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| Super-Freq: Oscillators |
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| TrentO:
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 |
| GeekGirl:
--- Quote from: TrentO on October 31, 2009, 07:50:05 am ---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? --- End quote --- Well, 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" circuits :) this 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 wave :) --- Quote from: TrentO on October 31, 2009, 07:50:05 am ---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.... --- End quote --- You 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 am ---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. --- End quote --- Excellent 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 it ;) we can give you pointers :) |
| Mastro Gippo:
DIY oscope? Did I mention http://www.seeedstudio.com/depot/digital-storage-oscilloscope-diy-kit-with-panels-p-515.html ? ;D |
| TrentO:
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 |
| TrentO:
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 |
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