Touchless lavatory applications are becoming increasingly common: automatic flushing assemblies and faucets, soap dispensers and towel dispensers. Silicon Labs has the solution for the key design considerations for touch-free lavatory applications: low power operation to minimize maintenance, designing for various lighting conditions, and increasing end-user ease of use.

Specifically, the Si1141 is a single-channel, reflectance-based proximity detector with an integrated ambient light sensor and can be used as a touchless sensor IC in lavatory appliances. As a proximity detector, the Si1141 has two infrared photodiodes, flexible ADC integration time, and multiple signal ranges. In addition to the configurable ADC sensitivity configuration settings, the Si1141 can dynamically drive an irLED with anywhere from 6 to 400 mA. This high level of flexibility in the ADC, photodiode choice, and irLED drive strength all contribute to allow the end product to operate under various ambient light conditions.

In general, lavatory appliances operate indoors, typically under CFL lighting. However, it is common for these appliances to be exposed to direct sunlight when the product is near a window. Therefore, having the flexibility to allow operation under various light sources is key to making a robust product and helps provide end product differentiation.

Another product feature that makes the Si1141 compelling in touchless lavatory appliances is the low system power. Most touchless lavatory appliances, such as flushers and faucets, are battery operated since power mains are typically unavailable in most lavatory stalls. A lavatory appliance spends much of its time waiting for the target to enter its proximity. Minimizing the current draw from the battery benefits the end product by extending its lifetime use. The Si1141 achieves this low power by taking proximity measurements using a single 25.6 μs irLED pulse instead of performing the multiple pulses commonly used in discrete photodiode approaches.

In addition to the Si1141 proximity and ambient light sensor, Silicon Labs offers an array of low-power MCU devices (C8051F9xx series). When combined, these devices offer best-in-class, low-power operation. In general, lavatory appliances are subdivided into the following categories:

• Lavatory flushers
• Lavatory faucets
• Soap dispensers

These assemblies are typically battery powered since a power plug is generally not available nearby. Toilet flushers generally aim to detect the presence of a human body, while faucets and soap dispensers are designed to detect the presence of hands. All of these application uses are similar in that the proximity detector generates an action, typically the driving of a motor.

The Si114x infrared multi-function board (IRMFB-EK) demonstrates the flexibility and configurability of the Si114x product family, the industry’s lowest power, longest range, multi-LED optical sensors. The two sides of the board exhibit distinctly different functions:

• The top side boasts an Si1143 three irLED “thumbscroll” implementation which allows a user to swipe over the sense array and navigate a 3 mm x 3 mm array of blue LED’s. A tap to select gesture is also supported on this thumbscroll demo which blinks the selected LED.
• The back of the board features a Si1141 single irLED range detection demo capable of sensing distances up to 30 cm for a hand and up to a meter for a torso. The blue LED array on the long range demo progressively lights up as a detectable object moves closer to the sensor.

The board illustrates the configurability of the Si114x product family, the industry’s lowest power, longest range, multi-LED drive optical sensors.