DIY Function Generator for Under $50

Discussion in 'The Projects Forum' started by AlphaDesign888, Aug 1, 2014.

  1. AlphaDesign888

    Thread Starter New Member

    Jul 27, 2014
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    *Function Generator 1MHz*

    Requirements:

    a. Waveforms sine, square, triangle
    b. Variable frequency
    c. Variable duty cycle
    d. Variable amplitude
    e. Sweep function
    f. Astable or monostable operation
    g. Mains powered
    h. Metal enclosure
    i. Analouge schema using pots, switches and buttons
    j. Can be built for under $50

    How would you do this one?
     
    Last edited: Aug 1, 2014
  2. Papabravo

    Expert

    Feb 24, 2006
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  3. alexfreed

    Member

    Oct 8, 2012
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    The right solution is to use a microcontroller. STM32 with built in DAC is perfect. The whole boad is $10.

    If you insist on an analog solution, search for 30 years old designs around MAX038.
     
  4. AlphaDesign888

    Thread Starter New Member

    Jul 27, 2014
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    I have used the XR2206 IC in an previous design. Sold some units on eBay.
    Looking for something different now.
     
  5. AlphaDesign888

    Thread Starter New Member

    Jul 27, 2014
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    Actually I am thinking of something that uses many discretes.
    Like a dozen or so OP AMPs.

    People will learn more from this, and it will take some time to build. Lots of people like soldering boards with lots of parts.
     
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  6. RichardO

    Well-Known Member

    May 4, 2013
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    Lots of questions...

    What frequency range? You need some fairly fancy op-amps for over a few MHz of operation.

    Does variable amplitude include an output attenuator? An output amplifier with 50 ohm output impedance is needed for high frequencies.

    Log or linear sweep of both? Log sweep is trickier than linear sweep but it is most likely what you want.

    How important is the monostable operation? By this I assume you mean trigger and gate modes?

    How important it the $50 dollar limit? Pots and knobs are expensive! The metal box alone can be more than $50. :(


    Maybe you should look at old Wavetek models and tell us which one you like. The model 181 is a good one to look at first.
     
  7. AlphaDesign888

    Thread Starter New Member

    Jul 27, 2014
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    I would compromise on whatever to meet the $50 target.
    There is psychology floating around that suggests that most people think long and much harder about spending more than $30.

    I have purchased metal project enclosure from Taiwan for $7.50 landed (on eBay)
    Pots, knobs, buttons & switches are cheap enough through Tayda Electronics (Taiwan)

    I feel something can be done for $50. A toy perhaps. But still something.
     
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  8. MrChips

    Moderator

    Oct 2, 2009
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    Why not use a 8038 (ICL8038, XR8038, MAX038) or XR2206?
     
  9. RichardO

    Well-Known Member

    May 4, 2013
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    This is what I would do. But keep in mind that all of these old parts may be, or will soon be, obsolete.

    The project will still be interesting when you add all of the other stuff needed to do what you want such as an output amp, trigger/gate circuit, attenuator, power supplies, log sweep circuit, enclosure/front panel, etc.

    p.s. I would go with the MAX038 The MAX038 is no longer made but parts are still available.
     
  10. RichardO

    Well-Known Member

    May 4, 2013
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    Here is an example of a 10 MHz function generator. It is a design I did a long time ago. Features include: variable symmetry, AM, FM, trigger/gate, a 50 ohm pulse output and a 50 ohm waveform output with adjustable DC offset.

    This is the function generator I use the most although I have others including one done using a MAX038.

    This is only for reference since many of the parts were expensive when I did the original design and are hard, if not impossible, to get now.
     
  11. AlphaDesign888

    Thread Starter New Member

    Jul 27, 2014
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    Maybe I should realize the 21st century and go with an digital system.
     
  12. RichardO

    Well-Known Member

    May 4, 2013
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    Just like a digital scope is not the same as an analog scope, a digital signal generator is not the same as a function generator.

    Disclosure: I like my test equipment to have knobs and switches and not keyboards.
     
  13. AlphaDesign888

    Thread Starter New Member

    Jul 27, 2014
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    But either way it is an no winner right? Electronics has now become an situation whereas everyone just wants to do their own thing.
     
  14. RichardO

    Well-Known Member

    May 4, 2013
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    Sorry, I don't follow what you are getting at.
     
  15. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    If you are going to be making something to sell to "people" for $50 I don't think there will be any significant profit in it.

    Kits sales are at all time lows in the last few years.
     
  16. KLillie

    Member

    May 31, 2014
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  17. AlphaDesign888

    Thread Starter New Member

    Jul 27, 2014
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    That's what I mean by 'no winner'

    Whole thing has gone belly up. No money anywhere.
     
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