Minimal MQTT: Power And Privacy

June 2, 2016 by Elliot Williams 43 Comments

In this installment of Minimal MQTT, I’m going to cover two loose ends: one on the sensor node side, and one on the MQTT server side. Specifically, I’ll tackle the NodeMCU’s sleep mode to reduce power and step you through bridging MQTT servers to get your data securely out of your home server and into “the cloud”, which is really just other people’s servers.

If you’re just stepping into this series now, you should really check out the other three posts, where I set up a server, then build up some sensor nodes, and then flesh-out a few ways to control everything from your phone or the web. That’s the coolest material, anyway. This last installment just refines what we’ve built on. Let’s go!

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Shipwreck Exploration Vessels Fit In Minivan; Stream To Internet

June 2, 2016 by Donald Papp 2 Comments

Having to work away from the convenience of a workshop can be tough. But it’s sometimes unavoidable and it always means planning ahead. When the work area also happens to be 150m under a lake’s surface, it’s much more of a challenge – but it’s both doable and more accessible than you might think. To prove it, this DIY research vessel will be part of the robotic exploration of an underwater shipwreck. It is complete with an Ethernet bridge, long-range wireless communications, remotely operated underwater vehicle (ROV), the ability to hold a position, and more. The best part? It can all be packed up and fit into a minivan. We can’t put it any better than the folks at the OpenROV Forums:

In just over a week (June 6th – 9th), a bunch of people from OpenROV are going to attempt to dive a set of specially modified deep-capable ROVs to a 50m-long shipwreck at a depth of 150m below lake Tahoe. We’ll be using a deployment architecture that we’ve been perfecting over the years that involves a very small boat keeping station over the dive site while the rest of the people on the expedition run the mission from a remote location via long-range broadband radio. Since the mission control site will have an internet connection, we’ll be able to live stream the entire dive over the internet.

The purpose of the design was “to demonstrate that many of the capabilities one might think would require a large research vessel can actually be achieved with off-the-shelf parts that are more portable and much less expensive. […] There’s a lot to discover down there, and the technology readily available these days can allow us to explore it.” This mindset happens to wonderfully complement the kickoff of the Citizen Scientist Challenge portion of the 2016 Hackaday Prize.

For those times when your work can remain on solid ground, one method is to sidestep the entire issue of working away from the workshop by simply making your whole work area mobile like this incredible conversion of a truck trailer to a mobile lab.

Hackaday Meetup In The Middle Of Nowhere

June 2, 2016 by Brian Benchoff 21 Comments

Come one, come all, as the Hackaday community gathers at the childhood home of the worst president of the United States of America. Raise a glass, feast on roast pig, and don’t forget to Bring-A-Hack to show and tell. We’ll give away Hackaday Omnibus, stickers, and as a very special door prize a few people are going to walk away with a Raspberry Pi Zero.

The preamble about not-so-great heads of state is due to the venue. This gala is at the James Buchanan Pub & Restaurant in Mercersburg, PA on Sunday, June 5th, starting at 3PM. But that doesn’t really answer the question of why Mercersburg, does it? This is the location of one of the Hackaday World Create Day meetups. It caught my eye and since I live only 20 minutes away this is a great time for another get together.

Let’s fill the place with south central Pennsylvania’s greatest hardware hackers. There will be food, alcohol, and interesting people to talk to.

Tools Of The Trade – Reflow

June 2, 2016 by Bob Baddeley 40 Comments

In our previous issues in this series on making circuit boards, we covered placing solder paste and placing components. Now it’s time to bake our cake!

There are a variety of methods for reflowing a circuit board, but they all rely on a single principle: heat up the solder paste (a mixture of flux and solder) until the flux burns off and the solder becomes liquid, and then cool it down. Accomplishing this once or twice is easy; once you’ve played with a hot plate you’ll swear off through hole. Scaling it up and doing it repeatedly with high yield is extremely challenging, though. Continue reading “Tools Of The Trade – Reflow” →

Safely Creating A Li-Ion Pack From Phone Cells

June 2, 2016 by Jenny List 47 Comments

[Glen], at Maker Space Newcastle Upon Tyne, is refreshingly honest. As he puts it, he’s too cheap to buy a proper battery.

He needed a 1AH battery pack to power his quadcopter controller and FPV headset, and since inadequate discharge warnings had led him to damage lithium polymer cells with these devices, he wanted his pack to use lithium-ion cells. His requirements were that the cells be as cheap, lightweight, and small as possible, so to satisfy them he turned to a stack of mobile phone cells. Nokia BL-4U cells could be had for under a pound ($1.46) including delivery, so they certainly satisfied his requirement for cheapness.

It might seem a simple procedure, to put together a battery pack, and in terms of physical wiring it certainly is. But lithium-ion cells are not simply connected together in the way dry cells are, to avoid a significant fire risk they need to have the voltage of each individual cell monitored with a special balanced charger. Thus each cell junction needs to be brought out to another connector to the charger.

[Glen]’s write-up takes the reader through all the requirements of safe lithium-ion pack construction and charging, and is a useful read for any lithium-ion newbies. If nothing else it serves as a useful reminder that mobile phone cells can be surprisingly cheap.

Lithium cells have captured our attention before here at Hackaday. Our recent Hackaday Dictionary piece provides a comprehensive primer, we’ve featured another multi-cell build, and an interesting app note from Maxim for a battery manager chip.

Feeding The Cat, Reinventing The Wheel

June 2, 2016 by Elliot Williams 32 Comments

There are few projects that we see as many iterations of as the pet feeder or the plant waterer. (What is it with you people? Are you all as forgetful as we are?) Still, the fun is in the details of the implementation. Or at least that’s the case with [Emmaanuel]’s cat feeder.

The writeup is split into three parts: the worm-drive, the electronics, and the housing (here in English: worm, electronics, housing). And of course, there’s a video inlined below.

The auger and motor housing make great use of PVC pipe and 3D printing, and the dispenser unit looks quite professional. There’s not all that much to say about the electronics — an Arduino clone, an LCD, and a cheap gear motor do just about what you’d expect.

The CNC’ed case with spring-fit tabs steals the show, however. It’s made out of MDF, which doesn’t take well to screwing or glueing. With carefully routed pins and tabs that have a little spring in them, [Emmaanuel] was able to take the pieces off the mill table and just snap them together. Awesome.

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Hackaday Prize Entry: You Know, For Kids

June 1, 2016 by Elliot Williams 17 Comments

Like the fictitious invention of the Hula Hoop in Hudsucker Proxy, [David Spinden]’s big idea is small and obvious once you’ve seen it. And we’re not saying that’s a bad thing at all. What he’s done is to make a new kind of prototyping connector; one that hooks into a through-plated hole like a pogo pin, but in the horizontal direction.

This means that your test-points can do double duty as header connectors, when you need to make something more permanent, or vice-versa. That’s a lot of flexibility for a little wire, and it takes one more (mildly annoying) step out of prototyping — populating headers.

[David] makes them out of readily available header pins that already have the desired spring-like profile, and simply cuts them out and connects them to a standard Dupont-style hookup wire. Great stuff.

When we opened up the “Anything Goes” category for the Hackaday Prize, we meant it. We’re excited to see people entering large and small ideas that improve the world, even if it’s just the world of hackers.

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