CdS (light sensor) to VCF cv in

[isak]

i have this cool idea to be able to control the VCF with a light sensor.
i'v seen some one did it with his Korg monotron and i was like
he did it by connecting the CDS to the VCF cv in like this..






as u can see in the schematics he connect it to the VCO as well, i didnt wanted that so i connected it only to the VCF cv in, without a switch.
i took the power from J4 - 5.33, put a 520k resistor and it got me to 5.06V
i did as the schematics shows, unfortunately it didnt worked
i manage to get it working by connecting one side of the CDS to the VCF cv in and the other side to ground, it was lame..
it is so cool to have it in the x0x
http://www.youtube.com/watch?v=PZwvAu1e ... r_embedded

if u have any idea on how to make it happen i'll be more then happy to here about it

Iask E.

[antto]

cool
i guess you have to put it in the place of the cutoff pot.. which was 50K i think

[isak]

Ok....but how? i want the cutoff pot as well, do u have any idea on how can i use it and stay with the cutoff pot?
BTW the CDS is 60K so its cool

[guest]

do you intend to shine a light on the cds
or just put your hand over it to block the ambient light

you could use a switch to either engage the pot or the cds
you should also run the cds to 12v

[isak]

thanks for replying guest

do you intend to shine a light on the cds
or just put your hand over it to block the ambient light

does it matter?
yes, my intend is to use my hand.

you could use a switch to either engage the pot or the cds
you should also run the cds to 12v

u got me confused a bit..
do i need to give the cds 12V when connecting to the pot or.. 12V to the scheme above (to the VCF cv in instead of 5V use 12V)?

[guest]

you can first try the scheme above but use 12v

measure the resistance of the cds with your hand over it
and then measure the resistance with it in ambient light
this will help me figure out better how to use it

the only difficulty with using ambient light as the control
is that ambient light can vary a lot
and its often dark in a peformance setting

[isak]

ho my god its working, its so cool !!!!
i can do very fast cutoff changes with my fingers
u are right guest, i needed to put 12V

the measurements of the cds..
when i dont cover it it gets the light of the room lamp i get 6k.
when i cover it with my finger i get 80k
when i cover it with my hand i get 170k
when i close my fist on the cds its 8.8M

the only thing is its fully open, its more open then the original cutoff when its all the way up, like there is no resistance at all and i didnt hear the metallic reso at all..
i was thinking its coz of the 4.7k so i checked with few resistor values,i put 300k it was too much, then i put 100k and i could hear the reso but i want it to be higher so i put a 47k and it was great.
i guess when i'm outside i will need a bigger resistor value, i will check it tomorrow in day light, i'll take it outside and try, in the end i'll put 3 position switch ..position 1 to my studio, position 2 to outdoors and position 3 will be OFF/to regular VCF cv in.
i love this mod very very much!!!! u should try it, its funnnnnnnnnnn

and its often dark in a peformance setting

mostly we play in nature parties and our music is more what u call in the trance scene morning music so we play mostly at 6 to 8 in morning time, so its cool mod for us

[izze]

Cool idea isak.. got any photos or wanna put on final shematics for the x0x ?
Thanks

[guest]

sounds awesome isak

you could try a potentiometer instead of a switch
that way you can adjust for the max frequency given the light level

[isak]

Hi izze
thank you for u'r interest.

first u'll need to do a VCF cv in mod, taken from here: http://www.ladyada.net/wiki/x0x/vcfmods

Connect a 100k resistor to the base of q10, and the other side of the resisitor would go to the tip of your CV jack. Note that there is no CvProtection.

There is also an issue with the voltage offset of the cutoff, because the signal is not referenced to ground, but is instead referenced to the emitter of q9 due to the way the envelope is applied to the signal. This is explained further in the VoltageControlledFilter section.

In practice this mod works very well, with the cutoff going between sub-sonically low to the normal maximum.

i used the mix in jack to do this mod, i didnt add another jack.
and only then u'll do the cds mod.
this is how i did it in the mix in..


the schematic above is ok, i did the same.
NOTE 1:
the 4.7k can change from one room ambient light to another, in my room i used 47k instead of 4.7k, just try different resistors to see how the mods react in u'r room.
NOTE 2:
the cutoff pot needs to be all the way down for the mod to take effect.
NOTE 3:
i advise u to put the cds in this thing (i dont know how to call it in english )

this way the cds will be sunken and u can really cover it with u'r finger or u'r hand

got any photos

my x0x is open and and its going to be open until i fix this matter.. http://forums.adafruit.com/viewtopic.php?f=12&t=17106

[isak]

sounds awesome isak

you could try a potentiometer instead of a switch
that way you can adjust for the max frequency given the light level

u mean instead the 47k..?
i will still need a 2 position switch, position 1 to cds mod, position 2 to VCF cv in..or am i wrong?
do u got a way to use only with a pot? no switch involved?

PS..i just did the cds mod on the VCO cv in haaaaaaaaaaa so cool, twisted x0x from hell
i took the 5.33V coz the 12V didnt worked, i was assuming it will not work with 12V, i'm wandering what is the limit V to get the highest note..?
now i want the cds to be with the vco as well

[izze]

Hey isak..
Good to hear that it all works well.. even if i dont really get it.. So i just do the CV for Cutoff Mod that you quoted and then use your shematics ? I dont think i can do this mod because i havent found any 50k rated CdS yet. My x0x is well modded but a light sensor.. omg.. my friends would be like -> and i would be like -> and we all together would be like ->

But this is the future.. maybe i will do this mod as soon as you get the x0x nobel prize for it.I bet its really nice for real time interaction with the x0x... psytrance needs some fast hand movements

[isak]

my friends would be like -> and i would be like -> and we all together would be like ->

So i just do the CV for Cutoff Mod that you quoted and then use your shematics ?

yes.

its not a must to use 50k rated cds, u can use 60k and more i thing the limit for a room ambient light will be 100k..
i used 60k cds and if u want i can buy some here and send it over, its only coast 1$.

maybe i will do this mod as soon as you get the x0x nobel prize for it

naaaaaaaaaaa, there is a lot of talented guys here i'm nothing comparing to them man..i even dont know how to read schemes
but what i'm really good at is making music and sound synthesize,

psytrance needs some fast hand movements

indeed

BTW what is u'r favorite psytrance artist ?

[izze]

Well the Psytrance scene here in Austria Tyrol ist mostly real real Dark Psy! But i personally listen to Eskimo, Bliss, Bit-Head, Electrypnose, Mekkanika, Neuromotor, Ocelot, Insector, Painkiller, Wizack Twizack, Zion Linguist.. These would be my Top 11.. with no special order.
The music i make is only hardware.. i dont like to use a PC..i dont have much hardware at the moment because i started making music just 1 year ago.. So far i only got some gameboys with LSDJ Music Program and fully modded, a x0xb0x, a korg emx-1 and a nice mixer. I will soon have a SID (midibox sid hopefully) to get some cool C64 sounds too.
Heres a improvisation i made Gameboy and Korg: http://www.youtube.com/watch?v=-uZ2QTdjxww
I got some other tracks up on youtube.. just browse them.. i havent really finished a track yet, well i am just doing it for fun, but some hints would be greatly appreciated.

Nothing special but i will keep on going because music is my way to express myself.

Thanks for the offer with the CdS. I will have a look the next days hopefully i find one if not i will be happy to get back to you.
I listened to a couple of your tracks on myspace.. like it alot.. whats your gear ?

Analog greetz

[isak]

I listened to a couple of your tracks on myspace.. like it alot.. whats your gear ?

thanks
well my gear is..
2 X x0xb0x's
Virus C
Korg ms-10
Eventide 4000 (its a must!)
Line 6 pod xt (for x0x's )
UAD 1 and UAD 2
RME FireFace 400
Dynaudio BM6A (use by Dado, Infected, sub6 and many many more)
Evolution 4 octaves midi keyboard.

if u need any help with producing or any question feel free to ask