Room temperature plays a vital role in determining human thermal comfort. This digital thermometer is designed to measure room temperature and display it on a LCD screen in both Celsius and Fahrenheit scales. A PIC16F688 microchip is used as the main controller that reads temperature from DS1820, a 3-pin digital temperature sensor from Dallas semiconductors (now Maxim). The sensor is designed to measure temperature ranging from -55 to +125 °C in 0.5 °C increments. The room temperature doesn't go that far but the firmware written for the PIC is able to read and display the entire temperature range of DS1820.
Click here to download the full size of the above Circuit.
I have tested it from -4.5°C (my freezer temperature) to 105.5 °C (by bringing a soldering iron tip close to the sensor). If you want to measure your freezer temperature too, don't put the entire unit inside it, as some of the components (like LCD) may not work at that low temperatures. Rather put only the sensor inside the freeze and connect it to the rest of the system through three wires. For a better understanding of how DS1820 sensor works, I recommend to read the datasheet from Maxim website. Remember that DS1820 and DS18B20 (both are temperature sensors) have architectural differences, and so DS18B20 will not work here. This project works with DS1820, and it would work with DS18S20 (later version of DS1820) too by changing the temperature conversion time in the firmware. Read this to find the difference between DS1820 and DS18S20, http://www.maxim-ic.com/datasheet/index.mvp/id/3021
PIC16F688 reads data from DS1820 sensor through RA5 port, and the computed temperature is sent to the LCD through RC0-RC3 ports. It means the data transfer from PIC to LCD is achieved in 4-bit mode. The Register Select (RS) and Enable (E) signals for LCD are provided through ports RC4 and RC5. The Read/Write pin of the LCD is grounded as there is no data read from the LCD in this project. The contrast adjustment of LCD is done with the 10K potentiometer shown in the circuit diagram.
The temperature reading from DS1820 is 9-bits which...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
characters left: