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Index 141

ZENER_CONTROLS_BRIDGE

Published:2009-7-5 23:00:00 Author:May

ZENER_CONTROLS_BRIDGE
Amplitude of 10.5-kHz Wien-bridge oscillator outputis main-tained symmetrical above ground by using single zener with diode bridge,As output e0 approaches soft knee threshold of conduction for zener.its impedance decreases and shunts R2,This violates oscillator requirement that R2=2R1. so output begins decreasing sinusoidally. As swing decreases, gain increases until e0 reaches negative threshold. Signal then reverses and again starts going positive.-W. B Crittenden and E. J. Owings, Jr., Zener-Diode Controls Wien-Bridge Oscillator, EDN Magazine. Aug. 1. 1972. p 57-58.   (View)

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Electric Blanket And Rice Cooker Timer Circuit

Published:2011-7-28 6:55:00 Author:Robert | Keyword: Electric Blanket, Rice Cooker, Timer

Electric Blanket And Rice Cooker Timer Circuit
The picture shows the electric blanket and rice cooker timer circuit. This circuit's timing time could be set from 1 second to more than 10 hours. In the picture, C1 is timing element. When the power supply is connected, pressing the switch AN1, the C1 would be charging to DC 28V. The comparator A would output high voltage level and the transistor VT would be connected, the relay J would be powered up and have actions. The J1-1 would be conncted and the power would be self-locked. The J1-2 would be disconnected. C1 would discharge to the high-resistance input port. When the C1's voltage is decreased and lower than the A's out-phase input port, the A would output low voltage level, the transistor VT would be disconnected, J would lost the power and be released. Then the timing is over until next case that the timing trigger switch AN1 is pressed again.   (View)

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Power Supply Protection Circuit of TL431

Published:2011-7-24 7:11:00 Author:Michel | Keyword: Power Supply, Protection Circuit

Power Supply Protection Circuit of TL431
The a,b,c,d are power supply protection circuits of TL431.The picture (a) is constant current circuit of TL431 and the constant current I。=UREF/R2.Picture (b) is protection circuit of overvoltage and undervoltage and the voltage is equal to (1+R3/R4)UREF+UBE,when it is under voltage,the voltage is equal to (1+R1/R2)UREF when it is overvoltage.In the formula,UBE is the base-emiting voltage of VT1.Picture (c) is the current-limiting circuit and the limitting current I。=UREF/R2.Picture(d) is voltage monitoring circuit and LED displays when the voltage is lower than (1+R3/R4)UREF and higher than (1+R1/R2)UREF.   (View)

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Thermal Dissipation Control Circuit For Computer

Published:2011-7-28 7:08:00 Author:Robert | Keyword: Thermal Dissipation, Control, Computer

Thermal Dissipation Control Circuit For Computer
The Pentium 4 computer's thermal dissipation control circuit is shown in the picture. In this computer it all uses three thermal-dissipation fans. Among them, the first fan is special for the CPU's thermal dissipation. The second fan and the third fan are installed separately in the computer's front side and back side for the box's thermal dissipation. The VT is the the first channel's remote temperature sensor which is used for measuring the environment temperature. The temperature sensor in Pentium 4 CPU is used as the second channel remote temperature sensor. The ADT7460 would be connected to the power management chip produced by the Intel company through the SMBus bus. Once it has detected the over-temperature case, it would output the over-temperature interrupt signal from the ports. And then by the power management chip it would make the CPU generate a interrupt.   (View)

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On_resistance_current_tests

Published:2009-7-23 21:49:00 Author:Jessie

On_resistance_current_tests
Figure 2-I shows a basic test circuit for measuring on-resistance, r DS(ON) ,for the MAX326/27. Figure 2-J shows how r DS(ON) changes with various analog inputs and supply combinations. Although specified at TTL threshold levels, the logic thresh-old is about 1.5 V± 0.2 V. The IC switches properly with CMOS input levels from -15 V to +15V. Never allow logic levels to exceed supply voltages in any circuit!   (View)

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LOW_VOLTS_ALARM

Published:2009-7-5 22:50:00 Author:May

LOW_VOLTS_ALARM
Circuit Notes This inexpensive dc supply-voltage monitor sounds a warning when the voltage falls below a preset value. It is ideal for monitoring rechargeable batteries since it draws only a few microamperes when not sounding. The voltage at which the alarm sounds is determined by the zener diode. When the voltage falls below the zener voltage, the alarm sounds. The alarm tone is determined by the RC time constant of the 39 k resistor and 0.01 mf capacitor.   (View)

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Basic_rnux_function_tests

Published:2009-7-23 21:56:00 Author:Jessie

Basic_rnux_function_tests
Figures 2-O and 2-P shows the typical application circuit and pin configuration, respectively; for the MAX328/29. Figures 2-Q and 2-R shows the logic truth tables for the MAX328 and MAX329, respectively. This ultra-low-leakage CMOS analog mux is tested by applying and removing +5 V to the control pins, and checking that the corresponding switches open and close. Simple sine waves can be used at the analog inputs, and the op-amp output can be measured on a scope.   (View)

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AGC_WITH_SQUELCH_CONTROL

Published:2009-7-5 22:47:00 Author:May

AGC_WITH_SQUELCH_CONTROL
Automatic gain control is a very useful feature in a number of audio amplifier circuits:tape recorders,telephone speaker phones,communication systems and PA systems.This circuit consists of a HA-5144 quad op amp and a FET transistor used as a voltage-controlled resistor to implement an AGC circuit with squelch control.The squelch function helps eliminate noise in communications systems when no signal is present and allows remote hands-free operation of tape recorder systems.Amplifier A1 is placed in inverting-gain T configuration in order to provide a fairly wide gain range and a small signal level across the FET. The small signal level and the addition of resistors R5 and R6 help reduce nonlinearities and distortion.Amplifier A2 acts as a negative peak detector to keep track of signal amplitude.Amplifier A3 can be used to amplify this peak signal if the cutoff voltage of the FET is higher than desired.Amplifier A4 acts as a comparator in the squelch control section of the circuit,When the signal level falls below the voltage set by R10,the gate of the FET is pulled low-turning it off completely-and reducing the gain to 2.4.Theoutput A4 can also be used as a control signal in applications,such as a hands-free tape recorder system.   (View)

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The constitution circuit diagram of portable rapid pulse generator

Published:2011-6-30 5:39:00 Author:Rebekka | Keyword: portable rapid pulse generator, constitution circuit

The constitution circuit diagram of portable rapid pulse generator
Since the whole TTL series is the lack of a high-speed monostable multivibrator and the ECL requires a small voltage swing and a small range power supply. It drives us to use F series of gates which has fast transition time and small transmission time delay. This requires making a small portable fast pulse generator. It is used to test the high-speed photomultiplier that used in the study of gamma-ray astronomy. The use of only two integrated circuit is to help reduce the consumption and narrow the size(Figure 1). Output the pulse is width from the output gate G4 in IC2. The pulse width is less than 10ns and the rise and fall time of the normal high pulse is about 2.5ns. It is equivalent to the delay of three gates. These pulses are very suitable for decrease the cathode potential of HLMP-CB-15-speed blue LED. But the anode of LED is clamped to 5V. G4 forces almost the entire 5 V supply voltage adding to the LED, so that the large voltage swingof the LED which is printed on circuit board solder connecting to the edge has the best brightness. The rechargeable battery is fixed at the other side of the printed circuit board. The circuit uses CMOS timer IC1, it only costs less than 4 mA of current.   (View)

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Hongqi Century Star Engine Circuit

Published:2011-8-2 8:22:00 Author:Robert | Keyword: Hongqi, Century Star, Engine

Hongqi Century Star Engine Circuit
Hongqi Century Star Engine Circuit
Hongqi Century Star Engine Circuit
Hongqi Century Star Engine Circuit
Hongqi Century Star Engine Circuit
Hongqi Century Star Engine Circuit
Hongqi Century Star Engine Circuit
Hongqi Century Star Engine Circuit

The pictures shown the Hongqi Century Star engine circuits. In the first picture, the EO is ECCS ECU. The DB is electric fuel pump. The DS is AAC value. The BJ is electric fuel pump relay. The T10 is 10-hole connector and its colour is yellow (engine wire and engine left wire is connected). The T'10 is 10-hole connector and its colour is blue (engine left wire and the dashboard wire is connected).In the second picture the EO is ECCS ECU. The E1 is oil injector 1. The E2 is oil injector 2. The E3 is oil injector 3. The E4 is oil injector 4. The E5 is oil injector 5. The E6 is oil injector 6. The T26 is a 26-hole connector which is brown (instrument cluster socket engine speed signal). The T'26 is a 26-hole connector which is black (instrument cluster socket car speed signal). The T4, T'4 are 4-hole connectors (engine wire and oil injector is connected). The Si25 is fuse socket which is gray. And so on.   (View)

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MALFUNCTION_ALARM

Published:2009-7-5 22:42:00 Author:May

MALFUNCTION_ALARM
Motorola MOC3011 optoisolator serves as interface between CMOS logic of microprocessor and 5-W 115-VAC lamp.Input logic is connected to energize infrared LED of optoisolator by providing up to 50 mA.Once triggered, indicator lamp remains on until current drops below holding value of about 100 μA.-P. O'Neil, Applications of the MOC3011 Triac Driver, Motorola, Phoenix, AZ, 1978, AN-780,p2.   (View)

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25 ohm speakers overload protection circuit diagram

Published:2011-5-10 1:17:00 Author:Rebekka | Keyword: speakers overload protection

25 ohm speakers overload protection circuit diagram
25 ohm speakers overload protection circuit diagramThe power of overload protection is 650mW, power supply voltage is 12V, speaker 25ohm.Part of the component specifications:VT1: Transistor NB111EH/JVT2: Transistor NR001ETV3: Transistor NA11EB/JVT4: Transistor NA12EB/J   (View)

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IONIZATION_ALARM

Published:2009-7-5 22:38:00 Author:May

IONIZATION_ALARM
Gates in Motorola MC14572 CMOS IC form two alarm oscillators, one energized in presence of smoke at ionization chamber and other for low battery.Standby currents of circuits are low enough to give at least 1 year of operation from 750-mAh battery. R6 is adjusted to give desired smoke detection sensitivity. Gates 1 and 2 form MVBR that drives horn at astable rate of 2.5 s on and 0.2 s off in presence of smoke. When battery is low, comparator Q4-D2-D3 trips (about 10.5 V) and energizes inverter 4 of low-battery astable MVBR. DC horn is then powered at astable rate of about 1 s every 23 s to give early warning of need to change battery.-A. Pshaenich, Solid State Gas/Smoke Detector Systems, Motorola, Phoenix, AZ, 1975, AN-735, p 7.   (View)

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Volumn control circuit diagram

Published:2011-6-23 4:23:00 Author:Rebekka | Keyword: Volumn control

Volumn control circuit diagram
Volumn control circuit diagram.   (View)

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4-word control keyboard circuit diagram

Published:2011-5-10 1:34:00 Author:Rebekka | Keyword: 4-word control keyboard

4-word control keyboard circuit diagram
4-word control keyboard circuit diagram.   (View)

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ZERO_CROSSING_SWITCH

Published:2009-7-5 22:34:00 Author:May

ZERO_CROSSING_SWITCH
When switching loads with the aid of a thyristor, a large amount of RFI can be generated unless some form of zero crossing switch is used. The circuit shows a simple single transistor zero crossing switch. R1 and R2 act as a potential divider. The potential at their junction is about 10% of the ac voltage. This voltage level is fed, via R3, to the transistor's base. If the voltage at this point is above 0.2, the transistor will conduct, shunting any thyris-tor gate current to ground. When the line po-tential is less than about 2 V, it is possible to trigger the thyristor. The diode D1 is to re-move any negative potential that might cause reverse breakdown.   (View)

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Analysing Kewei Home-Use Hand Drier Circuit

Published:2011-7-29 7:32:00 Author:Robert | Keyword: Analysing, Kewei, Home-Use, Hand Drier

Analysing Kewei Home-Use Hand Drier Circuit
Analysing Kewei Home-Use Hand Drier Circuit

The analysis of hand drier circuit's woking principle.The PCB is the main component of the Kewei hand drier. The author has drew this hand drier's full circuit according to the physical PCB, which is shown in picture 1. And the author has also drew this hand drier's working principle diagram by analysing the circuit in picture 1, which is shown in picture 2.1.The power supply circuit.The Kewei hand drier's power supply uses the commercial power 220V as its power supply. The voltage, which the circuit needs, is the DC low voltage (9V). It firstly uses the capacitor C1 to current limiting and voltage step-down. And then it is rectified by diodes D1~D4 and filtered by the electrolytic capacitor C3. At last it would be regulated by the voltage regulator tube Z1. Then it would output the Vcc (9V) DC voltage to supply the hand drier's each part's power. It is added a capacitor C2, C4 for high-frequency pulses filter and a voltage varistor D5 for peak pulse spike limiting in the power loop circuit.   (View)

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FLIP_FLOPS_CONTROL_SAMPLE_AND_HOLD

Published:2009-7-23 22:07:00 Author:Jessie

FLIP_FLOPS_CONTROL_SAMPLE_AND_HOLD
Sampled slices of incoming radar pulse are converted to binary digital form at 10-Mc rate, using flip-flop to connect sample-and- hold capacitor Cs to signal amplifiers. Effective aperture time of sample gate is 20 nsec. Multiplex gate feeds sampled signal values to analog-digital converter at proper time as selected by multiplex counter of system.-A. Hakimoglu and R. D. Kulvin, Sampling Ten Million Words a Second, Electronics, 37:8, p 52-57.   (View)

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IONIZATION_ALARM_USING_TRANSISTORS

Published:2009-7-5 22:21:00 Author:May

IONIZATION_ALARM_USING_TRANSISTORS
Use of continuous smoke alarm signal rather than beeping horn simplifies transistor circuits needed to trigger fire alarm and low-battery alarm. When high impedance of ionization chamber is lowered by smoke or gas, amplifier Q1-Q2-Q3 supplies 100-μA base current to Darlington Q4 for powering hom continuously as Iong as smoke content exceeds that set by threshold control R5. Low-battery circuit is tdpped at voltage range between 9.8 and 11.2 V, as determined by R13, to energize MVBR Q8-Q9 for driving horn 0.7 s, with 50-s OFF intervals.Battery is chosen to last at least t year while furnishing standby current of about 70μA.-A.Pshaenich, Solid State Gas/Smoke Detector Systems, Motorola, Phoenix, AZ, 1975, AN-735,p 8.   (View)

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INTEGRATED_SOLID_STATE_RELAY

Published:2009-7-5 22:19:00 Author:May

INTEGRATED_SOLID_STATE_RELAY
A complete zero-voltage switch solid-state relay contains an input circuit, an output circuit, and the power thyristor. The circuit illustrates a triac power thyristor with snubber circuit and GE-MOVR II Varistor transient over-voltage protection. The 22 ohm resistor shunts di/dt currents, passing through the bridge diode capacitances, from the triac gate, while the 100 ohm resistor limits surge and gate currents to safe levels. Although the circuits illustrated are for 120-V rms operation, relays that operate on 220 V require higher voltage ratings on the MOV, rectifier diodes, triac, and pilot SCR. The voltage divider that senses zero crossing must also be selected to minimize power dissipation in the transistor optisolator circuit for 220-V operation.   (View)

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