And the Grandfather of the Year Award Goes to…

Hacker dads often have great plans for all the fun projects they’ll build for their kids. Reality often intrudes, though, creating opportunities for hacker grandfathers who might have more time and resources to tackle the truly epic kid hacks. Take, for instance, [rwreagan] and the quarter-scale model railroad he built for his granddaughter.

Taking inspiration from a 1965 issue of Popular Mechanics, grandpa hit this one out of the park. Attention to detail and craftsmanship are evident from the cowcatcher to the rear coupler of this 4-2-0 steam engine replica, and everywhere along the 275 feet of wooden track — that’s almost a quarter-mile at scale. The locomotive runs on composite wood and metal flanged wheels powered by pair of 350-watt motors and some 12-volt batteries; alas, no steam. The loco winds around [rwreagan]’s yard through a right-of-way cut into the woods and into a custom-built engine house that’ll make a great playhouse. And there are even Arduino-controlled crossbucks at the grade crossing he uses for his tractor on lawn mowing days.

The only question here is: will his granddaughter have as much fun using it as he had building it? We’ll guess yes because it looks like a blast all around. Other awesome dad builds we’ve covered include this backyard roller coaster and a rocketship treehouse.

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Join Hackaday And Tindie At The Southern California Linux Expo

Do you like Open Source? Join Hackaday and Tindie at the largest community-run Open Source conference in North America. We’ll be at the Southern California Linux Expo next week, and we want to see you there.

What’s happening at SCALE this year? Amateur radio license exams, a PGP signing party, Bad Voltage Live and The Spazmatics, and a ton of great talks.

Hackaday and Tindie will be at SCALE Friday through Sunday, showing off the coolest parts of Hackaday, Hackaday.io, and our lovable robotic dog, Tindie. We’ll be handing out t-shirts and stickers, and we’ll be giving tours of the SupplyFrame Design Lab located just two blocks away from the convention center. The Design Lab is a crown jewel of our corporate overlord’s emphasis on Open Hardware, and if you want to see where the magic happens, this is your chance. We’ll be running tours of the Lab on Friday, so find the Hackaday and Tindie crew in the expo area around 3:40 PM.

Here’s something cool: We’re offering discounted SCALE passes, too. They’re 50% off using the code ‘HACK’ at this link. That’s $45 for four days of fun. Continue reading “Join Hackaday And Tindie At The Southern California Linux Expo”

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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Weight Tracking, Wise Cracking IoT Bathroom Scale

For those fighting the battle of the bulge, the forced discipline of fitness bands and activity tracking software might not be enough motivation. Some who are slimming down need a little gentle encouragement to help you lose weight and keep it off. If that sounds like you, then by all means avoid building this weight-tracking IoT scale with an attitude.

Then again, if you live in fear of your scale, [Jamie Bailey]’s version is easy to hate, at least when your numbers are going in the wrong direction. Centered around a second-hand Wii Balance Board talking to a Raspberry Pi via Bluetooth, the scale really only captures your weight and sends it up to InitialState for tracking and feedback. Whether the feedback is in the form of jokes at your expense is, of course, is entirely up to you; if you’d rather get gentle nudges and daily affirmations, just edit a few files. Or if your tastes run more toward “Yo momma so fat” jokes, have at it.

Bathroom scales are a good hacking target, whether it’s reverse engineering a digital scale or eavesdropping on a smart scale. This build is snarky good fun, and if nothing else, it’s good for pranking your roommate. Unless your roommate is your husband or wife, of course. That’s just – no.

Instrumentation Amplifiers and How to Measure Miniscule Change

These days there a large number of sensors and analog circuits that are “controller friendly” meaning that their output signal is easily interfaced to the built-in Analog to Digital Convertors (ADCs) often found in today’s micro-controllers. This means that the signals typically are already amplified, often filtered, and corrected for offset and linearity. But when faced with very low level signals, or signals buried in a larger signal an Instrumentation Amplifier may be what’s needed. The qualities of an Instrumentation Amplifier include:

  • A differential amplifier with high impedance and low bias current on both inputs.
  • Low noise and low drift when amplifying very small signals.
  • The ability to reject a voltage that is present on both inputs, referred to as Common Mode Rejection Ratio (CMRR)

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How to Weigh an Eyelash

So you’re a boxer, and you’re weighing in just 80 micrograms too much for your usual weight class. How many eyelashes do you need to pluck out to get back in the ring? Or maybe you’re following the newest diet fad, “microcooking”, and a recipe calls for 750 micrograms of sugar, and you need to know how many grains that is. You need a microgram scale.

OK, we can’t really come up with a good reason to weigh an eyelash, except to say that you did. Anyway, not one but two separate YouTube videos show you how to build a microgram balance out of the mechanism in a panel meter. You know, the kind with the swinging pointer that they used to use before digital?

Panel meters are essentially an electromagnet on a spring in the field of a permanent magnet (a galvanometer). When no current flows through the electromagnet, the spring pulls the needle far left. As you push current through the electromagnet, it is attracted to the fixed permanent magnet, fighting the spring, and tugs the pointer over to the right. More current equals more pull.

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Fixing a Broken Postage Scale

[Starhawk] had an old Pitney Bowes G799 postage scale that wasn’t working as it should. After years of faithfully measuring packages and cooking ingredients, the scale stopped working. At first it fell out of calibration. Then the power up sequence stopped working. The scale normally would turn on, light up the entire display, then change to dashes, and finally set itself to 0.0 lbs. In this case, it would get stuck at the dashes and never change to 0.0.

[Starhawk] ended up purchasing another duplicate scale from eBay, only to find that when it arrived it had the exact same power up problem. Using deductive reasoning, he decided that since the scale was broken during shipping the problem would likely be with a mechanical component. He turned out to be correct. The cheap momentary power button was at fault. When pressing the button, the contact would get stuck closed preventing the scale from zeroing out properly. [Starhawk] easily fixed his problem by replacing the switch.

Next [Starhawk] replaced the old scale’s LCD module with one from the new scale, since the old one looked to be on its way out. The scale still had a problem correctly measuring weight. [Starhawk] tried swapping the load cell from the new scale to the old one, but he found that the new load cell had some kind of problem that prevented the scale from zeroing out properly. The solution ended up being to use the newer “analog board” as [Starhawk] calls it.  The end result was the old scale with two newer circuit boards, an older load cell, and a new power switch. Next time it might be easier to just build his own scale.