[sdiy] Henry Walmsley's page

[Grant Richter]

It might be helpful to mention the original purpose of the V to F  
converter. (like the RC4151) They were the original low cost analog  
to digital converters, just run the frequency into a counter chip  
(hence narrow pulse) gate the count time, and read the digital value  
out of the counter at the end of the gate pulse. Reset, repeat.

This was when a 16 bit now conventional A/D cost $15,000 and you had  
to buy them from NASA.

I always thought one could make a cool electronium from RC4151s and  
CD4089 (or other) rate multipliers. There was even an article on this  
sort of thing in Electronotes #42 pg. 5 "The Rate Multiplier in Music  
Synthesis" by Stephen Wilson.


On Dec 23, 2009, at 3:17 PM, Ian Fritz wrote:

> At 01:40 PM 12/23/2009, mark verbos wrote:
>> What is the actual difference between a VCO and a Voltage to  
>> Frequency
>> converter? I have heard them mentioned, but it has never made  
>> sense to
>> me. I need a square wave  oscillator that goes up to around 500kHz  
>> for
>> a project I'm planning. This may be the solution.
>
> V/F converters are a kind of VCO.  Often described as having a  
> linear response to input voltage, they are generally easy to use  
> with standard expo current sources.  They work on the charge  
> balance principle, which you can read up on in the datasheets/app  
> notes.  They are highly accurate because the control current keeps  
> flowing during the switching process, so there is no dead time.
>
> Their main drawback for synths is that the main output is a narrow  
> pulse.  (There is also a low-amplitude Saw which has been used  
> occassionally).  So if you need a true square wave, then you need  
> to run at twice the frequency.  You can check the data sheets for  
> the high performance devices to see if any will work up to the  
> frequency you need. (GL)
>
>   Ian
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