Designing a Memory/IO (ETA-3400) addon for the ET-3400 trainer

Dr. Scott Baker designed and built an ETA-3400 Memory/IO accessory for the vintage Heathkit ET-3400 trainer, that is available on GitHub:

I’ve always wanted one of these Heathkit microprocessor trainers, and finally one caught my eye on eBay and I pulled the trigger. The basic interaction with the trainer is through the onboard keypad and LED displays, but Heathkit also made an accessory that added additional ROM, RAM, serial port, and a cassette interface.
This allowed you to use a machine monitor over the serial port, and even featured a Tiny Basic interpreter in ROM that allowed the trainer to be programmed in Basic.

See the full post at smbaker.com.

Check out the video after the break.

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App note: TQFN package thermal pad via design guide

TQFN footprint pad via design guide for proper thermals from Diodes Incorporated. Link here (PDF)

TQFN packages have exposed pads to provide excellent electrical grounding paths to the PCB and transfer the device heat through thermal vias on the PCB thermal landing to the internal copper planes. In order to maximize the removal of heat from the package, the number of vias, the size of the vias, and the construction of the vias must be considered for the thermal landing pattern. The exposed pad must be soldered down to ensure adequate heat conduction from the package.

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App note: Understanding thermal resistance in the real world

App note from Diodes Incorporated about thermal resistance and how to manage them in real world scenario. Link here (PDF)

There can be significant differences between the thermal characteristics stated on a device datasheet and what actually happens in a realworld application. Semiconductor manufacturers usually provide thermal resistance values for Junction to Case (RθJC) and Junction to Ambient (RθJA); although these are extremely useful parameters to estimate a device power handling capability, there can still be a disconnection between those figures and reality.

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App note: Processing instructions for mounting of through-hole LEDs

Do and don’ts when mounting through-holes LEDs, app note from Vishay. Link here (PDF)

Through-hole LED cases usually consist of epoxy casting compounds with duroplastic properties. It is in the nature of things that optical semiconductor devices require transparent materials with the best possible optical features. Unlike standard IC mold compounds, which use reinforcing fillers like class fibers to achieve better mechanical stability, these optical materials must not be filled. In addition, due to the very small component dimensions, the wall thickness of the casted resin body is also small. All this results in some special aspects regarding mechanical stability during the soldering process to be considered for the processing of leaded LEDs.

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Nano sheet factory

Building a nano sheet machine @ Fablab RUC

Sometimes even very expensive and well build equipment breaks. This recently happened to researcher Biljana Mojsoska, a chemist at Roskilde University. She was working with nano sheets, an anti-bacterial coating for medical surfaces, as her machine stopped working.
The fact that such equipment can be so expensive to replace or repair triggered Jakub Klust and Bo Thorning at Fablab RUC. Could they build a machine with the same functionalities, using the equipment available at FabLab RUC? Would it be possible to build a much cheaper and easier to fix version of Biljana Mojsoska machine?

See the full post at fablab.ruc.dk.

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Thermocouple meter and datalogger

Thomas (LA3PNA) has designed and built a thermocouple meter, that is available on GitHub:

I have designed a thermocouple meter for use for obtaining temperature readings from thermocouples. Its used together with the thermal chamber described elsewhere on this site. The design is done primarily as a programmable instrument, but it has a OLED display, so it can show the current temperature. The programming uses SCPI, the same type of programming strings that most newer (1990 forward) instruments use.

See the full post on RF and electronics blog LA3PNA.

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App note: New reliability assessment practices for Tantalum Polymer Capacitors

App note from KEMET on their new suggested testing for Tantalum polymer capacitors. Link here

Tantalum polymer capacitors are expanding their market share in the commercial world because they offer superior electrical performance (primarily much lower ESR), have outstanding reliability, and display a more benign failure response than the incumbent MnO2-cathode tantalum capacitor technology. It is natural that engineers want to use this new technology in high-reliability applications.
However, a key reliability assessment tool for MnO2-cathode tantalum capacitors – Weibull grading per MIL-PRF55365 – is often ineffective when applied to tantalum polymer capacitors. Because this well-established tool often proves ineffective, a new reliability assessment strategy is needed and has now been developed by KEMET.
The basic principles behind the Weibull grading technique are reviewed, as are the reasons why it is often ineffective when applied to tantalum polymer capacitors. Then a new reliability assessment strategy for tantalum polymer capacitors is described. Special emphasis is placed on differences in the typical time-to-failure responses of tantalum polymer capacitors versus MnO2-cathode tantalum capacitors during this discussion. Finally, an example is given of successful use of this new reliability assessment strategy in a real-world high-reliability application.

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App note: Moving capacitors for mobile phones to the dashboard

This application note introduces polymer electrolytic technology, the electric performance of these parts, advantages relative to other capacitors, and how the commercial-grade product was improved to pass the stringent AEC-Q200 guidelines.

KEMET app note link here

Tantalum polymer capacitors are popular in many decoupling applications including high performance DC to DC converters. This created a perfect fit for polymer capacitors in telecom and industrial high performance applications. Now the automotive segment is showing an increased demand for these type of capacitors for use in infotainment and advanced driver assistance systems (ADAS). Most automotive applications require passive components to be qualified to the Automotive Electronics Council’s AEC-Q200 Stress Test Qualification for Passive Components. KEMET Electronics has addressed this need by developing new processes and materials to offer the market’s first polymer electrolytic capacitors qualified to AEC-Q200.

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Connect a Commodore with thermal printer

Connect a thermal printer to vintage Commodore computers using the IEC bus @ smdprutser.nl

Since a couple of months I have fascination for vintage computers like Commodore or Nintendo. I’m in the process restoring and pimping a Commodore SX64 and realized I did’t have a printer for it. After all it is an executive machine and how do I otherwise print my quotations and invoices? The solution was in a thermal printer I had lying around for years without a real purpose.

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App note: Paralleling linear regulators made easy

Various configuration of linear regulator for parallel operation discussed in this technical article from Analog Devices. Link here

Linear regulators provide a simple, low noise solution for dc-dc regulation. However, at higher VIN-VOUT differentials the low efficiency and high power dissipation of linear regulators limits the amount of output current that can realistically be delivered. Connecting multiple linear regulators in parallel spreads the load (and the heat) over several ICs, increasing the useful range of output currents a solution can deliver. However, connecting linear regulators in parallel is not always straightforward.

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