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Index 419

Relay status indication circuit

Published:2011/11/10 3:02:00 Author:Ecco | Keyword: Relay status indication

Relay status indication circuit
The relay has one or more sets of contacts, if one set of contacts'common port connect to the public power, and in the release state, the common port is connected to the normally closed contacts, then LED-R is red ; and in the pull-in state, the common port is connected to the normally open contact, then LED-G is green. (View)

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Digital hygrometer

Published:2011/11/7 19:12:00 Author:Ecco | Keyword: Digital hygrometer

Digital hygrometer mainly consists of the following circuits :(1 ) humidity / voltage conversion circuit; (2 ) humidity / frequency converter circuit; (3 )the circuit composed of LM331. (View)

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Christmas light circuit

Published:2011/11/7 20:30:00 Author:Ecco | Keyword: Christmas light

Christmas light circuit
The chart shows the Christmas lights circuit which uses simple, inexpensive CD4069 CMOS hex inverter to control four circuits with 200 light-emitting diodes (each circuit has 50 LEDs), and it is directly supplied by the 220V power source without power transformer. The power is bridge rectified by VD1 ~ VD4, differential pressured by R1, R5 and filtered by C1, then the two ends of the C1 gets about 6V DC voltage for IC1 (CD4069). Gates D5 and D6 form the low-frequency oscillator. RP can adjust its frequency. The output is reversed-phase shaped by the combination with D1 ~ D4 to control 4 pieces of high back pressure transistors (2N3440/2N3439) VT1 ~ VT4. (View)

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145MHz variable crystal oscillator with 200mW output

Published:2011/11/7 19:02:00 Author:Ecco | Keyword: 145MHz, variable, crystal oscillator, 200mW output

145MHz variable crystal oscillator with 200mW output
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Accurate variable frequency oscillator

Published:2011/11/7 19:01:00 Author:Ecco | Keyword: Accurate , variable frequency oscillator

Accurate variable frequency oscillator
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770FS monitor blueprint

Published:2011/11/3 2:25:00 Author:Ecco | Keyword: monitor blueprint

770FS monitor blueprint
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The power supply circuit diagram of AST-4 color display

Published:2011/11/3 2:24:00 Author:Ecco | Keyword: power supply , color display

The power supply circuit diagram of AST-4 color display
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The power supply circuit diagram of AST-3 color display

Published:2011/11/3 2:14:00 Author:Ecco | Keyword: power supply, color display

The power supply circuit diagram of AST-3 color display
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The power supply circuit diagram of CASPER TM-5154H SVGA multifrequency color display

Published:2011/11/4 3:25:00 Author:Ecco | Keyword: power supply , CASPER , SVGA , multifrequency color display

The power supply circuit diagram of CASPER TM-5154H SVGA multifrequency color display
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The power supply circuit diagram of CASPER TM-5158 VGA color display

Published:2011/11/4 3:24:00 Author:Ecco | Keyword: power supply, CASPER , VGA , color display

The power supply circuit diagram of CASPER TM-5158 VGA color display
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4-tube transmitter schematic diagram

Published:2011/11/11 2:19:00 Author:Ecco | Keyword: 4-tube transmitter

4-tube transmitter schematic diagram
Circuit Notes This circuit provides an FM modulated signal with an output power of around 500mW. The input Mic preamp is built around a couple of 2N3904 transistors, audio gain limited by the 5k preset. The oscillator is a colpitts stage, frequency of oscillation governed by the tank circuit made from two 5pF capacitors and the inductor. ( Click here for Colpitt Oscillator Resonant Frequency Equation.) Frequency is around 100Mhz with values shown. Audio modulation is fed into the tank circuit via the 5p capacitor, the 10k resistor and 1N4002 controlling the amount of modulation. The oscillator output is fed into the 3.9uH inductor which will have a high impedance at RF frequencies. The output stage operates as a class D amplifier , no direct bias is applied but the RF signal developed across the 3.9uH inductor is sufficient to drive this stage. The emitter resistor and 1k base resistor prevent instability and thermal runaway in this stage. (View)