Current Sensor Makes Intriguing Use Of Concrete

Getting a product to market isn’t all about making sure that the product does what it’s supposed to. Granted, most of us will spend most of our time focusing on the functionality of our projects and less on the form, fit, or finish of the final product, especially for one-off builds that won’t get replicated. For those builds that do eventually leave the prototyping phase, though, a lot more effort goes into the final design and “feel” of the product than we might otherwise think. For example, this current sensor improves its feel by making use of cast concrete in its case.

The current sensor in this build is not too much out of the ordinary. [kevarek] built the sensor around the MCA1101-50-3 chip and added some extra features to improve its electrostatic discharge resistance and also to improve its electromagnetic compatibility over and above the recommended datasheet specifications. The custom case is where this one small detail popped out at us that we haven’t really seen much of before, though. [kevarek] mixed up a small batch of concrete to pour into the case simply because it feels better to have a weightier final product.

While he doesn’t mention building this current sensor to sell to a wider audience, this is exactly something that a final marketable product might have within itself to improve the way the device feels. Heavier things are associated, perhaps subconsciously, with higher quality, and since PCBs and plastic casings don’t weigh much on their own many manufacturers will add dummy weights to improve the relationship between weight and quality. Even though this modification is entirely separate from the function of the product, it’s not uncommon for small changes in design to have a measurable impact on performance, even when the original product remains unmodified.

Thanks to [Saabman] for the tip!

Cheap Lab Balance Needs Upgrades, Gets Gutted Instead

What is this world coming to when you spend seven bucks on a digital scale and you have to completely rebuild it to get the functionality you need? Is nothing sacred anymore?

Such were the straits [Jan Henrik] found himself in with his AliExpress special, a portable digital scale that certainly looks like it’s capable of its basic task. Sadly, though, [Jan] was looking for a few more digits of resolution and a lot more in the way of hackability. And so literally almost every original component was ripped out of the scale, replaced by a custom PCB carrying an STM32 microcontroller and OLED display. The PCB has a complicated shape that allows the original lid to attach to it, as well as the stainless steel pan and load cell. [Jan] developed new firmware that fixes some annoying traits, for example powering down after 30 seconds, and adds new functionality, such as piece-counting by weight. The video below shows some of the new features in action.

Alas, [Jan ] reports that even the original load cell must go, as it lacks the accuracy his application requires. So he’ll essentially end up building the scale from scratch, which we respect, of course. At this rate, he might even try to build his own load cell from SMD resistors too.

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Let Your Pi Make A Pie Chart For Your Pie

March 14th is “Pi Day”, for reasons which should be obvious to our more mathematically inclined readers. As you are not reading this post on March 14th, that must mean we’re either fashionably late to Pi Day 2019, or exceptionally early for Pi Day 2020. But in either event, we’ve got a hack for you that celebrates the day using two things we have it on good authority most hackers overindulge in: food and needless complexity.

This project comes from [Mike MacHenry], and it’s just as straightforward as it looks. Put simply, he’s using a load cell connected to the Raspberry Pi to weigh an actual pie and monitor its change over time. As the pie is consumed by hungry hackers, a pie graph (what else?) is rendered on the attached screen to show you how much of the dessert is left.

One might say that this project takes a three dimensional pie and converts it to a two dimensional facsimile, but perhaps that’s over-analyzing it. In reality, it was a fun little hack [Mike] put together just because he thought it would be fun. Which is certainly enough of a motive for us. More practically though, if you’re looking for a good example for how to get a load cell talking to your non-edible Raspberry Pi, you could do worse than checking this out.

We’ve also got to give [Mike] extra credit for including the recipe and procedure for actually baking the apple pie used in the project. While we’re not 100% sure the MIT license [Mike] used is actually valid for foodstuffs, but believe it or not this isn’t the first time we’ve seen Git used in the production of baked goods.

Dumb Box? Make It Really Smart!

[Stephen Harrison]’s Really Smart Box is a great concept, it’s simultaneously a simple idea while at the same time being super clever. The Really Smart Box isn’t really a box; it’s a drop-in platform that can be made any size, intended to turn any dumb storage box into one that helps manage and track levels and usage of any sort of stock or consumable.

It does this by measuring the weight of the stuff piled on top of it, while also monitoring temperature and humidity. The platform communicates this information wirelessly to a back end, allowing decisions to be made about stock levels, usage, and monitoring of storage conditions. It’s clearly best applied to consumables or other stock that comes and goes. The Really Smart Box platform is battery-powered, but spends most of its time asleep to maximize battery life. The prototype uses the SigFox IoT framework for the wireless data, which we have seen before in a wireless swimming pool monitor.

This is still just a prototype and there are bugs to iron out, but it works and [Stephen] intends to set-and-forget the prototype into the Cambridge Makespace with the task of storing and monitoring 3D printer filament. A brief demo video is embedded below.

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Load Cells Tell You To Lay Off The Donuts

Our old algebra teacher used to say, “You have to take what you know and use it to get what you don’t know.” That saying always reminds of us sensors that convert physical quantities into things our microcontrollers can measure. Sometimes the key to a project is knowing what kind of sensor will read the physical properties of the system you are interested in. If that physical property is weight, you can use what is known as a load cell. [DegrawSt] uses four 50 kg load cells to create a bathroom scale using an Arduino.

Load cells typically contain strain gauges that change resistance when deformed. This actually measures force, but if you mount them so they measure the force exerted by you standing on a platform, you get a scale. A load cell usually has four strain gauges in a bridge configuration. This causes a voltage across the bridge, although the output can be noisy and on the order of millivolts.

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Turn Down The Bed, Turn Down The Lights

Home automation seems to be working its way to a computer-controlled future in which humans will be little more than an afterthought. Eventually they will take over Skynet-style, but until then, we will enjoy the relative comfort that a good home automation project provides. The latest from [Clement] certainly goes a long way towards this goal by automating his bed (Google Translate from French).

With four load cells and a microcontroller, [Clement]’s bed can tell whether or not he is sleeping. After taking a weight reading, the bed can send commands to the rest of his home automation system and tell it to turn off his stereo and turn the lights off in the house (or change them to a different color). And it doesn’t stop with just going to bed, but when he wakes up as well. The system can begin turning on lights, starting the coffee machine, and opening the blinds without any interaction from him at all.

This project goes well beyond simple home automation. With a little configuration and extrapolation, [Clement] can tell where in the bed he slept at night, what stages of sleep he was in at specific times, and the overall quality of his sleep. This could go a long way for someone who has a hard time sleeping and needs a little more information on how to correct the problem.

While we’ve seen various takes on tying a bed into one’s home automation system, this one goes above and beyond with the amount of data collected. You could even go one step further and have it turn on some Barry White if the normal weight in the bed suddenly doubles, for whatever reason. Maybe that will be a feature in Version 2.

Soda Fridge Hack To Fix A Lazy People Problem

[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.
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