Tag Archives: ADC

Thermometer with PIC Microcontroller

In the last tutorial we learn about the multiplexing technique used with seven segment displays. We learnt how it saves i/o line by using persistence of vision. Only one digit is lit at a time, but to a human eye it is too fast to catch, so we see all four digit lit the same time. In this tutorial we will make a practical use of multiplexed seven segment displays. We will use them to show current room temperature using a LM35 temperature sensor. Before reading further make sure you know the following concepts Multiplexing Seven Segment Display with PIC Micro. Using ADC of PIC Micro. Interfacing LM35 temperature sensor with PIC Micro. Schematic for PIC Thermometer Please note that this schematic is slightly different from our previous schematic on multiplexed seven segment display. The display select i/o pins were RA0,RA1,RA2,RA3 on that schematic. But in this schematic the display lines are RA1,RA2,RA3,RA4 this is because RA0 is used as analog input channel for LM35′s output. PIC Thermometer using LM35   Multiplexed Seven Segment wiring We use our PIC Development Board for making the above demo project. The PIC Development Board has all the core circuitry to sustain the MCU while the project specific part is developed on the expansion board. Multiplexed Seven Segment Display Setup   Multiplexed Seven Segment […]

Interfacing MMA7260 Triple Axis Accelerometer with ATmega32 – AVR Tutorial

Accelerometers are recently developed solid state electronics devices that makes it very easy to measure acceleration. They are completely modular and very tiny devices which gives voltage proportional to acceleration. These type are called analog accelerometers as their output is voltage. Some other gives a PWM output or direct binary digital data, they are called digital accelerometers. Accelerometers are used widely in modern devices. Apple iPhone,iPad and Nokia series 60v5 devices for automatic screen orientation changing. Also for motion gaming and other showoff stuff like Xpress Beer in above devices. Portable Hard disk and Notebooks for fall detection. Anti-theft devices. Motion Gaming Consoles like Nintendo Wii. Balancing Robots and UAVs. Experiments which needs to find force, like car crash experiments. And Possibly many other. Accelerometers can measure acceleration in 2 dimensional or 3 dimensional space. They are called 2D and 3D accelerometers respectively. Accelerometers have certain range, i.e. the maximum acceleration they can measure. It is specified in terms of g. ‘g’ is the acceleration due to gravity of earth and it is equal to 9.80665m/s2. Common accelerometers can have a range of 1.5g to 6g. It is obvious that 1.5g accelerometer is more precise than 6g. So use 1.5g where more accuracy is needed while use 6g for much more harsh experiments. Renault R26 can pick up 100km/hr is […]

Interfacing LM35 Temperature Sensor with PIC Microcontroller.

The are many cool sensors available now a days, ranging from IR distance sensor modules, accelerometers, humidity sensors, temperature sensors and many many more(gas sensors, alcohol sensor, motion sensors, touch screens). Many of these are analog in nature. That means they give a voltage output that varies directly (and linearly) with the sensed quantity. For example in LM35 temperature sensor, the output voltage is 10mV per degree centigrade. That means if output is 300mV then the temperature is 30 degrees. In this tutorial we will learn how to interface LM35 temperature sensor with PIC18F4520 microcontroller and display its output on the LCD module. First I recommend you to go and read the following tutorial as they are the base of this small project. Interfacing LCD Module with PIC Microcontrollers. Making the LCD Expansion Board for PIC18F4520. Using the ADC of PIC Microcontrollers. After reading the ADC tutorial given above you will note the the PIC MCU’s ADC gives us the value between 0-1023 for input voltage of 0 to 5v provided it is configured exactly as in the above tutorial. So if the reading is 0 then input is 0v, if reading is 1023 then input is 5v. So in general form if the adc read out is val then voltage is. unsigned int val; val=ADCRead(0); //Read Channel 0 voltage= […]


Using the ADC (Analog to Digital Converter) of PIC Microcontroller

Many electrical signals around us are Analog in nature. That means a quantity varies directly with some other quantity. The first quantity is mostly voltage while that second quantity can be anything like temperature, pressure, light, force or acceleration. For example in LM35 temperature sensor the output voltage varies according to the temperature, so if we could measure voltage, we can measure temperature. But most of our computer (or Microcontrollers) are digital in nature. They can only differentiate between HIGH or LOW level on input pins. For example if input is more than 2.5v it will be read as 1 and if it is below 2.5 then it will be read as 0 (in case of 5v systems). So we cannot measure voltage directly from MCUs. To solve this problem most modern MCUs have an ADC unit. ADC stands for analog to digital converter. It will convert a voltage to a number so that it can be processed by a digital systems like MCU. This enables us to easily interface all sort of analog devices with MCUs. Some really helpful example of analog devices are Light Sensors. Temperature Sensors. Accelerometers. Touch Screens. Microphone for Audio Recording. And possibly many more. In this tutorials we will learn to use the internal ADC of PIC18 devices (Example is for PIC18F4520 which is […]

Interfacing Temperature Sensor – LM35

By interfacing different types of sensors with our MCU we can sense the environment and take decisions, in this way we can create "smart" applications. There are wide variety of sensors available. In this tutorial we will learn about a popular sensor LM35 which is precision centigrade temperature sensor. It can be used to measure temperature with accuracy of 0.5 degree centigrade. We can interface it easily with AVR MCUs and can create thermometers, temperature controller, fire alarms etc. Things Required   S. No. Item Image 1 28 PIN AVR Dev Board Contains the core AVR circuit including 5v regulator, reset, ISP. 2 Seven Segment Display Module Four common anode displays multiplexed with driver transistors and current limiting resistors. 3 Single Pin Female to Female Burg Wires Used to interconnect the two boards. And the sensor.   4 USB AVR Programmer To upload the program to the development board. 5 LM35 Temperature Sensor   LM35 LM35 by National Semiconductor is a popular and low cost temperature sensor. It is also easily available. You can buy one from here online. It has three pins as follows. Fig – LM35 Pin Configuration     The Vcc can be from 4V to 20V as specified by the datasheet. To use the sensor simply connect the Vcc to 5V ,GND to Ground and the […]


ADC (Analog To Digital Converter) of AVR Microcontroller

Most of the physical quantities around us are continuous. By continuous we mean that the quantity can take any value between two extreme. For example the atmospheric temperature can take any value (within certain range). If an electrical quantity is made to vary directly in proportion to this value (temperature etc) then what we have is Analogue signal. Now we have we have brought a physical quantity into electrical domain. The electrical quantity in most case is voltage.To bring this quantity into digital domain we have to convert this into digital form. For this a ADC or analog to digital converter is needed. Most modern MCU including AVRs has an ADC on chip. An ADC converts an input voltage into a number. An ADC has a resolution. A 10 Bit ADC has a range of 0-1023. (2^10=1024) The ADC also has a Reference voltage(ARef). When input voltage is GND the output is 0 and when input voltage is equal to ARef the output is 1023. So the input range is 0-ARef and digital output is 0-1023. Fig: ADC Theory Inbuilt ADC of AVR Now you know the basics of ADC let us see how we can use the inbuilt ADC of AVR MCU. The ADC is multiplexed with PORTA that means the ADC channels are shared with PORTA. The ADC […]

Using Internal peripherals of AVR MCUs.

Each AVR MCU has several internal peripherals that give powerful abilities to your projects. For example internal ADC can be used to convert analog value (say voltage output of some sensor) to a digital value that you can use. And a USART(Universal Synchronous Asynchronous Receiver Transmitter) can be used to connect your MCU with PC. (Example use – A PC serial mouse or A PC controlled Toy Rocket Launcher). This tutorial gives you overview of the process used to interface with these peripherals. Internal peripherals. Now you know the basics of peripherals, lets see what peripherals are available in ATmega16 MCU. Two 8-bit Timer/Counters with Separate Prescalers and Compare Modes One 16-bit Timer/Counter with Separate Prescaler, Compare Mode, and Capture Mode Real Time Counter with Separate Oscillator Four PWM Channels 8-channel, 10-bit ADC 8 Single-ended Channels 7 Differential Channels in TQFP Package Only 2 Differential Channels with Programmable Gain at 1x, 10x, or 200x Byte-oriented Two-wire Serial Interface Programmable Serial USART Master/Slave SPI Serial Interface Programmable Watchdog Timer with Separate On-chip Oscillator On-chip Analog Comparator Interfacing Technique. Fig: Using internal peripherals of AVR MCUs. A peripheral is connected to MCU by some special registers. The different registers of any peripherals can be logically of two types- 1)Data registers – which usually contains some data, say byte received from USART or […]