AT89C2051/4051

The heart of the synthesizer is a set of 2 Analog Devices AD9850 direct digital synthesis (DDS) chips. These provide 2 channels of sinewave output which may differ in frequency and relative phase. The output stage of the synthesizer also includes separate variable attenuators for the 2 channels. These attenuators have a range of 0.0 - 63.9 dB of attenuation, in 0.1 dB steps. The user therefore has control over five parameters: 2 output frequencies, 2 output attenuations, and relative phase between the 2 channels.

This is an 8-input x-output audio/video switch module to be controlled from a computer, for example from the parallel port. Each audio/video output can be switched to any of the 8 inputs, separately. One module drives one audio/video output and has a 34-pin connector to plug into the system interface.You can use video OPA-s on the 4051 output instead. Note that you can get full integrated video multiplexers from Maxim.

Video multiplexers route video from several sources to a single channel. Low-end consumer products use CMOS analog switches and multiplexers, such as the 4066 and 4051. Unfortunately, these devices have a series on-resistance that ranges from approximately 100Ω to 1 kΩ, a resistance that is not constant with video level and that appears in series with the signal.

Figure 1 shows a circuit diagram of the Easy-Downloader. As shown, the circuit uses a 89C2051 with writer.hex firmware, 74LS373 8-bit latch, DS275-like, 7805, LM317 and two transistors, 2N2222A and 2N2907A. The programming voltage control circuit is the same as recommended by ATMEL application note. It can be raised from 0V, 5V and 12V by appropriated signal from P3.

The LED module with MAX7219 is a ready made having 10-pin header for easy plugin to the 4051 board. As shown in Fig. 1, four keys are used to set time for each timer. Each timer will have two digit LED. The right hand side, timer 1 and timer 2 are for minute counting, the left hand, timer 3 and timer 4 are for hour counting.

Its a digial clock which make use of AT89C4051 to work as a Real time clock. Port 1 of the controller (AT89C4051) is used as the data lines for the LCD (starting from pin 7- pin14 of LCD). As you can see there is not much change in the hardware except the LCD, here i am using a 20 x 4 lines LCD display.

The original version of xTimer used MAX7219 for driving 7-segment. This new design uses a cheap CMOS shift register, 4094 for LED interface. Each 4094 drives a 0.5" 7-segment without the need of limiting resistor. The left-hand LED is timer function with buzzer alarm output. The right-hand is for clock display.

Figure 1 shows complete hardware schematic of the Night Light Saver V6.0. The AC line was protected F1, a 1A fuse. Any short circuit caused by saver's components will blow the fuse. R1 and C1 limit current to the +5V zener diode, D3. R2 discharges capacitor C1 when power terminal of the circuit was opened. The super capacitor C2,+5V 0.01F filters DC supply. D4 acts as unidirectional switch for current supplied to MCU.

May be I can use 555 monostable for POT reading. So I got my lab at home finding old boards and parts on the shelf. I found MAX7219, 8-digit LED display module and two buzzers. The MAX7219 needs serial interface, like SPI. This enables me to use a 20-pin 89C4051 MCU, since the pin counts for i/o port is quite limited. The 8-digit LED lets me have four timers, each will have two digit. I can set say, 00-99mins or 0-99Hrs. The output would be open collector with my favorite 7407!

Figure 1 shows the circuit diagram of proto board. All port connections are available for user interface around the proto area including the power supply pins. MAX232 serial driver is used to provide a 3 wire RS232 interface for connecting to the PC or other rs232 devices. Switch S1 provide a manual reset to u-controller.

I am very happy to use sdcc for writing firmware of my project. The compiled code is very compact and nice. After I succeeded writing a new firmware of xtimer and Easy-downloader V1.1 with sdcc. I cannot stop preparing a new page that gives the idea how to use sdcc and of course it's time to renovate my old project with orcad. For now I can design the hardware, draw a schematic, write the firmware and layout the pcb. So I think why shouldn't begin with Easy-Downloader. Since the programmer board will enable learning and developing the small project with a cheap 20-pin MCU easily.

Build your own a personal writer for programming HEX code into Flash based microcontroller AT89C2051(2k) and AT89C4051(4k). Simple hardware and Easy use software in DOS and Window version. Single-side and double side PCB files included.

The design features low cost, easy installation, no battery backup and no EMI. The AT89C2051 uses external oscillator generated by schmitt trigger gate CD4093, ~680kHz. Reference frequency was derived from 50Hz main line. Time setting only allows at 18:00 by pressing time set button once. If main line has failed, functioning LED will blink at high rate . Since there is no battery backup, thus repressing the button is then needed. The output is capable of driving say, a 25W incandescent lamp.

The Clock Controller V1.1 was designed to be an exemplary of using 'C' language to control timer0 interrupt, 7-segment LED and keypad scanning. It provides 1-bit sink current driving output, for driving a relay, opto-triac, say. Many projects requiring 7-segment display and keypad interfacing may get the idea from the Clock circuit and software.

Build your own a laboratory instrument for measuring time and temperature. The DigiThermo demonstrates the use of 'C' language, a dual-slope converter, LCD interfacing, and digital filtering as well. The DigiThermo is a device designed for measuring time and temperature used in chemistry laboratory. The circuit of Digithermo employs a 89C4051, 20-pin CMOS Microcontroller with built-in 4kB code memory.

This is my long history the device that controls my home's night light, air-conditioner,etc. The device is a Miniature Real-time Controller. The circuit uses only three chips, a 89C2051, DS275(or MAX232), and 74LS07 open collector driver. The scheduler for time on/off of 6-channel output can be made by downloading from PC and saved into onchip RAM. Each output provides a 20mA sinking suitable for driving a homemade opto-triac or big solid-state relay for heavy load.

Award winner from VingPeaw Competition 2543, the robot built with 2051, L293D, and four IR sensors. Simple circuit and platform, quick tracking and easy-understand program using C language. I designed my Robot, which use two motors control rear wheels and the single front wheel is free.

This Project can be used with the three phase Induction motors. The circuit will take the full control of the motor and it will protect the motor from several faults such us over voltage and under voltage and the circuit will switch on the motor under safety conditions.

This Project takes over the task of Ringing of the Bell in Colleges. It replaces the Manual Switching of the Bell in the College. It has an Inbuilt Real Time Clock (DS1307) which track over the Real Time. When this time Equals to the Bell Ringing time, then the Relay for the Bell is switched On.

The Project presented here waters your plants regularly when you are out for vocation. The circuit comprises sensor parts built using op-amp IC LM324. Op-amp’s are configured here as a comparator. Two stiff copper wires are inserted in the soil to sense the whether the Soil is wet or dry.