Penny and Paper Clip Heat Sinks

A bunch of audio heads over at the Head-Fi forum were discussing handy and quick heat sinking methods, leading to much speculation and conjecture. This finally prompted [tangentsoft] to take matters in his own hands and run some tests on DIY Heat Sinks.

The question that sparked this debate was if a paper clip is a good enough heat sink to be used for a TO220 package. Some folks suggested copper pennies (old ones minted 1981 and earlier – the new ones are zinc with copper plating and won’t help much). [tangentsoft] built a jig to test six LM317 regulators in constant current mode set to 0.125A and 2w dissipation. The six configurations were a paper clip, a single penny bolted to the regulator, a regular Aavid TO220 heat sink, a set of 4 pennies bolted, a single penny epoxy glued and finally a single penny soldered directly to the regulator.

The results were pretty interesting. The paper clip scored better than any of the single pennies! The quad-penny and the Aavid heat sink fared above all the other configurations, and almost at par with each other. [tangentsoft] posts his review of each configurations performance and also provides details of his test method, in case someone else wants to replicate his tests to corroborate the results. He tested each configuration independently for one hour, gathering just over 10000 readings for each setup. Other nearby heat sources were turned off, and he placed strategic barriers around the test circuit to isolate it from the effects of other cooling / heating sources. He even removed himself from the test area and monitored his data logging remotely from another room. When he noticed a couple of suspect deviations, he restarted the test.

[tangentsoft] put all the data through Mathematica and plotted his results for analysis, available at this link [pdf, 2.8MB]. So the next time you want to heat sink a regulator for cheap, just hunt for Clippy in your box of office supplies. Do remember that these methods will work for only a couple of watts dissipation. If you would like to cast and build your own heat sinks out of aluminum, check out this post about DIY Aluminum heat sink casting. And if you need help calculating heat sink parameters, jump to 12:00 minutes in this video from [Dave]’s EEVBlog episode on Dummy loads and heat sinks.

Thanks to [Greg] for sending in this tip.

Looking inside the KR580VM80A Soviet i8080 clone

The folks at Zeptobars are on a roll, sometimes looking deep inside historic chips and at others exposing fake devices for our benefit. Behind all of those amazing die shots are hundreds of hours of hard work. [Mikhail] from Zeptobars recently tipped us off on the phenomenal work done by engineer [Vslav] who spent over 1000 hours reverse engineering the Soviet KR580VM80A – one of the most popular micro-controllers of the era and a direct clone of the i8080.

But before [Vslav] could get down to creating the schematic and Verilog model, the chip needed to be de-capped and etched. As they etched down, they created a series of high resolution images of the die. At the end of that process, they were able to determine that the chip had exactly 4758 transistors (contrary to rumors of 6000 or 4500). With the images done, they were able to annotate the various parts of the die, create a Verilog model and the schematic. A tough compatibility test confirmed the veracity of their Verilog model. All of the source data is available via a (CC-BY-3.0) license from their website. If this looks interesting, do check out some of their work that we have featured earlier like comparing real and fake Nordic dies and amazing descriptions of how they figure out the workings of these decapped chips. If this is too deep for you check out the slightly simpler but equally awesome process of delayering PCBs.

Design & Build Part 2: Multi-Band, Phasing SSB, and SDR


Amateur radio is the ultimate hacker’s hobby. You can design, build, and put on the air your own high power transceivers. And with this homemade gear you are able to reach out directly, not relying on any infrastructure whatsoever, to connect with people all over the world. It is a thrilling experience to communicate with that long distance station using equipment you created, where you know at that instant what every single transistor is doing as you key down the mic.

In a previous post I described how SSB radio equipment worked and provided an example of a single-band 20m SSB transceiver. In this post I will discuss a multi-band SSB transceiver, an entire homemade amateur station including amplifiers, and conclude with software defined radio (SDR) that you can make in one weekend.

Continue reading “Design & Build Part 2: Multi-Band, Phasing SSB, and SDR”

Using The Red Pitaya As An SDR

The Red Pitaya is a credit-card sized board that runs Linux, has Ethernet, and a good bit of RAM. This sounds a lot like a Raspberry Pi and BeagleBone Black, but the similarities end there. The Red Pitaya also has two RF inputs, two RF outputs, and a load of digital IOs, all connected to an Xilinx SoC that includes an FPGA. [Pavel] realized the Pitaya had all the components of a software-defined radio, and built an implementation to prove it.

The input for the SDR taps directly into one of the high impedance inputs with a simple loop antenna made out of telephone cable. The actual software-defined part of this radio borrows heavily from an Xilinx application note, while everything is controlled by either SDR# or HDSDR.

[Pavel] included a pre-built SD card image with all his software, so cloning this project is simply a matter of copying an SD card and building an antenna. The full source is also available, interesting if you would like to muck about with FPGAs and SDRs.

The Wisest Wizard Doesn’t Drink from Cans

“Wizard Staff” or “Wisest Wizard” is a drinking game played at parties where the attendees participate by taping the empty cans of the drinks they’ve consumed on top of one another to form a staff of inebriated power. A person with a longer staff is considered to be at a higher level and can therefore command lesser wizards to pound their current beverage to a point they see fit. Not everyone at a party necessarily drinks their tasty libation of choice from a can however. So, [Ahmed] and his group came up with a solution for those of us who might alternately prefer to wield a pint glass of power instead.

In their hardware project for Hack Illinois 2015, [Brady Salz], [Ahmed Suhyl], [Dario Aranguiz], and [Kashev Dalmia] decided to add a zest of tech to the game. For their updated rendition, glasses are equipped with battery packs for mobility, a Spark micro-controller, and different colored LEDs as indicators. A couple of wires reach into the bottom of each glass to measure conductivity and keep track of the number of times it is filled and then emptied. In leu of towers of aluminum husks and duct-tape, the group developed a simple Android app for participants to log into which will track and visualize the standings of each player registered to one of the glasses. They even created a pebble version of the app that will display all the same information in case you don’t want to risk handling your phone while drinking… heh.

For an added level of fun, once a player reaches a certain level above someone else, they unlock the option to “challenge” the lesser adversary. By selecting that person’s user name in the app, the LED and buzzer on their glass will spring to life, letting them know they’ve been chosen to chug the rest of their drink. If you’re curious how they made it work, you can check out the team’s code on Github and maybe take a stab at giving the game a makeover of your own.

Continue reading “The Wisest Wizard Doesn’t Drink from Cans”

Low-Voltage Tesla Coil Uses a Relay Instead of a Spark Gap

[Teodor] writes in with a unique Tesla coil he designed and built. Unlike most Tesla coils, [Teodor]’s design is able to run with a fairly low input voltage because it doesn’t use a static spark gap like most Tesla coils. Instead, his coil uses a relay in place of a spark gap.

[Teodor] built his coil using leftover components from his old school, making good use of some parts that might have otherwise been thrown away. The most critical component of his circuit, the relay, is just a standard normally-closed relay that is rated at 20A. [Teodor] wired the relay so that it energizes its own coil whenever it is shut. This causes the relay to briefly open every time the coil is energized, creating a resonant circuit. The resonant circuit charges a tank capacitor and places it in series with the primary coil inductor every time the relay closes, forming the tank circuit of his design.

With [Teodor]’s design, the resonant frequency of the secondary is nearly identical to that of the primary. This creates a significant voltage boost, helping produce very high voltages from such a low input voltage. The only downside to this design that [Teodor] recently discovered is that the relay contacts get red-hot after a few minutes of operation. Not optimal, but it still works! Check out [Teodor]’s writeup for more details and instructions on how to build your own.

Reverse Engineering Wireless Temperature Probes

[bhunting] lives right up against the Rockies, and for a while he’s wanted to measure the temperature variations against the inside of his house against the temperature swings outside. The sensible way to do this would be to put a few wireless temperature-logging probes around the house, and log all that data with a computer. A temperature sensor, microcontroller, wireless module, battery, case, and miscellaneous parts meant each node in the sensor grid would cost about $10. The other day, [bhunting] came across the exact same thing in the clearance bin of Walmart – $10 for a wireless temperature sensor, and the only thing he would have to do is reverse engineer the protocol.

These wireless temperature sensors are exactly what you would expect for a cheap piece of Chinese electronics found in the clearance bin at Walmart. There’s a small radio operating at 433MHz, a temperature sensor, and a microcontroller under a blob of epoxy. The microcontroller and transmitter board in the temperature sensor were only attached by a ribbon cable, and each of the lines were labeled. After finding power and ground, [bhunting] took a scope to the wires that provided the data to the radio and took a look at it with a logic analyzer.

After a bit of work, [bhunting] was able to figure out how the temperature sensor sent data back to the base station, and with a bit of surgery to one of these base stations, he had a way to read the temperature data with an Arduino. From there, it’s just a data logging problem that’s easily solved with Excel, and [bhunting] has exactly what he originally wanted, thanks to a find in the Walmart clearance bin.