How to interface MAX232 with 8051 micrcontrollers?

To receive data from i.e. a PC, you need a level converter, like a MAX232, or use standard components and make your own level converter (diagrams can be found via Google). A level converter is needed because the COMmunication port of a PC switches the data between approx. -9.23 to 9.23 Volt (I measured these levels, can vari a bit from PC to PC), -9.23 Volt corresponds with a logical '0' (lo), 9.23 Volt corresponds with a logical '1' (hi), both on TTL level of 5 Volt, so can be connected directly to the i/o's of an AVR. The MAX232 can convert at a maximum speed of 120kbit/sec. Here a very simple diagram of an RS232 converter (receive data only):

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How to interface 7-Segment Display with 8051 micrcontrollers?

The 7 segment display is found in many displays such as microwaves or fancy toaster ovens and occasionally in non cooking devices. It is just 7 LEDs that have been combined into one case to make a convenient device for displaying numbers and some letters. The display is shown on the left. The pin out of the display is on the right.

This version is a common anode version. That means that the positive leg of each LED is connected to a common point which is pin 3 in this case. Each LED has a negative leg that is connected to one of the pins of the device. To make it work you need to connect pin 3 to 5

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How to interface Keypad with 8051 micrcontrollers?

keyboards are organized in a matrix of rows and columns. The CPU accesses both rows and column through ports; therefore, with two 8-bit ports, an 8*8 matrix of keys can be connected to a microcontroller. When a key pressed, a row and column make a connect; otherwise, there is no connection between row and column. In IBM PC keyboards, a single microcontroller (consisting of microprocessor, RAM and EPROM, and several ports all on a single chip) takes care of software and hardware interfacing of keyboard. In such systems it is the function of programs stored in the EPROM of microcontroller to scan the keys continuously, identify which one has been activated, and present it to the motherboard. In this section

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How to interface LCD with 8051 micrcontrollers?

There is a simple technique to display characters from both the internal character generator and user designed characters on an LCD character module.The controlling microcontroller is a AT 89C52. The LCD module is connected to the microcontroller through its I/O ports. The process of displaying character to this module is divided into three steps. First the module must be initialized. This sets up the built-in LCD controller chip. Second, some user designed characters are uploaded to the CGRAM. This allows the displaying of up to 8 custom characters in addition to the 192 character permanently stored in the module. Lastly, a message consisting of a mix of standard ASCII characters and custom designed characters is displayed on the module.

The LCD

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IR Remote Control Jammer

Don't like your little brother's TV channel selection? Hate the volume your wife sets the stereo at? Want to just annoy someone? This circuit does all that and more by jamming most IR remote signals. The circuit releases a flood of pulsing IR light that confuses the reciever by corrupting the data stream. And hence, you jammed the remote control.

Part Total Qty. Description Substitutions R1 1 100K 1/4W Resistor   R2 1 150K 1/4W Resistor   R3 1 10K 1/4W Resistor   R4 1 1K 1/4W Resistor   R5 1 22 Ohm 1/4W Resistor See "Notes" C1 1 10nF Ceramic Disc Capacitor   C2 1 1uF Electrolytic Capacitor   D1, D2, D3 3 High Output IR LED   Q1 1 2N4403 PNP Transistor   Q2 1 2N4401 NPN Transistor   S1 1 Normally Open Momentary Push Botton   B1 1 4.5V Battery (Three "AA"'s In Series)   MISC 1 Wire, Case, Board  

Notes:

1. Email Carl with questions, comments, etc.

2. You may need to adjust the value of R3 for the right

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Fire Alarm

With the onset of summer, chances of fire accidents increase. Such fire accidents can be prevented if timely alarms are available. The circuit presented here warns the user against such fire accidents. The circuit should be placed in fire-prone areas such as a kitchen. Everyone is aware that when anything catches fire, smoke is produced. When this smoke passes between a bulb and an LDR, the amount of light falling on the LDR decreases. This causes the resistance of LDR to increase and the voltage at pin 2 of IC 555 goes below 1/3 Vcc, thus triggering IC 555 which is used here in bistable mode. As a result the voltage of pin 3 goes high. This high voltage (approximately

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Musical Light Chaser

This music-operated lighting effect generator comprises five sets of 60W bulbs that are ranged in zig-zag fashion. The bulb sets glow one after another depending on the intensity of the audio signal. No electrical connection is to be made between the music system and the lighting effect generator circuit. You just need to place the gadget near the

speakers of the music system. Fig. 1 shows the complete circuit  of the musical light chaser, while Fig.2 shows pin configurations of 9V regulator 7809, triac BT136 and level meter IC LB1403.      

 

The circuit is powered by regulated 9V DC. The AC mains is stepped down by transformer X1 to deliver a secondary output of 12V AC at 250 mA. The transformer output

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