Battery Basics – Choosing a Battery for Your Project

If choosing a rechargeable battery for your project intimidates you, [Afroman] has prepared a primer video that should put you at ease. In this tutorial for battery basics he not only walks you through a choice of 5 rechargeable chemistries and their respective tradeoffs, but gives a procedure that will allow you to navigate through the specs of real-world batteries for sale – something that can be the most intimidating part of the process.

You cannot learn everything about batteries in 9 minutes, but watching this should get you from zero to the important 80% of the way there. Even if your project does not give you the specs you need to begin buying, [Afroman] tells you what to measure and how to shop for it. In particular, the information he gives is framed in the context you care about, hopefully ensuring you are not waylaid by all the details that were safe to ignore. If this is not enough, [Afroman]’s prequel video on battery terminology has more detail.

Much like your high school English teacher told you, you need to know the rules before you can choose to break them. Many of battery absolute Dos or Don’ts are written for the manufacturer, who provides for the consumer, not the hacker. Hackaday has published hundreds of battery articles over the years; search our archives when you are ready for more.

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2014 Advent Calender of Circuits

Every day this month and until Christmas, [vk2zay] is (has already been!) posting a simple but useful hack in his 2nd sort-of-annual “Advent Calender of Circuits” that many of you will want to be bookmarking. For those already saturated with the season of holiday hacks, don’t worry – other than being festively generous of him to tutor and demo a new hack every day, the hacks themselves have nothing to do with Christmas. Though he missed the last couple years we here at Hackaday covered his first month of hacks back in 2011 (now in playlist).

The daily hacks posted so far cover a wide variety of useful projects (leaning towards HV) for the electronics hobbyist who might not have all the fancy tools in their shop: DIY high voltage probes, a 1-hour tesla coil from junk, measuring RF power, a stud detector, how to test an  unknown transformer’s saturation, and many others. We cannot predict what will be posted the rest of the calender (the author hints to be making them up as he goes), but by now it is safe to say that they will not disappoint.

We would be stealing his thunder to cover them all, so, we will just pick our favorite for now:

The 1-hour tesla coil is a delightful all-shortcuts-taken hack project. If one were to listen to aficionados, teslacoiling is a highly precise hobby to get into. It appears to require careful planning, much calculation, special-ordered or soviet-surplus parts, custom jigs, fine tuning, etc. [vk2zay] shows otherwise.

Every single component of the assembly is itself a hack.

No fancy tungsten-infused grade 8 copper being water-cooled via heat pump here – the spark gap is just the bent leg of a capacitor hovering near the start of the primary winding. The power supply is a backlight inverter with a chain of Cockcroft-Walton voltage doublers. The high voltage resistor is a bunch of series-chained resistors shoved into a silicone tube. The topload is a couple cheap pie tins masking-taped together to “resemble something like a sphere.” The primary is a loose, unsupported spring of copper wire. The secondary was calculated to be whatever the height of the tube he had handy and coiled only as smoothly as a first attempt would allow. He does not even bother using wires or a switch – the circuit is completed by clipping a couple of test leads.

After all this hodgepodgery the circuit was then carefully tuned to optimize how little time it took to build (additional time used: zero). Since the frequencies do not match (1.7 vs. 2.6 mhz – 35% apart) the only thing this circuit resonates with is a hacker’s appeal for making do. Does not matter, still works. The streamers easily reach 2 inches and the author claims double that in dark lighting.

In the just 6 minute video he also manages to explain roughly what is going on theory-wise and suggest the time-effective things to considering upgrading. Almost a dozen hacks in the bag and over a dozen more to come before Christmas.

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Direct Digital Synthesis (DDS) Explained by [Bil Herd]

One of the acronyms you may hear thrown around is DDS which stands for Direct Digital Synthesis. DDS can be as simple as taking a digital value — a collection of ones and zeroes — and processing it through a Digital to Analog Converter (DAC) circuit. For example, if the digital source is the output of a counter that counts up to a maximum value and resets then the output of the DAC would be a ramp (analog signal) that increases in voltage until it resets back to its starting voltage.

This concept can be very useful for creating signals for use in a project or as a poor-man’s version of a signal or function generator. With this in mind I set out here to demonstrate some basic waveforms using programmable logic for flexibility, and a small collection of resistors to act as a cheap DAC. In the end I will also demonstrate an off-the-shelf and inexpensive DDS chip that can be used with any of the popular micro-controller boards available that support SPI serial communication.

All of the topics covered in the video are also discussed further after the break.

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How To Get 50 More Zed From Your Rigol DS1054Z

[Chris] has been spending a lot of time in the wife’s sewing room lately, and things got pretty serious late last night as he hacked his shiny new Rigol DS1054Z to unlock the 1104Z capabilities lurking within.

The rumors are true, and ungoverning the software is as simple as looking up your serial number and knowing the right URL for generating a valid license. [Chris] ran into a dud site, but that’s the price of doing business in the shadowy parking garage basements of the interwebs. Once he knocked on the right door and uttered the secret word, however, he became the proud owner of 50MHz additional bandwidth, decoders for SPI, I²C, and RS-232, twice the storage depth, and all teh triggers that ship with the 1104Z.

Stick around for [Chris]’s video walk-through. Can’t rationalize the purchase even at the ridiculously low price point? Here’s one way to make it happen. You’ll laugh, you’ll cry, you’ll learn some French.

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Which Way Are We Going? Concepts Behind Rotary Encoders

[Pete] needed a rotary encoder for one of his project so he set out to build his own. As the name implies, a rotary encoder measures rotation by encoding “steps” into electrical signals which can be measured by a microcontroller (or used in numerous other ways). Knowing the degrees of movement for each step will allow you to calculate precise distance traveled in applications like robot wheels. Or you can simply use the rotating shaft as an input device which navigates menus or settings.

This concept is a good one to understand. We had originally planned to build rotary encoders for the multi-person Duck Hunt at Hackaday’s 10th Anniversary but the build-off crew had difficulty getting the system to work. In [Pete’s] case he’s using photointerrupters (apparently the IR beam is easily detected through the white paper but usually these parts would be cut out of the disk). We were using reflectance sensors. Either way there’s a trick to detecting which direction a rotary encoder is turning. We’ll explain that for you after the break.

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Use a Cheap PIN Diode as a Geiger Counter

After the Fukushima nuclear power plant disaster, radiation measurement became newly relevant for a lot of people. Geiger-Müller tubes, previously a curiosity, became simultaneously important and scarce.

Opengeiger.de (English-language version here) has complete instructions for making a Geiger counter without a Geiger-Müller tube. Instead, this counter uses a PIN photodiode and some carefully chosen operational amplifiers. The total cost of such a device is significantly cheaper than the alternative: under $1 for the diode and around $5 for the rest. And since the PIN photodiode in question is used in many other devices, it’s not a niche component like a Geiger tube is.

The secret sauce is in component selection and tuning. Opengeiger uses the BPW34 diode because it is relatively common and has a large surface area, but also because it has a very low capacitance when reverse-biased. The first-stage opamp choice is also fairly critical. Considering that an average gamma radiation event produces only around 10 nanoamps for about 50 microseconds, a lot of amplification (100,000x), low noise, and high bandwidth are a must.

If you want to get started with this project, you could first browse through the explanation (PDF) to get an overview of the project’s goals, read up on all the technical considerations (PDF) or just head straight for the DIY instructions for the “Stuttgarter Geigerle” (PDF, schematic is on the last page). All of the documentation is chock-full of relevant references and totally worth the read.

How To Reverse Engineer, Featuring the Rigol DS1054Z

For a few years now, the Rigol DS1052E has been the unofficial My First Oscilloscope™. It’s cheap, it’s good enough for most projects, and there have been a number hacks and mods for this very popular scope to give it twice as much bandwidth and other interesting tools. The 1052E is a bit long in the tooth and Rigol has just released the long-awaited update, the DS1054Z. It’s a four-channel scope, has a bigger screen, more bells and whistles, and only costs $50 more than the six-year-old 1052E. Basically, if you’re in the market for a cheap, usable oscilloscope, scratch the ~52E off your list and replace it with the ~54Z.

With four channels of input, [Dave Jones] was wondering how the engineers at Rigol managed to stuff two additional front ends into the scope while still meeting the magic price point of $400. This means it’s time for [Dave] to reverse engineer the 1054Z, and give everyone on the Internet a glimpse at how a real engineer tears apart the worth of other engineers.

The first thing [Dave] does once the board is out of the enclosure is taking a nice, clear, and in-focus picture of both sides of the board. These pictures are edited, turned into a line drawing, and printed out on a transparency sheet. This way, both sides of the board can be viewed at once, allowing for a few dry erase marker to highlight the traces and signals.

Unless your voyage on the sea of reverse engineering takes you to the island of despair and desoldering individual components, you’ll be measuring the values of individual components in circuit. For this, you’ll want a low-voltage ohms function on your meter; if you’re putting too much voltage through a component, you’ll probably turn on some silicon in the circuit, and your measurements will be crap. Luckily, [Dave] shows a way to test if your meter will work for this kind of work; you’ll need another meter.

From there, it’s basically looking at datasheets and drawing a schematic of the circuit; inputs go at the left, outputs at the right, ground is at the bottom, and positive rails are at the top. It’s harder than it sounds – most of [Dave]’s expertise in this area is just pattern recognition. It’s one thing to reverse engineer a circuit through brute force, but knowing the why and how of how the circuit works makes things much easier.

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