An electric balance-wheel clock uses electrical energy to sustain a spring-controlled oscillation. This illustration shows a moving-magnet balance with a stationary coil. Its accompanying calculator compares an ideal electrical pulse budget: applied voltage, energy per pulse, pulse duration and complete oscillations per second.
Electric Balance Wheel Clock Interactive Calculator
Explore a moving-magnet balance clock and compare an ideal two-pulse electrical energy budget. The physical arrangement and the simplified pulse model are explained separately.
Equation Used
- Two equal electrical pulses per full back-and-forth oscillation.
- Constant voltage and current during each equivalent pulse.
- No standby power, battery capacity or conversion efficiency model.
- Illustrative amplitude and spring shape, with frequency supplied as an input.
Two ideal electrical pulses per complete oscillation. Excludes standby current, mechanical losses and timekeeping accuracy.
Magnets move; the coil stays fixed
The construction reference is the single-coil balance described in US4340948A. Two plates share a spindle and carry paired magnetic poles on opposite sides of a stationary coil. As the plates oscillate, the magnets sweep across the coil faces. A spiral balance spring connects the spindle to a fixed outer anchor.
The main view shows the moving upper carrier above the coil. The lower section explains the separate heights of the two carriers and the stationary winding between them. That section is held at the central position for clarity. It is not a second simultaneously moving mechanism.
The patent uses electronic feedback associated with induced voltage. Its waveform and circuit are more complex than a rectangular pulse. The illustration borrows the physical arrangement; the calculator below is an explicitly simplified energy comparison, not a simulation of that patented circuit. A going train and clock hands are omitted so the oscillator remains visible.
Compare an electrical pulse budget
Enter the number of complete back-and-forth oscillations each second. This differs from a beat count: the calculator assumes two equal drive pulses per complete oscillation.
Energy means electrical energy supplied during one ideal pulse. It is not the mechanical work delivered to the balance. Pulse voltage and duration determine the constant current that would deliver that energy in a rectangular pulse.
The replay is slowed twenty times. Its fixed illustrative amplitude is 80° to either side. Changing frequency changes replay speed and the pulses counted per second. Energy, voltage and pulse duration change the current display and pulse diagram, without pretending to solve the balance amplitude.
Energy, pulse current and average drive power
For a constant-voltage, constant-current pulse, E=VIt. With E in microjoules and t in milliseconds, the equivalent current in milliamperes is I=E/(Vt).
The assumed pulse rate is r=2f. Daily pulses are 86400r and average electrical drive power in microwatts is E×r. Pulse duty is 2f×t/1000 when t is entered in milliseconds.
Changing pulse duration at fixed energy changes the equivalent pulse current but not average drive power. Changing voltage at fixed energy also changes current without changing power. These are consequences of the selected inputs, not unresponsive controls.
The output previously called peak current is now labeled equivalent rectangular-pulse current. A real inductive winding has a time-varying current governed by its resistance, inductance, induced voltage and driver circuit. Those quantities are not entered here.
Default energy budget
At 2.5 complete oscillations per second and two pulses per oscillation, the assumed rate is 5 pulses per second, or 432000 per day. A 2.5 µJ pulse at 1.55 V lasting 3 ms has an equivalent rectangular current of approximately 0.538 mA.
Average drive power is 12.5 µW and the pulse duty is 1.5%. Doubling pulse duration to 6 ms halves equivalent current to about 0.269 mA while average power remains 12.5 µW. Doubling frequency instead doubles pulse count and average power.
These values describe the chosen mathematical scenario. They are not a measured performance specification for the patent mechanism or a particular clock.
What this model leaves out
Spring stiffness, balance inertia, damping, magnetic geometry and electrical-to-mechanical conversion are not solved. Frequency is an input, not a prediction from spring dimensions. The spring drawing keeps its endpoint connections while illustrating deformation; it is not a stress or spring-shape solution.
Average power includes only the entered ideal drive pulses. Electronic standby current, switching losses, battery capacity and voltage decline are excluded. The calculator therefore does not predict battery life or daily timing error.
The previous article mixed moving-coil and moving-magnet descriptions and gave unsupported timing, service-life and failure thresholds. Those claims have been removed. The present reference is one concrete arrangement, not a claim that all electric balance clocks share this construction.
Electric balance-clock questions
Does the coil turn?
Not in the illustrated arrangement. The magnet carrier oscillates around the spindle while the coil stays attached to the frame.
Why are there two pulses per cycle?
That is an explicit energy-budget assumption, one pulse for each crossing. A different drive circuit can use another pulse pattern.
Is the entered energy mechanical impulse energy?
No. It is electrical energy. Converting it into mechanical work would require additional motor and loss information.
Why does pulse width change current but not average power?
The same energy is spread over a different time. Pulse energy and pulse count still determine the average drive power.
Is the rectangular plot the real coil waveform?
No. It is the constant-current equivalent used in the energy calculation. The patent reference shows a more complex induced-voltage and feedback waveform.
Construction reference
- John W. Goodnight, Single-coil balance wheel for driving a mechanical movement, US4340948A — Figures 1A and 1B show the coil, magnet plates, spindle and spring; Figures 2 and 3 explain magnetic sweeping and induced-voltage waveforms.
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