[sdiy] AR envelope and 4066 (now complete)

[ryan williams]

hi,

you were both right. I did realize it was pushing a huge current though. 
Actually, I didn't check what the data sheet said until I blew the first 
4066. I was a little confused (and still am) because some people seem to 
have managed to short it to ground, or V+ without limiting. atleast that 
is what thier schematics show. I also was thinking that the 'on' 
resistance would help and that only short bursts of high current would 
be ok. I still think the short bursts probably allow a larger current 
but I don't know how to check something like that without destroying the 
chips. For now, I put in 1K resistors and it hasn't burnt, or gotten 
warm yet (12ma). My test was to set min attack and decay and run a VCO 
through it to switch it quickly. I ran it for about 30 minutes so far. A 
bit shorter attack time might be better but I think this is good enough 
for me.

an example of shorting switch is ray wilson's other retriggerable adsr 
here: http://www.musicfromouterspace.com/analogsynth/adsr_new.html

I'm also looking at my oakley ADSR which uses only 47ohm resistors. 
There is a note in the user's manual that says with fairchild 4066s, the 
resistor would be better at 330ohm. My 4066s just happens to be  a 
fairchild.

I have updated my webpage with a picture, and new schematic. it is here:
http://www.sdiy.org/destrukto/modular/ar-ad_transient.html

-ryan williams


Simon Brouwer wrote:
> Hi Ryan, Gabriel,
> 
> gabriel at lindeborg.org wrote:
> 
> 
>>Hi Ryan!
>>
>>You do realise that you by closing the 4066 switch and setting the Attack
>>to 0ohms will have a hefty current running thru the 4066 until the cap is
>>fully charged? Sort of like shortening the 15V to ground...
>>
>>//Gabbe

> 
> According to the data sheet the maximum DC current into any pin is 10
> mA, and the on resistance of a switch @15V is 125 ohms, so in your case
> the peak current is 120 mA. I would add a 1k5 series resistor.
> 
> See: http://www.ee.washington.edu/stores/DataSheets/cd4000/cd4066.pdf