Hundred dollar capacitive discharge welder


[Robert] needed to weld metal tabs on a few batteries. In a proper manufacturing situation, this is usually done with outrageously expensive welders. Not wanting to spend thousands of dollars to attach bits of metal together, [Robert] built his own capacitive discharge welder for only $100.

Instead of the giant transformers you’d find in a spot welder, a capacitive discharge welder uses a huge bank of capacitors – greater than 1 Farad – to weld pieces of metal together. Huge caps like these are commonly used for ridiculous car stereo setups, so with the addition of a car battery charger purchased from Walmart, [Robert] had most of a welder on his workbench.

To control the mass of power coming from his huge cap, [Robert] used a 13o amp Silicon controlled rectifier to improve the control of his welder. With the battery charger, cap, and SCR, [Robert] only needed a few bits of heavy gauge wire to tie the entire build together.

[Robert]’s build welds metal tabs on battery terminals beautifully, but the possibilities don’t end there. This welder could easily be repurposed to build the skeleton of outrageously intricate dead bug circuits, or maybe even keeping that thing you made with your Erector set in one piece permanently.

Hackaday Links: July 13, 2012

Testing LEDs

Over at the Albuquerque, NM hackerspace Quelab, [Alfred] needed to test a bunch of surface mount LEDs. He ended up building a pair of 3D printed tweezers with a pair of needles attached to the end and a space for a coin cell battery. It works and Quelab got a new tool.

Woo Raspberry Pi

[tech2077] added an FTDI chip to his Raspberry Pi to do a little single cable development. We’ve seen a few similar builds, but surprisingly nothing related to the on board display serial interface. This wiki page suggests it’s possible to connect an iPhone 3G or iPhone 4 display directly to the Raspi. Does anyone want to try that out?  Nevermind, but it would be cool to get a picture from a display plugged into that display port on the Raspi.

I like to ride my bicycle, I like to ride my bike

Over at the 23b hackerspace a few people were having trouble finding a good bike cargo rack that wasn’t overpriced. They built their own with $30 in materials and a salvaged milk crate. It looks great and is most likely a lot more durable than the Walmart model.

If that cargo rack fell off, it would look like this

Apparently you can get ‘spark cartridges’ to attach to the underside of a skateboard. [Jim] saw these would look really cool attached to his bike so he did the next best thing. He attached them to his sandals. It does look cool…

Less heat, less noise

[YO2LDK] picked up a TV tuner dongle for software radio and found it overheated and stopped working after about 15 minutes (Romanian, Google Translate). He hacked up a heat sink from an old video card to solve this problem. Bonus: the noise was reduced by a few tenths of a dB.

Hot glue appendages may be predecessor to the flow metal of the T-1000

The T-1000 was the shape-shifting robot from T2 (the second Terminator movie). It was so amazing because it could assume the form and texture of anything; humans, piercing weapons, inanimate objects. This robot doesn’t even compare, except for one small trait. When it needs a tool, it can build it as its own appendage. This really is nothing more than making tools with a 3D printer. However, the normal boxy infrastructure is missing.

The print head is mounted on a single robot arm, and the tool is printed using hot melt glue in order to stick to a plate which makes up the business end of robot arm. In this case the robot needed to transport some water. It sets down the plate, uses the hot melt extruder to print a cup on that plate, then picks it up again and uses it to move water from one bowl to the other. You can see it all in the video clip below the fold.

Sure, it’s just baby steps. But hot melt glue sticks are light weight, and don’t require much energy to melt. This makes for a perfect combination as a portable tool shop.

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Turning a rotary tool into a PCB drill press

Drilling holes in PCBs is nearly always an exercise in compromise; the holes are small, precision is paramount, and the common solutions, such as a Dremel drill press, aren’t of the highest quality. In a quest to find the best way to drill holes in PCBs, [reboots] even went so far as to get a pneumatic dental drill, but nothing short of a high-quality micro drill press would do. Not wanting to spend hundreds of dollars to drill a few holes, [reboots] did the sensible thing and made one from scratch.

[reboots] ended up buying a Proxxon Micromot 50 after reading the consistently good reviews around the Internet. To use this rotary tool as a drill press required more work, though. Two precision steel rods from a dot matrix printer were salvaged and pieces of aluminum C-channel and small bearings were bolted together into a very high-precision drill press. Only hand tools were used to build this drill press, and the results are amazing.

[reboots] was originally inspired to check out Proxxon tools from one of Hack a Day’s rare tool reviews. The Proxxon TBM115/220 earned the skull ‘n wrenches seal of approval (and found its way into other Hack a Day-ers labs), but sometimes a few hundred dollars is too much of an investment for something only used occasionally. Considering [reboots]’ scrap aluminum drill press is a better tool than the sloppy consumer rotary tool presses, we’ll call this a success.

ElectroDroid – your Android electronic reference app

Earlier this week, fellow Hack a Day-er [Mike Nathan] reviewed Adafruit’s new iPhone/iPad app Circuit Playground. The comments on [Mike]’s review turned to suggesting ElectroDroid as an alternative to Circuit Playground. Surprisingly,  Hack a Day authors actually pay attention to the comments, so I’ve decided to throw my hat into the ring and offer up my review of ElectroDroid. For purposes of full disclosure, I have to add that I paid the $2.59 donation for a copy of ElectroDroid without ads, and have had no contact with the developers.

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Circuit Playground – An electronics reference app from Adafruit

It’s not everyday that we review software around here, but the folks at Adafruit recently put together an iOS app that I figured might be of interest. Their iPad/iPhone compatible application is called “Circuit Playground”, and it includes all sorts of handy electronics reference tools. For the context of this review, it should be noted that I paid for the application myself, and that I have had no communication with the Adafruit team regarding my assessment of the app.

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Building a ’60s guerilla homebrew square wave generator

What do you do when you’ve got three broken function generators? Build your own, obviously. Since your workshop has already gone through three of these bad boys, you might find yourself repairing your build. Better not use any fancy ICs and go with a transistor only build.

When [Miroslav] sent in his ‘guerilla homebrew’ square wave generator, we were really impressed. With a relatively simple schematic that uses parts that could be salvaged from old radios, this is a real MacGyver build.

The generator is based around a simple astable multivibrator. It doesn’t provide sine waves, but it’s the easiest circuit to get working. The build started off with a quartet of 2N4401 transistors, but according to the datasheet and the venerable Tektronix 502A, these had a very bad rise time compared to 2N3904s.

[Miroslav]’s project generates square waves up to 2.22 MHz and pulses with a variable duty cycle from 1-49% and 51-99%. Output is either 5 Volt TTL levels or an adjustable 0-3.38 level. The generator is exactly what [Miroslav] needed, so that makes it a great tool in our book.