Super-Freq:  Oscillators - Page 1
Forum section: electronics / general

author: Unknown
author_rank: Unknown
timestamp: October 31, 2009, 07:50:05 am
content: I seek opinions on using standard through-hole clock oscillators to generate 'test-patterns,' if you will, that I can pump through my oscilloscopes, and my eventual o-scope project...COTS frequency generators appear to be freeking expensive for anything above 5Mhz or so. I do have my eye on the Rigol DS1022 20Mhz for approximately $700US, but I have a feeling I'm going to outgrow that limit fairly quickly. The 120Mhz unit is about $4000US-- I don't think I would use it enough to justify that kind of purchase. However, paging through my favorite Digi-Key catalog, I see that there are myriad crystal and/or oscillator offerings-- could I simply provide the requisite +5v / +3.3v to the OSC can and use the output for testing? I could simply buy 10-20 OSC's in xMhz steps to get to my 120Mhz requirement! Are there limitations in doing so? What kind of circuit (apart from power) would I have to build in order to support this?And finally, if I wanted to amplify these signals (and change the amplitude displayed on my o-scopes,) could someone recommend a circuit that I could build to do so? I would assume that an op-amp or two would be sufficient....As for my O-scope project, I'm looking to build a three-chip DSO out of a PIC32, AD9283 ADC, and FIFO-- for no other reason than to learn about microcontroller development, ADC's and FIFO's.! But step one, in my opinion, would be to have the capability to produce a signal of known quantities/qualities.Any and all assistance, comments and opinions are sincerely appreciated!-Trent

author: Unknown
author_rank: Unknown
timestamp: October 31, 2009, 10:08:35 am
content: Quote from: TrentO on October 31, 2009, 07:50:05 amWell, lets treat this as a learning exercise, first step is to get the datasheet, there will be a link on the page, read it well, it will have some "typical" circuitsthis will do EXACTLY what you want, only thing is it will be a square wave only from the can. A simple external circuit will allow you to turn it into a sine or triangle waveQuote from: TrentO on October 31, 2009, 07:50:05 amYou would need to find an opamp that will give the required output voltage, and have a reasonable bandwidth.Quote from: TrentO on October 31, 2009, 07:50:05 amExcellent idea, cheap graphic LCD (or use a computer for waveform display), a decent ADC with a PRECISION REFERENCE supply, do not make the mistake of thinking that the +5v out from the linear reg is good enough for the vref of an ADC. Something like an LM4040 is a good choice.If you brainstorm, draw up a schematic (if you post it here, please make it an image from screen cap or PDF, so everyone can view itwe can give you pointers

author: Mastro Gippo
author_rank: Regular Contributor
timestamp: November 02, 2009, 09:41:54 am
content: DIY oscope? Did I mentionhttp://www.seeedstudio.com/depot/digital-storage-oscilloscope-diy-kit-with-panels-p-515.html?

author: Unknown
author_rank: Unknown
timestamp: November 02, 2009, 11:24:20 pm
content: Mastro Gippo--I have seen this before, and I would have tried it, had it been based on the PIC architecture... I decided about two months ago to take the PIC route and not the Atmel route, in (re-) learning microcontrollers. I'm not looking to build an Oscilloscope for anything practical-- just to learn more about the practice of A to D conversion and perhaps driving a graphical LCD display.-Trent

author: Unknown
author_rank: Unknown
timestamp: November 02, 2009, 11:34:17 pm
content: Andrew,Awesome response. I think I'll take your suggestions on as a project by itself. Are there any books on HF circuit design that you would recommend? (NOT that I want to build a frequency generator from scratch!)Thank you very much for your opinions on the DG-1022-- I never really considered the PC-driven aspect of such a device-- I didn't think I needed the arbitrary-waveform aspect... but now that you bring it up, its probably worth considering-- I might have a need for it down-the-road.-Trent

author: Mastro Gippo
author_rank: Regular Contributor
timestamp: November 05, 2009, 05:01:47 pm
content: Quote from: TrentO on November 02, 2009, 11:24:20 pmI'm a pic guy too, but that thing is a nice way to learn something new! Also, it's a basic oscope for very little money! I think I'm going to get it just for the cool factor, I don't think I'll ever use it