Stringed Instrument Tuner, Ideas?
Posted: Tue Sep 16, 2008 10:34 pm
Hello,
Using a microcontroller to make a guitar tuner is a very
simple task. The program changes the state of an output
pin every 1/2 cycle of the tuning frequency and this creates
an almost perfect square wave and the frequency can be
adjusted to be very very close to the actual frequency
of a typical guitar string, within a small fraction of a
percent. The output pin is then used to drive a set
of headphones through a rather large value resistor and
the result is a tone at the required frequency. It takes
about 30 minutes to get the program going and uploaded
to the ic chip and then we're up and running, so it truely
is a very simple project.
What i was hoping to do however, is to drive a small white
LED, and that LED will be directed at the string of choice
and it will act as a strobe, so that when the string is
at the right frequency it will appear to be still rather
than vibrating back and forth. This will form a tuning
system that is far more accurate than the human ear because
that string will appear to move slowly even if it's frequency
is only off by a small amount.
There is a slight problem with this idea however, and i just
starting to think about this. When the string is plucked it
vibrates back and forth (guitar or other instrument laying on
its back) and this causes the string to be ever so slightly
tighter at the two extremes of its travel, and this causes
a change in movement especially since the string vibrates to
less and less extremes as the tone volume dies down. Thus,
it's a little hard to narrow down the frequency with a strobe
of a fixed frequency because the frequency varies slightly
as the string vibration damps out. The ear averages this
out a bit but the strobe doesnt have the ability to change
frequency as a string would, and i feel that would be too
complicated to build into the system.
Any ideas how to improve the system? Perhaps a short duty
cycle instead of a square wave? Perhaps a light sensitive
pickup to sense movement and analyze with the uC or send
the data to the computer for some analysis?
Any ideas/comments/suggestions?
Using a microcontroller to make a guitar tuner is a very
simple task. The program changes the state of an output
pin every 1/2 cycle of the tuning frequency and this creates
an almost perfect square wave and the frequency can be
adjusted to be very very close to the actual frequency
of a typical guitar string, within a small fraction of a
percent. The output pin is then used to drive a set
of headphones through a rather large value resistor and
the result is a tone at the required frequency. It takes
about 30 minutes to get the program going and uploaded
to the ic chip and then we're up and running, so it truely
is a very simple project.
What i was hoping to do however, is to drive a small white
LED, and that LED will be directed at the string of choice
and it will act as a strobe, so that when the string is
at the right frequency it will appear to be still rather
than vibrating back and forth. This will form a tuning
system that is far more accurate than the human ear because
that string will appear to move slowly even if it's frequency
is only off by a small amount.
There is a slight problem with this idea however, and i just
starting to think about this. When the string is plucked it
vibrates back and forth (guitar or other instrument laying on
its back) and this causes the string to be ever so slightly
tighter at the two extremes of its travel, and this causes
a change in movement especially since the string vibrates to
less and less extremes as the tone volume dies down. Thus,
it's a little hard to narrow down the frequency with a strobe
of a fixed frequency because the frequency varies slightly
as the string vibration damps out. The ear averages this
out a bit but the strobe doesnt have the ability to change
frequency as a string would, and i feel that would be too
complicated to build into the system.
Any ideas how to improve the system? Perhaps a short duty
cycle instead of a square wave? Perhaps a light sensitive
pickup to sense movement and analyze with the uC or send
the data to the computer for some analysis?
Any ideas/comments/suggestions?