Audio VCO design
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From: Jim Thompson on 21 Nov 2009 09:42 On Sat, 21 Nov 2009 10:31:27 +0000, David Chapman <dave(a)minda.co.uk> wrote: > > Many thanks to all those who have taken the time to contribute to >this thread. > > I'm overwhelmed by the number of different and interesting suggestions >that have been offered. As I said in my original posting, I'm not >looking for an ultra-linear or accurately repeatable solution so the >simpler the better for this application. The cross-coupled >multivibrator arrangement looks very simple and effective so I'll >probably be trying that to start with and then checking out the other >design suggestions. > > Thanks once again for all of your suggestions. MUCH appreciated. > > - Dave [snip] Just read my patent about linearized control.... 3,665,343 Voltage Controlled Multivibrator (In PDF form on my website) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | "The source of well-being in this country is employment." - Steve Wynn, on Fox News Sunday, 11 October 2009
From: Frank Buss on 21 Nov 2009 11:43 David Chapman wrote: > As part of a larger system, I need to design and build an audio VCO > which will produce tones ranging from around 50Hz to 4KHz or so when the > applied DC input voltage changes from 0.5volts to 2.5volts. > This will be used simply as a tuning aid for visually impaired users > so the actual voltage/frequency relationship, and waveform produced, is > not at all critical. Supply voltage of the VCO can be in the range 3.3v > - 5v DC. I would use a microcontroller, as Joerg suggested, because then you'll need just one chip and one capacitor and you're done. I've tried it with a PIC: http://www.frank-buss.de/vco/ The lite edition of the HI-TECH C compiler has even floating point support, so it is very easy to implement it. You can get the PIC for less than $ 1 for 10 parts: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=PIC12F675-I/SN-ND Works from 2V to 5V. And you'll need a programmer. I have this one: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=PG164120-ND Don't use the PICkit3, until they have fixed the firmware :-) The MPLAB IDE and the compilers (the non-optimizing versions, which works good for most projects) are free. -- Frank Buss, fb(a)frank-buss.de http://www.frank-buss.de, http://www.it4-systems.de
From: David Chapman on 22 Nov 2009 04:36 In article <cwhtkdo9z24b$.wqaa2raqk59g$.dlg(a)40tude.net>, Frank Buss <fb(a)frank-buss.de> writes >David Chapman wrote: > >> As part of a larger system, I need to design and build an audio VCO >> which will produce tones ranging from around 50Hz to 4KHz or so when the >> applied DC input voltage changes from 0.5volts to 2.5volts. >> This will be used simply as a tuning aid for visually impaired users >> so the actual voltage/frequency relationship, and waveform produced, is >> not at all critical. Supply voltage of the VCO can be in the range 3.3v >> - 5v DC. > >I would use a microcontroller, as Joerg suggested, because then you'll need >just one chip and one capacitor and you're done. I've tried it with a PIC: What an elegant solution! Many thanks Frank. Your proposed way of solving the problem really highlights the difference between my ancient way of thinking which usually involves discrete components and some digital or analogue ICs, and the modern 'micro fits all' approach. I do feel old :-( ....but then I am, so many thanks for bringing me up to date. I'll certainly give the PIC approach a go now. Thanks again - Dave -- David C.Chapman - (dcchapman(a)minda.co.uk) --------------------------------------------------------------------------
From: Frank Buss on 22 Nov 2009 14:45 David Chapman wrote: > What an elegant solution! Many thanks Frank. My pleasure! > Your proposed way of solving the problem really highlights the > difference between my ancient way of thinking which usually involves > discrete components and some digital or analogue ICs, and the modern > 'micro fits all' approach. > > I do feel old :-( ....but then I am, so many thanks for bringing > me up to date. I'll certainly give the PIC approach a go now. It is never too late to learn new things, e.g. I'm 36 and trying to learn piano playing :-) http://www.youtube.com/watch?v=RC9pS9lOrNw BTW: the PIC is not the best solution if you want high precision, because of the missing capture compare timer, which would be possible with some AVR microcontrollers or better PICs. The best would be a hardware PWM module, which are integrated in bigger microcontrollers, but you wrote that it is not important, so my very simple solution might work for you. -- Frank Buss, fb(a)frank-buss.de http://www.frank-buss.de, http://www.it4-systems.de
From: Rich Grise on 23 Nov 2009 17:38
On Fri, 20 Nov 2009 14:14:56 -0800, whit3rd wrote: > On Nov 20, 1:39�am, David Chapman <d...(a)minda.co.uk> wrote: >> � �As part of a larger system, I need to design and build an audio VCO >> which will produce tones ranging from around 50Hz to 4KHz or so when the >> applied DC input voltage changes from 0.5volts to 2.5volts. > >> � �I'm considering using the CMOS 4046 PLL IC, > > The thresholds in a '4046 (CMOS) are variable unit-to-unit, some better > precision can be had with a linear design; I'm thinking of XR2206, LM331, > and similar chips. The basic scheme is to use the voltage input to > program tracking current source + sink elements, onto an > integrator-connected amplifier into a comparator with suitable hysteresis. In other words, a 555. ;-) > Analog switches, diode switches, current mirrors, or transconductance > amplifiers are the key components. Cheers! Rich |