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Old 16th March 2007, 07:37 PM   #1
eris is offline eris  United States
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Default Inexpensive Function Generator Kit for Testing!

Hey all...

I was looking for an inexpensive kit to generate sine, square and triangle waves for my new amplifier. I looked for several days and most of the kits were based on either the Exar or Analog Devices ASICs and required a bit more dedication in terms of building / purchasing than I wanted to spend.

(For the record, commercial generators cost anywhere from several hunder to serveral thousand dollars depending on the quality)

Then I found this:

http://www.myplace.nu/avr/minidds/

Thats an incredibly inexpensive and quick to build function generator based on an Atmel AVR microcontroller. For waveforms it uses Direct Digital Synthesis for extremely stable peformance. Its good from DC to almost 300Khz. The only limitation I can see is that it's only using 8 bits for its DAC, but that could easily be extended to more bits of resolution at the price of decrease frequency. Even then 150Khz is well beyond what I believe we need for testing.

If anyone wants to do a group buy on PCBs for this let me know. Of course the thing is so simple -- AVRs can be programmed in-circuit from a simple parallel port. You could easily build this on a proto board if you only needed it once or twice.

eris
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Old 17th March 2007, 11:49 PM   #2
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You could create synthetic waveforms in 16 bits, burn them to a CDROM and use your CD player as the signal generator.

I_F
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Old 18th March 2007, 11:02 AM   #3
dangus is offline dangus  Canada
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Or if you don't need signals into the RF range, use a computer sound card. A little searching will turn up various programs for generating waveforms.
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Old 18th March 2007, 12:07 PM   #4
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Hi,

Have a look at the Maxim MAX038: http://datasheets.maxim-ic.com/en/ds/MAX038.pdf

Although not supported by Maxim anymore, there are many DIY kits around based on this chip.

Cheers
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Old 18th March 2007, 12:47 PM   #5
AndrewT is offline AndrewT  Scotland
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Hi,
Quote:
Originally posted by I_Forgot
You could create synthetic waveforms in 16 bits, burn them to a CDROM and use your CD player as the signal generator.

I_F
How?
Software?
Process?
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Old 18th March 2007, 02:08 PM   #6
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I don't know the specs, but you can try this:
http://www.marchandelec.com/fg.html

You can create the waveforms in SwCAD and send them to a .wav file- you can even go 24/96 with this method. It will be slow, but very accurate.

Try this if you have a Mac
http://www.blackcatsystems.com/softw...iotoolbox.html

Try this:
http://www.e-dsp.com/software-functionsignal-generator/

Audacity can generate sine, square, and triangle waveforms and store to .wav files, too. You can get it for Linux and M$.

I_F
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Old 18th March 2007, 02:31 PM   #7
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Yes, there are many wave generator programs for use with your soundcard around on the web.

For creating arbitrary wav files have also a look at Goldwave. It has an equation editor build in to describe a wave function mathematically.

Also many audio analysis software has nice wave generators build in like the one I like most: Arta

But for building amplifiers and judging your builds, a separate sine generator up to 1 MHz 10 MHz and a real 20 MHz oscilloscope is indispensable in the end IMO.

Cheers
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