Planet Arduino

Some sundials are as simple as a stick pushed into the dirt, but they’re still reliable and accurate. The sun is, after all, quite consistent. But there are some caveats. The Earth’s orbit and its rotational tilt mean that the lengths of our days are variable and that means the simplest sundials are only perfectly accurate once a year. To compensate for those factors, Redditor Onemywaybackhome built this sundial that is capable of self-correction.

This sundial automatically compensates for the difference between solar noon (the time at which the sun is at its highest point) and civil noon (the time when the local clock is at 1200). Solar noon is dependent on the exact location on the planet’s surface. This sundial stays in a fixed location, so that variable in the solar noon calculation is known. The other important variable is the date. With the location and date, this sundial knows how to adjust itself so that it reads noon at the same time as a local clock.

The device uses a real-time clock (RTC) to keep track of the date, which is ironic, because it knows the time. An Arduino Nano board uses the data from the RTC in its adjustment calculation. It adjusts the dial using a small 28BYJ-48 stepper motor. Power comes from a battery and a solar panel keeps that battery charged. The sundial’s frame and enclosure are a combination of laser-cut and 3D-printed parts.

The post This sundial adjusts itself to compensate for daylight savings time and more appeared first on Arduino Blog.

Sundials, one of humanity’s oldest ways of telling time, are typically permanent installations. The very good reason for this is that telling time by the sun with any degree of accuracy requires two-dimensional calibration — once for cardinal direction, and the other for local latitude.

[poblocki1982] is an amateur astronomer and semi-professional sundial enthusiast who took the time to make a self-calibrating equatorial ‘dial that can be used anywhere the sun shines. All this solar beauty needs is a level surface and a few seconds to find its bearings.

Switch it on, set it down, and the sundial spins around on a continuous-rotation servo until the HMC5883L compass module finds the north-south orientation. Then the GPS module determines the latitude, and a 180° servo pans the plate until it finds the ideal position. Everything is controlled with an Arduino Nano and runs on a 9V battery, although we’d love to see it run on solar power someday. Or would that be flying too close to the sun? Check out how fast this thing calibrates itself in the short demo after the break.

Not quite portable enough for you? Here’s a reverse sundial you wear on your wrist.