Output Relay Delay Audio Amplifier Circuit

2 September, 2010 (18:26) | Power Amplifier | By:

Output Relay Delay Audio Amplifier CircuitOutput Relay Delay Audio Amplifier Circuit

This is a simple circuit which I built to one of my audio amplifier projects to control the speaker output relay. The purpose of this circuit is to control the relay which turns on the speaker output relay in the audio amplifier. The idea of the circuit is wait around 5 seconds ofter the power up until the spakers are switched to the amplfier output to avoid annoying “thump” sound from the speakers. Another feeature of this circuit is that is disconnects the speaker immdiatly when the power in the amplifier is cut off, so avoinding sometimes nasty sounds when you turn the equipments off.

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12V Stroboscope 250-400V DC Circuit

2 September, 2010 (17:18) | Other Circuits | By:

The stoboscope tube needs about 250-400V DC to operate. This high voltage is generated using simple voltage step up circuit built from transistors Q1,Q2 and transformer T1. This circuit gives out about 230V AC voltage which is then rectified with rectifying bridge U1 (must have at least 400V voltage rating) and stored to the main capacitor C1.

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Atmel at89c51 Office-Home Security System

31 August, 2010 (20:00) | Microcontroller | By:

Home security project
Securiy is a matter of great concern to all of us in this world. Normally there are four types of security threat to our property.

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a ckt diagram of at89c51
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