Taplfo questions.

[digi2t]

Hi folks!

I'm working on tracing out the Spaceman Explorer phaser (optical phaser), and I've noticed that it uses some sort of AVR or Attiny (or whatever you call it) chip for the LFO. In a nutshell, there's an output for an LFO rate LED, as well as a 6 position rotary for the waveform. The phaser is optical, so the chip powers an LED for a Stonehenge 6 LDR arrangement. There is also a CV pedal jack, where the pedal will control the rate in 5 of the waveform positions. The added plus is that the 6th position on the selector is a "Manual" setting, which then allows the CV pedal to control the LED intensity directly, allowing for a Mutron Phaser-like foot control of the sweep.

My question is...

Can the the aforementioned capacities be accomplished using Electric Druid's Taplfo chip? I've been reading up on it, and I see how it can drive the LDR's LED.

- Can I use the "Clock out" to drive a rate LED?
- Is it possible kill the LFO and then drive the LDR's LED from an external CV directly?

Basically, I think it would be cool to "upgrade" this really nice sounding phaser to include the ability to tap tempo or sync the LFO to an external source. The Taplfo looks like it would be perfect for this, but I would like to retain the ability to drive the phaser manually, as it is now.

I apologize for not having a schematic ready yet, I'm still tracing it out, but I thought I would throw a hook in the water regardless and see what you guys can tell me.

[slacker]

Yes you can use the clock out to drive a rate LED or you can drive multiple LEDs from the main output, there's a few examples of this in the datasheet https://www.electricdruid.net/datasheets/TAPLFO2Datasheet.pdf/

You can control any of the parameters with CV but the code would need changing to give you a setting where it acted like a manual control. It might be easier just to have a separate switch that physically switched out the LFO and switched in manual control of the LDR LED.

[ElectricDruid]

+1 agree what Slacker said, but this is the datasheet for the current version:

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

(The new chip has more features and is simpler to use - the old one needed a crystal and so on..)

How do you feel about tweaking the code? Do you program any PICs? Do you have any friends that could? Otherwise, a hardware solution is easier.

[garcho]

Using the TAPLFO, or the STOMPLFO and a DP6T rotary switch you could have 5 wave forms hard wired like a resistor ladder to the first 5 throws, ignoring the 6th throw, for the first pole. For the second pole, you could have continuation from the collector of the transistor to the LED for the first 5 throws, and then a pot in an expression pedal going from 5V to 0V, with the wiper connected to the LED, maybe with some low value resistor in series. Would that work? It would leave the collector of the resistor hanging, maybe that's bad?   

[digi2t]

I ended up ordering both. I've traced out the phaser section, and I plan on using the Stomplfo chip. As Tom suggested, I'll use the external CV to drive the offset, with the depth control setting how much the territory the offset CV will cover. I may use the Taplfo chip for something else.

This should provide much more versatility then the present system. And... we can keep all the waveforms too.

I've never worked with PIC's or Attiny's, or anything like that.

[Kipper4]

Good choice Dino.

[digi2t]

Stompflo's are on their way, and the phaser section is traced out. I'll update on the results when I get the chip wired in.

[digi2t]

So, if I understand the documentation correctly, something like this should work?



Vd is filtered 5vdc.

[ElectricDruid]

Looks perfect to me.

You've got that Offset CV socket wired up to suit the expression pedal you've got around, right? They're not all the same, annoyingly.

[digi2t]

Um yeah... I just used an EV-5 expression pedal schematic for that. I plan on using an old Crybaby shell I have kicking around. Ultimately, folks can adapt to what they wish to use.

[Mark Hammer]

The switching circuit for selecting waveforms is VERY useful (says a guy who has had to jiggle the waveform pot to find the one he wants)  Do you view Dino's divider-ladder values as likely to provide accurate selection?

[digi2t]

I took those right from Tom's datasheet.

[Mark Hammer]

Must be the one datasheet I didn't look at. 

[bluebunny]

The switching circuit for selecting waveforms is VERY useful (says a guy who has had to jiggle the waveform pot to find the one he wants)  Do you view Dino's divider-ladder values as likely to provide accurate selection?

Tom also has some examples where you don't want all six (or whatever...) number of options, just two or three - which you control by the smart use of an on-off-on switch and four cleverly-chosen resistors. 

[digi2t]

Must be the one datasheet I didn't look at. 

Here ya go buddy!

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

Yup. That part doesn't seem to be mentioned in the Stomplfo datasheets. You gotta sorta borrow from Peter to dress Paul.

[Mark Hammer]

I'm trying to figure out if I can persuade a 3P4T rotary, that can be set with collar to have 8 positions, to be a SP8T.  It might be simpler to find a SP12T rotary with a similar type of collar.

[digi2t]

Tom, I'm wondering if you can clear up my confusion with the StompLFO....

On page 4 of the datasheet, it states that the "Level CV", if not required, should be tied to maximum, 10K resistor to +5v.

Do I take that to mean "Depth CV"? And wouldn't max be to ground? Looking at the example schematic on page 6, I see a 1K (not 10K) resistor, and max CW would be ground.

(Actually... this question applies to the Freq. and Offset CV's as well)

[ElectricDruid]

On page 4 of the datasheet, it states that the "Level CV", if not required, should be tied to maximum, 10K resistor to +5v.

Yep, that's right.

Do I take that to mean "Depth CV"?

Yes, Depth CV = Level CV. Same difference.

And wouldn't max be to ground? Looking at the example schematic on page 6, I see a 1K (not 10K) resistor, and max CW would be ground.

Argh, that's an error  That pot is the wrong way up. Probably copy-pasted from a schematic where the pots can be inverted, like the VCDO or the ENVGEN8. Sorry! I'll get on it and fix that. And thanks for spotting it, too.

If you're just tying one of the CV inputs to a high level, the actual value of the resistor isn't critical. If it's too high, the ADC cap won't charge quickly enough and the reading won't be accurate, but otherwise it really doesn't matter and probably anything under 47K would be fine. I go with "10k" just to be sure, and because that's the standard value I use for logic pull-ups too, but there's nothing magical about that value.

Does that clear up the confusion? (and my apologies for having created the confusion in the first place!)

[digi2t]

Perfect Tom! Thank you so much.

EDIT: Shishe! There's one more thing...

For the wave form selector, what is the order from +5 to ground? Just so I can figure out what I want on the rotary pin 1, and which direction I want my knob to be going.

[ElectricDruid]

Perfect Tom! Thank you so much.

EDIT: Shishe! There's one more thing...

For the wave form selector, what is the order from +5 to ground? Just so I can figure out what I want on the rotary pin 1, and which direction I want my knob to be going.

This is the order from 0V on the left to 5V on the right:



It starts with ramps at the bottom, and finishes up with random waves at the top.