Posted on Friday, April 30, 2010 • Category:
FM Transmitters
This new FM transmitter is very simple and doesn't need any RF tuning.
First of all ,we have used an integrated VCO: The POS150 from Mini-circuits.
This excellent RF circuit covers all the FM Band in a voltage range of 4V to 8V.
The Kvco factor is very stable all over the FM band, consequently, we have applied the BF signal directly on the control voltage line coming from the PLL.
Posted on Friday, April 30, 2010 • Category:
FM Transmitters
The functioning of all is provided by a microcontroller from MICROCHIP "PIC16F84" which provides support for buttons, LCD 2 lines of 16 characters and the circuit pll "SAA1057.
The VCO is entrusted to the transistor Q8 associate of his two diodes varicaps "BB109, a floor buffer Q7 separates the VHF signal obtained in two ways, on the one hand to Q9 to enslave loop phase and on the other hand to the Q5 and Q6 together which takes care to amplify the signal before attacking Q11, a "BFR96" which plays the role of HF switch via a timer "NE555" which receives information from the push and "SAA1057" ensuring HF cutoff in the event of failure of a locking or unlocking of the pll.
Posted on Friday, April 30, 2010 • Category:
Test and Measurement
This circuit is ideal for adding a low cost frequency display to a function generator or other design. I doubt if it is possible to get a cheaper design using off the shelf components!. In fact, I challenge anyone to make a cheaper design using garden variety components!.
The upper frequency limit is dependent upon the upper limit of the 74HC390 chips which is roughly 40MHz.
Posted on Friday, April 30, 2010 • Category:
AVR
This board is a RDS coder using an ATMEL AVR ATmega32.
This board can be controled by a RS232 link, USB interface or SPI.
TA data is displayed wiyth a LED and can be controled by :
- Hardware input
- RS232
- USB
- SPI (not yet implemented)
Posted on Friday, April 30, 2010 • Category:
FM Transmitters
Filter used for eliminate unwanted harmonic frequency at second and third. Notch filter, Band Pass Filter (BPF), and High Pass Filter (HPF) sometime combined in constructing LPF design.
Schematic below for FM Broadcast Lowpass Filter 88-108 MHz. It has been tested with a good result.
Note : Make the coils at 74 nH and trim them to adjust exact value.
Posted on Thursday, April 29, 2010 • Category:
USB Interface Adapters
Control up to three devices from a PC with FT232 IC (USB to Serial UART) from Future Technology Devices International FTDI. Circuit is simple and does not require external microcontroller or any type of firmware programming. PC control software written in VB6 is included.
Posted on Thursday, April 29, 2010 • Category:
PIC
This is a digital thermometer based on USB PIC16C745 microcontroller from Microchip and DS1820 sensor from Dallas Semiconductor. Temperature readings are sent over USB port in HIDCOMM USB mode to VB6 program on a PC. Hex program and sample Visual Basic 6 application is included.
Posted on Thursday, April 29, 2010 • Category:
FM Transmitters
In order to simplify the transmitter design, we've used the new pll circuit from Motorola :the MC145170.
This PLL includes the prescaler and a serial standard bus called SPI.
Posted on Thursday, April 29, 2010 • Category:
PIC
Circuit measures the temperature and ambient brightness of the surrounding environment at the location it is placed. The data from the ADC is the calculated and displayed on the LCD. The main CPU unit on board the device is the PIC16F873.
Posted on Thursday, April 29, 2010 • Category:
Remote Control
This is a true 'minimalist' remote, having but three functions:
Volume Up, Volume Down and Mute
Volume is controlled by a motorized (motorized for US readers) pot rather than any of the 'digital' pots that now abound, and this was done for a number of very good reasons.
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