If you suffer from nostalgia, you might remember carving a block of wood into a car, adding some wheels, and racing it against other contestants in a pinewood derby. Today’s derby is decidedly high tech though, and we were impressed with this car scale that also figures out the car’s center of gravity.

Based on an Arduino, of course, along with a pair of HX711 load cells. Why a pair? That’s how the device measures the center of gravity is by weighing the front and rear of the car separately.

We really liked the wooden case and found the use of wood satisfying if not ironic. Our only input is that since you need the wheelbase of the car to do the CG calculations, we’d have glued a ruler down. On the other hand, probably any self-respecting pinewood derby creator knows their wheelbase by heart.

Why does CG matter? If you are too far forward, you lose some acceleration. If you are too far back, the front wheels might pop up. With this device, you can know exactly where your center is and make adjustments accordingly.

If you’d rather build something for the actual race, why not a photo finish system? Or, perhaps you need a jet-powered (illegal) entry.

Do you need a small weight scale? You can of course buy one, or you could instead make your own 3D-printed device with a load cell and an Arduino, as shown in the below video by MN Maker.

In his setup, the load cell first sends readings to an HX711 breakout board, which converts this analog signal into a digital output that the Nano can easily interpret. The output is displayed on a 0.96” 128×64 OLED, with a button on the back to switch power on and off, and another to tare the scale to zero. 

Code for the project is available here, while print files can be found on Thingiverse.

[Paul] participated in a hackathon at work and created a hack to help solve what was ultimately a people problem. A soda fridge at work wasn’t getting refilled when empty. Instead of trying to make people less lazy, [Paul] went with making the fridge more needy.

The first thing [Paul] did was make a soda fridge refill sensor from a scale. As the fridge got emptier, it got lighter. The scale senses that and can decide it’s time for a refill. The only part missing was how to read the output from the scale. To do that, he took an unusual approach.

The soda fridge sits on an analog scale with a dial. [Paul] saw there was no need to measure the exact weight of the fridge, only to detect a refill threshold. He came up with a simple hack: colored paper attached to the scale’s dial and an Arduino with an OSEPP COLOR‑01 color sensor pointed at the paper. The dial moves in response to the fridge’s changing weight, and the color sensor reads the color of the paper as it moves under the sensor. With a little bit of trial-and-error calibration and some barely modified sample code for the sensor, it was possible to reliably detect when the fridge required refilling. With the sensor done, it was time to use it to solve the lazy people problem.

In a way, the root problem wasn’t that people couldn’t be bothered to check if the fridge needed a refill – it was that the right people weren’t finding out at the right times. This resulted in spotty refilling as well as soda not being ordered when needed. This hack means that the fridge can now actively announce its state, which now allows things like notifying people via email that it is their turn to refill and re-order. It turns out that a fridge that can tell people what it needs has a much better chance of being serviced, compared to a one that has to wait for people to check up on it.

We’ve seen people interface directly to the load sensors in weight scales before, but this hack took a completely different approach.

Thanks to [Paul] for sharing.

Learn how to pull realtime sensor data from a beehive to monitor its weight, temperature, and humidity over the internet.

Read more on MAKE

The post The Internet of Bees: Adding Sensors to Monitor Hive Health appeared first on Make: DIY Projects, How-Tos, Electronics, Crafts and Ideas for Makers.

Stamps.com offers a free USB scale when you sign up for their service. The first versions of this scale did not have a display. In order to find the weight of an object the scale had to be connected to a computer running the stamps.com software. If you happen to have one of these old scales or are able to pick one up cheap, you may be interested in using it outside of the stamps.com service. There are several options on how to do that.

Stamps.com Scale Tool

Although ‘stamps.com’ is in the title, the two are not affiliated. This is a simple program that displays the scales output in both ounces and grams. There are 2 modes, Realtime that constantly updates the displayed output and Snapshot where the ‘Weigh’ button records and displays the weight at that moment.

Stamps.com USB Scale Reader

Here’s another similar Windows-based scale reader program. It claims to work with all stamps.com scale models. This has a unique feature where it hangs out in the system tray and pops up when it detects a change in weight. When an amount is displayed, the 3 lower buttons let you quickly copy the values to the clipboard.

Ultimate Scale

If you don’t own a Windows-based computer and/or you would like to weigh an apple, then Ultimate Scale is for you. This Android App automatically starts when the scale is connected and proceeds to display the weight on your phone. Tapping the main weight text zeros the scale. The amount is also spoken out loud for those too lazy to use their eyes. If you know the density of the object being weighed, this app will also calculate the volume!

Still not enough options for you? We’ve previously covered an Arduino project that displays the scale’s measurement on an LCD screen.