Bad Thermal Design And Burning Down The House

Control boards for 3D printers are a dime a dozen on the usual online marketplaces, and you usually get what you pay for. These boards can burn down your house thanks to a few terrible design choices. [Scott Rider] aka [Crow] took a look at the popular Melzi board, and what he found was horrifying. These boards overheat right at the connector for the heated bed, but the good news is these problems are easily fixed.

The Melzi board has a few problems with its PCB design. The first and most glaring issue is the use of thermals on the pads for the heated bed connector. In low-power applications, thermals — the method of not connecting the entire top or bottom layer to a hole or pad — are a great idea. It makes it easier to solder, because heat isn’t transmitted as easily to the entire copper layer. Unfortunately, this means heat isn’t transmitted as easily to the entire copper layer. In high-power applications, like a connection to a heated bed, these thermals can heat up enough to melt a plastic connector. Once that happens, it’s game over.

Other problems were found in the Melzi board, although you wouldn’t know it just by looking at the Eagle file of the PCB. [Scott]’s Chinesium Melzi board used 1-ounce copper, where 2-ounce copper would be more appropriate. The connector, too, should be rated above the design power loading.

[Scott] made a few tweaks to the board and also added a tiny DS1822Z temperature sensor to the high-current area of his version of a Melzi. Imagine that, 3D printer electronics with a temperature sensor. Slowly but surely, the state of 3D printer electronics is clawing its way to the present.

20kW Light Is As Bright As You’d Expect

[Photonicinduction] purchased a very very bright light. This 20,000 Watt half meter tall halogen will just about light the back of a person’s skull with their eyes closed. These are typically used to light film sets.

Most people couldn’t even turn such a light on, but [Photonicinduction] is a mad scientist. Making lightning in his attic, it’s easy to mentally picture him as the villain in a Sherlock Holmes novel. Luckily for us, if he has any evil tendencies, they are channeled into YouTube videos.

He gives a good description of the mechanical and electrical properties of the light. The body is as one would expect for an incandescent light. A glass filament envelope with the filaments supported within. The envelope is evacuated and filled with an appropriate gas. This light is dangerous enough that the outside must be thoroughly cleaned of fingerprints to keep a hot-spot from forming, which could cause the lamp to explode.

After some work, he managed to convince himself that the filaments within were not, in fact, garage door springs, and gave a demonstration of their properties. For example, their resistance goes up as they are heated. In order to keep from tripping the power supply, filaments this large must be preheated. Failure to do so passes a very large number of amps.

The next step was to hook the lamp up to his home-made 20 kW power supply. He gives a good demonstration of just how bright it is. Within seconds he’s sweating from the heat and definitely can’t even open his eyes to see with the tiny sun occupying the center of his abode. Video after the break.

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Hacklet 92 – Workbenches and Toolboxes

Everyone needs a place to work. While some of us have well equipped labs with soldering stations, oscilloscopes, and a myriad of other tools, others perform their hacks on the kitchen table. Still, some hackers have to be on the go – taking their tools and work space along with them on the road. This week’s Hacklet is all about the best toolbox and workbench projects on!

worktableWe start at the top – in this case, a bench top. [KickSucker] created Mondrian Inspired Work Table as a multi-use tabletop for all kinds of projects. Rather than slap down a piece of plywood, [KickSucker] took a more artistic route. Piet Mondrian was a dutch artist known for painting irregular grids of black and white lines. He’d fill a few of the rectangles up with primary colors, but leave most of them white. Between different off-cuts of wood, and colorful bits of skateboard deck [KickSucker] had the makings of an awesome work surface. The frame of the bench is an IKEA expedite shelf unit. The frame is made from MDF, with the offcuts laid on top of it. The fun part was arranging all the pieces to make lines and colors. The result is a great custom work table, and a heck of a lot less wood scraps lying around the shop. That’s a double win in our book!

toolboxNext up is [M.Hehr] with Portable Workbench & mini Lab. [M.Hehr] has wanted a portable electronic workstation for years. We’re betting he’s seen a few of them here on the blog. While cleaning up the lab before Christmas, [M.Hehr] found a couple of wooden IKEA boxes. Each box held some drawers. An idea formed in [M.Hehr’s] head. It was time to put the plan in motion! The boxes were attached and hinged. Custom brackets were cut on a Shapeoko 2 router. Everything – even the screws were recycled. [M.Hehr] created a perfect space for each tool, ensuring that things won’t end up in a tangled mess when the box is carried around. We really love the retractable power point and custom-made power supply!

roadcaseNext we’ve got [Tim Trzepacz] with Musician’s Road Box with 9 space rack. [Tim’s] sister [Tina] was playing a lot of music on the road, and needed a way to organize her gear. There are plenty of commercial solutions for this, but [Tim] decided to roll the perfect solution. He designed a plywood box with a 9U rack. [Tina’s] mixer and backing sound sources were located on the top, while effects and other modules were located in the rack. [Tim] spent a good amount of time designing the box. He was able to get the cut list down to a single piece of plywood, with room to spare. This is perfect for a 4′ x 8′ router like the ShopBot. When it comes time to hit the road, the case seals up to a rugged package. Standard roadcase corners and twist-latches finish this awesome piece.

boxtopFinally we have [Géllo] with protoBox. [Géllo] is into induction heating, which requires a Zero Voltage Switching (ZVS) flyback driver. ProtoBox started life as a place for [Géllo] to store his ZVS. It has evolved to become a small portable electronics lab. [Géllo] powers the box with a set of lithium-ion batteries sourced from old laptops. This particular ZVS design is plenty powerful enough to heat metal red hot, or create some nice arcs. [Géllo] added an Arduino Mega, a Bluetooth radio, and a 2×16 character LCD. The system is controlled with relays. A bluetooth enabled smartphone can be used to enable or disable any feature. [Géllo’s] assembly techniques are a bit scary, especially considering the fact that this is a high power design. However, this is a great proof of concept!

If you want to see more workbench and toolbox projects, check out our new workbench and toolbox list! If I missed your project, don’t be shy! Just drop me a message on That’s it for this week’s Hacklet. As always, see you next week. Same hack time, same hack channel, bringing you the best of!

Intense Brushless DC Stage Brings More E-Bike Power

[ZombieSS] wrote in to share the latest iteration of his new open hardware Brushless DC motor high power output stage posted on the Endless-sphere forums. The thread is a gold mine of useful information on designing, building and debugging high power electronics and the whole thing is worth reading. This includes the story of issues he faced with common mode noise picked up by the probe leads on his Rigol, which sidetracked the project for a while.

ebikeWe’ve covered various ebike hacks before, but the guys at endless sphere appear to be developing a number of solid open hardware designs in this area. This includes the Lebowski controller which [ZombieSS] used in conjunction with his design.

He has installed the controller and output stage on his electric bike, and you can see one of the first test runs in the video below. We look forward to hearing more from the awesome hackers at Endless sphere!

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Wall-wart retrofitted with a high-power LED supply circuit


This custom circuit board picks up some of the pieces from a wall wart to drive a high-power LED.  The basic concept is to keep the high-voltage components and swap out the low voltage ones for parts that will be able to drive the 10W load.

The PCB is custom designed, but you can see that it was shaped to match the wall wort’s original board. To the right is the original 500mA transformer. The low-voltage side uses an LM393 because of its dual-comparators. This provides feedback for both current and voltage and is a perfect compliment for the TOP242. We haven’t seen that part before, but [Mincior] says that it’s nice for this application as it has safety features that lock down the chip if power or temperature are above spec. Once the replacement is nestled inside of the plastic case it looks stock and makes sure that your custom LED fixtures will stand the test of time safely.