Question
Hi,
I am trying to locate the plans for a workable ELF generator that goes
from 0.01 to at least 35.01 Hz . Could also use a parts list with these
plans if possible; lastly, if there is someway to make this battery
operated it would be great. Thank you for any assistance in this matter.
Sincerely,
Greg
Answer
You don't say if you want sine wave output, or a simple square wave. Presuming sine, I'd suggest using a DDS (Direct Digital Synthesis) device. These are completely digital and highly programmable. Furthermore, they have no intrinsic minimum frequency - just drive them from a low enough reference oscillator (e.g a watch crystal) . Various people make these. I've given a link for the Analog Devices AD9832 . This includes a DAC on-chip. Pull up the PDF datasheet (link near top of page) and you'll get a full explanation of how it works, plus the schematic and parts list for their evaluation board. Their board costs $150 and connects to a PC. You could use it as-is, but to get decent waveforms at the low end of your range, you'll need to swap the crystal for a lower frequency one.<BR><BR>Search the web for Direct Digital Synthesis and you'll find out more.<BR><BR>Good luck.
http://www.analog.com/en/prod/0%2C2877%2CAD9832%2C00.html
DDS
http://vrd.askvrd.org/services/answerschema.xml
