Fabricate Your Own 7-Segment Displays

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We see more and more projects that use custom molds and casting materials. The latest is this custom seven segment display which [Ray74] put together. The idea of making your own LED displays couldn’t be much easier than this — everything but the LEDs and wire is available at the craft store.

He started by making models of each segment out of pink erasers. The lower left image of the vignette above shows the eraser segments super glued to some poster board. The decimal is a pencil eraser, with a fence of wood to contain the molding material. Amazing Mold Putty was mixed and pressed into place resulting in the mold shown in the upper right.

From there, [Ray] cast the clear epoxy three times. Once dried the clear pieces were sanded, which will shape them up physically but also serves to diffuse the light. They were then placed inside of another mold form and an epoxy pour — this time doped with black enamel paint — finishes the 7-segment module. The final step is to glue the LEDs on the back side and wire them up.

This definitely trumps the build which Hackaday Alum [Kevin Dady] pulled off using hot glue sticks as light pipes.

 

Hand soldering BGA wafer chips

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And here we’ve been complaining about Flat Pack No-Lead chips when this guy is prototyping with Ball Grid Array in a Wafer-Level Chip Scale Package (WLCSP). Haven’t heard that acronym before? Neither had we. It means you get the silicon wafer without a plastic housing in order to save space in your design. Want to use that on a breadboard. You’re crazy!

Eh, that’s just a knee jerk reaction. The wafer-level isn’t that unorthodox as far as manufacturing goes. It’s something like chip on board electronics which have that black blob of epoxy sealing them after the connections are made. This image shows those connections which use magnet wire on a DIP breakout board. [Jason] used epoxy to glue the wafer down before grabbing his iron. It took 90 minutes to solder the nine connections, but his second attempt cut that process down to just 20. After a round of testing he used more epoxy to completely encase the chip and wires.

It works for parts with low pin-counts. But add one row/column and you’re talking about making sixteen perfect connections instead of just nine.

Conductive ink circuit experiments

This glowing LED is proof that the experiments [Nvermeer] is doing with conductive ink are working. We’re filing this one as a chemistry hack because  you need to hit the lab ahead of time in order to get the conductivity necessary for success. He reports that this technique uses a copper powder suspended in an epoxy intended for spray painting. Before mixing the two he etched the powder in ammonium persulfate, then washed it in deionized water which made it a much better conductor.

We gather that the ink was applied with the brush seen in the photo. But since this uses that spray paint friendly solution to host the copper powder we wonder about stenciling with something like masking tape in order to spray the circuit paths onto the substrate.

There’s not too much info up yet, but [Nvermeer] does link to one of our other favorite conductive ink projects.

Macro lens for a Nexus One

[Thomas] tipped us off about a macro lens attachment for his Nexus One. As you’d expect, adding the lens helps the phone’s camera bring tiny details into focus. He re-purposed a lens from a pair of mini binoculars, using epoxy putty to make a mounting bracket. Now the last time we saw this putty used with a phone it was for a snap-in bracket that cradled the phone and included a lens adapter. Rather than go that route [Thomas] made use of the headphone jack just above the camera lens. An old headphone plug has been epoxied to the macro lens ring, holding it in place securely while remaining easily removable.

Building removable epoxy mounting brackets

[Jykazu] wanted to use an external lens with his Kodak Zi8 but he didn’t want to alter the camera or glue something onto it. His solution was to build a bracket out of epoxy dough. He first covers the camera in scotch tape to protect the finish, then he kneads the dough to mix the two parts together, using it to form the bracket that you can see above. After curing, the bracket barely sticks to the smooth tape and can be gently removed. A lens cap with a hole drilled in it is glued to this bracket and works like a charm for connecting the lens. Check out his manufacturing method in the videos after the break.

This is a great method for many applications. Last year we saw a product called Sugru which seems to be made for this type of thing but [Jykazu’s] epoxy method is just as impressive.

Continue reading “Building removable epoxy mounting brackets”

3D printing on a much larger scale

The end goal of this giant rapid prototyping machine is to print buildings. We’re not holding our breath for a brand new Flintstones-esque abode, but their whimsical suggesting of printed buildings on the moon seems like science fiction with potential. The machine operates similar to a RepRap but instead of plastic parts, it prints stone by binding sand with epoxy. This method is not revolutionary, but hasn’t really been seen in applications larger than a square meter or so. It’s fun to see the things we dabble in heading for industrial production applications.

[Thanks Juan]

Double sided surface mount PCB population

Above is a video detailing one method for populating a two sided surface mount PCB. We covered using a stencil to apply solder paste for a PCB a few weeks ago. In the comments there was a debate about the virtue of using stencils as well as a question about how two sided boards are populated. This was a good question because reflowing a board twice can cause components on the underside to fall off.

[Wim L’s] comment mentions that there are a couple of methods for two sided population. In the video you will see that a stencil is not being used, but instead, paste is applied by a pedal actuated syringe. The paste is applied to the underside of the board first, then a teeny dot of epoxy is added to hold the component in place. Each part is then positioned normally and baked in a reflow oven. This process both reflows the solder, and cures the epoxy. When the board is reflowed a second time, the epoxy holds the bottom components in place as the top solder reaches its melting point.

This method of applying solder paste is slower than using a stencil. But if done correctly, every component can get the amount of solder needed.