DDS Signal generator user guide

DDS Signal generator user guide
DDS Signal generator
user guide
NOTES: Please confirm the integrated circuit mounted in
correct direction!
After all the installation, connect the power supply,right
adjust the resistance 10K and you will see the character.
Adjust the character to clear type.
This signal generator has two outputs - one for DDS
signal and another for high speed [1,2,4,8MHz] square signal
- which may be used for reliving microcontrollers with wrong
fuse settings or for other purposes as well. High speed (HS)
signal is direct output from Atmega16 OC1A(PD5) pin. DDS
output is used for all other signals that are generated via R2R
resistor network and is adjusted via LM358N offset and
amplitude regulating circuits. Offset and amplitude can be
regulated by two potentiometers. Offset can be regulated in
range +5V..-5V while amplitude in range 0..10V. DDS
frequency range is from 1 to 65535Hz that is more than
enough for testing audio circuits and other tasks.
Main AVR DDS signal generator features:
•
Simple circuit with easily accessible and cheap
components;
•
Dedicated high speed (HS) signal output up to 8MHz;
•
DDS signal with variable amplitude and offset;
•
DDS signals: sine, square, saw, rev saw, triangle, ECG
and noise.
•
2×16 LCD menu;
•
Intuitive 5 button keypad.
•
Frequency adjusting steps: 1, 10, 100, 1000, 10000Hz;
•
Restoring last configuration after power up.
In the block diagram you may see logical structure of signal
generator:
As you can see device requires several voltages: +5V, -12V,
+12V, GND. -12V and +12V are used for offset and amplitude
control. In this case power supply is constructed by using
simple transformer and few voltagere gulators,
et:7812,7912,7805.
LCD menu control
All actions can be viewed in LCD menu. Menu can be
controlled with 5 buttons that are next to LCD module.
Up and down arrow buttons are used for browsing menu
while right and left arrow buttons are used for changing
frequency value. When middle button is pressed - signal
generating starts. Press middle button again to stop signal
generator.
Important to notice, that there is a separate menu for
changing frequency step. This is convenient if you need to
change generator frequencies in wide range. This allows to
set any frequency with relatively few button clicks.
Noise generation don’t have frequency setting. It uses simple
rand function where results are continuously output to DDS
output.
High speed signal has four frequencies available: 1, 2, 4 and
8MHz.
Circuit diagram of DDS generator is very simple with easy
accessible components. It uses following parts:
•
AVR Atmega16 microcontroller clocked with 16MHz
external crystal;
•
Standard HD44780-based 2×16 LCD module;
•
R2R DAC made of simple resistors(1% tol);
•
LM358N low power dual op amplifier;
•
Two potentiometers;
•
5 buttons;
•
several connectors and sockets.
We offer a programmed IC and all components in the suite.
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