Direct Coupled Discrete Astable Multivibrator

This flip-flop circuit? is a free running/astable multivibrator one,? with bases and collector of both emitter biased transistor are directly coupled to each other.? Switching action is supported by means of capacitor in each emitter circuit.? This configuration produce a triangle waves at emitters. Since neither transistor can remain permanently cut off, then a free running oscillation will be generated. We can use single 0.1 uF capacitor between emitters in place of C1 and C2.

53 dB Stereo Preamp for Tape or Phonographs

With the circuit shown in the following schematic diagram, both channels of this stereo preamp is constructed using? RCA  CA3052  quad AC amplifier.? this pre-amplifier circuit is featured with tone control (bass – treble). Make a similar circuit to complete the other channel, since the circuit for left and right channel are similar. To be high-fidelity, total harmonic distortion should be kept minimum, this circuit gives less than 0.3% distortion level at? at 1-kHz testing signal with 1-V amplitude.? Gain or amplification at 1 kHz is 47 dB,? and the tone control will curve the response with 11.5-dB boost at 100 Hz and 10 kHz at maximum bass and treble boost.? For minimum bass and treble knob position,? the attenuation will be 10dB? at 100 Hz? and 9dB at 10kHz. This circuit is operated by a single ended supply for wider range environment. Inputs can be from tape recorders pickup or magnetic-cartridge phonographs.

[Circuit's schematic diagram source: hqew.net]

2 Phase and 3 Phase Motor Drivers

The schematic diagram below show 2-phase and 3-phase motor driver circuits. This circuit can used to drive an AC motor because this circuit has an integrated power operational amplifier, built-in power-output stage and high amplification factor. The needed AC signal is produced by the op amp that is configured as oscillator. The motor is driven by the high-current that is supplied from the power output stage. The another op amp is configured as Wien bridge oscillator.? Here are the schematic diagrams of the? circuits:

The oscillation frequency is determined by following equation:

f0=1/(2π*squareroot(R1*R2*C1*C2))

The upper schematic diagram is the 2-phase motor driver, while the lower schematic is the diagram of 3-phase motor driver circuit. The oscillator frequency can be adjusted to a narrow range by varying R2 or R1. The signal attenuation? which occurs in the phase shifters is compensated by the second amplifier’s gain. The second amplifier’s gain is set by R3/R4 ratio. The output of this circuit is sinusoidal because of RC feedback networks that used as an active filters. An external source like square wave or pulse can be used to drive this circuit. [Circuit's schematic diagram source: hqew.net]

AM Radio Receiver Circuit Employs FM IC Chip

This AM receiver consists of a  TDA7000  single-chip FM receiver (U1) as the main radio component, and an  LM386 ? chip for low-voltage audio-power amplifier (U2) circuit. The receiving coils are hand-wound coils (L1 and L2), and a few additional components. This coils, together with the variable capacitor, is chosen to match the AM frequency. To wind your won coil, L1 and L2 are 100 turns of #28 wire on toroidal cores (about 240 μH each). At 30 turns, L1 is tapped . Here is the schematic diagram of the circuit:


[Circuit's schematic diagram source: hqew.net]

26V-to-5000V DC-DC Converter

This circuit can provide 5,000 VDC from 26 VDC. This circuit has ripple of under 0.01% due to Voltage-doubling capacitors. As sinusoidal oscillator, a 2N217 transistor is used. The diode and the capacitors at the output stage should be of high voltage type.? Here is the schematic diagram of the? circuit:

1 KW Power (Watt) Meter

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 not need external power supply. This circuit measures true power that is delivered to the load. Here is the schematic diagram of the? circuit:

At idle section, this circuit draw only 0.5W. This circuit has load current-sensing voltage of 10mV and load voltage loss of 0.01%. For linear loads, Rejection of reactive load currents is better than 100:1. When using a 50-μA meter movement, the nonlinearity of this circuit is about 1% full scale. Copper shunt can be used to give correct gain due to temperature. [Circuit's schematic diagram source: hqew.net]

Source: http://www.hqew.net/circuit-diagram/-1-KW-Power-%28Watt%29-Meter_2500.html

Foldback Current Limited High Voltage Regulator

This circuit is high voltage regulator which has foldback current limiter protection. This circuit uses  LM10  comparator with voltage reference, and this core integrated circuit is connected directly to high voltage circuitry. This high voltage direct connection is possible since the IC is inserted to a bias network and directly drop the applied voltage, so this IC is only suffering small voltage across its supply pins.

The foldback current limiter is different with ordinary current limiter in the way the limiter responds to dynamic load. When we plot the regular current limiter, when the load draw a linearly increasing current, the plot of the current will be linear ramp which stops at a specified level determined by the limiter. A foldback current limiter will give same response until the current reach the maximum level, but will fold the current back to a much lower current level if the load try to further increase the current. This foldback action will prevent the final driver? transistor in the regulator from overheating. [Circuit's schematic diagram source: National Semiconductor Application Note]

Mazda 626 GND distribution circuit diagram

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Drive circuit diagram of SCM on the air-condition remote control

Source: http://www.hqew.net/circuit-diagram/Drive-circuit-diagram-of-SCM-on-the-air$2dcondition-remote-control_2475.html

MEG8 Evaluation Board Schematic

Above is MEG8 Evaluation Board Schematic.

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Multiparty telephone switching device circuit diagram

The figure is Multiparty telephone switching device circuit diagram.

Mazda 626 2.0L cooling fan circuit diagram

Automatic dimming light circuit

Lamp dimmer. The figure below shows the circuit can be used for lamp dimming. It uses a small quantity of components, which can be installed inside the lamp seat. The circuit is commonly used in RC phase shift circuit. W can be adjusted to change the triac conduction angle, which changes the lamp brightness. KS is a bi-directional trigger  diode . C2 and L are anti-jamming devices. You can simplify the circuit if you do not ask more, such as reducing components, eliminating C2 and L2.

LAG673-monolithic Stereo Playback IC

LAG673  Japanese the Mi Zimi companies (MTTSVMI) single-chip stereo playback IC imports retractable audio player application is broader.
1. Box and the pin functions LAG673 Manifold within LAG673 containing pairs of pre-amplification and bi-amping. DC electronic volume control circuit, the circuit of DC motor speed stabilization. Manifold within the circuit block diagram shown. The IC uses a double row of flat package, the IC's pin functions and data are shown in Table listed.
2. LAG673 typical application circuit due to the complete functionality of LAG673 Manifold, put a LAG673 can constitute a stereo single put Walkman circuit, coupled with the stereo tune duo can form a stereo retractable Walkman circuit. LAG673 Manifold typical application circuit as shown.

3. Circuit works when the function switch in Figure 8-24 (3) allocated to the "tape" position, and then decentralization sound key the Manifold LAG673 on the tape playback signal processing state; only function switch to radio "position, the player in the radio state. At this time, the DC motor steady speed of LAG673 part of the circuit does not supply Vcc voltage Manifold LAG673 22 feet connected to the the Vec voltage, disconnect the front output of LAG673, machine work on the radio state. Amplifier stereo head to pick up the signals from ②, 27 pin input to the IC front, zoom in and compensate for signal (low frequency compensation) to get high, balanced, low-frequency signal IC from LAG673 ⑤, ⑧ pin output. Figure 8-24 circuit is added to pick Typical applications for the three-band equalizer amplifier. If you do not take the three-band equalizer, you can directly from ⑥, 23 feet into the amplifier in front of the electronic volume attenuator. The electronic volume attenuator is controlled at LAG673 the ⑦ feet of voltage, that is, peripheral to the center of the head of the volume potentiometer voltage. ⑧ pin volume telecommunications to provide a reference voltage. Signal IC internal electronic volume attenuator directly into the respective amplifier. ⑨ ⑧ pin is the power amplifier output feet, 11 feet is the public side of the amplifier output. Troubleshooting prompted the LAG673 Manifold pre-amplifier, motor steady speed integrated circuits in one, common faults addition to the power amplifier failure, as well as steady speed circuit failure. In this situation I wish only the overall change new LAG673 0 for steady speed circuit damage due to its relatively independent of the IC. Therefore, an additional substitution damaged circuit composed of a steady speed circuit.
Rest image at http://www.hqew.net/circuit-diagram/LAG673$2dmonolithic-Stereo-Playback-IC_2449.html

Common Mono Circuit

The circuit uses standard digital circuit voltage level as input, can activate or inhibit the circuit under any conditions that do not trigger the output pulse. Input switches Q3-Q4 from point A logic 1 activation was time to start the cycle B is a logic 0 and logic 1 inhibition. Q1 is a JFET2N3819, all the other transistors are2N3704.

Constant Current Limiting Charger Circuit

This circuit usesLM723Cregulator piece made of a constant current limiting charger. For charging a 12V sealed lead-acid batteries.
LM723C products of National Semiconductor Corporation in the United States, its stable output voltage of 12V DC, maximum output current is 420mA.

A Single Voltage Comparator of LM111, LM211 and LM311

The  LM111, LM211, LM311  of the power supply voltage range (± 5V to ± l5V), bias current, offset current is small, the differential input voltage range (± 30V), its output is compatible with TTL, DTL, and MOS circuits, and driving lights and relays. Single power supply can also be a dual power supply, the collector output and the emitter output of the two forms. Class comparator with external balance side and strobe control side, when used according to the select or adjust.

Source: http://www.hqew.net/circuit-diagram/-A-Single-Voltage-Comparator-of-LM111$2c-LM211-and-LM311-_2427.html

SM0038 and Microcontroller Interface Circuit

As shown in Fig. The  SM0038  external only three pins: VS, GND and a pulse signal output pin OUT, shape pin. VCC +5 V power supply and filter capacitor to avoid the interference of power; GND Ground (0V); pulse signal output to the CPU to the interrupt input pin (for example, the 8051 13-pin INT1). Take this connection, the software decoder can work in a query can also work in interrupt mode.