Equipment
Latest change
2023-12-24
In brief:
A description of the equipment in my house.
- Top
mount with Hall sensors to measure the behaviour of the
pendulum.
- Wire to suspend the bob.
- Bob, aluminium cylinder filled with ca. 6 kg
lead.
- Base assembly allowing precise
adjustment of the coil set consisting of:
- Zero cross
detection coil.
- Drive coil.
- Rim coil.
- Control electronics. Circuits to monitor the behaviour, detect
center and rim passages and to control the drive coil.
- PC program which takes
the data from the Bob Control unit and
presents it
graphically and logs the data for later study by the Analysis program.
- Firmware on the Arduino. Controls the Bob and reports the actual behaviour of the pendulum.
Top mount
The Top mount is rigidly mounted to a purlin of the roof, next to
the
open stairs. This gave me a height of about 4.5 meters for the
length
of the pendulum.
Read more.......
Wire
The wire is a piano wire of 0.75 mm diameter.
During the one-time experiment in the Vrijland Chapel we had a broken wire.
The story of the Broken Wire.
Bob
The bob consists of an aluminium cylider filled with lead. A
central
rod allows it to be attached to the wire. On the lower end of this
rod
sits a magnet which induces electrical signals in the
Zero-crossing
coil and in the Rim coil, and it experiences a repelling force
when the
Drive Coil is engaged.
Read more.......
Floor unit
The base assembly contains the Coil assembly and the mechanism for
precise centering of the coil assembly
Read more.......
Zero cross detection coil
This small coil at the center of the base-assembly detects the
passing
of the Bob. When the Bob is approaching the voltage will rise.
When the
Bob is nearly overhead the voltage will fall and cross zero at the
moment that the bob is exactly in the center.
The Arduino software detects this center-crossing and starts the
timing for a.o. the DriveCoil pulse.
When the time for one half of the swing differs from the time for
the
other half, our zero detection coil is not at the center of the
pendulum's swing. This can be corrected with the centering
mechanism.
Read more.......
Drive coil
The driveCoil, when engaged, provides a repelling force on the
magnet
in the Bob's lower stem. This will replenish the energy lost by
air
friction in each swing.
Read more.......
Rim coil
The rim coil sits at a somewhat large distance from the center.
Detecting the Bob's passages tells us quite precise what the
amplitude
of the pendulum is. Based on this information the duration of the
drive
pulse is modified to keep the amplitude as constant as possible.
Read more.......
Control
Electronics
The electronics for the BobControl unit consists of some
operational
amplifiers to condition the signals from the Center- and Rim coils
and
the Hall sensors, and to engage the DriveCoil at the proper moment
during the proper time. At the heart of the electronics sits an
Arduino Mega.
Read more.......
PC Program
This program GUI_2200 collects data from the Arduino
processor in the BobControl, present some
data graphically and logs all important data. It also allows to change several parameters of the
Pendulum Contol.
The Program Analyse2212 reads the log files and shows us
the behaviour of the pendulum over
somewhat longer time.
Read more.......
Firmware
The firmware on the Arduino processes the data from the sensing coils,
sends a current-pulse to the DriveCoils and passes the data from the
Hall sensors. It communicates with the PC Program (GUI) via Ethernet.
(Local Area Network)
In absence of the GUI the Arduino keeps the pendulum running as normal.
Read more......