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Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members. |
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19th May 2021, 11:33 am | #1 |
Nonode
Join Date: Aug 2007
Location: Walsall Wood, Aldridge, Walsall, UK.
Posts: 2,873
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Lab Quality Function Generator
Hi!
Most Function Generators based on the XR2206, MAX038, 8038, etc., tend to have a THD percentage of 0.5 to 1.5% thd on sine-wave ouput signals, not really good enough for audio testing! The design presented here has typically 0.03% THD max using a d/a filtering process. Frequency coverage 1 Hz - 99.99 kHz, Sine output 1V rms (original design) but an additional 50 ohm impedance power amplifier giving a higher voltage output will be included. I am going to present in this thread here my version of the Project presented by Elektor Magazine during October, November and December 1991. The Author of the original design was T. Giffard, who published quite a number of Elektor projects during this period. The original PCBs for this, nos. 910077-1 to 910077-4 have long been unobtainable from Elektor, but I will provide replacement designs and Gerber Files, produced from my Easy PCB software. All of the parts for this are still available at the time of writing this, altho' the Neosid 7A1s coil former kit isn't available in the UK, however I will suggest a modification to a Toko 10K coil assembly as a substitute! There are no EPROMs, GALs, or microcontrollers requiring programming in this unit. Circuit Diagrams and PCB layouts are my own derived from the original Elektor design. Chris Williams
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It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed! |
19th May 2021, 11:52 am | #2 |
Nonode
Join Date: Jun 2016
Location: Bognor Regis, West Sussex, UK.
Posts: 2,300
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Re: Lab Quality Function Generator
I look forward to this with interest!
If there is enough interest perhaps we could get an order together for the pcbs from JLCPCB (they have a minimum quantity of 5) Peter |
19th May 2021, 12:56 pm | #3 |
Nonode
Join Date: Aug 2007
Location: Walsall Wood, Aldridge, Walsall, UK.
Posts: 2,873
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Re: Lab Quality Function Generator
Hi!
I will be ordering the PCBs for this when my designs are complete, there will be three sets available to begin with! The design currently uses four 74HC696 up/down decade counter/shift register combination i.c. devices, I will design an adapter PCB to use separate counter/shift register devices if the 74HC696s become unobtanium – supplies of this device are currently available from Littlediode for £4.25 each – I've just had four delivered! The design is currently being entered into "Easy PC's" Schematic Editor for laying out the PCBs even as I write this! Chris Williams
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It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed! |
21st May 2021, 6:30 am | #4 |
Dekatron
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,667
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Re: Lab Quality Function Generator
Sounds interesting Chris,thanks for your hard work. Will it have a square wave function? For testing audio gear a must.
Andy.
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Curiosity hasn't killed this cat...so far. |
21st May 2021, 6:43 am | #5 |
Nonode
Join Date: Jun 2016
Location: Bognor Regis, West Sussex, UK.
Posts: 2,300
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Re: Lab Quality Function Generator
If its based on the Elektor one it will have Sine, Square and Triangle.
Peter |
21st May 2021, 2:42 pm | #6 |
Nonode
Join Date: Aug 2007
Location: Walsall Wood, Aldridge, Walsall, UK.
Posts: 2,873
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Re: Lab Quality Function Generator
Hi!
Yes it is Sine, Square and Triangle! The design doesn't appear to have an external VCO input but it's quite possible to use an 16 bit A/D module on the counter inputs but this a very expensive solution, a much cheaper one is to add a buffer amplifier whose output is fed to the varicap control voltage input. Chris Williams
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It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed! |
24th May 2021, 9:45 am | #7 |
Nonode
Join Date: Jun 2016
Location: Bognor Regis, West Sussex, UK.
Posts: 2,300
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Re: Lab Quality Function Generator
I have the original Elektor Article in pdf format.
I will not post it here because of copyright but if anyone wants a copy PM me with an e-mail address and will send it for personal study. Peter |
24th May 2021, 10:12 am | #8 |
Nonode
Join Date: Aug 2007
Location: Walsall Wood, Aldridge, Walsall, UK.
Posts: 2,873
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Re: Lab Quality Function Generator
Hi!
No need for anyone to worry about the wrath of the copyright moguls as I bought a "Green" Membership from Elektor themselves that includes every issue in high quality PDF scan all the way back to issue No. 1, November 1974, so I can reprint it any time! (I have no time for them as they're wanting to use "copyright" as an excuse to make you pay for a purchased item over and over again!) Chris Williams
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It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed! |
24th May 2021, 12:47 pm | #9 |
Hexode
Join Date: Jun 2018
Location: Buckinghamshire, UK.
Posts: 387
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Re: Lab Quality Function Generator
All three parts of the article are available on the worldradiohistory site:
https://worldradiohistory.com/UK/Ele...or-1991-10.pdf https://worldradiohistory.com/UK/Ele...or-1991-11.pdf https://worldradiohistory.com/UK/Ele...or-1991-12.pdf Cheers |
24th May 2021, 1:22 pm | #10 |
Nonode
Join Date: Jan 2009
Location: Bristol, UK.
Posts: 2,062
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Re: Lab Quality Function Generator
Sweep would be nice, with the generator producing a ramp / trigger I only briefly looked at the Elektor schematics but a clock signal into the up/down frequency control might do something interesting? But you might be doing something totally different
dc |
24th May 2021, 5:50 pm | #11 | |
Nonode
Join Date: Jun 2016
Location: Bognor Regis, West Sussex, UK.
Posts: 2,300
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Re: Lab Quality Function Generator
Quote:
as I say send a PM if you want a copy. Peter |
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