Joe @ hobbyelectronics.net:
Here you will find complete construction details including circuit diagrams, PCB layouts and PIC firmware (and the source code). The code was written in Proton PIC BASIC but the good news is that there is now a free version of this compiler available for download; AMICUS18.
PIC Digital Thermometer & Clock - [Link]
Davide Gironi writes:
DS18B20 is a programmable resolution 1-wire digital thermometer.
It has an operating temperature range of -55°C to +125°C and is accurate to ±0.5°C over the range of -10°C to +85°C.
This library is an AVR implementation to retrive temperature from DS18B20.
Built using the reference document: “Using DS18B20 digital temperature sensor on AVR microcontrollers” by Gerard Marull Paretas, 2007.
A DS18B20 1-wire digital thermometer AVR ATmega library - [Link]
praveen @ circuitstoday.com build a Digital thermometer using arduino and LM35
This article is about a simple three digit digital thermometer using arduino. Range of this thermometer is from 0°C to 99.9°C. There is also a provision for displaying the temperature in °F scale. Three terminal analog temperature sensor LM35 is used as the sensor here. LM35 can measure temperatures between -55°C to +155°C. The supply voltage range is from 4V to 30V DC and the current drain is 60uA. The LM35 is available in TO-92 package and it is very easy to use. The output voltage of the arduino increases 10mV per °C rise in temperature. That means if 25 °C is the temperature, then output voltage of the sensor will be 250mV. Circuit diagram of the digital thermometer using arduino and LM35 is shown in the figure below.
Digital thermometer using arduino - [Link]
This device is a receiver circuit for a Digital Remote Thermometer. The thermometer operates by converting the sensor’s output voltage, which is calibrated and proportional to the measured temperature, to output cycles. The output cycles are transmitted in the supply cables and the receiver section counts the cycles from the transmitter; the calibrated counting are then displayed in the 7-segment LED displays.
The receiver circuit uses the 4093 Quad two input Schmitt NAND Gate IC as one of the logic components. Another component used is the 74HCT4520 dual 4-bit synchronous binary counter which is a high-speed Si-gate CMOS device. It has a dual 4-bit internally synchronous binary counters with an active high clock input and an active low clock input and buffered outputs. In this circuit, only two output levels from each of the binary counters, are utilized and the rest are connected to ground. The 74HCT4520 is coupled to the 74HCT4017 5‑stage Johnson decade counter for synchronized clocking. The MC14553B 3-digit BCD counter is also used in this circuit. The MC14553B consists of three negative edge triggered BCD Counters that are cascaded synchronously. In this circuit, the MC14553B controls the most significant (leftmost) value of the thermometer display. Lastly, the HEF4511B BCD to 7-segment BCD decoder is coupled to the MC14553BCP 7-segment displays. The HEF4511B decoder controls each of the displays to indicate the calibrated temperature.
The circuit is ideal for room temperature measurement. It displays the temperature in centigrade within the range of 00.0 to 99.9 degrees centigrade. Adjustments in the circuit are necessary to change the temperature ranges that can be accommodated by the circuit. Read the rest of this entry »
rahulkar @ instructables.com writes:
This is a complete DIY project which requires a handful of components such as the ATtiny 85, LM35, MAX7219 and a couple of resistors and capacitors running off a regulated 5 V supply.
Temperature Measurement Range : 0 to 150’C / 32 to 300’F
Controller: ATtiny 85
Display type – 4 digit multiplexed 7 segment display (Common Cathode type)
Programming Language: Arduino
The setup can display both in Celsius and Fahrenheit. By default the temperature is shown in Celsius but can be toggled to display in Fahrenheit using the push button.
7 Segment Digital Thermometer using ATtiny 85 - [Link]
The MAX31629 I2C digital thermometer and real-time clock (RTC) integrates the critical functions of a real-time clock and a temperature monitor in a small-outline 8-pin TDFN package. Communication to the device is accomplished through an I2C interface. The wide power-supply range and minimal power requirement of the device allow for accurate time/temperature measurements in battery-powered applications. The digital thermometer provides 9-bit to 12-bit temperature readings that indicate the temperature of the device.
MAX31629 – I2C Digital Thermometer and Real-Time Clock - [Link]
Kerry Wong writes:
In this post, I will show you yet another thermometer/hygrometer build. But instead of using an LCD or 7 segment display for the output, I decided to go retro, using two “needles” to display the temperature and humidity readings instead. And to make the project more fun, I did not use analog meters for the output but chose to use two servos instead. The temperature humidity sensor I used is SHT21 from Sensirion, the same sensor I used in my temperature logging project before. In that project, the temperature and humidity readings were sent over the network and displayed on my web server (you can see the current readings in my lab here).
A digital thermometer hygrometer with analog displays - [Link]
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]
Ktulu_1 @ instructables.com writes:
The temperature in my office at work varies quite a bit depending on the time of day, season, and the whims of the other people I share the floor with. When I’m sitting at my desk shaking uncontrollably or sweating profusely it would be nice to know if it’s due to the temperature or just work related stress. A simple $5.00 thermometer would suffice, but where’s the fun in that? Making my own thermometer might cost ten times as much, but I might learn something in the process and it would be way cooler than any cheap store bought thing? I’d rather make something myself even if I have to pay a “maker’s premium.”
Tempduino – Arduino Based Temp and Humidity Display - [Link]
TrH Meter is a DIY microcontroller-based indoor thermometer plus hygrometer that displays temperature (F/C) and relative humidity on 4 seven segment LED displays which adjust their brightness level according to the surrounding illumination. The displays are 1 inch big, emits bright yellow color, and are readable from more than 50 ft away. It consists of a closed loop system that continuously assesses ambient light condition using an inexpensive light-dependent resistor (LDR) and uses that information to adjust the brightness of the display. The DHT11 sensor is used to measure temperature and relative humidity. The microcontroller used in this project is PIC16F688, and it runs at 4 MHz internal clock. A separate display driver chip (MAX7219) is used to control and refresh the display data on the seven segment LEDs. A 3-position slide switch controls power ON/OFF and Fahrenheit (F) or Celsius (C) scale select for temperature display. You can now preorder the project kit for a discounted price of $25 on Tindie. You will receive a preprogrammed PIC16F688 microcontroller in the kit.
TrH Meter project kit is now available for preorder on Tindie - [Link]