DIY Stompboxes > Building your own stompbox

Dream about a 4047!

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The clock outputs of the 4047 at pins 10 & 11 are half the frequency of pin 13. Using pin 13 to feed a 4041 will give you a 2 phase clock with the same frequency as the output of pin 13 (2x the f of pins 10 & 11, 4047). The 4041 does not halve the input f like the the 4013. Yes, you are not changing the ratio. You are however changing the delay range. Maybe this can be used to create  a flanger with 2 modes. "Standard" & "High Band". Like I said, this is all just the speculation of a bonzo like me. Maybe Mark H will read this and shed some light/thoughts/clarifacation on this matter. Damn Stephen! Now look what you started ;) Making people actually think "outside the box" :o

Well redeffect, if you are as bright as our 3 legged dog Bonzo, this is all good stuff. Anoter thought, put a few PWM phase stages in the flanger feedback path, controlled by pin 13.




--- Quote from: StephenGiles on September 20, 2006, 02:01:40 PM ---Well redeffect, if you are as bright as our 3 legged dog Bonzo, this is all good stuff. Anoter thought, put a few PWM phase stages in the flanger feedback path, controlled by pin 13.

--- End quote ---

I would easily give the nod to 'ol 3 legs...  :icon_wink:

Stephen: finally played around with scope & 4047...

pin13 is the buffered output of the oscillator you put up
by inserting a resistor & a capacitor on pins 1/2/3;
this R/C combination with the built-in gate-loop can only oscillate,
when the chip is allowed to do so by enabling circulation
by means of pins 4/5/6/8/12.

From this oscillator, the signal also goes to another buffer,
and from there to a flipflop (similar to half a 4013),
which makes a 50% duty-cycled half frequency signal out of it,
whose one output is again being buffered/inverted twice to feed pin11,
and is being buffered/inverted 3 times to feed output10.

(if the logic is programmed to output those signals, again with pins 4/5/6/8/12).

Those 3 last buffers to pins 10/11/13 are each comparable to one of the
inverters of the well-known 4049/4069 hex-types.

So pins 10/11 are always symmetrical half frequency of pin13
(when in astable mode).
However: the oscillator itself will only output a more or less symmetrical square,
(well-squared by the buffer)
when used with a "normal" (=linear) resistor.

As soon as you do the diode-trick to vary the frequency,
the wave (pin13) starts to deviate from 50% dutycycle at high frequencies
towards ~1% or less at low frequencies;
never more than 50%, though...
the variation from 50 to 1 doesn`t seem to take place linearly with the decrease
in frequency, and looks uselessly for "our" purposes, IMHO.

Interestingly, I did some testing with caps (resembling a BBD clock-input)
at pins 10 & 11.
Their loaded output looks the same like a single 4069`s inverter loaded output.
The more (2/3/4/5) inverters you wire up parallel, the steeper the slopes get
at higher frequencies (as expected...).

The MOST interesting part of playing with this chippy was however
(besides getting annoying heterodyning in my FM-radio above 800kHz clocks
when powering the breadboard with a 12V switchmode power-supply
instead of battery!!!),

was a new way to control the frequency:
by a variable resistor to ground!

in combination with a slightly modified "known" diode-trick voltage-control
(e.g. from an LFO), (or singularly...)
it is now possible to hook up a shielded mono cable to a passive external rocker-pedal
with a pot wired as a variable resistor,
on/off switchable by a SPST stompswitch,
to vary the clock-frequency of any device
between ~2Hz to ~1.7MHz. (without switching caps!)
One resistor can be added, of course, to limit Fmin,
and another one for Fmax...

In combination with the usual diode-trick voltage-control,
Fmin goes up to ~60Hz.

the circuit consists of a 4047, a 220p, and two 1N4148...


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