The clock was made by William Yeadon of
Stourbridge in around 1750. In a handsome
fruitwood case it is one of his early works.
If you don't have a downstairs maid, a thirty
hour clock takes a lot of work!
Now with a conputer controller upgrade the
clock keeps perfect time, doesn't need
winding and has a sweet chime.
The changes preserve the original clock
parts.
A Raspberry Pi is used to control a stepper
motor, a position sensor, an LED and a
solenoid chime actuator.
The software uses Free Pascal and has a
novel browser control interface.
Antique Clock Computer Automation
The original configuration controls a detent
arm using a pawl attached to the hour wheel.
When the minute hand is at the top of the
hour, the chime counter wheel is briefly
released and rotates anti-clockwise driven by
the chain weight. Slowed by a governor
paddle, the length of the chime counter wheel
'section' determines the number of times the
bell is struck before the detent arm is
re-engaged by the next 'cutout' stopping the
wheel rotation
In the computer cotroller configuration the detent arm is re-positioned near an IR beam
detector and the counter wheel mechanisim
isolated. The beam interruption is used to
detect when the minute hand is at the top of
the hour. The stepper motor counters can be
reset for the new hour to avoid systematic
errors and the appropriate computer
controlled hourly chime initiated.
An aluminium framework is clamped to the
existing carcass. The pendulum, chain,
weights and escapment are removed and
preserved. All changes can be reversed with
no damage by a future restorer,
Motive power and hand movement is now
controlled by a stepper motor
28BYJ-48
The stepper motor assembly must be
micro-adjustable. If you can't find exactly the
right teeth per inch for the driving cog, in low
torque applications like this one, use a close
match but angle, distance and offset the drive
to avoid "face to face" jams. i.e. to avoid top
of opposing teeth meeting perfectly
The chime clapper is replaced by
a ball bearing "fired" by a
computer controlled solenoid via a
relay.
// Wiring assignment
// TPIN uses GPIO numbering NOT HEADER PIN
// Stepper controller
gpioLine[1]:=tpin.create(17); // (GPIO 17) Header pin 11
gpioLine[2]:=tpin.create(18); // 12
gpioLine[3]:=tpin.create(27); // 13
gpioLine[4]:=tpin.create(22); // 15
direction:=clockwise;
for line:=1 to 4 do gpioLine[line].switchDelay:=1;
step:=0;
beamSensor:=tpin.createSensor(16); // IR beam interruption sensor attached
beamStatus:=beamSensor.sense;
chime:=tpin.create(23); // relay that operates the solenoid bell ringer
chiming:=true;
led:=tpin.create(26); // LED
