> What is the purpose of having two LEDs? Do they both blink exactly
> the same way?
It seems you pick from the menu a string and the frequency you want to
tune it to. The LEDs blink at that frequency. The motion-freezing strobe
effect with one LED would be a point but two LEDs give the appearance
of a standing wave, which would be easier to detect by eye
"The two LEDs on the board blink with the frequency that the chosen tone
has. When the string vibrates with the correct frequency, two lines are
projected at a fixed position on the string. If frequencies don't match,
the lines appear to be blinking or moving to the observer's eye. The
moving or blinking effect decreases with decreasing difference between
the two frequencies."
> ... If frequencies don't match,
> the lines appear to be blinking or moving to the observer's eye. The
> moving or blinking effect decreases with decreasing difference between
> the two frequencies."
I looked at the page cited and thought about that description.
It's not obvious (to me) from what is said there two LEDs aid this
effect more than one would.
The following MAY make sense if read carefully ;-):
However, it is possible that relative motion of the two lines may
occur when two LEDS are used. If so, then 3 may be better again (just
as 3 phases are ued in a traditional "light chaser" string of lights
in order to give an impression of motion rather than two ad from
flickering).
For a single LED, if the frequency is "off" very slightly then the
illuminated spot will tend to move in position, as stated. If the
string is moving "away" from the observer during two adjacent LED
flashes, then a too low string frequency will cause the spot to move
towards the observer and a too high string frequency will cause it to
move away. As the string reaches the end of its travel sideways and
reverses, the spot direction will also reverse.
If the second spot is not at an identical resonance node on the
string, which will usually be the case, then the moments of reversal
of motion of the spot will occur at different times for the two LEDs.
It MAY be that the comparative effect of two LEDs due to different
apparent spot motions will vary depending on whether the string
frequency is above or below thestrobe frequency. And, as above, it may
be that 3 spots may lead to a "light chaser" effect.
While it would be possible to simulate the above it is liable to be
MUCH more effective to "just try it". Two LEDs and 3 can be trialled
in very little time.
A point to note is that it is probably desirable to have LED
strobe-on time < to << a string-cycle period.
On 03/04/2011 15:56, RussellMc wrote:
> If the second spot is not at an identical resonance node on the
> string, which will usually be the case, then the moments of reversal
> of motion of the spot will occur at different times for the two LEDs.
I think it's probably just to make sure of this, like the old turntable strobes (for speed tuning) which generally had more than one line of dots which were slightly offset. This would be similar for the string, one point being slightly offset from the other which should make it easier to detect relative movement.
RussellMc wrote:
> I looked at the page cited and thought about that description.
> It's not obvious (to me) from what is said there two LEDs aid this
> effect more than one would.
I must say I've never tried this nor seen such a device (with two strobed
light sources) in use. However, it makes sense to me. If you had a single
strobe, the string would be frozen in space at one part of its cycle when
exactly in tune. When out of tune, it would appear to move thru its cycle
at the beat frequency (amount out of tune).
I can see how this kind of display could be confusing, especially since the
string vibrations will decay in amplitude and perhaps have some low
frequency components you are not trying to tune for. In other words, what's
lacking is a reference to what a fixed point in the cycle is, since the
cycle itself is always changing.
I assume the two strobes are fired 180 degrees apart. Now you can look at
the relative motion of what appears to be two strings. This allows you to
see beat effects while visually ignoring changes in the overall cycle. The
former make the strings move with respect to each other. The later cause
both strings to mostly move together.
> I think it's probably just to make sure of this, like the old turntable
> strobes (for speed tuning) which generally had more than one line of
> dots which were slightly offset. This would be similar for the string,
> one point being slightly offset from the other which should make it
> easier to detect relative movement.
The turntables (at least the ones I had) had different line for each
speed - 33 1/3, 45 and 78. They looked offset, but in fact did have
different number of blocks.
On 03/04/2011 18:24, John Coppens wrote:
> On Sun, 03 Apr 2011 16:20:08 +0100
> Oli Glaser<.....oli.glaserKILLspam@spam@talktalk.net> wrote:
>
>> I think it's probably just to make sure of this, like the old turntable
>> strobes (for speed tuning) which generally had more than one line of
>> dots which were slightly offset. This would be similar for the string,
>> one point being slightly offset from the other which should make it
>> easier to detect relative movement.
> The turntables (at least the ones I had) had different line for each
> speed - 33 1/3, 45 and 78. They looked offset, but in fact did have
> different number of blocks.
>
> John
The one I had (Technics 1210 Mk2) had four lines that were for various percentages of the correct speed (+3.3%, - 3.3%, +6%, 0%)
The point I was trying to make (badly) is that I think it's probably useful for the strobe to cover a larger area, as a vibrating string will have stationary nodes where it may be hard to see any difference.
Other possibilities maybe that the LEDs maybe fired 180 degrees apart, or maybe even one is fired at an overtone of the fundamental. Professional strobe tuners often have many overtone bands for precise tuning. I had a quick look at the schematic which shows the LEDs are connected to different pins, so something like this seems likely.
> If you had a single strobe, the string would be frozen in space at
> one part of its cycle when exactly in tune. When out of tune, it
> would appear to move thru its cycle at the beat frequency (amount
> out of tune).
> :
> I assume the two strobes are fired 180 degrees apart.
I am not seeing how it behaves differently than a single LED operated at twice the target frequency...
>
> On Apr 3, 2011, at 9:05 AM, Olin Lathrop wrote:
>
> > If you had a single strobe, the string would be frozen in space at
> > one part of its cycle when exactly in tune. When out of tune, it
> > would appear to move thru its cycle at the beat frequency (amount
> > out of tune).
> > :
> > I assume the two strobes are fired 180 degrees apart.
>
> I am not seeing how it behaves differently than a single LED operated
> at twice the target frequency...
>
>
Quite possibly, the two LEDs shine light in two different spots
'William Chops" Westfield ' <.....westfwKILLspam.....mac.com wrote:
>> I assume the two strobes are fired 180 degrees apart.
>
> I am not seeing how it behaves differently than a single LED operated
> at twice the target frequency...
I don't either, but they have two LEDs there that are driven from different
pins. Maybe the way the hardware is, it's easier to drive them separately.
More likely whoever did it wan't that thmart. Notice this wasn't a
commercial product. The schematic was poorly drawn and the board was
clearly homemade. Not thinking about one LED being able to do this fits
right in.
Olin Lathrop wrote:
> 'William Chops" Westfield ' <EraseMEwestfwspam_OUTTakeThisOuTmac.com wrote:
> > > I assume the two strobes are fired 180 degrees apart.
> >
> > I am not seeing how it behaves differently than a single LED operated
> > at twice the target frequency...
>
> I don't either, but they have two LEDs there that are driven from different
> pins. Maybe the way the hardware is, it's easier to drive them separately..
> More likely whoever did it wan't that thmart. Notice this wasn't a commercial
> product. The schematic was poorly drawn and the board was clearly homemade.
> Not thinking about one LED being able to do this fits right in.
This is getting really tedious ... is it really necessary to denegrate a
person who isn't even on this list, just because they don't do every project
up to your professional standards?
Obviously, you know a lot about electrical engineering, but not much about
making music in general, or playing the guitar in particular.
I thought the design was very clever. First, note that it says quite clearly
on the website that the PCB is itself intended to be used as a plectrum, to
pick the string being tuned. As such, the two LEDs are held physically close
to the string being tuned (by the other hand). They'll illuminate two nearby
spots on the string, which, because of the out-of-phase flashing, will
generally appear to be moving in opposite directions whenever the string is
out of tune, quite easy to see. Since the flashing isn't perfectly 180 degrees
out of phase, the user (with experience) gets a clue as to whether the string
is sharp or flat, from the pattern of the motion. When the movement stops,
the string is in tune. I'm guessing that this makes the whole process very
quick and precise, important in a peformance situation.
> I thought the design was very clever. First, note that it says quite clearly
> on the website that the PCB is itself intended to be used as a plectrum, to
> pick the string being tuned.
I noted that - a very nice touch indeed.
> As such, the two LEDs are held physically close
> to the string being tuned (by the other hand). They'll illuminate two nearby
> spots on the string, which, because of the out-of-phase flashing,
I did a quick leaf through the C source code.
They seemed to access LEDs at 2 timer values per LED offset by ... OK,
I'll look it up again - should have saved it ;-) ...
Trimmed code:
case 1:
LED_PORT |= (1 << LED0);
case 2:
LED_PORT &= ~(1 << LED0);
case 6:
LED_PORT |= (1 << LED1);
case 7:
LED_PORT &= ~(1 << LED1);
case 10:
timer = 0;
break;
ie seems to be two 10% duty cycle LED flashes offset by 50% of a cycle
BUT they could be offset by some other amount
Adding a third would be easy (although 10 steps may make that interesting :-).
I'm not sure why having the proficiency to home-make a prototype board
of this fineness should be seen as an indicator of general disability
(unless perhaps the perception was, perhaps, blinded by eg having
enough money or an overarching desire to always do such things as
perfectionistly* as possible. A valid choice, but the not the only or
necessarily universally best one.
Russell
* perfectionistically?, per ...?
NB - NOT "perfectly" as that has another meaning
On 03/04/2011 23:20, Dave Tweed wrote:
> This is getting really tedious ... is it really necessary to denegrate a
> person who isn't even on this list, just because they don't do every project
> up to your professional standards?
Ironically, apart from being tedious, it's also extremely unprofessional.
> Obviously, you know a lot about electrical engineering, but not much about
> making music in general, or playing the guitar in particular.
>
> I thought the design was very clever. First, note that it says quite clearly
> on the website that the PCB is itself intended to be used as a plectrum, to
> pick the string being tuned.
As a guitarist/musician (my other profession for a long time, performing/teaching/studio work - now just a hobby) I thought it was very nice also - the size will be a desirable feature, and also tuning that does not rely on signals/sound/unplugging cables, rather just light, would be a real benefit in a noisy, dimly lit environment (which is usually the case in clubs)
> On 03/04/2011 23:20, Dave Tweed wrote:
> > This is getting really tedious ... is it really necessary to denegrate a
> > person who isn't even on this list, just because they don't do every
> project
> > up to your professional standards?
>
> Ironically, apart from being tedious, it's also extremely unprofessional.
>
> > Obviously, you know a lot about electrical engineering, but not much
> about
> > making music in general, or playing the guitar in particular.
> >
> > I thought the design was very clever. First, note that it says quite
> clearly
> > on the website that the PCB is itself intended to be used as a plectrum,
> to
> > pick the string being tuned.
>
> As a guitarist/musician (my other profession for a long time,
> performing/teaching/studio work - now just a hobby) I thought it was
> very nice also - the size will be a desirable feature, and also tuning
> that does not rely on signals/sound/unplugging cables, rather just
> light, would be a real benefit in a noisy, dimly lit environment (which
> is usually the case in clubs)
>
I'm going to try redesigning it using a 16F866 or whatever else I have on
hand and a crystal
Q: What is the purpose of having two LEDs? Do they both blink exactly the
same
way? Or are they out of phase somehow? Why not just have one LED?
A: When the string vibrates with the correct frequency, two lines are
projected at a fixed position on the string. If frequencies don't match, the lines
appear to be blinking or moving to the observer's eye. The moving or
blinking effect decreases with decreasing difference between the two frequencies.
> the PCB is itself intended to be used as a plectrum, to pick the
> string being tuned
A couple of reservations -
Guitar strings are pretty abrasive. I'd add some extra PCB for
wear and tear
The g forces might upset the crystal and there'd be a lot of
vibration and knocks too
Guitarists are pretty fussy about picks. I use both hard and
soft. A stiff PCB would affect playing style. Unless you mount
a favourite pick on the other end of the board, but that's getting
a bit unwieldy
IVP wrote:
> I wrote:
> > the PCB is itself intended to be used as a plectrum, to pick the
> > string being tuned
>
> A couple of reservations -
>
> Guitar strings are pretty abrasive. I'd add some extra PCB for
> wear and tear
>
> The g forces might upset the crystal and there'd be a lot of
> vibration and knocks too
>
> Guitarists are pretty fussy about picks. I use both hard and
> soft. A stiff PCB would affect playing style. Unless you mount
> a favourite pick on the other end of the board, but that's getting
> a bit unwieldy
>
> I'd probably not use this as a pick
I really thought it would be self-evident that you would use this device
as a pick only during tuning, not during performance.
> I really thought it would be self-evident that you would use this
> device as a pick only during tuning, not during performance
Apparently not self-evident to at least one person ;-))
I used to use an A tuning fork but can do it by ear now, though
I realise some people prefer or might want silent tuning. It's not
unknown for tuning to be needed on the fly too and I'm sure by
ear is quicke
On 04/04/2011 03:19, IVP wrote:
>
>> I really thought it would be self-evident that you would use this
>> device as a pick only during tuning, not during performance
> Apparently not self-evident to at least one person ;-))
>
> I used to use an A tuning fork but can do it by ear now, though
> I realise some people prefer or might want silent tuning. It's not
> unknown for tuning to be needed on the fly too and I'm sure by
> ear is quicker
Yes, in the middle of a song tuners won't help you much. A quick adjustment is often needed, especially the first couple when the strings warm up - trick is to make it sound like it's part of the tune :-)
I used to give my guitar (les paul) a real hard time, often bending the neck to achieve a whammy effect which was not much good for the tuning (or the guitar either, it survived though :-) )
A good ear is a must for guitarists, especially lead as you are often bending notes in a subtle fashion, which takes some practice to do accurately and develop a feel for. I found this pretty much impossible to teach and decided I probably wouldn't want to anyway, as everyone eventually finds their own way, which is part of developing a unique style.
All this got me thinking of an automatic robotic tuner that could be built into the guitar and use a few highly geared motors. I checked and Gibson have already done it though. There is also a similar idea where you place the tuner on the machine head.
> Yes, in the middle of a song tuners won't help you much. A quick
> adjustment is often needed, especially the first couple when the strings
> warm up - trick is to make it sound like it's part of the tune :-)
> I used to give my guitar (les paul) a real hard time, often bending the
> neck to achieve a whammy effect which was not much good for the tuning
> (or the guitar either, it survived though :-) )
> A good ear is a must for guitarists, especially lead as you are often
> bending notes in a subtle fashion, which takes some practice to do
> accurately and develop a feel for. I found this pretty much impossible
> to teach and decided I probably wouldn't want to anyway, as everyone
> eventually finds their own way, which is part of developing a unique style.
>
> All this got me thinking of an automatic robotic tuner that could be
> built into the guitar and use a few highly geared motors. I checked and
> Gibson have already done it though. There is also a similar idea where
> you place the tuner on the machine head.
>
>
RussellMc wrote:
> I'm not sure why having the proficiency to home-make a prototype board
> of this fineness should be seen as an indicator of general disability
The homemade board is a indicator of low quantity, not quality. It's no
problem to use 2 LEDs if you're just making one board and that somehow saves
a minute of design. In a volume design you'd use a single LED if this was
reasonably possible. The point is that just because someone used 2 LEDs in
a one-off project doesn't mean it couldn't have been done with less.
The sloppily drawn schematic and poorly documented code are however
indications of the design quality. Look at how much trouble you had trying
to figure out whether the two LEDs are lit 50% of a cycle apart or not. In
fact, your final conclusion was that you're still not sure. There should
have been a discussion about the general strategy and certainly there should
have been a comment about what was actually done. Sloppiness in one part of
a design invariably indicates sloppiness in other parts.
Addressing specifics and not the more general by now very very very
well known Olin doctrine (not a comment on it's goodness or otherwise,
just that everyone could by now paste boilerplate text on the subject
which matches the OD or answer exam questions on what would be
said)(ie the lesson has got across ;-) ).
>... Look at how much trouble you had trying
> to figure out whether the two LEDs are lit 50% of a cycle apart or not.
The trouble amounted to having to open the code and search for "LED".
I agree that if you meant "has no documentation and it really needs
some" then that was trouble.
If you meant "hours of work, it wasn't.
> In fact, your final conclusion was that you're still not sure.
No. that's probably a "lost in translation" twixt NZ_Queen's Anglais
and USAmerican.
I said:
> " ...BUT they could be offset by some other amount ...".
I meant that they would be readily able to be offset by some other
fraction of a cycle if desired, not that I was uncertain what the
present fraction was.
I also tend to use 'it seems" in the sense recommended by Benjamin
Franklin. ie something like "my quick look indicates to me that this
is almost certainly the case and I'm probably correct in saying so BUT
there may be some arcane unseen thing lurking in the code that I've
missed at a quick glance so i'll indicate a degree of uncertainty" or
something.
Whatever.
> There should
> have been a discussion about the general strategy and certainly there should
> have been a comment about what was actually done.
If you mean "Should have at least a shred of documentation" then, yes,
it would be 'nice'.
> Sloppiness in one part of
> a design invariably indicates sloppiness in other parts.
That may be true for a wide range of "substantially".
But one man's sloppiness may be eg another man's Ret Butler approach,
for a range of reasons. (* Frankly my dear, I don't ...)
If all the world did things as Olin says they should, the world would
be a tidier more structured, often more logically consistent and
easier to follow place. It would also lose some of its sparkle and
wonder, while gaining some sparkle and wonder in other slightly more
mundane places. Even when "doing it more normally" has great appeal.
"having done it at all" can add nicely to the vector sum of human
achievement.
> The sloppily drawn schematic and poorly documented code are however
> indications of the design quality. Look at how much trouble you had
> trying to figure out whether the two LEDs are lit 50% of a cycle
> apart or not. In fact, your final conclusion was that you're still
> not sure. There should have been a discussion about the general
> strategy and certainly there should have been a comment about what
> was actually done. Sloppiness in one part of a design invariably
> indicates sloppiness in other parts.
Sometimes it seems you're approaching stuff like this more as a priest
than as an engineer. IMO one of the most important concepts in
engineering is "good enough". If whatever this guy had enabled him to
create a device that fits his requirements, within his budget (effort
and money), it is quite likely that spending more effort on it just
isn't worth it -- in an engineering sense, even if it's not more than a
scrap of paper with the schematic and some quickly written code.
The other question is then whether or not to publish at that point what
has been done so far. Some may think that there's a lower quality
threshold on "worth publishing", and there probably is one, but it also
seems that at least for some this is above it. Which is probably enough
to make it a good thing he did publish whatever he had -- even without
raising the documentation quality level. If it's below one's quality
threshold, by all means ignore it. IMO anything beyond this wouldn't be
engineering, it would be religion (as in "belief system").
Gerhar
V G wrote:
>
> I'm going to try redesigning it using a 16F866 or whatever else I have on
> hand and a crystal.
> --
If you have the free time, why not developing guitar-like keyboard. A
certain guitar chord would mean certain symbol. A list reader would
not only read a message but also would listen to it. Some will sound
like Wagner's works, some - like Mozart's, some - like Thrash Metal
:-
Gerhard Fiedler wrote:
> IMO one of the most important concepts in
> engineering is "good enough". If whatever this guy had enabled him to
> create a device that fits his requirements, within his budget (effort
> and money), it is quite likely that spending more effort on it just
> isn't worth it
Leaving out comments in the interest of speed is a fallacy. Good comments
*save* time. It does take a little more effort to draw a schematic
properly, but it really isn't that hard.
The main difference is not one of effort but of mindset, which is why
schematic and code clarity is some indicator of quality in other aspects of
the design.
> The other question is then whether or not to publish at that point
> what has been done so far.
The fact that this guy wasn't embarassed enough to not show his schematic
and code to the world says a great deal about him, and therefore about the
quality of his design.
On Mon, 04 Apr 2011 14:10 -0400, "Olin Lathrop" wrote:
> Gerhard Fiedler wrote:
> > IMO one of the most important concepts in
> > engineering is "good enough".
>
> The fact that this guy wasn't embarassed enough to not show his schematic
> and code to the world says a great deal about him, and therefore about
> the
> quality of his design.
I wonder if this repeating "discussion" will ever break through and "the
one true way" will be developed as a result.
It sure sounds to me like "SSDD" and I don't mean single sided double
density.
If either of you manages to convince the other to change his position on
even one point, let us all know :)
On 04/04/2011 19:30, Bob Blick wrote:
> On Mon, 04 Apr 2011 14:10 -0400, "Olin Lathrop" wrote:
>> > Gerhard Fiedler wrote:
>>> > > IMO one of the most important concepts in
>>> > > engineering is "good enough".
>> >
>> > The fact that this guy wasn't embarassed enough to not show his schematic
>> > and code to the world says a great deal about him, and therefore about
>> > the
>> > quality of his design.
> I wonder if this repeating "discussion" will ever break through and "the
> one true way" will be developed as a result.
>
> It sure sounds to me like "SSDD" and I don't mean single sided double
> density.
>
> If either of you manages to convince the other to change his position on
> even one point, let us all know:)
>
I've seen good designs on napkins, beermats and envelopes. It's not mandatory to tidy them for publication, especially when it's not for a commercial product and no-one is paying you to publish.
Anyone seen any of the above photographed with 320x240 web cam or cheap camera phone and published, maybe just as a Forum post?
talktalk.net> wrote:
