This simple project is a digital thermometer using LM35 sensor and Attiny26 mcu to read the sensor value and display it on the LED display. LM35 output is amplified by 11 so can be read by mcu internal ADC. The hardware design files and firmware source code are available on the project’s page.
The sensor section is composed of LM35, OPA344 and some passive components. The LM35 is a precision temperature sensor that outputs 10mV per °C. Therefore, LM35 will output 0.25V or 250mV if it is measuring 25°C. The OPA344 is an operational amplifier that is configured as non-inverting amplifier with a gain of 11. The gain of OPA344 is set by R15 and R16. The OPA344 is used to multiply the voltage output of LM35 by 11. So, the output of OPA344 is 2.75V if the output of LM35 is 0.25V. R17 and C6 serves as a low pass filter for the output of OPA344. The values for R17 and C6 were arbitrarily chosen but for optimum performance, these values must be carefully chosen.
Simple Attiny26 based LM35 digital thermometer - [Link]
Tushar @ embedds.com writes:
In this new tutorial, we will be interfacing a LM35 based temperature sensor with ATMEGA32. The 3 main types are thermometers, resistance temperature detectors, and thermocouples. All three of these sensors measure a physical property (i.e. volume of a liquid, current through a wire), which changes as a function of temperature. In addition to the 3 main types of temperature sensors, there are numerous other temperature sensors available for use.
Interfacing LM35 to ATMEGA32 - [Link]
At the heart of this circuit is a precision integrated temperature sensor, LM35 (IC1), which provides an accurate linear and directly proportional output in mV, from 0 to +155 degrees C. Designed to draw a minimal current of its own, the LM35 has very low self heating in still air. Here the output of the LM35 is applied to the non-inverting input of a comparator wired around a CA3130 opamp (IC2). A voltage divider network R3-P1 sets the threshold voltage, at the inverting input of the opamp. The threshold voltage determines the adjustable temperature trip level at which the circuit is activated.
When the measured temperature exceeds the user-defined level, the comparator pulls its output High to approx. 2.2 V causing transistor T1 to be forward biased instantly. T2 is also switched on, supplying the oscillator circuit around IC3 with sufficient voltage to start working. The 555 set up in astable mode directly drives active piezoelectric buzzer Bz1 to raise a loud alert. Components R7, R8 and C4 determine the on/off rhythm of the buzzer.
Overheat Detector Alarm - [Link]
Probably, some of you have tried buying cool but cheap products from Ebay. Like some of you, I also have bought items from Ebay several times already. One of the items that I got from Ebay is a small ENC28J60 based ethernet module.
As you can see from the image above, the ENC28J60 module is very small. The PCB is more or less one-inch square which is almost as small as the included ethernet jack.
Simple Sensor Webserver – [Link]
A digital multimeter is a very useful instrument that combines several measurement functions in one unit. A typical multimeter includes features of a variable-range ohmmeter, voltmeter, and ammeter. Some of them also include capabilities of testing diodes and transistors. In this article, I am going to talk about a technique of adding thermometer feature to a regular digital multimeter. The technique is very simple and uses one temperature sensor along with two resistors and a DPDT slide switch.
Add a thermometer to your digital multimeter - [Link]
There are quite a variety of active analog temperature sensor ICs that provide an output voltage proportional to the temperature. They usually don’t require any external calibration and signal conditioning, and as such their output can be directly fed to the input of an ADC for digital processing. A few examples of such sensors are LM34, LM35, TMP35/36/37, and MCP9701. If you are having any trouble using any of these sensors in your project, here is a quick way to test if your sensor is working or not.
Testing active analog temperature sensors with a multimeter - [Link]
I designed this version in the need of a thermometer for my room, built in a small pack and easy to control. The hardware is designed on a way so that the pcb can be wall mounted. At the top side of the device the PCB extents giving space for two keyhole type holes which are able to keep the device mounted on the wall. The LCD display plugs at the front side of the PCB, covering all the electronic components and giving a compact design view. The user can interact with the device using the left side switch button. The design includes a 6-pin header which gives connectivity for UART (RX,TX,GND) and for the external sensor DHT-11 (VCC,GND,DATA). Also there is an ISP-6 pin header which gives the option of on board programming. Finally there is an optional Bluetooth plug on the back side connected with AVRs UART for possible communication to other devices like mobile phones, home automation devices, pc’s or whatever you imagine.
The code is written in C and is well performed in a readable way so anybody can read and modify it. For the LCD driving i have used Peter Fleury’s library.
AVR Atmega8 and DHT-11 Thermometer V2.0 - [Link]
This is General purpose Temperature meter for measuring Temperature from -55 ºC to 150 ºC ..It is a very useful bench test equipment for testing and finding out the temperature of various devices with unknown temperature such as room temperature , cpu cabinet, etc. The meter provides very stable readings and has excellent input sensitivity thanks to LM 35 Temperature sensor from National Semiconductor , so it can even measure small temperature change.
The LM35 is three terminal temperature sensor which gives output in the form of analog voltage. LM35 linear to the whole temperature range it generate 10 mV/ºC. this analog voltage is feed to the internal 10 bit analog to digital convertor of the PIC 18F458 which convert it into temperature and then display to the NOKIA 3315/3310 LCD.
Nokia 3315 LCD Based Temperature Meter - [Link]
This is a revised version of my LM35 based digital thermometer project that I posted last year. Although it is one of the simplest projects, it is very popular among newbies who are just starting to learn microcontrollers. There was a little flaw in the original project as pointed by some readers. I was using a 1.2 V reference for A/D conversion with PIC16F688 microcontroller. However, the PIC16F688 datasheet says Vref should be equal to or higher than 2.2 V to ensure 1 LSB accuracy of A/D conversion. Here, I am rewriting the same project but this time I am using a MCP1525 IC to generate a precise 2.5 V reference for A/D conversion. This will improve the accuracy of temperature measurements.
Revised version of LM35 based digital temperature meter - [Link]
Stephen Zahra writes:
This Digital Thermometer Design is done by using the 8051 microcontroller AT89C51AC2 and interfaced with an LCD to outputs the Temperature. THe sensor used for this design is the LM35 which output an analogue voltage per centigrade celcius. A circuit amplification is done between the LM35 and the microcontroller.
8051 Digital Thermometer – [Link]