ELECTRONIC
Wind Chimes
Part 2 – by John Clarke
Last month, we described how our new
Electronic Wind Chime worked, and how
to build the electronics. Now we get to the
tricky bit – modifying the wind chime itself so
it can be driven by a series of solenoids. Fear
not, because we have detailed instructions
on how to accomplish this, and finish the
build by putting it all together and setting up
the electronics.
W
e modified a Carson Home
Our finished Electronic Wind Chime.
It’s based on a commercial wind chime
but ours works when there’s no wind.
30
Accents Amazing Grace
640mm Sonnet Wind
Chime to incorporate the solenoid
drivers (but you could experiment
with any similar model). It is a
5-chime type with 31.5mm outside diameter tubes. The longest tube is 590mm and shortest
at 450mm.
The solenoids are supported on a circular ring made
from 9mm MDF (medium-density fibreboard). This ring is held in place
with an inverted U-shaped piece made
from MDF and a couple of right-angle
brackets. The whole frame is attached
to the wind chime’s attachment hook
with an M5 screw and nut.
For our prototype, the clapper plate
was made using an 80mm diameter
piece of 1mm aluminium sheet. The
plate (shown in Fig.7) is designed to
cater for the 5-chimes arranged 72°
apart around the diameter.
The plate includes holes for the
strings and a slot to allow the clapper plate to be placed over the clapper while its central support string is
still attached.
The frame needs to be sized so the
base plate can be positioned at a height
where the solenoids and levers are inline with the top of the clapper plate.
There are two holes for the string
attaching each solenoid to its chime.
These need to be far enough apart
so that the string does not touch the
chime tube when pulled taut. This
clapper plate can be glued in place, or
held with a small self-tapping screw
into the clapper after the string has
been threaded.
The 100mm x 10mm rectangular
solenoid levers are made from 1mm
aluminium sheet; the two end holes
are 3mm in diameter. Note that two
holes are not centred, but placed close
to one side, to give the best rotational
movement when attached to the solenoid plunger.
The pivot point is a wood screw into
the base plate. This should be long
enough and screwed in sufficiently for
the lever to sit horizontally, without
being too tight to move.
The hole in the solenoid plunger
was drilled to 2.5mm and then tapped
for an M3 thread. That allows the lever
to be secured at the fulcrum with just a
10mm-long M3 screw and no nut, with
the screw acting as a bearing. Alternatively, you could drill 3mm diameter
holes and secure them with machine
screws and nuts.
The pivot hole is slightly elongated
by about 1mm, to allow for the lever
to move freely, allowing for length
changes between the screws as it rotates with solenoid movement. A
6.3mm-long untapped spacer keeps
the pivot raised and is secured with a
15mm-long No.9 countersunk wood
screw into the base plate.
The solenoids are attached using
screws into the solenoid housing.
Our solenoids have M2.5-tapped
mounting holes, so they are secured
Practical Electronics | March | 2022
using M2.5 x 12mm screws. If no
holes are provided, they can be glued
in place instead.
Other options
The clapper plate and levers could be
made from a material other than aluminium. The levers need to be thin
enough to freely rotate within the solenoid plunger slot.
An easier material to work with is
Presspahn or similar electrical insulation material (eg, Jaycar HG9985). This
can be cut with scissors and a sharp
craft knife.
The sizes given for the wooden
frame and base plate are notional;
these really depend on the wind chime
you are using.
The circular ring base plate needs
to have an inside hole large enough
so the chime tubes can freely swing
without hitting it.
The outer diameter needs to be sufficient for attaching the solenoids, with
room for the pivot screws.
While we used MDF for the frame
and base plate, you could make the
frame from solid timber instead. The
base plate does not need to be circular – it could be made in a polygonal
shape instead.
The number of straight sides could
equal the number of chimes; for our
5-tube chime, that would be a pentagon.
Note that once the solenoids and
levers are in place, there is not necessarily a convenient point to attach the
frame to the chime where it will not
interfere with at least one lever. This
is especially true with an odd number
of solenoids.
However, there should be one side of
the frame that can be directly attached
to the base plate. The other leg can be
supported with a bracket that is raised
above the base plate using a screw and
nuts to clear lever movement (see our
photos for details).
Alignment
The frame needs to be aligned correctly
to the base plate. This is so that when
the frame is held by the wind chime
attachment hook, the solenoid levers
and strings are positioned correctly,
so that the clapper is pulled along the
radial line from the centre of the clapper to the centre of the chime tube for
each solenoid.
If it is not possible to get this alignment without the frame interfering
with the solenoid drivers, the positioner at the top of the wind chime
may need to be rotated.
Rotating the chime positioner will
effectively twist up the strings at the
attachment hook, so it will not stay
in this rotated position. The solution
Practical Electronics | March | 2022
A close-up of the ‘business’ end of the electronic wind chimes, showing how
the solenoids are placed around the ring. The solenoids do not strike the chime
tubes; rather, they pull the clapper towards the tube which makes the sound.
In this photo, some of the catch strings and pull strings were removed from the
closest chime tubes for clarity.
is to tie the chime positioner against
the side of the frame. A small hole in
the side of the chime positioner and
another in the frame will allow for a
short length of string or stiff wire to
hold the chime positioner in its rotated position.
Stringing the chime
The pull strings must normally be
loose. These pull the clapper toward the
chime near the end of the lever travel.
The loose stringing is for two reasons: first, the solenoid pulling force
is not particularly strong at the beginning of its movement from its
resting position, and it is greatest
when it fully pulls in the plunger.
The looseness allows the solenoid
to ‘build up strength’ before it starts
moving the clapper.
The second reason is so that when
one solenoid pulls the clapper in its direction, it is not affected by the strings
becoming taut on the opposite side.
The looseness needs to be a compromise between being tight enough to
be able to pull the clapper against the
chime, and loose enough not to affect
the opposing solenoid pulls.
The strings pass through the clapper holes and back to the lever, and are
secured by passing the string through
the lever hole. An M3 x 6mm screw
and M3 nut can be used to secure the
string in the hole. This more easily
allows fine adjustments compared to
tying a knot.
A refinement to the design is to include catch strings. These catch and
hold the chime tube, preventing it
from swinging back to re-strike the
clapper after striking the chime tube.
Their lengths are such that they are
loose when the tube sits in its usual
position, but tight enough to prevent
it swinging back and hitting the clapper. The string ends are held to the
base plate by clamps.
We used polyester string, which becomes unravelled if cut with scissors
or a knife. Instead, the string was cut
to lengths with a hot soldering iron
tip that both cut and welded the string
ends to prevent fraying. We don’t
recommend you use your primary,
high-quality iron to do this, though!
You can also cut the string and then
use a lighter to weld the ends before
they unravel.
Wiring
Use sufficient gauge wire (eg. 19 x
0.1mm strands) or similar for the
larger solenoids, so that voltage drops
will not affect solenoid operation. If
the wire cross-sectional area is too
small, then the solenoids may not
work with longer wire runs back to
the main PCB.
We used a 7mm tube loom to hold
the wires in place and keep the
31
attached the wire loom to the top of
each solenoid using cable ties so that
it won’t move around.
The main enclosure housing the
PCB can be located on a timber beam
above the wind chime attachment, or
further away out of sight.
Setting up
There are several options that need to
be set in the Electronic Wind Chime
controller before you can use it.
Reproduced from last
month, this shows
our recommended
arrangement for the
solenoids to drive the
wind chimes. The
solenoids press on levers
that pull the clapper
via a string to strike the
associated tube.
A second set of strings
prevents the clapper
from swinging around
and hitting other tubes
unless the associated
solenoid is energised.
appearance neat. The +12V wires to
each solenoid are connected together
and brought back to terminate into the
positive terminal of CON1 or CON6.
The second wire of each solenoid connects between the solenoid outputs at
32
CON1-CON6 and the negative terminal of the solenoid.
After soldering the solenoid wires
to the extension wires, insulate the
joints using electrical tape or heatshrink tubing. When finished, we
LDR adjustments
If you prefer not to have the Wind
Chime paused during darkness, place
a shunt on JP2. In this case, the LDR
does not need to be installed.
But if you do want it to stop at night,
remove the shorting block from JP2
and switch on the power. LED2 should
light, indicating that there is power.
VR2 can then be adjusted to set the
light threshold that switches the Electronic Wind Chime on or off.
With the LDR in normal shaded daylight, place your finger over the LDR
and adjust VR2 so that LED1 (the status
LED) starts flashing at 2Hz. This indicates that playback is paused.
Lifting your finger from the LDR
should result in that LED switching
off. The more clockwise VR2 is adjusted, the darker the light needs to
be to pause playback.
Calibration
The LDR is ignored during calibration
and recording. It is only used during playback, and only if JP2 is open.
This is so that calibration and recording are not interrupted by a change in
light level.
Each solenoid can be independently
calibrated for the drive voltage (using
PWM) and for the on-period. These
two parameters are adjusted using VR1
and JP1, as described below.
The 500Hz PWM duty cycle can be
adjusted between about 5% to 100%
in approximately 0.75% steps. This
varies the average voltage between
600mV and 12V in about 90mV steps.
The on-period can be set to between
2ms and 254ms in approximately 2ms
steps. Initially, all solenoids receive
the full 12V drive voltage (100% duty
cycle) for a duration of 254ms.
To initiate calibration, press and
hold the control switch (S13) at power-up. The status LED (LED1) lights for
200ms then flashes off for 200ms and
then on again. This indicates that calibration has been activated.
Press a solenoid switch (S1-S12)
to select which solenoid is to be calibrated. The status LED extinguishes,
and the solenoid drive par
ameters are now ready to be adjusted
Practical Electronics | March | 2022
for the chosen solenoid. When JP1 is
shorted, the PWM duty cycle can be
adjusted with VR1, and when JP1 is
open, the drive duration (on-period)
is adjusted with VR1.
Once you have set JP1 and adjusted
VR1 for the setting you want to make,
press the control switch (S13) to temporarily store that particular parameter. This will also drive the relevant
solenoid, so you can check whether the
setting is correct. If not, readjust VR1
and press S13 again.
If you want another solenoid to have
the same parameter, the switch (S1S12) for that solenoid can be pressed,
and the control switch (S13) pressed
again to store the current parameter
value for that solenoid.
We have also provided a means of
monitoring the current VR1 setting using a multimeter measuring the voltage
between TP1 and TP GND. That makes
it easier to replicate suitable values for
other solenoids.
The status LED (LED1) lights each
time you press the control switch for
the duration of the solenoid drive.
Lower PWM duty cycles will cause the
solenoid to move more slowly. Adjust
the solenoid on-period to allow sufficient time for the solenoid to pull the
clapper against the chime tube, but
short enough for it to pull away before the chime tube returns after being struck.
As mentioned, the solenoid parameters are initially only temporarily
stored. The values will be lost when the
power goes off unless they are stored in
Flash memory. This is also done with
the control switch.
While pressing the control switch for
a short period tests the solenoid drive, a
longer press (one second or more) will
store all solenoid parameter values into
the permanent Flash memory. LED1
will light again if the switch is held for
one second or more, to indicate that
the values have been written to Flash.
To exit the calibration mode, switch
off power. When power is switched on
again, without S13 being pressed, the
Wind Chime Player starts up in playback mode.
You can return to the calibration
mode again by repeating the above procedure, to re-adjust those parameters.
Only the parameters for the selected
solenoid or solenoids will be changed.
Previously stored parameters will remain unchanged unless new parameters are stored for that solenoid.
Table 1 – switch actions at power-up
S1
S2
S3
S4
S5
S6
S7
S8
S9
S10
S11
S12
Randomness off
Randomness on
Delay varies in 128 steps between 10s and 1280s (21:20)
Delay varies in 64 steps between 10s and 640s (10:40)
Delay varies in 32 steps between 10s and 320s (5:20)
Delay varies in 16 steps between 10s and 160s (2:40)
Delay varies in eight steps between 10s and 80s (1:20)
Delay varies in four steps between 10s and 40s (0:40)
Delay multiplier varies randomly between one and five times actual
Delay multiplier varies randomly between one and three times actual
Delay multiplier varies randomly between one and two times actual
Delay multiplier varies randomly between one and 1.5 times actual
You can then press the individual
solenoid switches to activate the solenoids, and it records the sequence you
provide and the pauses in between.
You can close one solenoid at a time.
The PCB includes white screenprinted squares above each switch so
you can write the perceived note using a fine marker pen. We say the ‘perceived note’ because the sound from
the chime comprises many overtones,
which may affect the apparent frequency. It may also appear to shift in
frequency after initially struck.
The perceived note cannot be easily
measured with a spectrum analyser.
Probably the easiest method is to use
a guitar tuner or similar device and
adjust it until its apparent frequency
matches the chime, then look at what
note you have selected.
For more information on the perception of sounds from wind chimes,
see: https://bit.ly/pe-mar22-ewc1 and
www.sarahtulga.com/Glock.htm
During recording, you can play out
a tune if you are musically inclined, or
just some nice sounds that appeal to
you. Short gaps between chime strikes
can be waited out in real time before
driving a solenoid for another chime.
Longer intervals may become tedious
to wait out in real time, but we have a
solution to that.
Time warp
By pressing the control switch for longer than one second, that period stored
for the current pause is multiplied by
ten. The status LED flashes at 1Hz to
meter out the time (one flash is one
second of real time, but ten seconds of
Fig.6: we cut a
sheet of aluminium
to this shape and
screwed it to the
top of our timber
clapper, to allow
the five strings to
be easily attached.
Recording a sequence
To make a recording, press the control
switch, S13, after power-up. The status
LED, LED1, lights and stays lit, indicating that recording has begun.
Practical Electronics | March | 2022
33
delay). Be careful when
pressing S13, since if
you press it for less than
one second, instead of
activating the time warp,
it will end the recording.
After a short press of
the control switch, the
entered sequence will be
written to Flash memory,
and it will return to playback mode. If no solenoid
switches were pressed
while in record mode,
the previous recording
will remain in memory.
+
SILICON CHIP
www.siliconchip.com.au
Wind Chime ePlayer
Power
+
+
. -
12VDC
Input
Playback
At power-up, the Electronic Wind Chime starts
in playback mode. This
plays back the recorded Two front panels designs are provided – one has provision for through-panel switch and LED
sequence, repeating it in whereas the other panel doesn’t. These can both be downloaded from the March 2022 page of
a continuous loop. The the PE website.
initial setting is for no
If you haven’t already pressed any
randomness in the delay periods be- rate; how often the random value
of
these switches at power-up, then
changes.
This
can
be
set
to
six
differtween chime strikes – in other words,
it faithfully reproduces your recorded ent values. The randomness changes the initial setting is with randomness
at an interval between ten seconds and off. If randomness is switched on (ussequence.
the maximum value selected. The op- ing S2), then the 10s to 1280s (21:20)
tions are 1280s (21:20), 640s (10:40), randomness change rate is selected,
Adding randomness
As mentioned earlier, you can add ran- 320s (5:20), 160s (2:40), 80s (1:20) and along with the 1-5 times delay range.
Note that you can press and hold
domness to the delay between chime 40s (0:40).
These options are selected by hold- more than one switch at power up
strikes. This is selected by pressing
switch S2 while powering up. Wait ing one of switches S3, S4, S5, S6, S7 to select more than one option at the
one time.
for the status LED (LED1) to flash after and S8 at power-up – see Table 1.
For example, you could switch ranYou can also change how much variabout one second before releasing S2,
indicating that the randomness feature ation you want in the delays. There are domness on (with S2), set the randomfour options, selected by holding one ness change rate at up to 320s with S5,
has been enabled.
The setting is stored in permanent of switches S9, S10, S11 or S12 down and the randomness variation to between one and three times with S10,
memory. If you want to switch the ran- at power-up.
The delay multiplier varies random- all at the same time.
domness off, hold switch S1 at power
up and wait for the status LED to light ly between one and the maximum value
selected. S9 selects a range of 1-5 times,
Reproduced by arrangement with
before releasing it.
SILICON CHIP magazine 2022.
There are two randomness param- S10 1-3 times, S11 1-2 times and S12
www.siliconchip.com.au
eters that can be adjusted. One is the 1-1.5 times variation (also see Table 1).
Here’s the Electronic Wind Chime PCB placed inside the case,
albeit without any cables connected, while at right the front
panel and label are placed.
34
Practical Electronics | March | 2022
For
swi
and
LED
