DIAC Frequency divider

[phector2004]

Hi everyone,

I posted here a while back about uses for DIACs, and learned that they can be used in place of neon bulbs. So I've been trying to build a frequency divider but I can't find any reference schematics to dissect and modify for guitar. Google just brings up a million sites that have copied wikipedia word-for-word, mentioning neon bulbs in frequency divider circuits and electric organs. I also found this on scribd, but I don't find it too helpful. (The schematics are Blurred Up Beyond Any Recognition)

Does anybody have any links on these circuits or neon-frequency-divider-organ schematics I can have a peek at? I'd like to SPICE this, see what it can do, and then breadboard it and hear what it actually does...

Thanks!

Oh and happy Thanksgiving/Columbus day

[merlinb]

Are you talking about neon lamp ring counters?
http://www.dos4ever.com/ring/ring.html

I believe they will only operate on constant frequency input signals (like you get from an LFO), and wouldn't work for the constantly changing guitar signal. Not that I've tried it...

[phector2004]

Interesting article, but that's not it... (At least I hope not!)

On the link I posted, there's a blurry schematic with a 12AX7 oscillating, and many 1/2 frequency dividers using neon bulbs dropping it down an octave. Supposedly, electric organs back in the day used something of the sort... Each divider in the circuit corresponded to a different octave of the note, and there were 12 separate circuits covering all 88 keys that could be pressed.

I'll have a look at the references in the article you posted... maybe some of them will relate to what I'm getting at

Otherwise, I could always just build a shocktave! 

[R.G.]

I'll dig for the neon dividers. I think they may have been oscillators that were running slightly lower than half the speed of the one above them, but were immune to triggering before they were near their trip voltage, but could be flipped when they were nearly at their full cycle, so the slower-running oscillator ran at half speed but synchronized. Seems like there was a true neon flipflop, but I can't remember how it worked.

It's worth knowing that a single NE-2 bulb all by itself is $0.25 to $0.50, and a CD4024 seven stage divider is $0.50 or so depending on where you buy it. Then there's that 100Vdc supply for the NE-2s. 

[Taylor]

It's worth knowing that a single NE-2 bulb all by itself is $0.25 to $0.50, and a CD4024 seven stage divider is $0.50 or so depending on where you buy it. Then there's that 100Vdc supply for the NE-2s. 

But....


TOOOBZ!!!! 

[amptramp]

The typical diac has s breakover voltage of 22 volts which is a lot less than a neon tube and the necessary voltages can be generated by a 16 VAC wall wart and a voltage doubler.  If you want a truly obscure reference, the October 1964 issue of Electronics World has an article entitled "4 and 5 Layer Diodes" that shows astable, monostable and bistable multivibrators including frequency dividers, a ring oscillator, a power inverter and a Class D switching-type amplifier.  The advantage over neon tubes is low voltage operation, no light sensitivity, long life and minimal temperature sensitivity.

BTW, I was the person who responded to your original question in the other thread.

[phector2004]

And I thank you for directing me towards neon circuits! (If I recall correctly, you mentioned Chet Atkins using neon circuits too??)

Any idea on where I can find that article? I'll try the McGill library, they usually have obscure old books and magazines, but they've been clearing out old stuff lately to make room for stuff the hipsters are interested in... Mustache grooming? Kant?


Thanks again!

[amptramp]

Chet Atkins was the cover story on one issue of Radio Electronics in the mid 1960's.  He showed the neon tube divider driven by the guitar.  He said it sounded like an organ since the
triangle wave from the divider has all harmonics with the second harmonic being 1/2 of the fundamental, the third being a third etc.  Radio Electronics was a much more popular magazine than Electronics World, so you stand a better chance of finding it.

[PRR]

> Seems like there was a true neon flipflop

Astable flop-flip in neon, calibrator for H-P 120B 'scope:



Most of the divider plans are "narrow dynamic". They are free-running oscillators, set a little slower than desired. If you inject a right-level 2X frequency, the first peak fails to trigger but the second peak triggers "early", synchronizing at half-rate. f/3 is possible but trickier. Higher ratios are possible if you live with your hand on a knob (either free-run rate or injection strength). It is how 'scopes older or cheaper than the HP120B did their sweeps. My arm still has cramps.

You want a static divider. It will act quickly or sit forever waiting for a trigger. In neon, this is possible, but very hard. Worse now that neons are the scum of the lighting world... anybody who could make "good" neons has moved to making fluorescents.

The DIAC is interesting. In its only real application (cheap lamp dimmers) it is not tightly specced, but perhaps mature Silicon processes turn out all-the-same in each batch.

> try the McGill library... they've been clearing out old stuff

University library? Ask a librarian. Where I worked, stuff that had not circulated recently got moved to a warehouse. The catalog indicated this with a code. Once you knew a book existed, you hiked to the far end of the parking lot, 11-3 MWF, made out a slip, and the clerk got the book for you.

[R.G.]

The typical diac has s breakover voltage of 22 volts which is a lot less than a neon tube and the necessary voltages can be generated by a 16 VAC wall wart and a voltage doubler.

Yep.

The CD4024 also works from 15-18Vdc, down to as low as 3V, as I remember.

IIRC, a tunnel diode will do the same trick in a suitable circuit down at a few volts, and probably a UJT and PUT can be rigged that way too, but up at 8V-12V. I'd have to go look.

I'll go dig out my Markus circuit compendiums and see what they say about dividers. I think I remember a whole chapter of divider circuits of various versions.