. The diagram… Read more »

Inverter Circuit For Soldering Iron

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Here is a simple but inexpensive inverter for using a small soldering iron (25W, 35W, etc) In the absence of mains supply. It uses eight transistors and a few resistors and capacitors. Transistors Q1 and Q2 (each BC547) form an astable multivibrator that produces 50Hz signal. The complementary outputs from… Read more »

Dual Relay Driver Board Circuit Schematic

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A simple and convenient way to interface 2 relays for switching application in your project. This relay driver boosts the input impedance with a regular BC547 NPN transistor (or equivalent). Very common driver. It can drive a variety of relays, including a reed-relay. Transistor Q1and Q2 are a simple common-emitter… Read more »

Intelligent Electronic Lock

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This intelligent electronic lock circuit is built using transistors only. To open this electronic lock, one has to press tactile switches S1 through S4 sequentially. For deception you may annotate these switches with different numbers on the control panel/keypad. For example, if you want to use ten switches on the… Read more »