Tremulus lune - getting things straight, component changes

[aaronkessman]

This's got to be the umpteenth thread on this circuit in the past two weeks. but anyway, i just want to get things straight.

1. On the "new" schematic on commonsound.org, there is no 2k2 resistor before speed control pots, but a 100R after. is it ok to leave these resistors out in order to increase maximum trem rate? Or does there need to be a small but present resistance in there (does not seem to be case judging from the rest of the circuitry around the IC).

2. On Fuzzcentral, Phillip has 2 diodes for the ramp up/down mod. I keep hearing about how you need 4 diodes to do this, but have never seen a schematic showing this. 2 makes sense to me, whats the deal with 4?

3. If i have a rounded-top LED, would i benefit from sanding down the top of it so that it can lay flush against the face of the LDR?

4. I spose matching the LED color to spectral peak of the LDR is a good thing?

5. plannin on using the Silonex NSL-5152 from small bear. light resistance of 15k, dark of 10M. If i understand correctly, the 10M should give me a very low volume at the bottom of a square-wave trem setting?

Thanks for help in advance folks.

Aaron

[LinuxMan]

Hey.

Since there were no answers I think I'll chime in. I'm no authority on the
matter since I haven't even built a Tremulus lune yet but here are some
of my thoughts.

My advice is to use the fuzzcentral's version for the up/down mod. Since it
worked for him, I see no reason why it shouldn't work for you too.

About the 2.2k resistor. I'm in the process of building a lune and I think
I'll use 100R before the speed controls. If that won't work I'll try the 2k
resistor instead.

I think there would be no benifit from sanding or matching the led. The
LDR specs aren't so important either. I've seen several reports where
people used the LDRs they had on-hand. No specs checking or anything of
the sort... I think It's really not that important to be true to the
specification for these.

Cheers
LM

[aaronkessman]

thanks...I posted this on the commonsound forum and got the following responses from dann:

1) yep you need a small resistance or else itll just go to "flatline"... a trim pot might be best if you want to get the absolute maximum speed

2) hmm.. i havent seen it done with 4... Two works OK, although it could be improved on, since the overall speed changes as you go from one waveshape to another

3) Wow. I have no idea if that'll work. I never thought of that...

4) Yep. every little bit helps, though ive had good results without paying attention to that. The brightness of the LED would probably be more of a factor than the wavelength

5) Thats right, 15M will be plenty quiet. Though you may not get down to 15M, and remember that CdS cells have a lag time, so it won't actually swing from max to min resistance at faster speeds..

So this may help others too..

100R is about as small as it gets - negligible considering the 10k speed pot. the rest I'll do as others have done. wont worry about the LED other than maybe using a superbright, but I dont know yet.

Aaron

[LinuxMan]

Hey.

Glad to see you've got your answers. Don't forget to post the finishing results
here. It's always nice to see a successful Tremulus build.

Cheers
LM

[aaronkessman]

might be a few weeks while i finish up class work. but i'll order the parts maybe tomorow.

[RedHouse]

FWIW, on the LED/LDR thing, instead of sanding it flat (which I've tried  and didn't seem to help my application much) but I did have some improvement putting the link together differently.

I found a small diameter WHITE plastic drinking straw and cut a short length of it, enough to create an LED/LDR light pipe, then assembled as usual with the heat shrink tubing over the assembly. The white plastic straw inside seems to help the light link a little bit though it's a bit fussy to assemble.

[aaronkessman]

seems like a good idea. relects as much light into the LDR as possible.

what about the 15k light resistance of the LDR I want - is that ok? will a 100k gain pot on the second opamp be enough to compensate for this slightly heavy (and ideal) resistance?

[(doug harrison)]

How about bending the LDR around to make contact with the TOP of a round LED, then sealing it with a piece of heat shrink? You'd still have a hole in the top of the heat shrink, but it won't really matter since there's no light inside the box anyway, right?  If the box is light-tight, that is.

[LinuxMan]

Heh.

Btw, the way I'll do it is with a rectangular LED + LDR (leads bent to face the
LED). No sealing with heat shrink etc. I saw it done on Mike's Infinitphase
(which I'm building right now), my guess is it should work just fine with the
Tremulus.

For those that don't know what I mean, here's a nice little picture:


Cheers
LM