A cam timer turns a mechanical profile past a switch follower. The shaft speed sets the program duration, while the cam determines when a circuit changes state. Explore one channel below and compare the angular ON interval with its time duration.
Cam Timer Interactive Calculator
Set the effective ON angle and time for one shaft revolution. The animation shows a cam pressing a guided follower and a conceptual switch contact, with the same ON/OFF interval used by the calculator.
Equation Used
- Constant shaft speed, one revolution per program cycle and one ON interval.
- The drawn point follower and half-lift switching threshold are idealized; this is not a manufacturing profile or a replica of an ATC product.
- Timing outputs use minutes. Playback is accelerated, not real-time.
- No electrical rating, wear, torque, contact bounce or switch hysteresis calculation.
Compare the effective switching angle with ON time, OFF time, shaft speed and duty cycle. Follow the rotating cam, spring-return follower and switch contact through one timing channel’s cycle.
From cam rotation to a timed contact
A geared motor turns the camshaft. A follower tracks the profile and operates a switch. Several cams on a common shaft can control separate channels in sequence. The manufacturer’s ATC 324C documentation illustrates a real cam stack and switch row, with adjustable split cams and selectable gearing.
This animation isolates one channel in an end view. The central bearing stays fixed, the cam rotates, and a spring returns the guided follower. The enlarged contact view indicates the switching state. It represents the operating principle, not the internal construction of a specific timer.
Where mechanical timing is useful
Cam timers provide repeatable sequences for equipment with a defined cycle. Multiple cam channels can issue separate switching events. Suitability depends on the equipment and the selected timer’s documented cycle range, contact ratings and enclosure; the calculator does not select or rate electrical components.
Angle becomes time
For cycle time T minutes per revolution, angular speed is 360/T degrees per minute. If the contact is ON over θ degrees, ON time is Tθ/360 minutes. OFF time is the remaining part of T, and duty cycle is 100θ/360 percent.
Use the angle between the actual switch actuation and release positions. It need not equal the flat high-dwell portion of a cam because ramp shape, follower geometry and switch thresholds affect where switching occurs.
A four-minute ON interval
With a 45-minute cycle and a 32° effective ON interval, shaft speed is 8°/min. ON time is 4 minutes, OFF time is 41 minutes and duty cycle is approximately 8.89%.
Changing cycle time to 90 minutes doubles both ON and OFF duration while leaving duty cycle unchanged. Changing the effective angle to 180° gives equal ON and OFF times. These are timing examples, not instructions for modifying an appliance.
What the illustration includes
The simplified profile uses smooth transition ramps and an ideal point follower. Half lift is the illustrative switch threshold; the profile is constructed so the interval above that threshold equals the entered angle. An actual timer needs its own follower shape, clearances, actuation and release data.
The animation is accelerated so a 30–90 minute cycle can be inspected quickly. The numerical results retain the entered real cycle time.
Questions about timing
Why does the follower move gradually while the contact switches abruptly?
The cam has transition ramps, while the conceptual contact changes state when the follower crosses its threshold. The ideal model omits switch hysteresis.
Does increasing cycle time change duty cycle?
No. The ON and OFF times increase together. Duty cycle depends on the effective ON angle.
Can I use the high part of a cam as the switching angle?
Only if its boundaries correspond to the actual switching positions. Follower geometry and switch actuation travel can shift those positions.
Is the drawing a replacement-part design?
No. It explains timing and motion; it does not specify a cam suitable for an actual timer or an electrical load.
Construction reference
Automatic Timing & Controls, 324C Precision Switch Cam Programmer technical sheet. The product photograph and description show the motor, adjustable cam stack and follower-operated switches. The single-channel point-follower drawing here is a conceptual illustration.
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