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FANCY LEDS
Posted on Friday, April 11, 2008   •   Category: LED


The idea of this project came from my youngest son. He was dreaming of a small tool able to write symbols or pictures on a screen. As a graphic LCD (even bought at Crownhill :) ) was too expensive (or too easy??), the solution adopted was to pilot a matrix of Leds. This way, with only some cheap transistors, common red Leds, and a 16F628 , the dream could become reality.


Fading LEDs
Posted on Friday, April 11, 2008   •   Category: LED


Two strips of LEDs fading in a complementary manner 9V Battery-operated portable unit. 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.


Class-A Headphone Amplifier
Posted on Friday, April 11, 2008   •   Category: Headphone Amplifiers


Even if simple the circuit, plirej' all condition, regarding the distortion and the response of frequency. The resistance of entry is 250K and the load that can drive is between 100R and 2K. The circuit use negative coupling. His exit functions in Class A, having as active charge the BC308 and resistance 39R. The bias current is roughly 14 mA and total 15mA. The gain of unit is 25. The power supply, can be from 6V up to 24V DC. The frequency response with load 200R, it is 37ΗΖ - 470KΗZ (-1dΒ), the output voltage is 1.5V (11mW), the distortion 0.5%.


1 GHz Frequency Counter
Posted on Friday, April 11, 2008   •   Category: Counters / Frequency Meters


This simple counter is useful for frequency measurements of various wireless equipments, especially transmitters, receivers and signal generators in VHF/UHF band. Features * Display range: 0,0 to 999,9 MHz, resolution 0,1 MHz * Correct rounding, reduced blinking of last digit * Over-range indication * Fast measurement - short measuring period * High input sensitivity in VHF/UHF band * Switchable intermediate frequency offset for use with receiver.


1 min - 2 hours Timer with Buzzer and Optocoupler
Posted on Friday, April 11, 2008   •   Category: Timer Circuits


A small circuit that can find a lot applications of measurement time. She has the possibility us inform with sound signal from the BZ1. At the same time, exist the possibility drive a external circuit via the optocoupler IC2, after we connect the applicable circuit in contacts [ A ] and [ B ]. The circuit is based on IC1 (4060), which include in his inside, oscillator and a binary divider of 14 stage. The frequency operation of oscillator is determined by a circuit R-C that connected in pins 9,10,11 of IC1. We give supply in the circuit, with switch S1, is presented a pulse in 12 [ RESET ] via C1 and R3, null him counter, require the measurement of pulses to begin from the zero. Than the count get at in 14th digit then exit Q14 in the pin 3, acquire high logic level. This voltage drive the base the Q1-2, the transistors turn on, thus buzzer BZ1 sound, also the IC2 is ready to drive, via contacts [ A][B ], any suitable external circuit. The time delay is regulated with the potentiometer RV1, in time delay that begin from 1 minute up to 2 hours, proportionally with the combination of prices that they will have the RV1 and C2.


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