Easyvibe + StompLFO: more power for the LEDs?

[KarenColumbo]

Dear experts, I breadboarded an Easyvibe (again *sigh*, I hear you say) and put in Tom's very cool StompLFO to have a go at mayhem. It all worked first time (which is epochal) BUT there's a question remaining:

I put the 4 LEDs (I rolled my own "Vactrols" with green 5mm LEDs and generic chinese LDRs) in parallel directly at pin 3 of the StompLFO, knowing that LEDs are too slow to need PWM filtering.
The Easyvibe now is some sort of great Tremolo (I'm sure I botched something on the breadboard)
Can I somehow boost the StompLFO's output a bit so the LEDs are brighter (maybe with a BC549C or some other transistor)?

Here's a schematic I hastily put together in Eagle: (R2 is actually 100k, I mis-copy-pasted)

[KarenColumbo]

A "sub-question": Should the voltage divider LEDs (LEDX and LEDY) pulse in time with the LFO?

[duck_arse]

as drawn, you'd get some sort of ripple trem, one led lit, the one with the lowest forward voltage. it's not the leds are slow, it's the ldr's. I don't know the stompLFO - are you allowed to run leds from it without current limiters? hmmmm?

you need a CLR PER LED EVERYTIME in parallel. this allows a voltage to drop across the resistor, so each led can have a different Vf and all will share the available voltage. even if the chip allows no clr led driving, 4 leds in parallel needs 4 clrs. I can't say a value, depends on what Tom says the chip can/can't do.

edit: sub: probably not. VB should be referencing, not current supplying.

another edit : doesn't matter what the chip can do, because it supplies 0-5V output, so, CLR per led. no arguments.

[jubal81]

The StompLFO data sheet has an example schematic for how to set up the LEDs to work with the chip. Use that.

[duck_arse]

can you link, please Jubal? the doc I have here doesn't have any mention of leds.

[jubal81]

can you link, please Jubal? the doc I have here doesn't have any mention of leds.

It's the one for the big brother - tapLFO. Look at example tremolo circuit.

https://electricdruid.net/datasheets/TAPLFO3Datasheet.pdf

If you want to use 4 LEDs, put them in series with V1 LED.

[KarenColumbo]

Thank you, Sirs. I terminated the LEDs with 100 Ohm resistors.
Then I got sidetracked and built an LED chaselight with a 555 and a 4017, connected only 4 LEDs (with 100uF in parallel to each one to achieve a ,,glissando") and bridged the reset to the 5th pin, so it only loops 1 to 4. Has a nice "phase vibe" to it now
Maybe i should use 2 instead of 1 StompLFO, each one lighting up 2 LEDs with different speeds/waveforms. Hm...

[KarenColumbo]

another edit : doesn't matter what the chip can do, because it supplies 0-5V output, so, CLR per led. no arguments.

Sir! Yes Sir! I immediately corrected my oversight/lazyness!

[ElectricDruid]

The FilterFX schematic gives another example of similar layout, and that uses the StompLFO:




(from https://electricdruid.net/filterfx-lp-bp-hp-lfo-filter/)

The StompLFO can only output 20mA or so max, so for driving multiple LEDs, a driver transistor is a good idea. Once you've done that, you should be able to handle loads of LEDs with no problems.

[KarenColumbo]

Yes! I admit I already did this but had the (acoustic) impression that it made the LEDs a bit "tamer" - no wonder, I guess, since I probably almost burned out poor Stompy with my brute force attack

Since I love my little chase light "LFO" so much with this Easyvibe, I would equally love to somehow combine trusty old Stompy with the (or some) timer to have tap tempo. Is it impossible? The 555 (a 7555 in my case) gets his "timing" through a 25k pot from V+ to pin 7. Now one COULD say that pin 7 gets a CV, couldn't one? And StompLFOs (or TapLFOs) provide such a CV. But how could I ever "translate" said CV to the actual tap tempo? Try and error? Or am I "saddling the horse from the false side" here?

Oh!

Why not program a PIC with tap tempo and respective chase light action? 8 LEDs (for those 8 stage phasers), 8 sequences including random order, fade-in/fade-out option and such ...

Hm.

[Kipper4]

Not quite sure from the description what you want to do.
I'll assume you want to use the same Stomplfo to control another effect with said Stomplfo.
Is that right. Maybe a block diagram will help me understand.
Rich

[KarenColumbo]

Nah, yesterday I put a LED chaselight (7555 timer and 4017 decade counter) in place of the StompLFO in an Easyvibe, and it sounded nice when the LED lit up in sequence instead of all 4 at once. That got me thinking that it would be nice to expand on that idea with a all-in-one chip just like the StompLFO that does the chase light thing. Druid got me going with some inside hints and code ideas so I think I'll try that I think I will call the box "Chase Phase" or something like that

[KarenColumbo]

I have an idiot question as only I can ask them:

What happens if I connect one and the same LED to several 4017 outputs at once?
Gut feeling tells me I will fry the respective outputs.
Or will I?

[ElectricDruid]

I have an idiot question as only I can ask them:

What happens if I connect one and the same LED to several 4017 outputs at once?
Gut feeling tells me I will fry the respective outputs.
Or will I?

The safe way would be to connect the LED to multiple outputs via 1N4148 diodes - a basic "diode or".

[duck_arse]

a 4017 has ten outputs - only one can be high at a time. you can either "source" current to your leds and one will be on at a time, or you can "sink" your led currents, and only one led will be OFF at a time.

you can create mayhem with 16 leds and a dual binary counter, by source/sink wiring them between the two counters and feeding a different clock to each. [circuit diagram available on application.]

[ElectricDruid]

Nah, yesterday I put a LED chaselight (7555 timer and 4017 decade counter) in place of the StompLFO in an Easyvibe, and it sounded nice when the LED lit up in sequence instead of all 4 at once. That got me thinking that it would be nice to expand on that idea with a all-in-one chip just like the StompLFO that does the chase light thing. Druid got me going with some inside hints and code ideas so I think I'll try that I think I will call the box "Chase Phase" or something like that

I don't get how *not* using some of the phase stages is going to improve anything. If you've got some phase stages that are static while others are moving, essentially all you've done is reduce the sweep depth. The end result is the notches made in the final mixer, and you'll get less notch movement the less phase stages you modulate. And it won't make any difference which one you modulate unless you have all the capacitors set for different values, in which case, you could have a single-notch phaser with a notch that jumped about, for example.
Ok, I think I've talked myself into it. Maybe it is interesting after all!

[KarenColumbo]

Nah, yesterday I put a LED chaselight (7555 timer and 4017 decade counter) in place of the StompLFO in an Easyvibe, and it sounded nice when the LED lit up in sequence instead of all 4 at once. That got me thinking that it would be nice to expand on that idea with a all-in-one chip just like the StompLFO that does the chase light thing. Druid got me going with some inside hints and code ideas so I think I'll try that I think I will call the box "Chase Phase" or something like that

I don't get how *not* using some of the phase stages is going to improve anything. If you've got some phase stages that are static while others are moving, essentially all you've done is reduce the sweep depth. The end result is the notches made in the final mixer, and you'll get less notch movement the less phase stages you modulate. And it won't make any difference which one you modulate unless you have all the capacitors set for different values, in which case, you could have a single-notch phaser with a notch that jumped about, for example.
Ok, I think I've talked myself into it. Maybe it is interesting after all!

The probability of me having botched something on the breadboard is high - but I "rolled my own" LED-LDR-combinations, so they're all but identical. May the different luminescences had the "nice" effect, maybe my swapping out filter capacitors did its part. But it sounds VERY Univibe-y. A smooth swishy warbly phaser kind off effect. I love it, that's why I seriously thought about further investigating this matter