Cap touch Controls for Aerospace Galley Appliance

Capacitive Touch Interface with LED Back Lighting and RS485 communication

Project Description

The coffee maker capacitive touch interface was developed by Blue Sparq, Inc. for Enflite, an aerospace company. This interface is an example of the PCB type capacitive touch interface designed by us. In this kind of an interface, the capacitive sensor layer and the electronics needed to determine the button press, reside on the same PCB. The custom graphic overlay and lighting layer are then mounted to the printed circuit board. This project is also an example of our FORE LIGHT™ technology. Note the thin profile needed to uniformly light the user interface.

The user interface communicated the button press and release codes to the main controller via RS485. The user interface in return accepted communication from the main controller about the status of the various LEDs and the brightness of the backlighting.

Uniform LED Lighting

One of the challenges during the prototyping stage was that the entire development needed to be completed within 3 weeks. Because of our know-how, experience, and equipment we were able to allocate engineering resources and ensured the product was completed and delivered to Enflite within 3 weeks.

Generally prototypes provided to the aerospace industry are subject to DO-160E and HALT testing. Our prototypes were subject to ESD test, magnetic susceptibility test, operational shock and crash test, voltage spike conducted immunity test, audio frequency conducted susceptibility test, RF susceptibility test, RF emission test and fire and flammability test as part of the DO-160E and passed them. The overlay materials used in our touch interface were subject to a 12 second burn test per section 14 CFR 25.853 and met the requirements.

Testing is a very expensive aspect of development for our aerospace clients. They need quick and responsive support during this period from their suppliers. For instance, while the prototype unit was subjected to the various DO-160E tests, the customer identified that the communication protocol needed to be strengthened. We went through the requested changes and implemented them in a week and sent new touch interfaces so that the customer may continue testing their product.

Another challenge while supplying products to the aerospace industry is that they have really long development and delivery cycles. During this time it is very important that the products produced meet the customer requirements all the time. To ensure this was the case, we developed a simulator test fixture. This fixture simulated the client’s main controller. This could be used to test every single unit once it has been manufactured. This way we ensured we delivered 100% working products to our client all the time.

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