Ask An Expert –Touch sensor into a home/commercial LED Lighting application

by  Steve Sheard  - 06-17-2016 

In the video below one of our touch sensor experts will explain the difference between self-sensing and mutual-sensing touch sensors, as well as implementation methods for LED lighting application. We will demonstrate proximity capabilities and explain how to turn an LED on and off.

Full transcription below.



Question: I am trying to integrate either a touch sensor or proximity sensor into a home/commercial LED Lighting application. What design considerations do I need to consider for each?

Great Question! I’m one of the many application experts here at ON Semiconductor and I have an answer for you. Consumers interact with touch and proximity sensors multiple times a day.

From doors opening and closing at stores to crash prevention sensors in automobiles, touch and proximity sensors provide two key advantages: convenience and safety.

In the past decade, a trend began to start utilizing these types of sensors for commercial and home applications. Before we begin discussing how to implement either a touch proximity sensor into an LED application, we need to understand how sensors work.

Depending on your requirement specifications, you could use any number of methods.

Let me show you one option using a sensor that could be implemented into an LED application as either a touch sensor or proximity sensor for your LED lighting application.

This solution uses a method of detection known as mutual differential-sensing.

With this type of sensing, capacitance is formed between the sensor pad and the excitation pad.

Mutual differential-sensing uses a reference that uses lines of electrical force to communicate with the sensor pad to monitor for irregularities.

When a finger gets close to the sensor pad it hinders the flow of electric flux and reduces the capacitance.

If there is a difference in the magnitude of electric force between the sensor pad and the reference, a response is signaled.

The use of this reference allows the circuit to continuously adapt and prevent Electromagnetic Interference, or (EMI).

This sensor also has flexibility to alter the gain and sensitivity depending on the use of the application to either act as a touch or proximity sensor.

By increasing the gain, the sensor can be used as a proximity sensor and can be covered while not losing its functionality.

Because this proximity sensor can be sealed underneath a panel, it enables the sensor to be UL certified.

What we have here is a touch sensor evaluation board featuring the LC717A10AR that is driving an external LED.

We’re going to use the proximity capabilities of the LC717A10AR to demonstrate how to turn an LED on and off.

We’ll start by setting our touch sensor with a low gain.

As you can see, I have to touch the board to turn on the LED.

Now we’ll switch to a high gain.

Now you can see we are allowed to be a distance away from the board while still turning the LED off and on.

If you liked this video, follow us on your favorite social media account to keep up-to-date with everything related to ON Semiconductor. 

Keep those questions coming. That’s why we’re here – to help you solve your touch sensor design challenges.  Until next time…

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