Free Microcontroller and Interface Programming

USB Power Source Circuit for Arduino

2022-09-08T07:57:00.004+07:00

Here’s is a circuit that used for the USB source, power will enter through the USBVCC section into a P-channel MOSFET FDN340P. Explaining briefly, MOSFETS are transistors that are normally closed (connected) until a certain amount of voltage triggers the gate. Consequently, triggering the MOSFET opens the transistor (disconnected). Using this characteristic, a comparator is connected to the gate terminal of the MOSFET to function as a switch mechanism. If you use the USB source, it will just power up the 3.3V regulator since the MOSFET is normally connected. If you plug a dc supply, the LMV358 op-amp will produce a high output triggering the gate of the MOSFET, disconnecting the USB source from the 3.3V regulator. So if both are plugged, the board will use the DC power supply. This is the figure of the circuit.

The 5V terminal here indicates a connection to the circuit powered by the DC power supply earlier. This means that the 3.3V regulator is powered by whichever powers the circuit. Lastly, the LED indicator circuit. Put simply, it lights the green LED up when it detects power from the 5V terminal.

Power Supply Circuit for Arduino

2022-09-08T07:44:00.002+07:00

This is the schematic diagram powers our Arduinos. For this, we can use either DC power supply or USB connection as a source. To trace how the circuit works, let us start with the 5V linear voltage regulator NCP1117ST50T3G. This regulator has a pretty straightforward function. It takes voltage input up to 20V and converts it to 5V. The Vin of this regulator is connected to the DC power supply via the M7 diode. This diode provides reverse polarity protection, which means current can only flow from the power supply to the regulator and not the other way around. This the figure of the circuit.

There are two kinds of capacitors used in this circuit. One, the polarized capacitors PC1 and PC2. They are used to filter supply noise. Two, the 100nF capacitor on the far right side acting as a decoupling capacitor. Decoupling capacitors “disconnects” circuit elements to reduce its effect on the rest of the circuit. Also, notice the +5V terminals circled in blue? You can see them around the schematic diagram. That is basically a connection. Designers often use these terminals so that they can fit their design in the least amount of pages. Labels like Vin and GND also works the same.

Microcontroller vs Microprocessor: Primary Differences

2020-06-03T08:09:00.002+07:00

Typically an MCU uses on-chip embedded Flash memory in which to store and execute its program. Storing the program this way means the MCU having a shorter start-up period and executing code quickly. The only practical limitation to using embedded memory is that the total available memory space is finite. Most Flash MCU devices available on the market have a maximum of 2 Mbytes of Program memory. This may prove to be a limiting factor, depending on the application.

MPUs do not have memory constraints in the same way. They use external memory to provide program and data storage. The program is typically stored in non-volatile memory, such as NAND or serial Flash. At start-up, this is loaded into an external DRAM and execution commences. This means the MPU will not be up and running as quickly as an MCU but the amount of DRAM and NVM you can connect to the processor is in the range of hundreds of Mbytes and even Gbytes for NAND.

Another difference is power. By embedding its own power supply, an MCU needs just one single voltage power rail. By comparison, an MPU requires several difference voltage rails for core, DDR etc. The developer needs to cater for this with additional power ICs / converters on- board.

From the application perspective, some aspects of the design specification might drive device selection in particular ways. For example, is the number of peripheral interface channels required more than can be catered for by an MCU? Or, does the marketing specification stipulate a user interface capability that will not be possible with an MCU because it does not contain enough memory on-chip or has the required performance? When embarking on the first design and knowing that, it is highly likely there will be many product variations. In that case, it is very possible a platform-based design approach will be preferred. This would stipulate more “headroom” in terms of processing power and interface capabilities in order to accommodate future feature upgrades.

STM32F4 Minimal Circuit

2020-06-03T07:02:00.002+07:00

This is a design PCB unit to support everything. This circuit is of course one of the main things on there is the micro. I am currently using the STM32F4 discovery board that has the 100 pin STM32F407VGT on board. Since this basically has everything that I need I decided to simply use that to keep it simple. This is the figure of the schematic.

We know that ARMs are a bit more complex so that's why this circuit is asking for help. or now we need a basic circuit that uses internal oscillators and needs as little hardware as possible (but will still work reliably). And we want it to be programmable using the SWD connector. Using different forums and the original datasheet I've come up with the circuit in the attachment. Is this OK or do I need anything else?

The data sheet mentions a 4.7uF capacitor on one of the power lines but I am not sure if this means that I need a 100nF capacitor and a 4.7uF one or just the 4.7uF. we are also not entirely sure about the VREF+ capacitor either. What else do I need if I want to use the internal RTC? Probably something connected to the VBAT pin? The datasheet mentions a power switch but I don't get how that's supposed to work. This article is based on roli’s blog in eevlog.com

MPC5554 Microcontroller Overview

2020-05-28T09:07:00.001+07:00

The MPC5554 microcontroller (MCU) is a member ofthe MPC5500 family of microcontrollers built on the Power Architectureembedded technology. This family of parts has many new features coupled with high performance CMOS technology to provide substantial reduction of cost per feature and significant performance improvement over the MPC500 family. The host processor core of this device complies with the Power Architecture embedded category that is 100% user-mode compatible (including floating point library) with the original PowerPC instruction set. The embedded architecture enhancements improve the performance in embedded applications. The core also has additional instructions, including digital signal processing (DSP) instructions, beyond the original PowerPC instruction set. This is the figure of the MPC5554 chip;

The MPC5500 family of parts contains many new features coupled with high performance CMOS technology to provide significant performance improvement over the MPC565. The MPC5554 has two levels of memory hierarchy. The fastest accesses are to the 32-kilobytes (KB) unified cache. The next level in the hierarchy contains the 64-KB on-chip internal SRAM and two-megabytes (MB) internal flash memory. The internal SRAM and flash memory hold instructions and data. The external bus interface is designed to support most of the standard memories used with the MPC5xx family.

The complex input/output timer functions of the MPC5554 are performed by two enhanced time processor unit (eTPU) engines. Each eTPU engine controls 32 hardware channels, providing a total of 64 hardware channels. The eTPU has been enhanced over the TPU by providing: 24-bit timers, double-action hardware channels, variable number of parameters per channel, angle clock hardware, and additional control and arithmetic instructions. The eTPU is programmed using a high-level programming language. The less complex timer functions of the MPC5554 are performed by the enhanced modular input/output system (eMIOS). The eMIOS’ 24 hardware channels are capable of single-action, double-action, pulse-width modulation (PWM), and modulus-counter operations. Motor control capabilities include edge-aligned and center-aligned PWM. Off-chip communication is performed by a suite of serial protocols including controller area networks (FlexCANs), enhanced deserial/serial peripheral interfaces (DSPIs), and enhanced serial communications interfaces (eSCIs). The DSPIs support pin reduction through hardware serialization and deserialization of timer channels and general-purpose input/output (GPIOs) signals.

The MCU has an on-chip enhanced queued dual analog-to-digital converter (eQADC). 324 s40-channels. The system integration unit (SIU) performs several chip-wide configuration functions. Pad configuration and general-purpose input and output (GPIO) are controlled from the SIU. External interrupts and reset control are also determined by the SIU. The internal multiplexer submodule provides multiplexing of eQADC trigger sources, daisy chaining the DSPIs, and external interrupt signal multiplexing.

Inside A Microcontroller

2020-05-28T08:47:00.002+07:00

A microcontroller can be seen as a small computer, and this is because of the essential components inside of it; the Central Processing Unit (CPU), the Random-Access Memory (RAM), the Flash Memory, the Serial Bus Interface, the Input/Output Ports (I/O Ports), and in many cases, the Electrical Erasable Programmable Read-Only Memory (EEPROM). Figure 1 shows a great diagram of the main parts and also other parts in the microcontroller. Let’s dive into each of these components and see how they work inside the microcontroller. This is the figure of the inside part of a microcontroller.

The CPU, sometimes called a processor or microprocessor, controls all of the instructions/data flow that it receives. You can think of it as the brains of the system, processing all the data input it receives and executes the required instructions. Its two main components are the Arithmetic Logic Unit (ALU), which performs arithmetic and logical operations, and the Control Unit (CU), which handles all of the processor’s instruction executions. Figure 2 shows a usual "machine cycle" that the CPU goes through.

RAM (Random Access Memory) is a component that temporarily stores data, and can be accessed quickly. It provides quick read-and-write access to the storage device. This differs from most other memories as it takes longer for data to be extracted since the data isn’t readily available. You can see it as RAM having access to the surface of data – easily reachable – but anything that dives deeper will require a different type of memory. RAM improves total system performance because it allows the microcontroller to work with more information at the same time. Since RAM is temporary data, its content is always erased when the microcontroller is shut down.

Flash Memory is a type of non-volatile memory that, unlike RAM, retains its data for an extended period, even if the microcontroller is turned off. This keeps the saved program that you might have uploaded to the microcontroller. Flash Memory writes to a “block” or “sector” at a time, so if you need to just re-write one byte, Flash Memory will need to re-write the whole block that the byte is in, which can wear out quicker.

EEPROM is like Flash Memory, being a non-volatile memory and retaining its data even after shutdown. The difference is that, while Flash Memory re-writes a “block” of bytes, EEPROM can re-write any specific byte at any time. This extends the life of EEPROM compared to Flash Memory, but also means that it is more expensive.

A Serial Bus Interface is the serial communication in the microcontroller, sending data one bit at a time. With microcontroller boards, it connects ICs with signal traces on a printed circuit board (PCB). For ICs, they use serial bus to transfer data to reduce the number of pins in a package making them more cost effective. Examples of serial buses in ICs are SPIs or I2Cs.

I/O ports are what the microcontroller uses to connect to real-world applications. Inputs receive changes in the real-world, from temperature sensing, to motion sensing, to push buttons, and much more. The input then goes to the CPU and decides what to do with that information. When it’s time to do a certain command based on a certain value from the input, it sends a signal to the output ports, where it can range from a simple LED light going off, to running a motor for a certain part, to many more. Figure 3 shows some common input and output components.

Temperature to Digital Converter Circuit

2013-02-11T14:53:00.000+07:00

This is a design circuit for temperature to digital converter circuit that is based control by LM35 IC. This LM35 is precision integrated-circuit temperature sensors, whose output voltage is linearly proportional to the Celsius (Centigrade) temperature. The LM35 thus has an advantage over linear temperature sensors calibrated in ° Kelvin, as the user is not required to subtract a large constant voltage from its output to obtain convenient Centigrade scaling. The LM35 does not require any external calibration or trimming to provide typical accuracies of ±1⁄4°C at room temperature and ±3⁄4°C over a full −55 to +150°C temperature range. This is the figure of the circuit schematic;

How this circuit can work? This circuit is supply the power using 5VDC that produce by power supply. And then the voltages enter the circuit as analog signal. This signal is enter to the LM35 to detected and calculate by the sensor. The output signal from LM35 send to the ADC converter to processing the digital signal. Before the digital signal is send to the controller by pin 8, there are voltage for reference that given to the amplifier. This reference is using as compare when calculating in microcontroller or microprocessor.

Single Chip Temperature Data Logger

2011-03-30T17:25:00.000+07:00

A data logger is a device that records measurements over time. The measurements could be any physical variable like temperature, pressure, voltage, humidity, etc. This project describes how to build a mini logger that records surrounding temperature values. This is the figure of the circuit;
Temperature will be measured with a DS1820 temperature sensor. DS1820 is a one wire digital temperature sensor from Dallas Semiconductor (now MAXIM). The operating temperature range of the device is -55°C to +125°C with an accuracy of ±0.5°C over the range of -10°C to +85°C. The temperature sensor output is 9?bit Celsius temperature measurement, and so the temperature resolution corresponds to the least significant bit, and which is 0.5°C. But in this project we will use only the most significant eight bits. Therefore, the temperature resolution will be 1°C. The measured temperatures will be recorded into the internal EEPROM memory of PIC12F683.

The first location of the internal EEPROM will store the sampling interval of data logger. Sampling interval defines the time gap between two successive measurements. This project will have 3 options for sampling time: 1 sec, 1 min, and 10 min. These are user selectable. The second location of EEPROM will store the number of measurements recorded so far. And the remaining 254 EEPROM locations will store 8?bit temperatures. So, using 10 min sampling interval, 254 bytes of EEPROM will provide data logging for 42 hours. The recorded measurements can be sent to PC at any time through a serial link at 9600 baud.

LCD Module Control Using PC

2011-03-30T17:22:00.000+07:00

Here’s a design circuit for simple circuit controls a popular 2-line x 16-character LCD by a PC via printer port. It doesn't use the Bi-directional feature found on newer printer ports, thus it should work with most, if not all Parallel Ports. These LCD Modules are very common these days, and are quite simple to work with, as all the logic required to run them is on board. This is the figure of the circuit;

The LCD panel's Enable and Register Select is connected to the Control Port. The Control Port is an open collector/open drain output. While most Parallel Ports have internal pull-up resistors, there are a few which don't. Therefore by incorporating the two 10K external pull up resistors, the circuit is more portable for a wider range of computers, some of which may have no internal pull up resistors. The 10k Potentiometer controls the contrast of the LCD panel. The software source code has been written in Borland C++.

Electronic MIDI Drum

2011-03-30T17:16:00.000+07:00

Here’s a design circuit for a MIDI interface between drum pads and computer or hardware sequencer. Using this circuit you can hit pads with drumsticks and store the MIDI data in real time. This is the figure of the circuit;

This circuit is based around the PIC16C84 microcontroller which scans the inputs on RB0 to RB7 and when a high is detected the software transmits the equivalent note-on (and then the MIDI note-off after a short delay) for the required drum sound on the MIDI output on RA0.

Digital Light Sensor to Microcontroller Circuit

2011-03-30T17:06:00.000+07:00

This is a design circuit for digital light sensor circuit using microcontroller. The ISL29001 is an integrated ambient light sensor with ADC and I2C interface. With a spectral sensitivity curve matched to that of the human eye, the ISL29001 provides 15-bit effective resolution while rejecting 50Hz and 60Hz flicker caused by artificial light sources. This is the figure of the circuit;

In normal operation, the ISL29001 consumes less than 300µA of supply current. A software power-down mode controlled via the I2C interface disables all but the I2C interface. A power-down pin is also provided, which reduces power consumption to less than 1µA. The ISL29001 includes an internal oscillator, which provides 100ms automatic integration periods, or can be externally timed by I2C commands. Both the internal timing and the illuminance resolution can be adjusted with an external resistor.

Led Matrix Circuit With AT90S2313 Microcontroller

2011-03-19T02:29:00.000+07:00

LED ball physically assembled in a matrix of dimension 20 Rays and 7 LEDs. LEDs are governed microcontroller and two decoder K155ID10. Operating current 80mA decoders, this is enough to connect the LED matrix in the dynamics of directly between the microcontroller and decoders, excluding transistors, the brightness of LEDs is sufficient. The control circuit assembled on two boards, located in the center of the ball, moving away from them rays – soldered in one line cathodes, LEDs, and the anodes are connected by layers of thin wire as a cobweb. This is the figure of the circuit;

Before installing the need to bend legs of chips at 90 degrees, solder all the details of one party to the first charge, then at the opposite conclusions to put a second charge and finish soldering. Podpayat supply wires and programming, flash microcontroller and check the output signals. Only then can continue mounting LEDs. To facilitate the work necessary to prepare a template – a hole in the cardboard (plywood, plastic) 7 holes for the LEDs on the same line two centimeters. Then bend cathodes of LEDs 90 degrees right next to their body, insert the LEDs into the template and unsolder beam deflected conclusions. Each of the 20 rays soldered into the board and turn down under the picture. To give the rigidity of the whole structure, anodes maximum distance from the center LED solder together a 10-centimeter segments of tinned copper wire, giving the correct type of construction of the dodecahedron (face-pentagon at each vertex, three edges). Then solder each layer remaining anodes of LEDs and connect each layer to the relevant conclusions resistance. With proper installation will start building a microcontroller embedded in his light effects. For a change, it automatically changes the number of repetitions, speed, brute force effects. This is enough to exclude the interference of the operator. The program is written in a medium BASCOMAVR, if desired in the source code can add or change inherent effects.

Infrared and Ultrasonic Scanner Using ATMega

2011-03-19T02:23:00.000+07:00

This is a project that is a short range, infrared and ultrasonic scanner that uses a standard hobby servo to move the sensors and a color LCD screen to display the information from the distance sensors. The information displayed on the LCD is an overhead view of the scanning area, with increments of distance from the distance sensors. This is the figure of the project;

The core of the project is the ATMEGA32 microcontroller from Atmel. It controls the servo, gathers information from the sensors and places the information on the LCD screen. There is 32K of flash in the microcontroller and the software uses about 13K of that. Since the LCD uses a maximum of 3.3V, the microcontroller is run at 3.3V.

Counter Wall 7 Segment Circuit

2011-03-19T02:18:00.000+07:00

This is a design circuit that is simple counter can be used to count pulses, as the basis for a customer counter (like you see at the doors of some stores), or for anything else that may be counted. The circuit accepts any TTL compatible logic signal, and can be expanded easily. This is the figure of the circuit;

All pulses to be counted are to be TTL compatible. They should not exeed 5V and not fall below ground. You can add more digits by building a second (or third, or fourth, etc…) circuit and connecting the pin 11-6 junction of the 74LS90 and 74LS47 to pin 14 of the 74LS90 in the other circuit. You can keep expanding this way to as many digits as you want.

Compass Sensor Circuit Using Microcontroller Project

2011-03-19T02:11:00.000+07:00

This circuit is design circuit to build a digital compass that displays both the direction and cardinal points on a television. Other functionalities were added to complement the sensor interface, such as, temperature display, magnetic declination input and disability option. This is the figure of the circuit;

The HMC1052 two-axis magnetic sensor contains two Anisotropic Magneto-Resistive (AMR) sensor elements in a singleMSOP-10 package. Each element is a full wheat stone bridge sensor that varies the resistance of the bridge magneto resistors in proportion to the vector magnetic field component on its sensitive axis. The two bridges on the HMC1052 are orientated orthogonal to each other so that a two-dimensional representation of an magnetic field can be measured. The bridges have a common positive bridge power supply connection (Vb); and with all the bridge ground connections tied together, form the complete two-axis magnetic sensor. Each bridge has about an 1100-ohm load resistance, so each bridge will draw several milli-amperes of current from typical digital power supplies. The bridge output pins will present a differential output voltage in proportion to the exposed magnetic field strength and the amount of voltage supply across the bridge. Because the total earth’s magnetic field strength this very small (~0.6 gauss), each bridge’s vector component of the earth’s field will even be smaller and yield only a couple milli-volts with nominal bridge supply values. An instrumentation amplifier circuit; to interface with the differential bridge outputs, and to amplify the sensor signal by hundreds of times, will then follow each bridge voltage output.

Uninterruptible Power Supply Using PIC17C43 Microcontroller

2011-01-30T18:59:00.000+07:00

That is a design circuit for Microchip Uninterruptible Power Supply (UPS) reference design with PIC17C43 microcontroller. Here’s the figure of the power supply;

At times, power from a wall socket is neither clean nor uninterruptible. Many abnormalities such as blackouts, brownouts, spikes, surges, and noise can occur. Under the best conditions, power interruptions can be an inconvenience. At their worst, they can cause loss of data in computer systems or damage to electronic equipment.

It is the function of an Uninterruptible Power Supply (UPS) to act as a buffer and provide clean, reliable power to vulnerable electronic equipment. The basic concept of a UPS is to store energy during normal operation (through battery charging) and release energy (through DC to AC conversion) during a power failure. UPS systems are traditionally designed using analog components. Today these systems can integrate a microcontroller with AC sine wave generation, offering the many benefits. The PIC17C43 microcontroller handles all the control of the UPS system. The PIC17C43 is unique because it provides a high performance and low cost solution not found in other microcontrollers.

Centigrade and Fahrenheit Scale Digital Thermometer Using LCD Display

2011-01-30T18:54:00.000+07:00

This is a design circuit for Digital thermometers are cool devices as they show temperatures in human readable formats. This digital thermometer project is based on a PIC16F688 microcontroller and a DS1820 temperature sensor, and it displays temperature on a character LCD screen in both Celsius and Fahrenheit scales. I selected PIC16F688 for this project because it is cheap (I bought one for $1.50). DS1820 is a 3-pin digital temperature sensor from Dallas semiconductors (now Maxim) which is designed to measure temperatures ranging from -55 to +125 °C in 0.5 °C increments. Here’s the figure of the circuit;

The firmware I have written is able to read and display the entire temperature range of DS1820. In order to test for temperature measurements below 0°C, I put the sensor inside my freezer. While trying this, don’t put the whole unit inside the freezer as LCD display unit may stop working at the freezer temperature. Similarly, bringing a soldering iron tip close to the sensor can do testing for the higher range temperature values.

Using Reset IC in Microcontroller

2011-01-25T20:28:00.000+07:00

This is a the design of microcontroller based electronics project, the use of Reset IC is critical for highly critical applications that need to ensure that the MCU will only operate at its optimum voltage. Without the use of reset circuitry, the MCU may go into a tristate of which it may go into abnormal operation. This is the figure if the circuit;

During power up, once Vcc exceeds the reset threshold, the reset line will be kept low for a period after which the line will be pulled high. This resets the MCU afterwhich it will go into normal operation.

If the Vcc drops below the reset threshold, the reset pin will go low. It will stay low for at least the reset time out period and go back to high again. This operation will ensure that the MCU power supply is monitored and will only go into operation when the Vcc is within the range of its operation. The threshold voltage of the IC is chosen based on the minimum Vcc of the MCU. MCU supply can range from 1.8V to 5.0V and a suitable IC can be chosen to monitor the supply voltage to the MCU.

The Voltage Regulator

2011-01-25T20:20:00.000+07:00

The DC voltage produce by this circuit is depend on the load; the heavier the load (more current to the load) means the capacitor discharge time will be more faster and as a result the DC voltage output level will be drop. The circuit above is called unregulated AC to DC converter; because it could not maintain its voltage output level, this kind of power source could not be use in electronic circuit that required constant voltage level in order to operate properly such as in digital and microcontroller circuit. Therefore we need what is called Voltage Regulator Circuit and at the same time works as the DC to DC voltage step down.

The first one is the analog voltage regulator, this type of regulator operate the transistor in its linear region (current gainer). The current supplied to the transistor base lead is depend on the voltage different between the reference voltage and output voltage apply to the error amplifier input; for example when the output voltage is greater than the reference voltage, than the error amplifier will make the transistor to conduct less, this mean the voltage drop across the collector and emitter (Vce) will be increase this will make the output voltage to decrease and vice verse. With output voltage being continuously compared to the reference voltage (close loop feedback) by the error amplifier, this kind of circuit could maintain its voltage output level constantly. The disadvantage of using this type of voltage regulator is the power dissipation (power lost as a heat) on the transistor is high especially when we want to use 5 Volt output from 11.33 volt from the unregulated DC source or drain lot of current from it.

The second one is the most efficient voltage regulator as this type of voltage regulator operates the transistor in its saturate region or known as a switching voltage regulator. The working principal is the same as the analog one, but instead of using the constant current to the transistor base lead; this voltage regulator type use pulse current or known as PWM (Pulse Width Modulation) to the transistor base lead and this make the transistor to turn on and off according to the PWM duty cycle supplied by the error amplifier. Therefore by changing the PWM duty cycle we could change the average voltage drop across the collector and emitter (Vce). The inductor (L) is used to release its energy to the load through the diode (D) when the transistor is turn off; and when the transistor is turn on then the transistor will supply the current to the load and the inductor will store the energy in the electromagnetic form; in other word the inductor and diode will ensure that the load will always get a constant current when the transistor is turn off.

Making a Binary Clock Using a PIC Microcontroller

2011-01-25T20:17:00.000+07:00

This is a design circuit for binary clock circuit. This circuit is the same hardware as the led matrix project using a 16F88 PIC microcontroller and an LED matrix. Its worth taking a look there as the same hardware description applies on how to multiplex the display. This is the figure of the circuit;

To display hours, minutes and seconds (2 digits each) you need 6 binary digits in total (depending on whether you use a 24 hour clock the top digit needs only 1 or 2 LEDs).

DC to DC Step-Up Regulator

2011-01-25T20:12:00.000+07:00

This is a design circuit for the Maxim MAX756 is the sample of easy to use DC to DC step-up switching regulator; this chip is used to increase the typically low input DC voltage 1.1 volt - 1.8 volt to the output DC voltage of 3.3 Volt or 5 Volt at maximum 200mA load (300mA on 3.3 Volt output). This is the figure of the circuit;

This means you could easily power your microcontroller project using just a single AA/AAA battery. This kind of step-up power is widely use on digital and microcontroller circuit that powered by low input voltage battery such as micro alkaline 1.5 volt battery. The basic schematic for 5 volt output from 1.5 volt battery. The output voltage of Maxim MAX756 could be selected from 5 volt or 3.3 volt by putting logical low or high on pin 2 (3/5), it also supply the low output indicator detector to the circuit if needed through the pin 4 (LBO). The following picture shows the Maxim MAX756 IC circuit powering the microcontroller’s board using just 1 AA alkaline battery (1.5 Volt).

PIC Frequency Counter Operating Up To 50 MHz

2011-01-17T22:41:00.000+07:00

This is a design circuit for general theory of operation of this circuit and notes on frequency counting. This circuit is based on PIC microcontrollers for the main control unit of the circuit. This is the figure of the circuit;

The LCD is used in 4 bit mode interface so you only need 4 data lines and three control lines and it then fits into a single 8 bit port.

The crystal oscillator is simply a crystal and two capacitors connected to the PIC oscillator port at OSC1 and OSC2. The capacitors can both be fixed at the same value unless you want to tune it using a frequency reference. If you don't have an accurate reference then use fixed capacitors. The PIC micro can be any type that has a Timer 1 hardware and and has enough memory to hold the program. The LED is toggled at the end of every gate time to indicate that the processor is alive - so if there is no input signal you can tell that the software is working.

Multiple PIC16F84 Proteus Simulated Projects

2011-01-17T22:39:00.000+07:00

Proteus is a software tool that allows simulation of various circuits including microcontroller based ones. You can complete entire project with simulator including hardware and software parts. And only then you can move towards manufacturing real device. This page is dedicated only to PIC16F84 microcontroller projects where you can download ready to simulate about 31 complete project.

Projects include implementation of popular interfaces like LCD, Timers, EEPROM writing, Interrupts, I2C and 1-wire communication, motor control and so on. Each project include Proteus project file and microcontroller hex file that has to be attached to model to start simulate.

MIC 702 Mictronics Circuit

2011-01-17T22:35:00.000+07:00

This is a design circuit that can be used to convert a standard LCD interface parallel to serial interface model, use a microcontroller or a dedicated circuit such as the MIC 702 Mictronics you can download the complete data sheet and French by clicking this link. This is a circuit specially designed to transform the parallel interface and LCD display logic integrated asynchronous serial interface standard. This is the figure of the circuit;

The MIC 702 is connected directly to the display with which it is perfectly compatible. Notice the connection with only 4 data bits of high weight since the MIC 702 operates in the display mode twice 4 bits. PC side, the connection with the serial output of the PC does not involve any level converter for RS 232 TTL, this role being played by the only resistor R1 22 ohm whose presence is essential. BAUD The tab allows you to choose the operating speed of the circuit between two speeds: 9600 bps up with S1 or S2 with 2400 baud up. The leg POL allows the circuit to interpret the serial data as direct or inverted. As it is in direct RS232 link should be link this foot to ground to indicate the MIC 702 that receives data reversed. Linkage to +5 volts it would receive direct evidence as would be the case if we wanted to use this circuit with a Basic Stamp example.

Subject to use a display not backlit, the total consumption of the circuit is low enough that it can take its power directly from the output control signals to the RS 232. It is the role of diodes D2 and D3 associated with IC1, which is a regulator with low dropout voltage and low consumption. If you insist on using a backlit display, it is possible that consumption of its single backlight exceeds the possibilities of the PC's serial port. You can use an external power supply via the diode D1. A voltage of 9 volts at a flow rate of a hundred mA appropriate.

Driver an RGB LED Using Three Microcontroller Pins

2011-01-17T22:31:00.000+07:00

The RGB LED contains three LEDs encased in one shell: Red, Green and Blue (some contain an extra blue led - as blue LEDs generate less output intensity (candela) per mA). It looks like a single white led except that it has four leads - one for the common ground connection and one for each led. This is the figure of the circuit;

This project uses puls width modulation to drive each of the leds in the RGB led. By changing the duty cycle of each PWM signal you can control the average current flowing through each led creating any color you want. The limit is set by the resoelution of the PWM (set at 256 steps per channel). The project relies on persistence of vision to make it appear that the led is continuously driven (the PWM signals must be repeated quickly enough so that you do not see any flicker) at a rate greater than 50Hz (approx). Too slow and you begin to see the led flickering.

By varying the current through each led you can create almost any other color but at close range you only see the individual colors of each LED. To see the 'merged' color view it from a distance or put a diffuser over it. I used a small piece of baking paper - which is transparent enough to let the light through and opaque enough to diffuse the light from the three LEDs. In a proper design you would use a semi-transparent plastic.