How to build a Solar Powered Clock

We now know that the ancient Egyptian civilization had the knowledge to build a solar powered clock even as early as the 13th century B.C. Before the discovery of the Valley of Kings sundial, it was thought that the solar clock was only in use since the 4th century B.C. That’s nearly 1,000 years later.

Today, you can also make one of these extraordinary gadgets yourself. All you need are a few basic supplies, a rough idea of the type of clock you want to make, and a bit of patience.

How many types of Solar Powered Clocks are there?

Although ancient civilizations used outdoor solar clocks, you needn’t restrict yourself to this type. Sure, there’s a rustic charm to adding a sun dial to your garden, both for decorative and utility purposes. In the summer, you’ll be able to tell what time it is without checking your phone or having a solar wristwatch on.

Imagine lying in your hammock, dozing off, and knowing exactly what the time is when you wake up. Like solar calculators, these solar clocks are also incredibly cheap to make. The odds are you already have everything you need lying around the house or in your closet.

However, there’s plenty of affordable technology that you can readily repurpose to make a 21st century solar powered clock. If you happen to want a specific type of alarm clock, like a device that has a backlight on, for instance, you can easily convert a regular, battery-powered clock. You can do this with your child, too. It will often take less than an hour to make the upgrade, not to mention the fact that it’s an invaluable educative and bonding experience. Afterwards, they can repeat the experiment for a class science project.

How Does a Solar Powered Clock Work?

Like solar dancing toys, a solar clock works similarly to a mechanical or battery powered one, with the difference that the energy is produced by the sun. In order to harness the latter, we need a photovoltaic (PV) cell. These solar cells are sensitive to light, which means they produce a small electric charge when exposed to the sun.

Although artificial light can also achieve this, the sun’s rays are much more powerful. If you want to make sure the clock has energy to run 24/7, the best way to do this is to connect the solar cell to a rechargeable battery that can store excess energy. This way, the battery can power the clock when there’s no light around.


What You Need to Make a Solar Clock?

You can easily convert any regular wall or alarm timer into a solar powered clock with a few basic supplies. Here’s what you’ll need:

  • A model that runs on a single AA battery. You could do it with those that have two as well, but it’s slightly more complicated.
  • Several basic tools – a screwdriver, electrical tape, and a cutter. Although optional, a soldering iron and a heat shrink can help a lot.
  • A cheap solar-powered garden light that has a small solar cell.

After you’ve gathered your supplies, this is what you should do next:

  1. Get the necessary parts from the solar garden lamp. With a screwdriver, open the latter’s case and remove the battery. This is the rechargeable accumulator that will store excess sun energy to be used by the solar powered clock during the night.
  2. Once the battery is out, the next step is to recover the solar cell itself. The latter should have two wires going into it, a positive (+) and a negative (-) one. Cut these two leads as close to the circuit board as possible, so as to have a bit of wire length available for the clock.
  3. Remove the PV cell from its case. Depending on the model, you might need a screwdriver, cutter, or just a bit of force to pry it out. The plastic surrounding it is useless, but the cell itself is quite fragile, so take good care of it.
  4. Keep the switch and the LED light from the lamp – they will definitely be useful for other projects in the future.

Building the Solar Clock

Now that you have everything you need, it’s time to build the solar timer. First, put the rechargeable AA battery into the donor clock. Then, wedge the contacts from the solar cell between the two ends of the battery and the clock’s contacts. The negative contact from the small PV panel (if you’re looking for a guide to building your own solar cell, click the preceding link) usually has a spring on it, which you can go ahead and remove.

At this point, you should decide where you want the clock to be. If you plan on hanging it in a window, then you just need to stick the cell above the battery and you’re good to go. Otherwise, you might have to get a little creative in order to fixate the solar cell on top, underneath, or on the side of the clock. You can just as easily stick it to the front of the clock if you have a longer wire or don’t mind drilling two small holes for the wires to reach behind.

That’s it! You now have a 21st century solar clock whose battery does not need replacing. The same instructions can be followed with more complex chronographs, such as the ones with digital display.

How Does an Outdoor Solar Clock Work?

To make an outdoor solar clock, you need even fewer supplies than we’ve mentioned so far. If they managed to do it in the first millennium B.C., we can definitely do it today. The problem with this type is that it’s not as reliable. For instance, you can’t tell the time when there’s no sunlight or during the night. Although there are many types of sundials, they all work according to the same principle.

Each of them consist of a gnomon (a thin rod, stick, you name it) that casts a shadow onto a dial. The latter is drawn or marked onto a flat, immovable surface. As the sun’s position changes relative to the sundial, the rod casts a shadow that marks the passage of time.


How to Make a Sundial?

In order to make an outdoor solar clock, you need a fairly open space area. Make sure there’s nothing around that can cast a shadow or prevent the sun from reaching it. Your yard, lawn or concrete sidewalk are all viable choices. The sundial is entirely dependent on your geographic position, which means it will only be accurate for the place you live in and its nearby surroundings. To do this as accurately as possible, it’s best to rise early, preferably no later than 8 A.M.

After you’ve chosen the place where you’ll build your future outdoor solar clock, get a hammer, a pencil, a flat white surface (such as a piece of sturdy cardboard), and a nail. Place your board in the open space as early as possible and secure it with several tiny rocks or weighted objects. Next, hammer a nail in the center of your surface.

At regular time intervals, i.e. at 8 A.M., 8:30, 9:00, and so on, mark the place where the nail casts a shadow onto the cardboard, writing down the exact hour on it, until the sun goes down. Eureka! Now you can tell the time in your geographic location as long as there’s light outside. If you draw a perfect circle around the hour markers, you’ll notice that this is the semi-circular version of an outdoor solar clock, since it shows the time only on half of the circle.

In order to achieve a circular dial, you need to make sure that your gnomon (the nail in the center) sits at an angle. To determine the latter, you need to start from your geographic position. If you happen to live in the region of the equator, the gnomon’s angle from the board must be parallel to the Earth’s axis – so all you need to know is your latitude. If you’re in LA, this is 34 degrees, while for Seattle, it’s 47.

DIY Solar Clocks

Solar powered clocks are a great way to experiment with time-keeping technology, both new and old. Whether you have a clock and a solar garden light lying around or you only have a nail and a piece of cardboard, you can make your very own solar clock with minimal effort. All you need is a bit of patience and a sunny day. The outdoor clocks are a great way to tell the time according to the diurnal cycle. Naturally, the later changes as the Earth moves closer or further away from the Sun.

If you’re repurposing an older alarm clock to use solar energy, this is a great learning opportunity for young children. By spending time together in this manner, they’ll find out how solar power works, as well as how to recycle things they no longer use. Later on, they can attempt the project on their own for a class science assignment and, perhaps, improve on this design by getting more creative with the aesthetics or by using more rigorous measurements. (Looking for other cool solar-powered devices? Check out our list of our favorite solar showers!)