Micro Function Generator


Posted on Feb 5, 2014

There are two main types: the most common is the Wein Bridge oscillator variety, which has low distortion, but offers only sinewave output and can suffer from amplitude bounce as you change frequency. The type which offers greater versatility of waveform and frequency range, the usual function generator type, typically lack stability and accuracy. This unit meets all these requirements, and is small - fits in the palm of your


Micro Function Generator
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hand - and is battery operated. It also has no "front panel" - you control it from a PC or computer terminal. The generators are quite inexpensive to build - just two or three ICs and a couple of transistors. One of the ICs is an AVR RISC microcontroller - inexpensive, and quite powerful. It operates in an unusual manner, using a Direct Digital Synthesis (DDS) technique developed by Jesper Hansen to create very accurate signals. Some of the features of the Function Generator are: Many of the parameters, such as frequency range, step size and frequency response can be tailored to suit other applications. The picture below, of the simple PC control panel for the generator, shows a 4MHz version in use, with an upper limit of about 133 kHz. The absolute upper frequency limit of any generator using this microcontroller technique is set by the maximum clock frequency (currently 16 MHz). The upper limit of the generator is thus about 500 kHz. There is no lower limit. A 12. 8MHz version for use as an Exciter for the Amateur LF bands is also available. Power for the unit comes from a tiny 5V regulator, which runs from a DC supply (battery or AC adaptor) with an output of between 6V and 15V. The supply is reverse voltage protected. The RS232 communications with the PC uses simple transistor level shifters. The transmit signal from the microcontroller requires a negative voltage supply, and for simplicity, this voltage is derived...




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