Easyvibe LED color

[mcasey1]

Does it really matter if all the LEDs (that will be incorporated into the LED/photocell assemblies) are the same color?  I have 3mm LEDs: 2 green, 3 red, 2 yellow.  I am planning on using 2 of the red LEDs for the non-photocell positions.  If the circuit is picky about this, is there a better way to do arrange them other than randomly putting different colors in different positions, or am I better off to spend more money on reds all around?

[Seljer]

well the LDRs shining on the leds are the critical ones (as LDRs respond differently to different wavelengths of light) and you generally want them all sweeping over the mostly same range together.

i'd go and measue green+LDR, yellow+LDR and red+LDR and see what 2 colors have the least of difference regarding the resistance of the thing

[Aharon]

I've built two EasyVibes,one with red LEDs and one with yellow LEDs.......they both work magnifencently.
I was wondering if using diferent LED colors would be advantageous adding some "wobble" to the EasyVibe since OP amps and LEDs are not the same as light bulbs and transistors.
Worth experimenting I guess....
Aharon

[John Lyons]

I would think that the LEDs should all be the same color. Varying the color would change the sound and resonce, maybe a good thing but maybe bad. Putting a small thickness or two of white paper between 2 LEDS and the LDR seems  to change the sound to more of a phase/flange tone (sharper sound). Thanks to Petemoore for that one. My Easyvibe has stacked LED/LDR sets and the Combo has a short length or drinking straw covered in black tape that slips over them. This way you can take off the Light shield to slip in a piece of paper to experiment.

John

[swt]

yes. it depends on what ldrs you're using. there are two types. one type responds to green light, the other responds better to red light, so you'll have deeper swing. wait a minute...i'll search...
i copy this from a thread...

There are two types of LDRs, those made out of cadmium sulfide (CdS) or those made out of cadmium selenide (CdSe). CdS types, which seem to be all that Small Bear carries at the moment, exhibit the problem that you are worrying about, slow decay time. CdSe types have a turn off time nearly as fast as their turn on time and are perfectly suitable for applications where a CdS types turn off time is too slow, such as phasers and tremolos, among others.
Cadmium Sulphide (CdS) reacts best to green light wavelengths, Cadmium Selenide (CdSe) reacts best to red light wavelengths.
The only real difference is in the wavelength that they respond to with CdS responding to red light (about 500 nm) the best and CdSe  responding to green light (about 600 nm) the best.
hope this can help...

[dxm1]

I think, more importantly, are the two LEDs used to generate Vbias. I used
superbright green LEDs for my optocouplers, but using the same LEDs for
LED5 and LED6 gave me a Vbias of 5.25 volts. Changing these to standard
3mm red LEDs got Vbias down to 3.75 volts.

[John Lyons]

Cadmium Sulphide (CdS) reacts best to green light wavelengths, Cadmium Selenide (CdSe) reacts best to red light wavelengths.
The only real difference is in the wavelength that they respond to with CdS responding to red light (about 500 nm) the best and CdSe  responding to green light (about 600 nm) the best.
hope this can help...

SWT is this what you are saying?

Cad Sulphide = Slow responce in general. More sensitive to green light
Cad Selenide = Fast Responce...  More sensitive to red light.

Cad Sulphide + Red LED = Slowest
Cad Sulphide + green LED = Moderate fast
Cad Selenide + Red LED  = Fastest
Cad Selenide + Green LED + Moderate fast

So Faster is better for phasers/tremolo?
Isn't the Univibe and other optical devices based on the (revatively) slow turn on of LEDs and bulbs?  Or is this really relative to othe super fast turn on devices?

John

[swt]

yes. if you want deep swooshing, you want the ldrs to be fast to get the most range. Using leds is a different story, adn you can compensate for that. What is important is that using the right color, will give you the largest range, from dark to light, in resistance on the ldrs.

[mcasey1]

I have cadmium sulfide.  I suppose I will use the green LEDs for best results.

[axeman010]

My Easy Vibe has the following LDR

Min. resistance @ 10lux: 9kΩ
Max. resistance @ 10lux: 20kΩ
Typ. resistance @ 100lux: 3.5kΩ
Dark resistance after 1 sec.: 0.06MΩ
Dark resistance after 5 sec.: 0.18MΩ

peak wavelength of 600n

I am using 3mm red LEDs through out and I get a reasonable  sound - just wondering if the green LEDs will really make that much difference ?

Should I change all LEDs to Green or just the Opto Couplers ?

Axeman