Well then, let the fault be mine for not communicating more clearly.
<chuckle> I have two fine, neodymium rod magnets, one above the other,
inside a stainless steel capsule, around which are wound two coils of
opposing flux. 300-series non-ferromagnetic stainless. The two rod magnets
have like poles facing each other so that if left alone they repel one
another. So far I'm using 32 gauge magnet wire for both coils. The lower
of these two rod magnets is stationary, and the upper magnet is free to
resonate between the two coils at between 200Hz and 300Hz according to the
waveform through the two coils. A sawtooth wave driving the two coils
"feels" best with a pulse width of somewhat greater-than 10%. One rod
magnet works fine as it is, but adding this second, lower, stationary magnet
makes the thing go into serious over-drive. The mentioned cube magnet was
just for experimentation, and is not used for the actuator. Remember that a
solenoid of whatever design is more efficient when it is fatter, rather than
longer, no matter how much longer.
How's that?
Charles
-----Original Message-----
From: reinoud
Sent: Tuesday, May 19, 2015 3:14 PM
To: optacon-l@xxxxxxxxxxxxx
Subject: [optacon-l] Re: Reinoud, how many coils and their relationship to
the permanent magnet?
Charles,
I still couldn't make too much sense of it so decided to try to reproduce
the effect you described with materials at hand (that is, 1mm diameter
magnets at various lengths and coils/bobbins to fit). So far, driving with
square pulses, I didn't notice any force or power larger than usual.
What I did notice is that this way it can be effectively like driving with
AC while using only pulsed DC, which makes sense because the field from the
stationary magnet provides an 'offset' to the actuator. When driving at low
frequencies (<100Hz) this would under the right circumstances give an
impression of stronger vibration because of the longer stroke than just
pulsed DC would give. But this approach seems actually less power-efficient
than driving with AC? So I don't see much of an advantage to this in
practice.
But maybe it's because I still don't understand it, like before I find it
hard to make sense of it all the way you describe it.
- Reinoud
On 19/05/15 12:58, C. Pond wrote:
Reinoud: to show the very strong effect of a second magnet, if you place ato view the list archives, go to:
larger cube magnet just beneath the single moving magnet in yor coil, you
will instantly see anf hear and mostly feel the sudden increase in power
output in newtons or grams. I have considered using an Halbach array at
the
bottom of the entire display rather than separate stationary Power Magnets
for each actuator, but at this point it would mess up the straightforward
interconnections which are so simple at this point, so why disturb them.
If
I can figure another equally easy way to interconnect the actuators to
keep
manufacturing simple as it now is, I would go with the Halbach array, but
for now it is individual Power Magnets for each actuator, and after all,
this does just fine as it is.
Notably, as one might expect, the Moving Magnet pushes upward away from
the
like pole of the Power Magnet until it hits the stops. However, it takes
no
more power to move the Moving Magnet downward than it does to move it
upward. This might seem counter-intuitive since it has to overcome the
repulsive force of the Power Magnet, but so it is. So, anything in the
waveform below the zero-line if the lower part is equal to the upper part
of
the waveform is a waste of energy. So, the waveform might be a sawtooth
with most of its duty cycle above this zero-line, and only a portion below
the line. It does save a lot of energy. The more, the better.
Charles
-----Original Message-----
From: Marie-Aline Oliver
Sent: Tuesday, May 19, 2015 6:33 AM
To: optacon-l@xxxxxxxxxxxxx
Subject: [optacon-l] Re: Reinoud, how many coils and their relationship to
the permanent magnet?
Very impressive Charles and Reinoud. Keep up the great work gentlemen!
--MAO
On 18-May-15, at 8:58 pm, C. Pond wrote:
Thanks, Reinoud. The function of the second stationary magnet
positioned
below the moving magnet is to act as a kind of flux booster. It
adds flux
density and intensity to the entire magnetic circuit, like a big
second
battery adding power to a motor already connected to a first smaller
battery. The combination of the two coils, the moving magnet and this
stationary "power magnet" completely saturates the flux gap, so
adding more
magnetism does nothing more. Adding this second magnet gave the
tactuator
such a lot more power that it was shocking; like day and night. So,
between
the two coils resonating and moving the "moving magnet" and the "power
magnet", the force generated by the actuator is very high. It can
generate
more force than the R2 optacon's entire 100-pin bimorph-based
display. and
each actuator is in overdrive when using 200mV. The impedance of each
actuator I haven't measured or calculated; their static resistance is
meaningless, but it is about 1.6 to 2 ohms. I think the
electromagnetic
oscillating field does not move the moving magnet; it moves the
flux, which
in turn moves whatever is in the flux field. Like waves of water in
turn
moving a boat afloat upon the watery waves. The boat does not move
itself;
the waves of water move the boat.
Charles
-----Original Message-----
From: reinoud
Sent: Monday, May 18, 2015 6:33 PM
To: optacon-l@xxxxxxxxxxxxx
Subject: [optacon-l] Re: Reinoud, how many coils and their
relationship to
the permanent magnet?
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