You might be a geeky dad if: your kids practice spelling in Morse code

Kids learn better if they’re engaged in the topic at hand. [Todd] found something that has his son just begging to practice his spelling words each night. He converts them all to Morse code and taps each out on the Morse code practice station they built together. To start off Todd connected the keyer to his Fluke 87 meter, using the continuity tester to sound a beep each time the key is depressed. But this is just a temporary setup until [Todd] could help guide his young one through some circuit design and assembly.

The replacement is based on a 555 timer. They grabbed an electronics project book and found the schematic along with a Morse code primer. With parts in hand [Todd] films as his son hones his soldering skills with each connection. The finished project uses the timer chip to produce the audio frequency heard from the on-board speaker. If you’ve never had the joy of teaching a kid how to solder, you’re going to love seeing the video.

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Homebrew solder pot is too dangerous even for us

[rue_mohr] is building a hexapod robot, and that meant he needed to tin a whole bunch of ribbon cables with solder. Using a soldering iron for this task would take far too long, so he built a homebrew solder pot to tin all those wires quickly. While [rue] was able to get solder on all those wires quickly, we need to question his method – he used a halogen light and reflector to melt all that solder.

The build began with a recycled halogen light fixture. After taking apart the entire assembly, [rue] reassembled it into something resembling a solder pot; a concave reflector and halogen light bulb sit perfectly flat on the table, ready to accept pieces of solder.

After throwing the switch and putting a few bits of solder in the reflector, the solder pot surprisingly worked. [rue] was able to quickly tin his ribbon cables, and the halogen bulb and reflector didn’t break yet.

This is one of the least safe solder pots we’ve ever seen – the bulb could easily explode, and melted solder could come pouring out of the reflector at any time. [rue] is aware of the safety implications and make sure to wear a pair of goggles. If it works though, we really can’t complain.

Check out the video of [rue]‘s solder pot (with an awesome temperature indicator light right in the middle of a pool of solder) in action after the break.

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How to etch your own solder paste stencils

We’re kind of surprised we haven’t covered this concept before since it only uses techniques that are commonly avaialable for home PCB fabrication. [Ray] made this solder paste stencil out of a sheet of copper using the same etching techniques you would for a circuit board. He designed and printed a resist pattern, with toner everywhere except the places where there should be holes in the stencil. He transferred the toner to the copper using an iron.

The difference here should be obvious; this a thin copper sheet with no substrate. Because of that, you must protect the copper surface before etching. he covered the entire thing, both sides, in packing tape. After that it’s into the Cupric Chloride bath to dissolve the exposed parts. Once the tape and toner has been removed you can scree a precise amount of solder paste onto your boards.

This isn’t for everyone, but if you’re assembling many boards it’s not a bad approach. If the stencil is no longer used it can be recycled, but we do wonder how corrosion on the copper will affect the stencil’s performance.

The idea for this technique came to [Ray] from a guide that’s been around for years.

Toaster oven reflow control without modifying the oven

[Eberhard] wanted his own reflow oven but didn’t really want to mess around with the internals that control the heating element. He put his microcontroller programming experience to work and came up with an add-on module that controls the oven by switching the mains power.

The image above shows a board in the midst of the reflow process. If you’re not familiar, solder paste usually comes with a recommended heat curve for properly melting the slurry. [Eberhard] managed to fit three of these temperature profiles into his firmware.

The ATtiny45 which makes up the controller samples oven temperature via the thermistor seen next to the board. A PID algorithm is used to calculate when to switch mains power on and off via a relay. One button and one LED make up the controller’s user interface for scrolling through the three preprogrammed temperature profiles.

It looks like it works great, see for yourself in the clip after the break.

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Reworking Ball Grid Array circuit board components at home

[Jack Gassett] is developing a new breakout board for an FPGA. The chip comes in a ball grid array (BGA) package which is notoriously difficult to solder reliably. Since he’s still in development, the test boards are being assembled in his basement. Of the first lot of four boards, only one is functional. So he’s setting out to rework the bad boards and we came along for the ride.

To reflow the surface mount components he picked up a cheap pancake griddle. The first thing [Jack] does is to heat up the board for about two minutes, then pluck off the FPGA and the FTDI chips using a vacuum tweezers. Next, the board gets a good cleaning with the help of a flux pen, some solder wick, and a regular soldering iron. Once clean, he hits the pads with solder paste from a syringe and begins the soldering process. BGA packages and the solder paste itself usually have manufacturer recommended time and temperature guidelines. [Jack] is following these profiles using the griddle’s temperature controller knob and the timer on an Android phone. In the video after the break you can see that he adjusts the timing based on gut reaction to what is going on with the solder. After cleaning up some solder bridges on the FTDI chip he tested it again and it works!

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512 LED cube

Get out the soldering iron and clear your schedule, it’s going to take you a while to assemble this 8x8x8 LED matrix which contains a total of 512 LEDs. We’ve looked in on a 3x3x3 cube, and [Chr], who is responsible for this one, has assembled a 4x4x4 cube before, but this one is quite a leap in complexity. It isn’t just physical assembly problems that increase with scale, you’ll need to consider a power supply too since one layer of a 3x3x3 cube would need at 90 mA, but a single layer of the cube above requires 640 mA to light all of the diodes. Multiplexing is handled per-layer, controlled by  ICs which share 8 data lines and are latched by a shift register. This means the display only requires 11 microcontroller pins for addressing. It is striking how well [Chr] explains the design process, and how cleanly he builds the driver circuits on protoboard. There’s a lot to look at and a lot to learn, not to mention the stunning results which can be seen in the video after the break.

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Vapor phase reflow soldering

Ditch that old toaster oven and move to the next level of surface mount soldering with this vapor phase reflow method. [Ing.Büro R.Tschaggelar] put together this apparatus to use vapor phase reflow at his bench instead of sending out his smaller projects for assembly. It uses the heating element from an electric tea kettle to boil Galden HT 230 inside of a Pyrex beaker. There’s a copper heat break part way up the beaker to condense the chemical and keep it from escaping. When a populated board is lowered into the heated chamber, the solder paste reflows without the need to stress the components with unnecessary heat. Better than traditional reflow? At this level it’s hard to say, but we do find his method quite interesting.

[Thanks Chris]


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