Equipment
Latest change
2017-10-02
In the last months of 2019 many changes were made in the
electronics hardware and in the firmware / PC program.
In 2020 I hope to report about these new versions.
In brief:
A description of the equipment made for the Chapel.
- 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.
- Bob Control electronics to detect
center and rim passages and to control the drive coil.
- PC program which takes
the data from the Line Sensors and the Bob Control unit and
presents it
graphically and logs the data for later study.
- Analysis program to study the
logged data.
- Firmware for the BobControl and Power
units.
- The story of the broken
cable.
With similar equipment at home I've seen a very regular behaviour
of the
pendulum and a Foucault precession which very good matches the
calculated value for this lattitude.
The setup has no Charron ring or something equivalent, but obeys
the
timing requirement from Schumacher, that is, to give the drive
impulse
at a very particular moment in the swinging period.
There is a substantial amount of ellipse, changing periodically in
direction. But it has hardly any effect on the velocity of the
Foucault
precession.
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.
In the Chapel the Top Mount is attached to a raft of the roof at
approx. 8.5 m height.
Read more.......
Wire
The wire at home is a piano wire of 0.75 mm diameter, in the
chapel it is 0.925 mm diameter (gauge 16).
Read more.......
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.......
Bob 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 hart of the electronics sits an
Arduino
Nano.
Here you find the zipped code for the Nano.
Look here for the schematics and a detailed description of the
electronics.
Read more.......
Power supply
Electronics
The whole system is supplied from a 24 Volts battery, which is
constantly charged by a mains power supply.
Read more.......
PC Program
This program collects data from the Arduino
processors in the BobControl unit and the Power unit, present some
data graphically and logs all important data to a server in the
network.It also allows to change several parameters of the
Pendulum Contol.
Read more.......
Analysis Program
The Analisys Program, also written in FPC and Lazarus IDE shows us
the behaviour of the pendulum over
somewhat longer time, as it emerges from the
logfiles.
Read more.......
Firmware
The Arduino firmware for the units Bob Control and Power.
Read more.....