Guitar Amp builder notes — AF power amplifier dummy load

DSC_2129-1 (1)Vasily Ivanenko has written an article detailing his AF dummy load project:

I’ll describe a simple 8, or 4 Ω dummy load to test your home brew guitar power amplifiers.
Low cost 16 Ω / 25W wire wound, aluminum shell, chassis mount resistors seem abundant.  I got mine on eBay.  Wire wound resistors vary in quality, design and tolerance. Some even exhibit low inductance by winding with an Ayrton-Perry bifilar technique.  Resistor tolerances range from 10% down to ± 0.5 % + 0.05 Ω.  Typical manufacturer power ratings are done at 25C, however, these devices are meant to sit on a heat sink when used and that’s why the aluminum housing contains 2 relatively large mounting holes.

Project info on QRF HomeBuilder blog.

CurrentRanger: auto-ranging current meter


An auto-ranging nanoAmp meter from LowPowerLab:

CurrentRanger is a nanoAmp current meter featuring auto-ranging, uni/bi-directional modes, bluetooth data logging options and more.
It is a highly hackable and affordable ultra low-burden-voltage ammeter, appropriate for hobby and professional use where capturing fast current transients and measurement precision are important.

More details on LowPowerLab site.

Check out the video after the break.



A full review of EasyEDA: A circuit EDA online tool


Yahya Tawil wrote in to share his review of a web based EDA tool, the EasyEDA. He explains the general structure of this tool and some of its cool features:

EDA cloud tools which are related to electronics are emerging exponentially in almost all aspects (i.e. simulation, PCB design, footprint creation, gerber files viewing and 3D PCB viewing). Even well-known desktop programs like EAGLE CAD and Altium are trying to compete in this field by making their own services or by acquiring others.
Web-based EDA tool suites like EasyEDA and Upverter are getting rapidly famous. These online tools offer some outstanding solutions for collaboration and providing some viable features for teams with financial limits like multi-layer PCB designing, while it costs a lot to buy a licence for other EDA tool with a multi-layer feature, for example.

More details at

Getting control over a 50 watt CO2 laser cutter from China


Unboxing laser cutter Co2 50 watt from China:

There are people around me who think I’m crazy. And they are probably right. Who else would buy a machine from someone he does not know. I have to pay upfront. It is not clear how things will get delivered, what gets delivered, or if it gets delivered at all. Up to the point I can lose the money I have spent. Best of all: that machine is dangerous enough to potentially kill me. And it has the potential to put my home on fire too. Well, that sounds like an exciting weekend project, or not?

See the full post at MCU on Eclipse homepage.

DIY robot design


A computational abstractions for interactive design of robotic devices by Ruta Desai, Ye Yuan and Stelian Coros from Carnegie Mellon University’s Robotics Institute:

We present a computational design system that allows novices and experts alike to easily create custom robotic devices. The core of our work consists of a design abstraction that models the way in which electromechanical components can be combined to form complex robotic systems. We use this abstraction to develop a visual design environment that enables an intuitive exploration of the space of robots that can be created using a given set of actuators, mounting brackets and 3d-printable components. Our computational system also provides support for design auto-completion operations, which further simplifies the task of creating robotic devices. Once robot designs are finished, they can be tested in physically simulated environments and iteratively improved until they meet the individual needs of their users.

Full details at

Check out the video after the break.

Adjustable constant current source


Dilshan Jayakody has published a new build:

The current source introduced in this article is capable to handle current up to 6A with maximum input voltage of 50V. This is an operational amplifier based adjustable current source and it uses LM358 in a general voltage follower configuration. To handle large currents we use four 0.1Ω 20W resistors as “load resistor”, and those load resistors are drive through pair of 55N06 N-channel MOSFET transistors.
The power supply unit of this project is build around 9V x 2 (2A) step-down transformer and it is design to get regulated 12V DC voltage. In our design this 12V power source is used to drive LM358 Op-Amp and 12V cooling fan.

More details at Dilshan Jayakody’s blog. Project files are available at

DIY polarity Led tweezers


Jesus Echavarria shared detailed instructions of how to make a simple tweezers for checking led polarity:

I usually assemble by hand all the boards I make. I use SMD components, especially in 0805 format for resistors, capacitors and leds. With the last ones, I always have the same problem: I need to check the polarity of it, to ensure that I assemble on the right way. To do it, I need the multimeter, select the diode position and test the led’s for the right polarity. Because on the assembly process I don’t usually the multimeter, why don’t make a tweezers to test the led’s? It’s an easy and very cheap project, and you’ll have a usefull tool when assembly boards. Here’s the result, after a couple of hours working on it ;).

More details at Jesus Echavarria’s blog.

In Defense Of The Electric Chainsaw

Here at Hackaday we are a diverse bunch, we all bring our own experience to the task of bringing you the best of the hardware scene. Our differing backgrounds were recently highlighted by a piece from my colleague [Dan] in which he covered the teardown of a cordless electric chainsaw.

It was his line “Now, we’d normally shy away from any electric chainsaw, especially a cordless saw, and doubly so a Harbor Freight special“. that caught my eye. I’m with him on cordless tools which I see as a cynical ploy from manufacturers to ensure 5-yearly replacements, and I agree that cheap tools are a false economy. But electric chainsaws? Here on this small farm, they’re the saw of choice and here’s why.

“I’ve Got A Bran’ New Chainsaw, You’ve got 43!”1

A small British farm is not a forestry business, but it’s fair to say that a chainsaw is a tool that sees fairly regular use. Branches come down, pieces of hedge need taming, and with a hungry woodburner to satisfy, firewood needs to be cut. You won’t be surprised then to find that my dad has had more than one chainsaw over the years, but you may be surprised to find that this long experience has led us to rely on electric saws exclusively for the last couple of decades.

So why do we load a generator on the back of the tractor and set upon fallen branches with a power cable trailing behind us when we could do it to the buzz of a 2-stroke motor? The answers are simple enough: maintenance and safety.

If you are a very occasional chainsaw user the chances are your saw will never be challenged. You’ll use it, put it away in the garage, and a year later when you pull it out again it’ll be ready to go after a bit of fettling. And if you’re a forestry worker your saw will be your livelihood, it’ll be an expensive piece of kit and you’ll maintain it to within an inch of its life. If however you are a small farmer without a big budget like my dad, you won’t be able to afford the forester’s maintenance schedule or deluxe saw, and you enter an abusive relationship with a nasty little 2-stroke motor and its work-any-way-up carburetor.

The Curse Of The Tiny 2-Stroke Motor

Let me say this, little 2-strokes really are horrible pieces of machinery when you have to rely on them. Half the parts are made of cheese, the other half vibrate apart if you stop looking at them, and they simply love to coat their insides with nasty gunk. They hate any suggestion that they might start at their owner’s first pull on the cord, and play hard-to-get through a half-hour of careful checking fuel mixtures and heating up plugs. And when you really want them to stop, like for instance when it’s a chainsaw safety issue, they refuse and stutter on for a few revolutions as the blade kicks up in the air and your life flashes before you. No, they save stopping for moments they consider opportune, such as when you’re at the top of a ladder with all the ropes set up to lop off a branch.

By comparison an electric chainsaw is easy to maintain, starts on the button, stops dead when it is asked and when that safety bar is triggered, and won’t cover you in smoke or 2-stroke mix. The inconvenience of carrying a 4-stroke generator, RCD, and extension lead is minor compared to the joys of operating a petrol saw on a small farm as I’ve just outlined.

So there you are. It may not put us in with the cool kids when we say that an electric chainsaw is our saw of choice, but we do so from the position of experience even if it means that using it away from the house involves firing up the tractor.

There is one snag though, and I’ll forestall you commenters from pointing it out. When the zombie apocalypse is upon us we’ll be in trouble if the undead can remember how to unplug an electrical cord.

Electric chainsaw header image: Harisingh&sons [CC BY-SA 4.0], via Wikimedia Commons.

1My deepest apologies to the Wurzels.

Filed under: Hackaday Columns, rants, tool hacks

Building an IoT Drill Press for Reasons Unknown

He’s a little cagey about the reasons, but [Ivan Miranda] plans to put a drill press on the internet. What could go wrong with that?

We’ll take [Ivan] at his word that there’s a method to this madness and just take a look at the build itself, in the hopes that it will inspire someone to turn their lowly drill press into a sorta-kinda 2-axis milling machine. [Ivan] makes extensive use of his 3D printer to fabricate the X-axis slide that bolts to the stock drill press table. And before anyone points out the obvious, [Ivan] already acknowledges that the slide is way too flimsy to hold up to much serious drilling, especially considering the huge mechanical advantage of the gearing he used to replace the quill handle for a powered Z-axis. The motor switch was also replaced with a solid state relay. The steppers, relay, and limit switches are all fed into a Teensy that talks to an ESP8266, which will presumably host a web interface to put this thing online.

The connected aspects of the drill press become a little more clear after the break.

Turns out [Ivan] had a sort of an Internet performance art piece in mind, wherein visitors to his website would get to vote on which of two phones would be executed by lethal drill pressing. The ways in which this project failed were manifold, from website errors that let the first visitor select a phone within eight minutes of going live, to inability of the stepper to drive the quill, to the surprisingly sturdy screens on the cheap phones. Oh well, these failures are a great satirical representation of the ills IoT has in its near future.

Perhaps you’ll enjoy these other drill press tricks, like turning a drill press into a spindle sander, or  even giving a benchtop press a column transplant to allow bigger workpieces.

[via r/Arduino]

Filed under: internet hacks, tool hacks

Qinsi-QS5100 Sn63Pb37 solder profile


Alan Hawse from IOT Expert writes, “About 2 years ago, I bought a Qinsi QS5100 reflow oven from China via  My decision was based almost completely on the nice youtube video that Ian Lesnet from Dangerous Prototypes posted about his results.  After I got the oven, I successfully built a series of Physics Lab boards with it.  Then one day about a year ago, I got two boards in a row with horrible results which I attributed to the temperature profile.  A few weeks later, I dug around on the internet and decided to change to the Lesnet profile and things seemed to be working again.”

More details at IOT Expert site.

Via the forum.