Use a Cheap PIN Diode as a Geiger Counter

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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

frontend 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.

[Read more...]

Think Before You Measure – Old Test Gear and Why It Is Awesome

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Good, workable test gear is key to enabling our hobby. In this post we will discuss where to procure it at rock-bottom prices, what to look for, how to fix it, and how to tailor your laboratory practices around gear that may not be reliable.

We are lucky to be living in an era with plentiful high-quality test gear. Since the Second World War, surplus test gear has been in abundance at low costs enabling hobbyists, innovators, and academics to experiment and build great things. If you are willing to think before you measure you can save serious amounts of money and have a professional laboratory in your home.

Where to buy
The obvious answer is eBay, but the deals on test equipment are at the hamfests. Don’t be fooled by the name. Hamfests sell much more than amateur radio equipment. Hamfests are swap meets where hobbyists trade electronics of all kinds. Check out the ARRL hamfest calendar to find the next local one near you! I suggest you arrive early, however. The culture of hamfests tends to favor showing up as soon as the doors open and leaving about two hours before the official end. The early bird gets the worm!

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Palatable Pallet Procurement Procedures

pallet wallpaperWooden pallets are a versatile and widely-available starting point for a multitude of projects. Best of all, they can usually be acquired free of charge. But choose the wrong kind of pallet and you could end up paying dearly. [Eric] has compiled a great deal of useful information about pallets that will help you find ideal candidates and prepare them for whatever project you have in mind, be it a coffee table or a backyard roller coaster.

Pallets come in several styles and loader configurations. Some are made with space between the boards, and others are closed. If you take nothing else away from his article, just remember to look for plain, untinted pallets with no markings and you’ll be fine.

No markings means the pallet was used domestically, so markings aren’t required. Marked pallets from abroad should feature the IPPC logo as well as a treatment code indicating the method used on the material. Debarked (DB), heat treated (HT), and pallets with the European Pallet Association logo (EPAL) are all safe choices. Pallets labeled (MB) were treated with methyl bromide, which is a poisonous fungicide. Colored pallets should be avoided as well. If you find one in a cool color, take a picture of it and find some paint in a similar hue.

Safe pallets can be had from many places ranging from hardware stores to feed and tack supply stores. Find someone you can ask for permission to take pallets—they might even help you load them. Keep some gloves in your trunk to avoid splinters.

PCB Drill Press Gets a Microscopic Upgrade

PCB Drill Microscope

If you get into more complicated PCB design, you’ll find the need to drill tiny and accurate holes much more often. Wouldn’t it be nice to have a precise way of doing that? Maybe even something as simple as strapping a $10 USB digital microscope to it?

That was [mlerman's] thought anyway, and from the looks of it, it seems to work quite well! If you already have a PCB drill press then it’s just a matter of installing the microscope opposite the drill — align it to the center point with some cross hairs and boom you’re in business.

But if you don’t yet have a PCB drill, [mlerman's] got you covered there too, as he explains in great detail how to modify a cheap drill press into an inverted PCB drill press.

Inverted PCB Drill Press

Wait, why is it inverted? Besides making more room for the USB microscope to sit, it also ensures the microscope lens doesn’t get covered in the PCB fairy dust that would fall on it if it were in a normal orientation.

[via Embedded-Lab]

Unjettisoned Inkjet Turned Tumbler

printer parts tumblerDon’t throw out that old printer! Not that you would, but even if you’ve already scavenged it for parts, you can use the shell and the rollers to make a rock/coin/what-have-you tumbler. If your printer is part scanner, it might end up looking as cool as [th3_jungle_inv3ntor]‘s. You’ll have to laser-cut your own arachnid to supervise from above, though.

Somewhere between having an irreparable printer, being inspired by another tumbler, and the desire to make a mancala set for his sister-in-law, [th3_jungle_inv3ntor] was sufficiently motivated to get out his hacksaw and gut the printer. He used the main paper roller and its motor to do the tumblin’, and a smaller roller to help accommodate different jar sizes.

Aside from adding those sweet blue LEDs, he wired in a toggle switch, a speed control pot, and an LM317 to govern the tumbling rate. Unfortunately, the rocks in [th3_jungle_inv3ntor]‘s town are too soft and crumbly, so he can’t make that mancala set after all. But hey, (almost) free stuff tumbler.

No dead printers lying around? If you have a drill and a vise, you could always make a tumbler that way, and nothing is compromised but the peaches jar.

DIY UV Lamp Is the Cure for Nails and More

DIY UV lampWe must admit to wondering how Adafruit’s [Becky Stern] gets anything done with those fingernails of hers. They’re always long and beautifully painted without any chips, dings, or dents. As it turns out, she uses UV gel nail polish. It’s much more durable than standard air-dry polishes, but it requires UV light to cure. [Becky] bought a lamp to use at home, but it’s very bulky and must be plugged into the wall. She knew there was a better way and devised her DIY UV mini manicure lamp.

She really thought of everything. The open source 3D-printed enclosure includes a small compartment in the top for cuticle sticks, emery boards, and tweezers. The Li-poly battery is rechargeable over USB in conjunction with Adafruit’s PowerBoost 500c. The lamp itself is made from 30 UV LEDs and 100Ω resistors. [Becky] lined the inside of hers with silver sticky paper to help distribute the UV light evenly.

You know, this can also be used to erase EPROMs or to cure small DLP 3D prints. Do you have another use for it? Tell us in the comments. Introductory and partially hyperlapsed video after the break.

[Read more...]

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