Tag Archive: design

 Among the final amplifier we called. Regional Power Amp, will it work on several well-known as Class A, Class B, Class AB etc. Each class of the above, to honor the Class A was superior to the sound quality. best. However, class A power output to a low of 20 percent compared with a loss of power or the power consumption of about 5 times the power output. Therefore, the problem of heat Although it has not paid any audio. But anyway, despite the low-watt power, it also provides crystal clear sound quality than Class B and Class AB.

      Principles of integrated amplifier class A is IC1 – NE5532 to extend signal input through the C1 to increase 15-fold. The signal output from the pin 1, signal hemisphere positive through C2 to access Q1-BD139 and Q3-2N3055. is powered by Darling ton, amplifiers and signal the intensification of the negative side of C3 through the amplifier with the Q2-BD140 and Q4-MJ2955. This is the Darling ton, too.

Then the output signal from the positive side of the pin E of the Q3 and the negative side of the pin out of the E in Q4 through R10 and R11, to prevent short circuits and then output to the speakers. This will power up to 5 watts. The D1-D4 acts as a rectifier in the DC bias for Q1 and Q2. And VR1 is adjusted to a constant current bias is at work. The Q1-Q4 will be attached sheet cooled, Q3 and Q4, especially the thermal plate must be large. Because the circuit has high energy loss.


My H-Bridge consume 3ma@3.3v when there is no load and both inputs are zero,

    How can i reduce it ?
    my goal is <100uA
Q2 and Q8 are SS8550 and Q3 and Q9 are SS8050, other Qs are 2N2222A


  The following CD4017 circuits have not been tested and is presented here as a possibility only. If you experiment with this circuit, please send me any problems found so that the circuit can be updated.

  The following circuits are designed to change the duration of each positive output pulse from the astable timer. The circuits use a CD4017 Decade Counter / Decoder to provide nine or ten steps in the cycle.

  The first circuit operates with a repeating ten step cycle. Each output pulse is longer than the previous until a count of ten is reached at which time the cycle will repeat.

  The second circuit has a nine step cycle that stops at the end of the cycle. The cycle is restarted or reset when the RESET input is briefly made high.

  The CD4017 can be configured to give count lengths between 1 and 10. Refer to the timing diagram in the CD4017 data sheet for a better understanding of the IC’s operation.

The MAX705CSA is a microprocessor (μP) supervisory circuit which reduces the complexity and number of components required to monitor power-supply and battery functions in μP systems. The device significantly improves system reliability and accuracy compared to separate ICs or discrete components. The applications of the MAX705CSA include Computers, Controllers, Intelligent Instruments, Automotive Systems, Critical μP Power Monitoring.
MAX705CSA absolute maximum ratings: (1)VCC: -0.3V to 6.0V; (2)All Other Inputs: -0.3V to (VCC + 0.3V); (3)Input Current, VCC: 20mA; GND: 20mA; (4)Output Current (all outputs): 20mA; (5)Continuous Power Dissipation, Plastic DIP (derate 9.09mW/℃ above +70℃): 727mW.
MAX705CSA features: (1)μMAX Package: Smallest 8-Pin SO; (2)Guaranteed RESET Valid at VCC = 1V; (3)Precision Supply-Voltage Monitor, 4.65V in MAX705/MAX707/MAX813L; 4.40V in MAX706/MAX708; (4)200ms Reset Pulse Width; (5)Debounced TTL/CMOS-Compatible Manual-Reset Input; (6)Independent Watchdog Timer—1.6sec Timeout (MAX705/MAX706); (7)Active-High Reset Output (MAX707/MAX708/MAX813L); (8)Voltage Monitor for Power-Fail or Low-Battery Warning.

Microlab ATX 400w KA7500 Power supply micro lab 400watt atx ka7500 lm339 2sc2625 st3040 st1020 sbl2040 microlab atx 400w 2sc5027 fr107 2sc5344y atx tamir şema atx smps circuit, atx smps repair schema.


The main structure is H-bridge that combines 2 N-channelMOSFETs and 2 P-channel MOSFETs. After testing several MOSFET, in the end wechoose IRFR5305 as P-channel MOSFET and IRFZ48N as N-channel MOSFET. Due tofuture using purpose to apply PWM (Pulse-Width Modulation) as DC motor controltools we choose MOSFET which have lower switch time (include delay, rise andfalling time) to allow us to set high frequency PWM.


For IRFZ48N, Switch ON and delay total take 80ns,Switch OFF with delay take 84ns. As for IRFR5305, total ON state take 90ns andOFF state take 102ns. Due to the design, the most critical action is to changethe H-bridge currect flow direction. This action closed 1 P-MOSFET and 1N-MOSFET. At the same time switch on other 2 MOSFET. Thus we take P-channelMOSFETs OFF state as longest calculation which is 102ns. We multiply it by 2,due to a full consist 2 action (change direction and change back). For safetyreason we advice to apply the period 100 times bigger value than the MOSFETdelay and turn state period, this will make the change state period to bealmost 1% of the total period. This action believes to help on maintain theMOSFET temperature in room temperature. At the same time reduce the chances ofshoot-through situation to happen. The maximum frequency to apply on PWM is 49kHz or 50 kHz.


Besides that we do consider the maximum Vds and peak currentrating. Due to motor maximum voltage is not very high but the current may shootup to very high value when it is hang thus we go for low voltage, high currentMOSFET. Beside both of the MOSFETs we using have very low Rds (on) which is 65and 14 mohm. Assume normal case which is running in 0.5A. Total voltage drop isonly (0.065+0.014)*0.5 = 0.04V. 0.04V is 0.33% loss if we use 12V source.


Diode placed across Drain and Source on every MOSFET asprotection. The Diode will be the path ways to let the back EMF current toflow. Instate of the currect pass through the MOSFETs from Drain to Sourcewhich may burn the MOSFETs. But at the first place we use normal diode and itcause many problem and keep on burn our mosfet. This is due to the recoverytime for our diode is too long compare to our mosfet. The mosfet is notfunction at all. That is why we are now using Fast Recovery Diode, UF4002. Itsturn ON time is 50ns which is faster than the MOSFET switching period. Besidethat it allow 30A currect surge less than 8.3ms, continues current 1A. This isbeyond our safety consideration.


ImageThe entire control is handled by a Microchip PIC18F46K20-I/PT microcontroller, programmed with a firmware that controls the GSM/GPRS module’s activity, reads the logic condition of the two opto-isolated inputs and sends commands to the two relays in the device. Having said that, let’s take a better look at the electrical scheme: power is supplied by continuous voltage, not always stabilized (applied to PWR, + and -) at a value between 5 and 32 V; such voltage is filtered at the bottom by the diode protecting against polarity inversion (D1) through condensers C1 and C2. Fuse F1 enables you to protect both the circuit and the power source in case of short circuit in the integrated regulator discussed below, which is necessary to obtain the 3.6 V, needed for the rest of the circuit to work. The switching regulator U1 is based on a MC34063 chip, used in the classic configuration of the PWM regulators series, charged by inductance, whose output voltage depends on the energy stored in L1; the regulator is stabilized by the component demoted from resistive divider R2/R3, which is needed to set the output tension at 3.6 V. The impulses produced by the inducer’s switching are then leveled by condensers C4 and C5. The 3.6 volts at the bottom of the above mentioned condensers are then filtered by other condensers placed on the power lines of the microcontroller and of the GSM module; which presents, during transmission, absorption peaks compensated for by C7, C8, C13, C14, C15 and C16, thus avoiding that an impulsive current request may cause the microcontroller to be disturbed. The PIC is used in the configuration with an internal clock oscillator; both the scheme and the printed circuit are nevertheless equipped with external quartz, intended for those who want to modify the firmware and develop applications requiring an external oscillator. Once the I/O lines have been initialized, the microcontroller verifies the logical state of the opto-isolated inputs at voltage level (RB4 and RB5) as well as that of lines RC4, RC5, RD0, RD3, RX, which are needed to receive the main notifications from the cellular module; more specifically, RD3 is used to detect incoming calls (it interfaces with RI of the cellular module), while RC4 controls the GSM “field LED”, whose output (dubbed LED) pulses at a frequency of 1 Hz when the module is searching for the radio-mobile network, and supplies impulses at logical zero, lasting 0.5 seconds, followed by a 2-second pause, when the module has grasped the signal. The frequency and duration of the impulses enable the PIC to understand the conditions of the radio-mobile network range and to behave accordingly; for example, if the opto-isolated input goes off and therefore needs to send SMS or make calls, but detects that the cellular module has no reception, it waits for the module to get reconnected to the GSM/GPRS network before making any calls. The microcontroller contains a UART accessible via pins 44 (transmission) and 1 (reception) which it uses in order to communicate with the mobile; more precisely, through the first pin (TX), it cyclically questions the module to check whether any SMS has been received, whereas both TX and RX are used for the communication between the microcontroller and the GSM module when making calls and receiving or sending messages. Regarding the UART, the following control signals are used: CTS (Clear To Send), RTS (Request To Send) and DCD (Data Carrier Detect), which correspond to those of the cellular module being used.
Lines RC5 and RD0 complete the set of I/Os destined to the mobile; the former controls the turning on and off of the GSM (through a transistor placed in the small board of the mobile), the latter takes care of resetting the mobile. The button for locally handling this device’s operating mode is read through line RA3, set as input and equipped with an external pull-up resistor (R11), therefore active at a low level. Inputs are read through lines RB4 and RB5, both of which are set as input and equipped with an internal pull-up; each of them reads the state of the output transistor of the corresponding optocouplers (the optos used here are TLP181). Each of the two available inputs (IN1 and IN2) is active when under voltage between 3 and 30 V. When a 3-volt voltage (at a minimum) is applied to input IN1, the optocoupler’s LED is switched on and the output phototransistor is in conduction state; therefore, the collector (pin 5) is at about zero volt during the I/O initialization, due to the fall on the resistor of the internal pull-up that was configured.  If the input is not polarized, the opto-isolator gets inhibited and its pin 4 is at a high level. As for the relays, they are controlled by the microcontroller’s RC0 and RE2 lines, through two NPN transistors driven by current amplifiers; line RE2 controls transistor T1, while line RC0 controls transistor T2.
A high logical state causes the transistor to saturate, thus determining the mount of current flowing in the coil of the corresponding relay.  Each instance of activation is signaled with a LED, powered along with the coil.  In order to protect the transistors’ collector junction as it goes from saturation to inhibition, when the relay’s coil inductance generates peaks of inverse voltage, we have connected a diode parallel to the coil, such diode eliminates unwanted impulses.  The full exchange is made available from the relays so as to allow for the handling of circuits requiring a normally closed contact or a normally open one.  Still regarding the relay, we should note that, although it is a 5-volt-coil type, it works on just 4 volts in our circuit; this is possible because the model we have chosen can prompt relay exchange even at less than 3.5 volts.
The PIC is programmed in-circuit, through the ICSP connector, which is attached to lines /MCLR, PGU and PGC; the microcontroller’s power and mass are also connected to the ICSP. But we didn’t think that was enough, so we included a serial communication interface enabling users to program the data related to the various functions (e.g., list of phone numbers, handling of input levels, text of SMS sent by the circuit following commands, etc.) through a PC: this allows users to program their remote control before activating it, thus avoiding having to send configuration SMS, which can anyway be used at any time, but are best used only once the system has been installed in situ.
Since the UART is already busy communicating with the cellular module, serial communication occurs via lines RE0 and RA5, respectively used as TX and RX; AN3, assigned to the internal A/D converter, is needed to detect the presence of the 5 volts and therefore the connector insertion.
The serial interface is at a TTL level and can easily be connected to a USB converter USB such as FT232 by FTDI, in order to interface the microcontroller with a PC equipped with USB. For the interface, you can use the FT782M, a small module produced by Futura Elettronica , already equipped with a pin-strip connector at a pitch of 0.10 inches (2,54 mm) that can be directly inserted in our circuit, on the TTL connector, a female SIL at a pitch of 0.10 inches (2,54 mm).
Still regarding the device’s configuration, it is important to note that the corresponding data is not saved in the microcontroller’s EEPROM, but in an external memory chip, dubbed 24FC256-SN; it is a 256- kbit EEPROM CMOS with serial access, and with an I²C-Bus interface.  In order to communicate with such chip, the microcontroller initializes its I/O lines RD4 and RD5, used, respectively, as SDA (data line) and (clock line).
Moving the remote control’s configuration data into an external memory allows us to take advantage of the entire internal EEPROM to enhance its available functions.



The flight controller’s primary goal is to maneuver the aircraft in the desired manner as well as keep it from falling out of the sky. It operates by reading in data from an array of sensors as well as commands sent from the main processor. The main processor sends commands via UART communication to the XMEGA128, which acts as the control for the flight controller. The XMEGA128 then takes these commands, and runs it through different algorithms to convert the command to separate PWM signals that can be sent to the servos and motors to control the aircraft. The XMEGA128 is also reading in data from 4 seperate sensors to gain knowledge about its current orientation as well as predict its motion and help compensate for unwanted changes in position.

The first sensor that the flight controller is interfaced with is the gyroscope. The gryoscope communicates with the XMEGA128 via SPI communication protocol. The gyroscope is used to determine the angular acceleration of the aircraft, so the flight controller can determine if unwanted rotation is beginning to occur on any axis. The gyroscope that is being used is the L3G4200D by STMicroelectronics. This gryoscope offers a number of features that are beneficial to the flight controller. It offers three selectable resolution modes that give a resolution of either 250, 500, of 2000 degrees per second. This will provide us with a high accuracy for low angular accelerations as well as solid accuracy for high angular accelerations. This gyroscope also utilizes an external filter to provide better readings, which consists of R9, C9, and C10 in the schematic. To provide a more steady supply voltage and also improve results further, decoupling capacitors (C7 and C8) are added to the voltage input of the gyroscope.

In order to further monitor the position of the aircraft, two accelerometers are used on the flight controller. The accelerometers that are being utilized are the ADXL345 by Analog Devices. The reason that two accelerometers are being used is so an averaging of the two signals can be performed. Averaging the two signals will allow for a more accurate reading of the orientation of the aircraft and will help to compensate for the noise generated by the vibration of the motors and aircraft in general. The accelerometers provide many nice features including four selectable resolution modes (2G, 4G, 8G, and 16G), as well as data transfer via SPI. The accelerometers also provide programmable interrupt pins that can be used to trigger interrupts on events such as 0-G detection, and activity detection with programmable thresholds. This will allow for full customization so that the accelerometers will tailor to all of the important needs. This accelerometer also utilizes many different decoupling capacitors (C1, C2, C3 for accelerometer 1, and C4, C5, C6 for accelerometer 2) to better clean the input voltage and allow for more accurate results. The reason that three are chosen is so there is a wider frequency response to any noise generated on the line.

Another device which is being utilized is the proximity sensor. The proximity sensor that was chosen was the XLEZ4 by Max Sonar. This sensor will be used primarily in landing sequences, where a high resolution value for altitude is required. This sensor provides an accuracy of 1cm anywhere between 1cm and 765cm. This will allow the flight controller to determine its height very precisely and land without smashing into the ground. This proximity is ideal not only for its long range and high resolution, but also for its UART communication. The only issue faced with this sensor, is that it runs off of 5V, and the UART is between 0 and 5 volts. This is handled with the use of two level shifters which each consist a 2N7002 NMOS (U11 and U12) and 4 10k resistors (R10, R11, R12, and R13). These level shifters convert the 5V signals to 3.3V signals and 3.3V signals to 5V signals, all while requiring very little power to operate.

The flight controller also provides an override system for the user. It utilizes the current receiver on the aircraft, and becomes enabled when the remote control is powered on. The outputs of the receiver are connected into the flight controller and are attached to an array tri-state buffers. The servo outputs of the flight controller are also connected to an array of tri-state buffers. The tri-state buffers that are being used are the SN54HC365, which have 6 internal tri-state buffers as well as enable pins to enable all six tri-state buffers. In order to switch between the flight controller and the override, an inverter is placed on the input of one of the buffer chips, so that when the receiver triggers an override, one buffer is enabled and the other one is disabled, switching which signal is driving the servos. The inverter that is being used is a low power SN74LVC1GU04DBVR.

Lastly, the flight controller provides an array of LED’s. D1 and D2 are being used to signal that power is connected and are being current limited with R14 and R15. D3 through D10 are connected to PORTA of the XMEGA and are used for testing purposes and as status LED’s. They are being current limited by R1 through R8.

This siren circuit simulates police, fire or other emergency sirens that produce an up and down wail.

The heart of the circuit is the two transistor flasher with frequency modulation applied to the base of the first transistor. When the pushbutton is depressed, the frequency of oscillation climbs to a peak and when the button is released, the frequency descends due to the rising and falling voltage on the 22 uF capacitor. The rate of change is determined by the capacitor value and the 100k resistor from the pushbutton.  The oscillation eventually stops if the button is not depressed and the current consumption drops to a tiny level so no power switch is needed.

The 0.1 uF determines the pitch of the siren: A 0.047uF will give a higher pitch siren and a 0.001 uF will give an ultrasonic (at least for me, anyway) siren from 15 to 30 kHz which might have an interesting effect on the neighborhood dogs! The 33k resistor from the collector of the PNP to the base of the NPN widens the pulse to the speaker giving greater volume.

The flasher circuit drives a PNP transistor which powers the speaker. This transistor may be a small-signal transistor like the 2N4403 in most applications since it will not dissipate much power thanks to the rapid on-and-off switching. The 100 ohm and 100uF capacitor in series with the speaker limit the current to about 60 mA and they may be replaced with a short circuit for a louder siren as long as the transistor can take the increased current. The prototype drew about 120 mA when shorted which is fine for the 2N4403.

Transistor substitutions should be fine – try just about any small-signal transistors but avoid high frequency types so that you do not end up with unwanted RF oscillations.

This circuit simulates a chime similar to the sound many cars make when the keys are left in the ignition. The bottom two gates form a squarewave audio oscillator that drives the base of the 2N4401, turning it on and off at an audio rate. The top two gates produce a short low-going pulse about once per second that discharges the 10 uF capacitor through the diode. The voltage then jumps up and slowly decays through the 15 k collector resistor when the 2N4401 is conducting. The result is a squarewave on the collector of the 2N4401 that jumps up quickly then decays slowly. The darlington emitter-follower buffers the squarewave and drives a small speaker.  


The tone frequency is set by the 1000 pF capacitor and the cadence of the chime is set by the 0.1 uF capacitor. The 10 uF capacitor determines how quickly the chime dies out and the 3.3 k/3.3 uF soften the attack time of the leading edge of the chime. The volume is set by the 22 ohm resistor and 100 uF bypass capacitor. These values may be experimentally varied to produce the desired sound.

This learning board has the following features:

    A 9V DC input socket with power on switch

    Regulated +5V power supply using 7805 IC

    3 output LEDs and 1 power on LED

    2 input tact switches

    2 potentiometers: one for analog input and the other for providing reference voltage for ADC

    Transistor-based TTL-RS232 level converter for serial communication.

    A DC motor with a transistor driver.

    A piezo-buzzer

Most of these features on the board are accessible through female header pins. None of the 6-I/O pins of PIC12F683 are hardwired to anything and they are accessible through header pins too. The figures  below show PIC12F683 pins, the type of female headers and jumpers used to make connection on the board, and the detail circuit diagram of the learning board. Only the ISCP pins are accessible through male header pins. The entire circuit is built on a 8 x 12 cm general prototyping board.


 As you see the output LEDs have 470Ω current limiting resistors in series so that a PIC pin can be safely drive them. The piezo buzzer is also driven directly by a PIC pin through a series resistor. The DC motor, however, is connected as a load to the collector of S8050 transistor as the required current to drive the motor cannot be supplied by the PIC port. So, the PIC port can switch on the transistor by pulling its base HIGH and the collector current of the transistor provides the sufficient current to drive the motor.

The TTL to RS232 level converter and vice-versa is achieved with two transistors and few other components. The negative voltage required for RS232 level is stolen from the RS232 port of a PC itself. Note that there is no hardware UART inside PIC12F683, so the serial data transfer from the microcontroller to PC will be possible only through a software UART through any of GP0, GP1, GP2, GP4, and GP5 ports (GP3 is input only). The transmitter and receiver port on microcontroller side are denoted by uTx and uRx, whereas on the PC side are denoted by Tx and Rx, respectively.

The circuit diagram shows that the two input tact switches with the two potentiometer outputs and all the eight PIC12F683 pins are accessible through female headers. The tact switches are active low, i.e., under normal condition, a tact switch output is HIGH and when it is pressed, the output is LOW. There are couple of extra headers for Vcc and Gnd terminals which may be required while doing experiments.

The power supply circuit is the standard circuit of 7805 regulator IC. A power-on LED is connected across Vcc and Gnd with a 470Ω series resistor.

The in-circuit serial programming (ICSP) of PIC12F683 can be done with two pins: ICSPDAT (pin 7), and ICSPCLK (pin 6). The programming voltage, Vpp, should be provided to pin 4 of PIC12F683 while programming. All the required ISCP pins are available through a male header, so the PIC can be programmed through any ICSP PIC programmer. Make sure that the sequence of ISCP pins on the programmer side and our learning board match.

Important: During ICSP, pins 4, 6, and 7 of PIC12F683 should not be connected to anything; leave them open so that there won’t be any voltage conflict between the programmer and the external circuit.