| Electronics > Beginners |
| transistor replacement for VCO? |
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| RandallMcRee:
Have you seen the analog parts kit? http://store.digilentinc.com/analog-parts-kit-by-analog-devices-companion-parts-kit-for-the-analog-discovery/ It contains the parts (e.g. the SSM2212) needed to construct the projects shown in the analog wiki that you linked to. All the parts are breadboardable even the surface mount ones, using adapters. Very reasonably priced, I think. There are also some pretty cool things like sensors, etc. You probably don't need the resistors and capacitors but it seems to me the ICs alone are worth the price. |
| FrankBuss:
Thanks, interesting selection of parts in this kit, but did you add the individual parts cost? Might be the same when buying it at Digikey, and you are right, I have already kits for capacitors and resistors. |
| FrankBuss:
Forgot to mention: I also changed the 2N4392 with the easier to get MMBF4392. And adding or removing the 15 pF capacitor near the LM311 doesn't change anything. |
| FrankBuss:
I found the problem: I used 10 pF instead of 10 nF for the integrator capacitor. Looks good now, with 20 nF for lower maximum frequency: |
| FrankBuss:
Full working circuit: I replaced the LM329 with a TL431, because the LM329 is not available as SMD. And I added a frequency range switch: Now I can adjust from about 0.1 Hz to 100 Hz, and from about 100 Hz to 20 kHz. But the main modification is two inputs for control voltages: With one input you can select the rising speed and with the other the falling speed of the triangle. With this method I can adjust it continuously from nearly sawtooth, to triangle and to inverse sawtooth. The control voltage will be created by a DAC from a microcontroller, so no problem to do some calculations, to make the user interface easier, e.g. the user selects just the frequency and the angle, or pulse width for the square output. |
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