Reverse Engineering The Charge Pump Of An 8086 Microprocessor

You’d think that the 8086 microprocessor, a 40-year-old chip with a mere 29,000 transistors on board that kicked off the 16-bit PC revolution, would have no more tales left to tell. But as [Ken Shirriff] discovered, reverse engineering the chip from die photos reveals some hidden depths.

The focus of [Ken]’s exploration of the venerable chip is the charge pump, a circuit that he explains was used to provide a bias voltage across the substrate of the chip. Early chips generally took this -5 volt bias voltage from a pin, which meant designers had to provide a bipolar power supply. To reduce the engineering effort needed to incorporate the 8086 into designs, Intel opted for an on-board charge pump to generate the bias voltage. The circuit consists of a ring oscillator made from a trio of inverters, a pair of transistors, and some diodes to act as check valves. By alternately charging a capacitor and switching its polarity relative to the substrate, the needed -5 volt bias is created.

Given the circuit required, it was pretty easy for [Ken] to locate it on the die. The charge pump takes up a relatively huge amount of die space, which speaks to the engineering decisions Intel made when deciding to include it. [Ken] drills down to a very low level on the circuit, with fascinating details on how the MOSFETs were constructed, and why eight transistors were used instead of two diodes. As usual, his die photos are top quality, as are his explanations of what’s going on down inside the silicon.

If you’re somehow just stumbling upon [Ken]’s body of work, you’re in for a real treat. To get you started, you’ll want to check out how he found pi baked into the silicon of the 8087 coprocessor, or perhaps his die-level exploration of different Game Boy audio chips.

Creating Easy Glass Circuit Boards At Home

This tip for creating glass substrate circuit boards at home might hew a bit closer to arts and crafts than the traditional Hackaday post, but the final results of the method demonstrated by [Heliox] in her recent video are simply too gorgeous to ignore. The video is in French, but between YouTube’s attempted automatic translation and the formidable mental powers of our beloved readers, we don’t think it will be too hard for you to follow along after the break.

The short version is that [Heliox] loads her Silhouette Cameo, a computer-controlled cutting machine generally used for paper and vinyl, with a thin sheet of copper adhered to a backing sheet to give it some mechanical strength. With the cutting pressure of the Cameo dialed back, the circuit is cut out of the copper but not the sheet underneath, and the excess can be carefully peeled away.

Using transfer paper, [Heliox] then lifts the copper traces off the sheet and sticks them down to a cut piece of glass. Once it’s been smoothed out and pushed down, she pulls the transfer paper off and the copper is left behind.

From there, it’s just a matter of soldering on the SMD components. To make it a little safer to handle she wet sands the edges of the glass to round them off, but it’s still glass, so we wouldn’t recommend this construction for anything heavy duty. While it might not be the ideal choice for your next build, it certainly does looks fantastic when mounted in a stand and blinking away like [Heliox] shows off at the end.

Ironically, when compared to some of the other methods of making professional looking PCBs at home that we’ve seen over the years, this one might actually be one of the easiest. Who knew?

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Color-Tunable LEDs Open Up Possibilities Of Configurable Semiconductors

The invention of the blue LED was groundbreaking enough to warrant a Nobel prize. For the last decade, researchers have been trying to take the technology to the next level by controlling the color of emission while the device is in operation. In a new research paper, by the guys over Osaka University, Lehigh University, the University of Amsterdam and West Chester University have presented a GaN LEDs that can be tuned to emit different colors from the same substrate.

GaN or Gallium nitride is a wide band-gap semiconductor that has been employed in the manufacturing of FETs that are known to have higher power density due to its high thermal capacity while increasing efficiency. In the the case of the tunable LED, the key has been the doping with Europium for creating energy bands. When an electron jumps from a higher band to a lower band, it emits energy in the form of light and the wavelength or color depends on the gap of energy jumped as per Plank-Einstein equation.

By controlling the current density and duty cycle, the energy jumps can be controller thereby controlling the color being emitted. This is important since it opens up the possibility of control of LEDs post production. External controllers could be used with the same substrates i.e. same LEDs to make a lamp of different intensity as well as color without needing different doping for R,G and B emissions. The reduction in cost as well as size could be phenomenal and could pave the way for similar semiconductor research.

We have covered the details of the LED in the past along with some fundamentals on the control techniques. We are hoping for some high speed color accurate displays in the future that don’t break the bank on our next gaming build.

Thanks for the tip [Qes]

Building A Bioactive Vivarium From An IKEA Shelf

Pets are often worth a labour of love. [leftthegan] — in want of a corn snake — found that Sweden’s laws governing terrarium sizes made all the commercial options to too small for a fully-grown snake. So they took matters into their own hands, building a bioactive vivarium for their pet!

[leftthegan] found an IKEA Kallax 4×4 shelving unit for a fair price, and after a few design iterations — some due to the aforementioned regulations — it was modified by adding a shelf extension onto the front and cutting interior channels for cabling. For the vivarium’s window, they settled on plexiglass but strongly recommend glass for anyone else building their own as the former scratches and bends easily — not great if their snake turns out to be an escape artist! In the interim, a 3D printed handle works to keep the window closed and locked.

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State-Aware Foldable Electronics Enters The Third Dimension

Still working with PCBs in 2D? Not [Yoav]. With some clever twists on the way we fab PCBs, he’s managed to create a state-aware foldable circuit board that responds to different configurations.

From his paper [PDF warning], [Yoav] discusses two techniques for developing foldable circuits that may be used repeatedly. The first method involves printing the circuit onto a flexible circuit board material and then bound front-and-back between two sheets of acrylic. Valid folded edges are distinguished by the edges of individual acrylic pieces. The second method involves laying out circuits manually via conductive copper tape and then exposing pads to determine an open or closed state.

Reconfigurable foldable objects may open the door for many creative avenues; in the video (after the break), [Yoav] demonstrates the project’s state-awareness with a simple onscreen rendering that echoes its physical counterpart.

While these circuits are fabbed from a custom solution, not FR1 or FR4, don’t let that note hold your imagination back. In fact, If you’re interested with using PCB FR4 as a structural element, check out [Voja’s] comprehensive guide on the subject.

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Gold Leaf Circuit Board

Ah, the glitter of gold… or fake gold, we’re not really sure. But [Mike Hogan] and [PJ Santoro] have been working with faux gold leaf as a conductor on circuit boards. The device you see above is mounted on metal-covered paper substrate and it really works.

They started by applying spray adhesive to heavy paper to make the gold-clad they needed. This was cut down into hexagons in homage to their hackerspace, Hive76 in Philadelphia. From there the shape of the microcontroller (an MSP430 G2211 in this case) to prevent shorts under the chip. The leads were flattened to interface well with the gold contacts, and a hobby knife was used to score the traces. Some careful soldering made up the final connections, and they were in business.

Oh, wait; chip on board but nothing on chip. They forgot to program it first! Since there’s no header they needed an easy way to interface with the board. The clever guys used the power of magnets to hold alligator clips in place. See how they did that in the demo video after the break.

They’re also working on some boards that use conductive ink similar to this hack┬ábut we haven’t seen a write-up from these two about┬áthose experiments… yet.

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