portable handheld function generator

Discussion in 'General Electronics Chat' started by relicmarks, Oct 7, 2009.

  1. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
    355
    0
    HI

    I'm looking for a very small portable handheld function generator that will give me

    1.) sine,triangle,square,pulse waveforms
    2.) Shape/symmetry control
    3.) Start and stop frequency
    4.) sweep linear or Log

    Who makes one that is very cheap and small?

    Just a cheap brand name that is very small so its portable
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Have you searched with Google?
     
  3. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
    355
    0
    ya i have

    been looking at the KITS but i can't find one

    Any cheap brand names?

    1.) sine,triangle,square,pulse waveforms
    2.) Shape/symmetry control
    3.) Start and stop frequency
    4.) sweep linear or Log
    5.) DC Offset

    I have found some KITS but they don't have the shape/symmetry control which i need

    I guess i would have to get function generator IC chips & build it DIY? that supports all of these parameters?

    1.) sine,triangle,square,pulse waveforms
    2.) Shape/symmetry control
    3.) Start and stop frequency
    4.) sweep linear or Log
    5.) DC Offset
     
  4. someonesdad

    Senior Member

    Jul 7, 2009
    1,585
    141
    You don't define what you mean by "cheap" and "small" (weight or physical dimensions or both?), but AFAIK, what you're looking for doesn't exist -- at least, I've never seen one on the web nor as a project for a hobbyist.

    However, I think this would be an excellent product opportunity for a manufacturer. Put it into a box the size of a paperback book perhaps 25 mm thick (or smaller) and make it battery operated. The frequency range could be from e.g. 1 Hz to 0.1 MHz. Cost would be $100 or less. It would run from e.g. three AA batteries. Maximum amplitude would be 4 V p-p into a large impedance, 2 V p-p into 50 ohms. It would have two amplitude ranges, selected by switch: 1 to 100 mV and 0.1 to 4 V. Pot adjustments would be those little PCB-mounted ones with the approximately 10 mm adjustment wheels (the frequency adjustment should be a better pot though). There would be both banana jacks and a floating BNC female connector for output. No display is needed. A small LED would indicate that the unit is on.

    I suspect this is eminently doable with a DDS architecture in one or a few ICs.

    Hmm, maybe it should run from a 9 V battery so that it could provide TTL level output...
     
  5. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
    355
    0
    cheap i mean under $100 dollars
    Small i mean handheld portable not a desktop function generator

    surface mount would be better cause its small

    The only thing i found to be cheap is to buy the function generator chips that supports doing these parameters

    1.) sine,triangle,square,pulse waveforms
    2.) Shape/symmetry control
    3.) Start and stop frequency
    4.) sweep linear or Log
    5.) DC Offset
     
  6. wr8y

    Active Member

    Sep 16, 2008
    232
    1
    relicmarks:

    You, sir, have GOT to visit hamfests once in a while! ;)

    I have seen some real deals on test equipment at hamfests in the USA. Not sure you can buy a NEW one for under $100, but anything is possible at a Hamfest!

    You can find local Hamfests listed at arrl.org !
     
  7. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
    355
    0
    Ya i went to a couple of really old surplus stores that have alot of old oscilloscopes and function generators but they are so big and heavy and the price is high too

    Look at how this company got a function generator with SHAPE/symmetry control inside a small box

    http://www.amazon.com/dp/B000JJHJQU...e=asn&creative=380341&creativeASIN=B000JJHJQU

    Look at the SHAPE control diagram symbols how it changes the triangle waveform and squarewaveform
     
  8. wr8y

    Active Member

    Sep 16, 2008
    232
    1
    You might look at the websites of:

    Long's Electronics
    Ten-Tec USA (the bunch in Tennessee)
    Jameco
    Ham Radio Outlet (HRO)

    there is another one, can't THINK of the name, I have their catalog at home. MAN, I just am drawing a blank here! I'll be home in about four hours and TRY to remember to grab the name and post it. Can't believe I can't remember the name - they make a lot of inexpensive test equipment - we order from them maybe twice a year.
     
  9. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    Go to good stage suppliers and look for some stage audio test gear, Phonic, Roland, Teac etc.

    But they won't come cheap.
     
  10. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Here is a basic sine, square and triangle wave function generator kit (1Hz-1MHz) for about $40:
    http://www.electronickits.com/kit/complete/meas/fg500k.htm

    Here is the manual for the kit:
    http://manuals.elenco.com/manuals/fg-500k.pdf

    The kit as designed does not provide for waveform symmetry adjustment, DC offset, nor frequency sweep. However, the symmetry inputs to the XR2206 are available, if you would choose to connect them to something - like a 25k pot. You could also add a sweep function by connecting an additional circuit to pin 8, and enabling the sweep using pin 9 (FSK input). A DC offset might be a bit more problematic, but could possibly be arranged using an opamp to provide an artificial ground reference. If you were to do that, you would likely need to add a negative power rail or 2nd battery.
     
    Last edited: Oct 7, 2009
  11. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
    355
    0
    SgtWookie do you know any function generator IC chips i can get that will do all of these parameters?

    1.) sine,triangle,square,pulse waveforms
    2.) Shape/symmetry control
    3.) Start and stop frequency
    4.) sweep linear or Log
    5.) DC Offset

    How do you think the designer did the LFO for this? what do u think he did or used?

    http://www.amazon.com/dp/B000JJHJQU/...SIN=B000JJHJQU

    I think the company used a IC op-amp function generator that has a SHAPE/symmetery control

    But i can't find a schematic that has a IC op-amp function generator that supports all of these's or some

    1.) sine,triangle,square,pulse waveforms
    2.) Shape/symmetry control
    3.) Start and stop frequency
    4.) sweep linear or Log
    5.) DC Offset

    Don't they make function generator IC chips that will do all of these?
     
  12. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Nope, sorry.
    The XR-2206 will do much of it, and that Elenco kit I posted a link to uses a single XR-2206 function generator. The MAX038 was a much more capable function generator, but the factory that made them was destroyed.

    Most lab function generators nowadays use digital synthesis techniques; that way they can generate waveforms of arbitrary shapes.
    It's probably using opamps such as the TL071/TL072/TL074 family. It's only operating in the audio spectrum, so the frequency requirement is low.
    Nope, not a single IC that I know of, sorry.
    However, you could combine a couple of XR-2206 IC's; use one to generate the ramp for the frequency sweep, and another for the signal output.

    You'd still need a method for generating the offset. I already mentioned using an opamp as a virtual ground. Just connect it as a voltage follower, with a pot on the noninverting input between Vcc and Vee.
     
  13. relicmarks

    Thread Starter Active Member

    Oct 13, 2006
    355
    0
    I read The Intersil ICL8038 and Maxim MAX038 function grnerator ICs are also not made anymore.

    Do you think the XR-2206 is the only function generator IC chip now?

    opamps such as the TL071/TL072/TL074 family. It's only operating in the audio spectrum, so the frequency requirement is low.

    Do you guys know any Op-Amp function generator schematics that supports theses parameters instead of using a function generator IC chip

    1.) sine,triangle,square,pulse waveforms
    2.) Shape/symmetry control
    3.) Start and stop frequency
    4.) sweep linear or Log
    5.) DC Offset
     
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