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Monday, October 13, 2014

DIY Digital Thermometer in Wireless Form Overview and explanation

Digital

Overview

This digital thermometer project uses any standard FM broadcast band radio at regular intervals in order to report the temperature.

Explanation

An Atmel AT90S1200 is used to construct the prototype along with a modified low cost wireless microphone kit that function as the transmitter in order to save design time. The device can be used as standalone or as part of a PC-based weather station or HVAC system since it uses a simple low bit rate tone signaling scheme which can be interpreted easily by both machines and humans. The design allows the use of any inexpensive FM radio to monitor the temperature with easy set up of any number of monitoring locations.

There are various circuits used in this project including, the thermometer interface, audio interface, and power interface. The operation consists of applying power and tuning the unit to any unused FM channel. A 9V transistor radio battery was chosen since the 5V regulator used can accept any DC voltage between 5.5V-12V. A programs tests if larger or lesser and converts the binary format temperature output from the thermometer clip to a format that can be transmitted a digit at a time.

LCD Module in 4 bit Mode

LCD Module in 4-bit Mode Circuit diagram. In many projects use is made of alphanumeric LCDs that are driven internally by Hitachi’s industry-standard HD44780 controller. These displays can be driven either in 4-bit or 8-bit mode. In the first case only the high nibble (D4 to D7) of the display’s data bus is used. The four unused connections still deserve some closer attention. The data lines can be used as either inputs or outputs for the display. It is well known that an unloaded output is ﬁne, but that a ﬂoating high-impedance input can cause problems. So what should you do with the four unused data lines when the display is used in 4-bit mode? This question arose when a schema was submitted to us where D0-D3 where tied directly to GND (the same applies if it was to +5 V) to stop the problem of ﬂoating inputs.

The LCD module was driven directly by a microcontroller, which was on a development board for testing various programs and I/O functions. There was a switch present for turning off the enable of the display when it wasn’t being used, but this could be forgotten during some experiments. When the R/Wline of the display is permanently tied to GND (data only goes from the microcontroller to the display) then the remaining lines can safely be connected to the supply (+ve or GND). In this application however, the R/Wline was also controlled by the microcontroller. When the display is initialised correctly then nothing much should go wrong. The data sheet for the HD44780 is not very clear as to what happens with the low nibble during initialisation.

LCD Module in 4-bit Mode Circuit diagram :

LCD

LCD Module in 4-bit Mode Circuit Diagram

After the power-on reset the display will always be in 8-bit mode. A simple experiment (see the accompanying schema) reveals that it is safer to use pull-down resistors to GND for the four low data lines. The data lines of the display are conﬁgured as outputs in this schema (R/Wis high) and the ‘enable’ is toggled (which can still happen, even though it is not the intention to communicate with the display). Note that in practice the RS line will also be driven by an I/O pin, and in our schema the R/W line as well. All data lines become high and it’s not certain if (and if so, for how long) the display can survive with four shorted data lines. The moral of the story is: in 4-bit mode you should always tie D0-D3 via resistors to ground or positive.

Basic devices in the car audio system

Entertainment in the form of music, news or even movies, generated from a series of audio devices found in a car. The series device known as a car audio system.

What tool or device contained in car audio system?

Car Head Unit - Head unit is the core of a car audio system, part of the car audio system that plays sound. The continued development of technology makes the head unit is no longer only serve as a radio receiver FM / AM CD player and a player, some have additional functions to be able to play MP3s. There is also a car head unit that has the ability to play DVDs complete with monitors and can be connected with IPOD.
Power Amplifier - The function of the power amplifier is to amplify the signal coming out of the head unit. In the world of various types of car audio power amplifiers are divided into several classes, such as class A, B, AB, and D. Each class power amplifier has the advantage that its usefulness can be tailored to our needs in building a car audio system. In addition to class division, the division of power amplifiers can also be seen from the number of channels (channels) and the amount of power generated by the power amplifier.
Speaker - A device that functions convert electronic signals into audible sound. The speakers were divided into several parts / components, namely, subwoofers, woofers, mid-range, and tweeter. In order for speakers to work properly, required a series of electronic components that serves as a filter (cross over).
Processor - With advances in technology processors play a significant role in a car system. Inside there is a processor features like time correction, cross-over-active, etc. equalizer. With the functions it will be very easy at the time of tuning car audioaudio system.

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