Strobe tuner

[nexekho]

Starting too many threads lately :p
Anyway, I'm going to be buying certain components in packs of 10 at Christmas because quite often a 10 pack is cheaper than 5-10 individual components and this means I have a LOT of 555s/comparitors/4017s left over.  I've noticed there are few if any tuner designs on here so I wanted to contribute something :p



There's only one bit I'm unsure on, the notch filter - I don't know if it'd be good enough or not without adding loads of active components.

The 555 feeds 10/20x the frequency you want into the 4017, which will power one LED at a time.  The signal goes through the notch filter to try and separate the strings.  (combined with the comparitor, probably good enough)  The comparator sees if the input wave is above/below a threshold and uses the MOSFET to block the ground for the LEDs. (probably want a resistor too - a 4017 gives out 5V logic level right?  Also probably a fine tuner fixed pot for the 555) If the frequencies match up, the resulting line of lit LEDs should be static, while a difference of even 1Hz will cause a very noticable slide to the left or right.

Falstad:
http://www.falstad.com/circuit/#%24+1+5.0E-6+38.696464541249114+50+5.0+50%0Aa+416+320+512+320+1+5.3+0.0+1000000.0%0AR+384+368+384+400+0+0+40.0+5.0+0.0+0.0+0.5%0Ag+448+416+448+448+0%0A174+448+368+384+336+0+1000.0+0.203+Resistance%0AR+416+304+384+304+0+1+441.0+2.0+2.65+0.0+0.5%0Af+512+320+560+320+0+1.5%0Aw+560+304+608+304+0%0A162+608+368+608+304+1+2.1024259+1.0+0.0+0.0%0A162+640+368+640+304+1+2.1024259+1.0+0.0+0.0%0Aw+608+304+640+304+0%0Aw+640+304+672+304+0%0A162+672+368+672+304+1+2.1024259+1.0+0.0+0.0%0A162+736+368+736+304+1+2.1024259+1.0+0.0+0.0%0Aw+704+304+736+304+0%0Aw+672+304+704+304+0%0A162+704+368+704+304+1+2.1024259+1.0+0.0+0.0%0A162+832+368+832+304+1+2.1024259+1.0+0.0+0.0%0Aw+800+304+832+304+0%0Aw+832+304+864+304+0%0A162+864+368+864+304+1+2.1024259+1.0+0.0+0.0%0A162+800+368+800+304+1+2.1024259+1.0+0.0+0.0%0Aw+768+304+800+304+0%0Aw+736+304+768+304+0%0A162+768+368+768+304+1+2.1024259+1.0+0.0+0.0%0A162+896+368+896+304+1+2.1024259+1.0+0.0+0.0%0Aw+864+304+896+304+0%0A163+576+400+656+400+0+10+0.0+5.0+0.0+0.0+0.0+0.0+0.0+0.0+0.0+0.0%0AL+896+464+944+464+0+1+false+5.0+0.0%0Ag+560+336+560+352+0%0AR+576+432+576+480+1+2+4400.0+2.5+2.5+0.0+0.5%0Ar+448+416+448+368+0+1000.0%0Ao+4+64+0+35+5.0+9.765625E-5+0+-1%0A
(NOTE: no input/output buffers, only one string, no tuner pot, 555 astable or LED resistor)

Is this how one would usually work if not done with a microcontroller?

[greaser_au]

Hi nexekho

This is a microcontroller version of a strobe tuner  (it's a 'pay to view' site, but if you click on the 'Fig.1' block diagram, you get a popup that allows you to view the images that accompany the article (the block diagram & the circuit are useful), which uses a very similar idea from a few years back. The microcontroller takes user input through the buttons (to select note & octave)  & generates the reference frequency for feeding to an octal counter which cycles through the anodes of a ring of LEDs.  The cathodes are fed by the (amplified) instrument signal.    http://www.siliconchip.com.au/cms/A_110736/article.html

Over 20 years ago Electronics Australia did the same thing with a top-octave generator chip feeding a 12-way switch (note selection), a binary counter/divider feeding a 6-way switch (octave selection) feeding a similar counter/LED ring (anodes) with the (amplified) instrument signal feeding the cathodes.  

I built both kits over the years, and I've found these are excellent tools for doing guitar intonation (especially with the demise of tuners with analogue meters) - the drift of even very slight (fractions of Hz) frequency differences are quite obvious.

In both cases there isn't much in the way of filtering of the instrument signal - if anything I would use it to drive a one-shot, perhaps with a period suited to the octave in use! I intend to build a 32-led strobe tuner at some point, perhaps with auto note selection (I have to admit to being inspired by matzzz's design and 'the gimmick' for the autonote read).

david

[nexekho]

Cool stuff, cool stuff!  Thanks!

I have been playing around with passive filters in a simulator to try and roll off the signal to within 2-3 semitones of where each string should be so I can run six of the above and go polyphonic.  Not having much luck.  I like the idea of only having one though and a note/octave selector - I could use the signal generated (two of the 4017 outputs tied to a D type flip flop to divide the frequency by 10) with a transistor to modulate it with the signal to get some nice effects.  Also would allow for arbitrary tunings and use outside of guitars.