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Intrinsically Safe LCDs

Intrinsically Safe LCDs

Sep 28th 2020


Focus LCDs can customize an LCD’s voltage inputs and other components according to your requirements to produce a product that meets intrinsic safety standards.

Purpose of Intrinsic Safety

Explosions and flash fires are a concern for many industries. Risks increase when confined vapors, dust and flammable gasses build up due to lack of ventilation.

All a fire requires is fuel (oxygen) and an ignition source such as a spark, excessive heat, or a short circuit. When developing electronics that will be used in explosive environments, it is important to ensure that there is nothing in the application that can act as an ignition source.

Industries

Refineries, natural gas locations, high concentrations of dust such as grain elevators, pipelines, hospitals, and anywhere pure oxygen or other highly flammable vapors are present.

How to Reduce the Risk of Ignition

Reduce Internal Temperatures:

Design a circuit that senses excessive temperatures. Shutting down the system when thresholds are exceeded. Resistors convert power to heat and need to be considered when choosing resistance values.

Ambient temperature can be reduced by providing ventilation near heat generating components. 

Increase Spacing Between Components on a PCB:

In most applications, the more components you can fit on a PCB the better since less real estate reduces price.

Not so in explosive environments. LCD circuitry can be modified to increase space between the components on the printed circuit board to reduce dust-caused shorts.

Obviously, the better sealed your product, the less dust and contaminants will enter.

(Yes, dust does build up on PCBs. Take apart your computer’s tower someday and see just how much resides after just a few years of use.)

Reduce or Eliminate Capacitors and Inductors

Capacitors are basically batteries that charge slowly and discharge quickly. A common application is the flash of a camera. This discharge is enough to create the spark.

Greatly reducing the size of the capacitors (capacitive values) and inductors (Inductive value) will reduce the probability of an arc. Lower capacitive values can affect LCD performance. Especially in TFT displays.

Your display may not operate as well as you would like when key components are limited. It’s a tradeoff between performance and design specifications.

Series Resistors as a Fuse

Place your resistors in series. If one fails, the circuit is broken (similar to a fuse or circuit breaker). 

Zener Diodes

The use of several Zener diodes will reduce the current.

Reduce Overall Power

Limiting the amount of power available to the electrical equipment to less than 1.3 Watts. This can be difficult when driving the LCD and its backlight and any other power-hungry component. It may require that some components be off when others are on to keep the total amount of power below the threshold.