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Topic: Building a function generator (Read 3293 times) previous topic - next topic

compuslave

Contrary to popular opinion, google is not always your friend. I've been googling like crazy trying to find schematics to build a function generator. I did see the one that is arduino based that consists of nothing more than resistors attached to the digital pins, but I want a standalone unit. I also saw several that were based on various ic's that were made for wave generation, none of which I have. I have most of the basic bits and pieces laying around to build one, I just don't know how. I have a quad op-amp and a couple 555's, plenty of resistors and capacitors, switches and potentiometers. Can you guys please help me build one so I can learn something and see something besides a square wave on my brand new oscilloscope?

I'll sacrifice as many of what ever animals I have to, in order to appease you guys.
Never judge a man until you walk a mile in his shoes. But, by that time you're a mile away and you got his shoes, so screw em'

baum

If you are willing, you can shell out $10 for a DAC and make some wave forms. Note that they won't be perfect. (but it is easier)

http://www.sparkfun.com/products/9719

But if you want better waveforms, check out this:

http://www.falstad.com/circuit/e-index.html

these are great circuit simulations. (check all of them out!) Scroll about half way until you see "Op-Amps" and then "Oscillators." That should help!


Good Luck!
baum

James C4S

If you have a 555, there are a ton of projects (that can be found through google using "555 based function generator").  Better defining what you are trying to build, in terms of specifications, and you'll have a better search to use on google.  What frequencies, wave shapes, amplitudes, and current loads are you looking to have?
Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

compuslave

Thanks for the reply. I am also building a rodin coil and would like to experiment with all waveforms. But most of all I would like to learn something I can apply to other projects. I have one of the sparkfun function generator kits in my cart but I can't decide on whether I should spend the $35 on what is probably a pretty nice little unit, or try to build one myself. You're right, I should do both :^D

I really don't have an specifications, persey. As I said in my first post, I have this brand new oscilloscope and it's begging me to generate some functions.

Here's the oscilloscope I got http://www.sparkfun.com/products/9484 I can't figure out to link it properly, sorry.
Never judge a man until you walk a mile in his shoes. But, by that time you're a mile away and you got his shoes, so screw em'

compuslave

#4
May 01, 2011, 04:02 am Last Edit: May 01, 2011, 04:18 am by compuslave Reason: 1

If you are willing, you can shell out $10 for a DAC and make some wave forms. Note that they won't be perfect. (but it is easier)

http://www.sparkfun.com/products/9719

But if you want better waveforms, check out this:

http://www.falstad.com/circuit/e-index.html

these are great circuit simulations. (check all of them out!) Scroll about half way until you see "Op-Amps" and then "Oscillators." That should help!


Good Luck!
baum

Thanks, baum. You should know that I have a problem with SparkFun, though. I'm trying to get help for my problem but like most addicts I love it too much.

Edit: Great site! I actually came across that one in my searches but didn't really check it out. Bookmarked now!

I also ordered the DAC, lol, Imma go broke.
Never judge a man until you walk a mile in his shoes. But, by that time you're a mile away and you got his shoes, so screw em'

baum

Quote
I'm trying to get help for my problem but like most addicts I love it too much.

Then try the op amp version. Sparkfun free!

compuslave


Quote
I'm trying to get help for my problem but like most addicts I love it too much.

Then try the op amp version. Sparkfun free!


Too late, read the edit :^|
Never judge a man until you walk a mile in his shoes. But, by that time you're a mile away and you got his shoes, so screw em'

u0421793

Wouldn't it be easier, and functionally identical, if you simply drew out various waveforms on small sheets of graph paper, and placed those sheets of paper individually over the top of the screen of the oscilloscope every time you want to look at one of the likely waveforms. In fact, if it were done like a flick book, you could have various flick books for sine, square, triangle, sawtooth, ramp. The flick-books could range from low frequency to high frequency as you flick through. Or other flick books could range from 1% to 99% symmetry. If you encounter a waveform you particularly like, you could photocopy that page and frame it and hang it on the wall along with your other favourite waveforms.

jluciani

You could make a function generator with a uC and a DAC. You store
the waveforms in wavetables (C arrays) and then periodically output
the values from the wavetable to the DAC. You can generate any arbitrary
periodic waveform. One name for this is a numerically-controlled
oscillator (NCO)

I make a board (NB1A) that integrates a '328 (Arduino bootloader)
and a DAC. I have a NCO sketch at http://wiblocks.luciani.org/docs/app-notes/nb1a-nco.html
You could wire the same DAC to an Arduino. The schematic is in
the NB1A datasheet http://wiblocks.luciani.org/NB1/NB1A-index.html

(* jcl *)
www: http://www.wiblocks.com
twitter: http://twitter.com/wiblocks

compuslave


Wouldn't it be easier, and functionally identical, if you simply drew out various waveforms on small sheets of graph paper, and placed those sheets of paper individually over the top of the screen of the oscilloscope every time you want to look at one of the likely waveforms. In fact, if it were done like a flick book, you could have various flick books for sine, square, triangle, sawtooth, ramp. The flick-books could range from low frequency to high frequency as you flick through. Or other flick books could range from 1% to 99% symmetry. If you encounter a waveform you particularly like, you could photocopy that page and frame it and hang it on the wall along with your other favourite waveforms.

I actually did this first. Sadly, I spilled coffee on it and can't seem to find the motivation to do it again. Also, I kept getting distracted from drawing waveforms in favor of the masturbating stick man. *sigh*, what a character that stick man was  =(

Even if I were to find the motivation to start that project over again, It would be very difficult, as I have broken all my pencils pencil fighting.
Never judge a man until you walk a mile in his shoes. But, by that time you're a mile away and you got his shoes, so screw em'

compuslave


You could make a function generator with a uC and a DAC. You store
the waveforms in wavetables (C arrays) and then periodically output
the values from the wavetable to the DAC. You can generate any arbitrary
periodic waveform. One name for this is a numerically-controlled
oscillator (NCO)

I make a board (NB1A) that integrates a '328 (Arduino bootloader)
and a DAC. I have a NCO sketch at http://wiblocks.luciani.org/docs/app-notes/nb1a-nco.html
You could wire the same DAC to an Arduino. The schematic is in
the NB1A datasheet http://wiblocks.luciani.org/NB1/NB1A-index.html

(* jcl *)


Well, I did order a DAC, and you guys are gonna have to teach me to play with it.
Never judge a man until you walk a mile in his shoes. But, by that time you're a mile away and you got his shoes, so screw em'

Eu não sou o teu criado. Se respondo no fórum é para ajudar todos mediante a minha disponibilidade e disposição. Responder por mensagem pessoal iria contra o propósito do fórum e por isso evito-o.
Se realmente pretendes que eu te ajude por mensagem pessoal, então podemos chegar a um acordo e contrato onde me pagas pela ajuda que eu fornecer e poderás então definir os termos de confidencialidade do meu serviço. De forma contrária toda e qualquer ajuda que eu der tem de ser visível a todos os participantes do fórum (será boa ideia, veres o significado da palavra fórum).
Nota também que eu não me responsabilizo por parvoíces escritas neste espaço pelo que se vais seguir algo dito por mim, entende que o farás por tua conta e risco.

Dito isto, mensagens pessoais só se forem pessoais, ou seja, se já interagimos de alguma forma no passado ou se me pretendes convidar para uma churrascada com cerveja (paga por ti, obviamente).

baum

Which one did you get? I accidentally got the I2C one, and it is awful (slow). Hope you got a parallel DAC!

compuslave


Which one did you get? I accidentally got the I2C one, and it is awful (slow). Hope you got a parallel DAC!

http://www.sparkfun.com/products/9719 the one you posted. I haven't actually ordered it, but it's in my cart. I'm hoping they will have the makerbeam back in stock soon and then I will go ahead with my order. As of now my cart is right by the register, but I'm waiting on that finally toy to be back in stock.
Never judge a man until you walk a mile in his shoes. But, by that time you're a mile away and you got his shoes, so screw em'

baum

Good. I thought I would save $5 with the serial version, but I2C is WAY to slow for anything meaningful dealing with audio or signal gen.

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