Facebook cofounder Mark Zuckerberg has built a wooden "sleep box" that emits a faint light in the early morning, to alert his wife when it's time to wake up without looking at her phone.

The device is a small wooden box that can be placed on a bedside table. The base of the box is raised roughly a centimetre above the table surface, to allow a faint light to shine out.

The box emits a soft light for an hour each morning, between 6am and 7am, to let his wife Priscilla know whether it's time to get up and check on their children, without resorting to looking at the time on her phone.

Box designed to not wake you up

"Being a mom is hard, and since we've had kids Priscilla has had a hard time sleeping through the night," said Zuckerberg in a post on Instagram, which is owned by Facebook.

"She'll wake up and check the time on her phone to see if the kids might wake up soon, but then knowing the time stresses her out and she can't fall back asleep."

View this post on Instagram A post shared by Mark Zuckerberg (@zuck) on Apr 27, 2019 at 9:45am PDT

The device isn't intended to wake the user. Instead, when Zuckerberg's wife wakes during the night and the sleep box isn't glowing, she knows that it's not yet time to get out of bed and can fall back to sleep more easily not knowing the time.

"Since it doesn't show the time, if she wakes up in the middle of the night, she knows to just go back to sleep without having to worry about what time it is," said Zuckerberg in the post.

"So far this has worked better than I expected and she can now sleep through the night."

Idea could be put into production

Zuckerberg goes on to suggest that entrepreneurs may want to turn his idea into a business, as "a bunch of my friends have told me they'd want something like this".

"As an engineer, building a device to help my partner sleep better is one of the best ways I can think of to express my love and gratitude," he said.

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Many designers and manufacturers have worked on products that aim to help users get to sleep, or stay asleep.

Nokia produced a sleep sensor that tracks slumber patterns and adjusts the lighting and temperature in the bedroom, whilst Bryte created a bed with smart technology that makes adjustments for optimum sleep.

Photo of Mark Zuckerberg is by Anthony Quintano/Wikimedia Commons.