Free electronic circuit design and schematic diagram
A discrete oscillator circuit shown in the schematic diagram below is a variable duty cycle and variable frequency oscillator, can be used to produce rectangular wave. This circuit has frequency range of 60 to 1,000 Hz. This circuit consist of one UJT (uni junction transistor) and two transistors that provide positive going output when emitter voltage exceeds NPN emitter voltage. […]
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A scope calibrator is a circuit that is used for calibrating the variable time base oscillator of general purpose scopes. This scope calibrator gives 100kHz reference, so if the scope is set to 10 cycles on 10 graticule divisions, then each division represents 10 microseconds or 100kHz. And each division will represent 1 Mhz or 1 microsecond if the scope […]
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This is an AM radio power amplifier circuit. What is different with other general amplifier is that this circuit has a low-pass filter (passive type), built using R1C1 to limit the input-output frequency response. Additionally, a ferroxcube K5-001-001/3B with 3 turns of wire is used as ferrite bead at output filter. All components should be spaced very close to the […]
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This watt-meter circuit has measurement range up to 1-KW. This circuit can give the complete (X)(Y) function although uses only one transistor. Actually, this circuit is used for 117 Vac±50 Vac operation. For lower or lower voltage, this circuit can be modified easily. This circuit only measure power on negative cycles. The advantages of this circuit is this circuit does […]
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This is a motor controller circuit that control the speed and direction of series-wound Motors. This circuit employs silicon controlled rectifiers (SCR) Q1-Q4, that are triggered in diagonal pairs. The switch St is used to control which pair is turned on because either coupling transformer T2 or coupling transformer T1 is connected to a pulsing circuit by this switch. Here […]
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Monostable multivibrator circuit produce a fixed pulse-width when the input is triggered. The input is fed to CR1, which should be an open collector source since the TR1 would short the input to ground during the active state appear on this circuit’s output. The output of this circuit is tapped from the collector of TR2. This monostable multivibrator output pulse […]
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NiCd/NiCad battery charger circuit is still needed since some application demanding high current is still rely on NiCd type, since this type is still superior in term of high current output (low internal resistance) and low cost. This battery charger circuit is used to charge 12V NiCd battery at around 74 mA until battery is fully charged. This circuit need […]
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