A Function Generator Project - not for the feint of heart

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sbench
Posts: 296
Joined: Fri Jan 28, 2005 3:45 pm

A Function Generator Project - not for the feint of heart

Post by sbench »

OK Folks,
After a rather long absense, I thought I update what I've been doing. The attached info produces a nice sine / square /triangle generator based on the AD9834 chip.

Function Generator Specs:
1 Hz to 1MHz in steps. (56 steps to be exact)
4 separate outputs:
- main output +3dBV (1.4VRMS), 100 ohms, about 0.025% dist sine wav
- lo dist 1kHz. +3dBV, 1000 ohms, about 0.008% dist
- Inverse RIAA output, 26dB below main output@1kHz, 50 ohms
- 5V P-P constant level square wave for trigger purposes
3 different sweeps available
- Fast 1Hz to 1MHz
- Slow 1Hz to 1MHz
- Slow 20Hz to 20kHz
Indicators: 48 LEDs indicate frequency(43) and function(5)
Push button / functions
- Up, Down (fixed frequencies)
- GOTO 1kHz
- GOTO 20Hz
- GOTO 20kHz
- toggle: sine/triangle/square
- toggle: fixed/sweep1/sweep2/sweep3
Powered from 4 AA batteries, current consumption about 20mA.
Output Level adjustment
- variable +3 to -10dBV
- stepped 0, -10, -20, -30, -40, -50, -60 dB
Active Devices (sorry, no tubes)
- 1 Analog Devices AD9834
- 1 Microchip PIC processor 16F59
- 2 KM4270 dual 10MHz op amps
- 1 KM4120 75MHz op amp
Size: About the size of a hand held Fluke 83 DMM

I have attached picture of the thing next to a Fluke 83 for comparison.
I have also attached .GIF schematics and a ZIP file containing:
- PDF schematic pages
- the picture
- PIC source code
- PIC object code (programming file)

This is a cute little unit, but reasonably intricate to build, but not too expensive.

Since it's software controlled, different / additional functions are certainly possible.

Steve
Attachments
fgen.ZIP
(160.01 KiB) Downloaded 1234 times
fgen_d.gif
fgen_d.gif (67.14 KiB) Viewed 12351 times
fgen_a.gif
fgen_a.gif (65.19 KiB) Viewed 12351 times
fgen.jpg
fgen.jpg (88.57 KiB) Viewed 12373 times
dave slagle
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Post by dave slagle »

Nice!

did the Lriaa ever show up from the ETF?

dave
sbench
Posts: 296
Joined: Fri Jan 28, 2005 3:45 pm

Post by sbench »

nope. Still waiting. Think Christian is holding it hostage 'til I send back "lil sister" that is here for repairs... it had made some crackling noise during the shootout. Seems to perform well here, but I did find and fix a broken "case ground" wire so that might have been it.

-Steve
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