RS232 transceiver circuits

RS232 transceiver circuits
There are serveral rs232 transceiver circuit which commond used for communicated between microcontroller and other devices such PC or any devices that use rs232.Here is a collection of rs232 transceiver circuits that popular for today.
The circit below use 2 transistor and some components to provide RS232 transceiver.It usefull for cheap application that dose not long lenght.

Fig 1. Transceiver with 2 transistor

MAX232(Full duplex)
The circuit below use MAX232 which is the MAXIM's devices.This circuit is very stable and use for professional design. This device is inexpensive and it can provides 2 channel for RS232 .
The MAX232 line drivers/receivers are designed for RS-232 and V.28 communications in harsh environments. Each transmitter output and receiver input is protected against ?15kV electrostatic discharge (ESD) shocks, without latchup.It can operate from a Single +5V Power Supply.

Fig 2. Use MAX232 for RS232 transceiver

DS275(Half Duplex)
This RS232 transceiver circuit use DS275 which is a small half duplex transceiver chip.I Compatible with RS–232–E signals and suitible for Low–power serial transmitter/receiver for battery-
backed application.Requies no external devices.

Fig 3. Circuit to use DS257 

 

 

source : http://www.coolcircuit.com

3V/3A switching regulator
I build this project when I have a problem to driver stepping motor that draw current 3A at 3V.After search the infomation on the internet I have found LM2576-ADJ which is an adjustable output version of 3A Step-Down Voltage switching Regulator and capable of driving 3A load with excellent line and load regulation. You can change R1 and R2 for your desired output voltage.In my design I use the circuit from the example circuit in data sheet and it works fine.source :http://www.coolcircuit.com
Figure 1. 3V/3A Step-Down Voltage Regulator circuit
Figure 2. PCB over lay

EEPROM PROGRAMMER

 
SI-Prog base: connect it to the PC DB9 serial port.
You can connect any of the following adapter card to the 10 pin connector. The interface sinks current from the PC serial port, so it doesn't need any external power.

SPI eeprom (25xxx, 95xxx) connect diagram to base board

 

 

 

source :http://www.lancos.com/siprogsch.html

GPS Vehicle Tracking - A Guide To The Tools Available

GPS ? What does it stand for?

Global Positioning System ? Now, it is mainly used for navigation, both terrestrial and marine. Initially it was used by the U.S. military for locating and identifying friends as well as foes. The system uses military and commercial satellites for tracking anything that moves and has an emitter with or on it. Error margins, for GPS, are nowadays within 100 meters, and this can be narrowed down by using differential base stations (DBS). However, they are hard to use since their range is quite limited.

A new substitute for the American satellites will be the Galileo Satellite System, developed and realized in Europe. The first satellite, called Glove, was launched in late 2005 from Baikonur, Russian Federation.

GPS ? What can I do with it?

Here are just a few of this wonderful piece of equipment. For instance, if you get lost, your GPS unit can pinpoint you your current position, or, it can make a breeze from an awful task such as planning a trip. However, its main uses are in vehicle tracking. Most trucking companies have GPS units on all of their trucks. This way it is very easy to finding out where a trucker has been to, or where he currently is. Since the first GPS units were installed on trucks and cars, specialized companies and sites appeared.

Lets look at a two GPS units and their characteristics.

Garmin StreetPilot 2730

This is one of the latest products available on the market. Its producer presents it as being a ?great utility, even when drivers know exactly where they are.? Some of its features include access to the XM NavTraffic (a data-traffic information service, based on low orbit satellites, covering all of the USA), allowing it to suggest faster routes, before traffic-jam. The navigation map on StreetPilot 2730, graphically represents any incident affecting the road, including man-made, like road-construction, or accidents. Weather forecasts are also shown on the GPS unit, for as many as 162 cities. The StreetPilot 2730, also reads MP3s, and the music can be sent to the car?s stereo through its stereo jack or through a FM transmitter. The unit is equipped with an antenna, Garmin GXM 30, which can be placed on the roof of the car, or on the dashboard. It is waterproof and has a magnetic end, for easier placement.

Initial GD-70X

This ?little? gizmo has a 7? color LCD, the obvious GPS navigational system, as well as a DVD player, thus making it ideal for family vacations. It can pinpoint your location on the map, as well as playback your favorite movie or tracks. It has a set of maps which includes both Canada ant the US. Its map database includes over two million points of interest and it has a 250MB internal memory, large enough for downloading maps and POIs. An interesting feature are the voice directions, which will help you focus on the road, an still know where you are, and what kind of conditions you are facing out there. Also, it includes a day/night mode, making it easier to read according to the time of use. The incorporated CD/DVD player can keep the passengers entertained as well, and if you don?t have a car stereo (who doesn?t), you can always listen to its built-in stereo speakers.

These are just two of the many products on the market that can help you with GPS vehicle tracking.

Source: http://www.ArticlePros.com/author.php?Steve Armstrong

AVR ISP Programmer

This AVR ISP original by ATMEL you can found on "AVR software and technical Library - April 2003" CD-rom.It small component count I design new PCB and change some component that easy to build small PCB .The new firmware was writen by John Samperi for AT90S2313. This code can program more devices.

Programmer supports the following devices AT90S1200 rev. A* AT90S1200 rev. B* AT90S1200 rev. C* AT90S1200* AT90S2313* AT90S2323* AT90S2333 AT90S2343* AT90S4414* AT90S4433 AT90S4434 AT90S8515* AT90S8535 ATtiny12 ATtiny15 ATtiny19 ATtiny28 ATtiny26 * ATmega8 * ATmega8 BOOT * ATmega16* ATmega16 BOOT* ATmega32* ATmega32 BOOT* ATmega64* ATmega64 BOOT* ATmega8515 * ATmega8515 BOOT* ATmega103 ATmega603 ATmega128 ATmega128 BOOT ATmega161 ATmega161 BOOT ATmega163 ATmega83 ATmega163 BOOT ATmega83 BOOT ATmega8535?? ATmega8535. 

 source :electronic-DIY .com

Battery Charger Display Using LT1639

Battery Charger Display Using LT1639

The Over-the-Top type of operational amplifier is ideal for use as a current sense for battery charger applications. The design described here can be used with chargers for rechargeable batteries (Lead/acid or NiCd etc). The 5 V operating supply for the circuit is derived from the battery on charge. The circuit uses a sense resistor R8 to determine the value of current flowing in or out of the battery. An LED output shows whether the battery is charging or discharging and an analogue output displays the battery charge or discharge current. The circuit can also be altered to shown different ranges of charging current to cater for higher capacity cells. IC1a and IC1b together with T1 and T2 form two current sources, which produce a voltage across R5. The voltage across R5 is proportional to the current through resistors R8 and R1 (for IC1a) or R8-R3 (for IC1b).

The current source formed by IC1a and T1 is active when the batteries are discharging and IC1b and T2 is active when the batteries are being charged. In each case the inactive opamp will have 0V at its output and the corresponding transistor will be switched off. IC1d amplifies the voltage across R5, which is proportional to the sense current. The component values given in the diagram produce an amplification factor or 10. A sense current of 0.1 A will produce an output voltage of +1 V. The supply voltage to the circuit is +5 V so this will be the maximum value that the output can achieve. This corresponds to a maximum charge/discharge current of 0.5 A To display currents from 0 to 5.0 A, resistor R7 can be omitted to give IC1d a voltage gain of 1.

Higher currents can be displayed by using a lower value of sense resistor R8. A DVM or analogue meter can be used at Vout to give a display of the charge/discharge current. The constant current sources can only function correctly when the supply to the voltage regulator circuit (UBatt. e.g. 6V or 12V) is greater than the operating voltage of the opamps (+5 V). The supply voltage to the LT1639 can be in the range of +3 V and +44V and voltages up to 40V over the supply voltage are acceptable at the inputs to the opamp. IC1c controls the charging/discharging LED output. The inputs to this opamp are connected to the outputs of the current source opamps and its output goes high when the battery is being charged and low when it is discharging.
source :www.extreamecircuit.net

ISP Flash Microcontroller Programmer

Introduction
This ISP Programmer can be used either for in-system programming or as a stand-alone spi programmer for Atmel ISP programmable devices. The programming interface is compatible to STK200 ISP programmer hardware so the users of STK200 can also use the software which can program both the 8051 and AVR series devices.

Hardware
Figure 1 shows the circuit diagram of the in-system programmer interface, the power to the interface is provided by the target system. The 74245 ic isolate and buffer the parallel port signals.

Software
The ISP-30a.zip file contains the main program and the i/o port driver. Place all files in the same folder.
The main screen view of the program is shown in figure 3. Also make sure do not program the RSTDISBL fuse in ATmega8, ATtiny26 and ATtiny2313 otherwise further spi programming is disable and you will need a parallel programmer to enable the spi programming. For the fuses setting consult the datasheet of the respective device.

For the auto hardware detection it is necessary to short pin 2 and 12 of DB25 connector, otherwise the software uses the default parallel port i.e. LPT1.

Following are the main features of this software,
Read and write the Intel Hex file
Read signature, lock and fuse bits
Clear and Fill memory buffer
Verify with memory buffer
Reload current Hex file
Display buffer checksum
Program selected lock bits & fuses
Auto detection of hardware

Note:
The memory buffer contains both the code data and the eeprom data for the devices which have eeprom memory. The eeprom memory address in buffer is started after the code memory, so it is necessary the hex file should contains the eeprom start address after the end of code memory last address i.e. for 90S2313 the start address for eeprom memory is 0x800.

The software does not provide the erase command because this function is performed automatically during device programming. If you are required to erase the controller, first use the clear buffer command then program the controller, this will erase the controller and also set the AVR device fuses to default setting. 

source : www.mytutorialcafe.com /By : Asim Khan