button-controlled "pots"

[Joe Davisson]

Not quite as slick as a digital control, but hey it's simple!
http://www.joefus.com/pedals/images/buttons.gif

There are some cool things about this: Multiple sets of buttons can be used for coarse/fine controls. Momentary stomp-switches could be used. And the capacitor will stay charged for a while, so if power is interuppted the circuit picks up right where it left off. Have fun!

-Joe

[ExpAnonColin]

That's a very cool idea!  Thanks!

-Colin

[petemoore]

Neat one.
 Wouldn't this and a stutter machine be about more than half of a Tremolo.
 Too kool looks like there are countless applications for this !!!

[Nasse]

Thanks for great circuit tip, Joe. I remember having seen somewhat similar approach done with j or bifet or mosfet opamps, but this is even more ingenious with less components. The cap may hold its voltage amazingly long, many times longer than is needed for live performance or practising some piece of music. And what about connecting some more switches and some preset voltages...

[Peter Snowberg]

Wow!  That's very Zen.

Cool!

-Peter

[Marcos - Munky]

Cool, Joe.

[smoguzbenjamin]

I looked around your site joe, I liked the RGB cycler But I was wondering, could I use this to make 7 LEDs orso set next together go from right to left? Because (with my minimal electronics knoledge) this thing seems to go 1-2-3-1-2-3 instead of 1-2-3-2-1-2 etc. Or am I wrong and does it do this anyway?

[R.G.]

R.A. Penfold used a very similar approach to create a swell pedal. Instead of a MOSFET, he used a CMOS-input opamp to generate a control voltage that directly controlled the gain of an OTA if I remember correctly. The up/down ramping was the same, I think. I'll have to dig out the article.

In doing this, you do have to watch the leakage on that 100uF cap. If you get a leaky one, it will leak away the charge pretty quickly. It will hold steady for much longer if you use a 10uF polypropylene cap and 1M resistors for the same time constant.

I think the 10M gate resistor could be anything from 1K up to 10M because the gate resistance is in the giga-ohm range, so no resistor you stick in there will change the amount of current going into the gate. But the resistor does help prevent self-oscillation of the MOSFET, and should be as close to the gate as is physically possible.

[smoguzbenjamin]

Uhm. You lost me there...  :oops:  :?

[Joe Davisson]

I had one on the breadboard overnight with no change I could notice. Thanks for the capacitor advice! I did try eliminating the 10M resistor and it seems to work the same. But I'll probably leave it in out of paranoia

The cycler circuit can drive any odd-number of lamps, and can be made into a stand-alone flasher by removing the switching transistor. The lamps should blend from one to the next, in order. It don't do no Knight Rider man.

-Joe

[smoguzbenjamin]

:mrgreen: Haha :mrgreen: I was actually thinking of using the circuit to make my buddies at school go green with envy    They judge pedals by looks  :roll: But left to right'll do Haha, This'll make the simple mixer (4 in 1 out) look really cool to look at... Now to get a LED bank. Cool idea though...

Isn't there a little mod you could make so it'd go back & forth? Or am I asking too much?  

[Mark Hammer]

To follow up on RG's note, although the presence of push-buttons prompts one to think of it as being used in a little-bit-more-little-bit-more fashion, press-and-hold is fine too.  Indeed, start thinking about this in terms of a stompbox with two heavy-duty momentary SPST switches.  Better yet, start thinking about it in terms of *four* momentaries:
- begin rise (gradually charge cap)
- move to full on (fully charge cap)
- begin fall (gradually discharge cap)
- move to full off (fully discharge cap)

The charge/discharge time is, as noted, set by the value of the resistors, so a transition-time pot or two would be a nice addition.

What can you use it for?  Lots.

The first use that comes to mind is obviously the same as the Geofex-LERA: namely ramp-up/down time for modulation devices when switching between slower and faster speeds.

But you can use it for other things like adjusting recirculation  in a variety of devices in real time.  Imagine, as well, that you hit a power chord, and use this (or the LERA for that matter) to automatically swell up the tone control on a RAT-like device, so that the chord goes from dull to bright as it sustains (or vice versa if that's your wish).

[petemoore]

You guys getting em?
 Thes ckt.s is just starting to look TOO Funny !!!

[petemoore]

I used to open up a monitor to scavenge, and scowl at all the button switches that had replaced the use and production of pots,
 I would briefly curse the technology that bred the beast that caused monitor manufacturers to use these button switches I could not implement in any of my projects, and that had caused my scavenging efforts to produce fewer  pots per scavenging minute !!!!
 I started feeling better instantly about this button technology, the moment I looked at this threads and a most unique and pracical schematic !!!
 Now the 'bounce' of ideas has me chuckling...

[smoguzbenjamin]

Welcome to the digital age, pete  

[rustylee]

I like it.  

And now I've been looking around for photocells available from the various sources (mouser, allied, circuit specialists - allied seemed to have a good selection). It's difficult to determine which one to choose as a straight replacement for common pot values. Not only is there the resistance min/max values of the photocell, but there's the question of the the amount of light needed from the LED for the photocell to operate within the range. Then maybe I'm making a mountain out of a mole hill.

Is there matrix or something out there that would simplify this? Or is this simple and I'm just missing.

-Rusty

[Peter Snowberg]

You also have to throw LED efficiency, LED wavelength(s), and LDR spectral sensitivity into the mix so the only way to come up with some real data (because of the huge number of variables) is to get a photocell with a range that includes the territory you're looking for, pair that with a known LED, and combine them in a repeatable way. A simple transistor driver can be used to adjust the response of the LED to give you some control of the min/max levels, but forget about things being too consistent. That reality is what makes VacTec parts to desirable to amp makers.

If you don't need the on/off time characteristics of the LDR material to get the "right" sound in your circuit, take a look at photoFET optoisolators like the H11F3. http://www.fairchildsemi.com/ds/H1/H11F3.pdf

If you want precise control the photoFET is the way to go, but the slow turnoff time of CdS is vital to some circuits for the "right" sound. That doesn't really apply as much here as it does in a compressor, but the "taper" will by more linear with a photoFET.

Take care,
-Peter