UC3842 CURRENTMODE PWM CONTROLLER

The  UC3842  is available in an 8-Pin mini-DIP the necessary features to implement off-line, fixed-frequency current-mode control schemes with a minimal external parts count. This technique results in improved line regulation, enhanced load response characteristics, and a simpler, easier to design control loop. Topological advantages include inherent pulse-by-pulse current limiting.

Frequency Divider by LM555 and 4040

 

U1 7555 is a CMOS version of 555 LM555 pdf datasheet.

The LM555 here is in Astable Oscillator mode, C1 and C4 are decoupling capacitors 0.1uF value, ceramic disc.

The output is around 100kHz, If C3 is plastic or mica the frequency output will be stable with temperature. It is better to use a crystal oscillator.

The 555 output is fed to clock input of 4040, the output of 555 will be a square wave, on every high to low transition (falling edge or negative transition) the counter increments by one and the output is 12 bit binary.

If input frequency is F the final output at Q12 is F/4096. The period T = 1/F.

If you make the 555 run at 1Hz, C3 around 7uF, Then this circuit becomes a long duration timer, the Q12 period will be 4096 seconds or 68 minutes

Digital voltmeter using ICL7107

The circuit given here is of a very useful and accurate digital voltmeter with LED display using the ICL7107 from Intersil. The ICL7107 is a high performance, low power, 3.5 digit analog to digital converter. The IC includes internal circuitry for seven segment decoders, display drivers, reference voltage source and a clock. The power dissipation is less than 10mW and the display stability is very high.

The working of this electronic circuit is very simple. The voltage to be measured is converted into a digital equivalent by the ADC inside the IC and then this digital equivalent is decoded to the seven segment format and then displayed. The ADC used in ICL7107 is dual slope type ADC. The process taking place inside our ADC can be stated as follows. For a fixed period of time the voltage to be measured is integrated to obtain a ramp at the output of the integrator. Then a known reference voltage of opposite polarity is applied to the input of the integrator and allowed to ramp until the output of integrator becomes zero. The time taken for the negative slope to reach zero is measured in terms of the IC’s clock cycle and it will be proportional to the voltage under measurement. In simple words, the input voltage is compared to an internal reference voltage and the result is converted in a digital format.

The resistor R2 and C1 are used to set the frequency of IC’s internal clock. Capacitor C2 neutralizes the fluctuations in the internal reference voltage and increases the stability of the display.R4 controls the range of the voltmeter. Right most three displays are connected so that they can display all digits. The left most display is so connected that it can display only “1” and “-“.The pin5(representing the dot) is connected to ground only for the third display and its position needs to be changed when you change the range of the volt meter by altering R4. (R4=1.2K gives 0-20V range, R4=12K gives 0-200V range ).

An Arduino Compatible Using CP2102

Standard Arduino boards use FTDI’s FT232RL to interface with computer’s USB port. Since FT232R is just a USB to UART converter, it is possible to build an Arduino compatible USB interface using other USB to UART chips.

One such alternative is Silicon Labs‘ CP2102. I particularly like this USB to UART transceiver because very few extra components are required for it to work. As an added benefit, this chip is also cheaper than the ubiquitous FT232R. Of course, there are also a few trade offs. First of all, CP2102 does not provide a bit bang interface (the X3 pins on the Arduino board on the other hand can be used for bit bang operations, but the X3 pins are not soldered with header pins by default and thus for the average users no bit bang support should not be an issue). Secondly, CP2102 does not have the configurable general purpose I/O pins to drive the TX/RX LEDs. There are other minor differences as well (for instance the maximum transmission speed for FT232R is 3Mbps while CP2102 tops at 1Mbps. Both chips are more than adequate for the maximum 115,200 baud rate supported in Arduino environment), but they do not affect the performance in our application of interfacing with Arduino.

Here is the schematics for using CP2102 with ATmega328p (the circuit below is compatible with the Arduino IDE):

ATmega64 Test Board

Achtung! Abweichend vom Plan müssen folgende Dinge beachtet werden:

Pin 20 ist der Reset-pin. Er ist active-low was bedeutet, er muss über einen Taster auf Masse geführt werden. Drückt man den Taster wird der Pin auf 0V (Ground) gezogen und der yC führt einenr Reset aus

Pin 64 ist die Versorgungsspannung vom A/D-Wandler. Sie muss an die 5V VCC-Leitung angeschlossen werden.

Vielleicht mache ich nochmal ein überarbeitetes Schema

Achtung! Je nach Bauform sind die Pinbelegungen unterschiedlich!!!!! Bei falscher Beschaltung reichen die 5V des USB-Portes aus um die gesamte Schaltung zu grillen. Also vorher mindestens drei mal überprüfen. Die Pinbelegungen im Schaltplan beziehen sich auf auf den ATmega64 Bauform TQFP/MLF und auf den FT232R Bauform QFN32.

H-Bridge Motor Driver Using Bipolar Transistors 2N2907A

The classic beginner’s DC motor driver circuit that appears in every electronics textbook is the bipolar transistor H-bridge.

An H-bridge is an arrangement of transistors that allows a circuit full control over a standard electric DC motor. That is, an H-bridge allows a microcontroller, logic chip, or remote control to electronically command the motor to go forward, reverse, brake, and coast.

For the purposes of this article, I’m focusing on a basic H-bridge that is a good choice for most robots (including BEAM robots) and portable gadgets. This H-bridge can operate from a power source as low as two nearly-exhausted 'AAA' batteries (2.2V) all the way up to a fresh 9V battery (9.6V).

In later pages, I'll compare the performance of three different part numbers of popular transistors (2N3904/2N3906 vs 2N2222A/2N2907A vs Zetex ZTX1049A/ZTX968) using a common robot motor from Solarbotics.

The H-bridge circuit (below) looks complicated at first glance, but it is really just four copies of a resistor + transistor + diode.


Schematic of a bipolar transistor hbridge circuit to drive a DC motor. Can you see the letter 'H'?
There are many different ways to draw the circuitry, but the above wiring diagram matches the model of most h-bridges.

Q1, Q3: These are NPN transistors. They connect the motor to ground (negative terminal of the battery).
Q2, Q4: These are PNP transistors. They connect the motor to +2.2V to +9.6V (positive terminal of the battery).
R1-R4: These resistors prevent too much current from passing through the base (labeled B) control pin of the transistor. The resistor value of 1 kilohm (1000 ohms) was chosen to provide enough current to fully turn on (saturate) the transistor. A higher resistance would waste less power, but might cause the motor to receive less power. A lower resistance would waste more power, but wouldn’t likely provide better performance for motors running on consumer batteries.
D1-D4: Diodes provide a safe path for the motor energy to be dispersed or returned to the battery when the motor is commanded to coast or stop. I notice many H-bridge circuits on the web lack these diodes. I suppose that’s safe enough for light loads at low voltages, but without diodes, a motor voltage spike can force its way through the unprotected transistors, damaging or destroying them.
M1: This is a direct-current (DC) motor. These are very common. You can find them in surplus stores online or in salvaged toys. The motor should have only two wires. Measure the resistance of the two motor wires using a multimeter. If the motor resistance is less than 5 ohms, then the transistor parts listed in this article are too weak to power the motor.

Упрощённый усилитель звука на TEA2025B

Упрощённый усилитель звука на TEA2025B
Можно использовать аккумулятор от сотового (3.7в) вполне пойдёт для питания схемы.