Mercury-Free Tilt Switches As Safe, Modern Alternatives To Mercury Switches
Mercury-free tilt switches are electronic components that trigger automated functions within a system. They are specifically constructed to respond to changes in angle or upsets to an object’s orientation.
These switches are a modern standard that has replaced devices known as mercury switches. Mercury switches include components that are used as part of thermostats, pressure switches, but mercury tilt switches, in particular, will respond to a tilt or tip-over event.
This action occurs when mercury within the switch rolls freely within the switch’s can or housing. Because of this functionality, mercury switches are responsive to upsets in balance. When a switch is configured so that the mercury rolls into or away from a switch’s electrodes, this will connect or interrupt the circuit, respectively, which will then trigger a system response.
Since mercury is conductive, has low electrical resistance, will not emit sparks or wear on leads, and is sensitive to drops in gravity, it is useful as a conductive element in tilt switch applications. These advantages, however, cannot counter the potential hazards of mercury switches.
The toxicity of mercury poses many environmental and health hazards. RoHS and EPA resections have led to the phase-out of tools, instruments, and components that contain this poisonous heavy metal. This includes all mercury-based tilt switches.
Although older equipment may still operate using old mercury switches, these devices are gradually being replaced. Older switches containing mercury must be handled and disposed of under hazardous waste requirements.
Modern tilt switches will sometimes include the qualifier mercury-free. These switches use a variety of components as an alternative to the mercury that served as a standard conductor.
Ball tilt switches are a common example. These switches use a ballbearing or similar rolling element made from a low-friction, corrosion-resistant, and electrically conductive material. Nickel is one such example. Much like mercury switches, ball switches work when the rolling conductor moves away from or into the switch’s leads.
In the case of a normally-open tilt switch, the ball will be positioned so that its normal state is away from the leads, which amounts to an open or interrupted circuit. When the switch is subjected to a change in angle beyond its preset, the ball will roll to the leads and close the circuit. As the electrical current is then able to flow between the ball and the leads, the switch is activated and will trigger a response within the broader system.
In a normally-closed tilt switch, the ball will remain in contact with the switch’s leads as its normal state. This maintains the flow of electric current and thereby completes a circuit. A change in angle that exceeds the switch’s preset will cause the ball to roll away from the leads and interrupts the circuit. This disruption of electrical current will shut down or activate a response within the system.
Whether a switch is normally-open or normally-closed is a specification that’s referred to as the switch detail. Tilt switches are inherently non-latching. This means the switch will return to its normal state when the object’s orientation is corrected, however, this may not reset the broader system.
Although ball-bearings are commonly used as the conductor within mercury-free tilt switches, other parts and substances have been used as an alternative to mercury. An electrolyte-rich fluid can also function in such a capacity.
As with the conductor, the leads of tilt switches must be highly-conductive and mitigate any electrical resistance. They must also resist wear, corrosion, and other issues that might interfere with the switch’s performance.
In mercury-free tilt switches designed for critical capacities, such as aerospace and military applications, leads will be made from enduring materials like nickel, which are often plated with gold or silver to further enhance conductivity and prevent corrosion.
The housing that keeps all of these elements contained is also vital in the switch’s performance and longevity. Switch housing must be electrically insulating. They must also permit friction-free rolling of the switch’s conductor.
Critical capacity tilt switches will often be hermetically sealed, which ensures complete isolation from exterior factors, including dust, lint, and other small particles, as well as moisture and effects from temperature fluctuations.
The overall design and configuration of all of these parts can vary from one type of mercury-free tilt switch to another. Tilt switches may have just one single lead or they may have several, which can be arranged in many ways and connect multiple circuits within one switch.
As a standard, tilt switches detect positional disruptions across a single, linear direction. This can be expanded with an adjustable tilt switch, which will respond to orientation upsets that occur in multiple directions.
Mercury-free tilt switches have long been a standard in vehicular and heavy equipment applications that require emergency mechanisms and alarms in event of a roll-over. These switches are also used to automate non-critical responses, such as the triggering of a light within a vehicle’s trunk or glove compartment.
Tilt switches are incorporated into safe-handling and anti-handling systems that are used in vocational training and simulation equipment. They are used in a similar capacity where security components are needed for the prevention of intentional tip-over or tampering of machinery such as safes, ATMs, vending machines, etc.
Mercury-free tilt switches will also be used to trigger automated shutdowns and disarming mechanisms in munitions, in order to prevent accidental detonation, and in appliances like space heaters, hotplates, and clothes irons for purposes of preventing fire hazards.
Tilt switches offered by modern manufacturers are mercury-free as a standard. Many of them are made to be direct drop-in replacements for older mercury switches.
In addition to standard devices used for equipment safety updates, custom tilt switches can be made to suit many unique application requirements. These can be acquired from tilt switch manufacturers that work directly with original equipment manufacturers.