Cam timers are mechanical devices that control switches through a rotating wheel. They were commonly used in production control, washing machines, vending machines, and water treatment systems. However, they were inaccurate and required disassembly to change operating parameters. Digital controllers have largely replaced cam timers since the 1980s due to their accuracy and flexibility.
A cam timer is an electrically powered mechanical device that controls a series of switches by the movement of a rotating wheel or cam. These timers were used extensively before the invention of programmable digital timers. Cam timers are useful when a machine or process needs to be controlled in a series of steps that occur one after the other.
Production control in industrial systems was a common use of a cam timer well into the 20th century. The timer was connected to mechanical switches that sent control signals to valves or pumps. Complex systems were difficult to control with cam timers, due to inaccuracy issues. Also, changing any operating parameters required disassembling the timer and replacing the cams.
Commonly used consumer products, such as household washing machines, cam timers. Moving the wash cycle knob rotated a cam behind it and aligned the desired wash setting with the cam switch. Early machines lacked flexibility for different wash loads or water pressures, so actual wash time was affected. Later machines added a water fill switch that turned off the cam timer motor until the washer was filled, resulting in more accurate wash times.
Cam timers have been used regularly in vending machines. Inserting money into a machine activates a timer that controls vending functions. Sales cam timers may not function like a standard timer, but rather were used to provide sequential or serial operation over a specific period of time.
Cam timers can function as clock timers, with a series of cams installed to provide functions at regular times. Water treatment systems also use them in some designs to activate backwash or water softening functions. The cam timer can run like a clock for a regular control operation such as backwashing a filter every day. It is also possible to activate the timer with a separate command, for example using a total water flow meter to activate the regeneration of the softener.
Digital or digital logic process controllers have replaced cam timers for many applications since the 1980s. Electronic controllers are more accurate for timing functions. Programming a change into a controller can be as simple as accessing a computer screen, rather than having to take apart a timer to change cams. Logic controllers can be programmed with a variety of control functions, rather than a single timer function. This can result in lower costs by requiring fewer controllers.
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