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Simple AVR Programmer
Posted on Monday, May 9, 2011   •   Category: AVR

This is a very simple and easy to build programmer for Atmel microcontrollers from AVR family. The microcontrollers must support serial programming. This programmer is connected to a PC through the RS232 serial interface and can be used with the PonyProg or Avrdude software programmer. The programmer is quite simple and it is based on the SI-Prog from the author of PonyProg software. The Zener diodes D2, D3 with the resistors R2, R3 reduce the voltage from the ouput pins DTR, RTS on the serial port to around 5V which is suitable for microcontroller (MOSI, SCK). MISO signal is connected directly to the input CTS pin. The Zener diode D1 with the resistor R1 drive the NPN transistor T1, which controls RESET signal. The AVR microcontrollers are in reset when the signal has low level. The resistor R5 works as a pull-up for reset signal. The resistor R4 helps to close the transistor T1. The programmer has standard 10 pins header.

FM Transmitter with Varactor Diode Tuning
Posted on Monday, May 9, 2011   •   Category: FM Transmitters

Presented here is a low-power FM transmitter with varactor diode tuning using surface-mount devices (SMD) that will be received with a standard FM radio. Soldering surface mounted devices is not so hard and actually is quite easy. There are many designs for small FM transmitters but they have some problems. First, you need an audio amplifier to get enough modulation. Second, the antenna is attached directly to the collector. Third, the coil L must be wound by hand and adjusted by stretching. It all ads with a weak signal that tends to drift in frequency. In contrast the transmitter schematic we present here eliminates some of those problems, using varactor diode for tuning and modulation, givin great sensitivity without an audio amplifier.

100W Transmitter Amplifier for 2200m
Posted on Sunday, May 8, 2011   •   Category: FM Transmitters

This particular transmitter was later shipped up to VY1JA in the Yukon where, thanks to Jay's excellent antenna system, it was heard in Europe as well as in New Zealand during one of the Trans-Pacific Tests! Running 24 volts on the final will produce 100 watts into a 50 ohm load. The transmitter utilizes a 4060 binary counter IC chip as both the crystal oscillator and frequency divider. I used a 2200 kHz crystal along with the 'divide-by' sixteen output to produce a signal at 137.5 kHz. Other combinations of crystal frequencies and 'divide-by' combinations may also be used since the 4060 features divided outputs for f/32 (pin 5) and f/64 (pin 4), among others. You may have a 4MHz crystal or an 8MHz crystal in your junk box that will put you in the band using these output pins.

8 Channel IR Remote Control
Posted on Sunday, May 8, 2011   •   Category: Remote Control

This IR remote control that you can use to control other devices or circuits up to 8 devices. The control codes are sent in RC5 format modulated to about 38 kHz carrier frequency.The IR transmitter powered by the CR2016 which is a 3V button Cells Battery CR2016.To extend the life of the battery this is done by putting the CPU into SLEEP mode for most of the time and wake-up only when a key is pressed. PIC16F630 is the heart of the transmitter used to send IR command to receiver.It also generate 38KHz carrier frequency.The CR2016 is 3V battery which is supply for the circuit. When any key not pressed the CPU work in SLEEP mode to reduce baterry power consumption and wake-up only when any key pressed. To wake-up the CPU from SLEEP mode the CPU use interrupt on change feature which interrupted when the state on PORTA change then the program execution after an interrupt is at the interrupt vector, if the global interrupt is not enabled, the program starts executing the first line of code right after the SLEEP instruction.In the interrupt service routine the software will scan the key that pressed and send IR command appropriate with key pressed.

8 Channel RF Remote Control
Posted on Saturday, May 7, 2011   •   Category: Remote Control

This is a 8 channel RF remote control project. The transmitter powered by 5V.the RF module I used had long start-up and power down period after receiving a high pulse. To counter all of this I kept the receiver in constant standby mode, but sending a information all the time. That way the noise is flooded out, and the receiver will always respond. I had been trying all sorts of error detection methods and different ways of encoding the bytes, when I just gave up. Since the link is so noisy I decided to cut out all of the error detection methods and just make it accept anything it receives, and see what happened from there. But what do you know, it worked!

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