Turning An Angle Grinder Into A Belt Sander

April 3, 2016 by James Hobson 23 Comments

Faced with a project requiring a lot of sanding, [George] had two options. Suck it up and buy a belt sander — or re-purpose a tool he already had to do the same job. He chose the latter, and turned an angle grinder into a belt sander.

Part of a series called Make It Extreme on YouTube, [George] built the entire project from scratch using raw materials. Using a lathe he created the aluminum rolling dowels the sanding belt will sit on. He pressed bearings into them, and then welded up a frame using scrap steel to hold them apart. He’s even added a spring-powered tension device to ensure the belt stays on.

As for mounting the angle grinder in place, it couldn’t be easier. It slides in between two metal guides, and attaches using the threaded hole for the angle grinder’s handle.

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Hack Your Multimeter

April 2, 2016 by Elliot Williams 28 Comments

A good multimeter (or a few of them) is an essential part of anyone’s electronics workbench. The only thing more useful than a multimeter is a logging multimeter that can take recordings over time. And the only thing more useful than that is one that can transfer that data back to your computer for analysis. But fancy meters often cost a bit of money.

[Kerry Wong] decided to take matters into his own hands and hack a serial-out port into his relatively inexpensive multimeter, giving him the ability to record anything the meter can measure roughly three times a second until he runs out of hard-drive space.

Our hack begins with the datasheet for the meter’s microprocessor. [Kerry] then tacked on a few wires, and dumped, modified, and reflashed the calibration and configuration EEPROM. With a single bit-flip in the EEPROM, he enabled serial output. With a few more, he made the backlight stay on longer, disabled auto power-off, and basically customized the meter the way he wanted it.

Getting the data out of the meter is the big coup, however. Not wanting to risk the computer that he’s connecting to the meter, [Kerry] knew that he needed optoisolation between the meter and the USART. He went with a beautifully minimal solution — simply wiring the meter’s serial output to an IR LED. Usually, transmitting data over IR is done by modulating the signal with a 38 kHz carrier for noise immunity. [Kerry] was going to put the receiver right up against the transmitter anyway, so he went with a plain IR photodiode on the PC side. sigrok takes care of the datalogging and display.

Adding more automation to our measurement bench has been on our to-do list for a long time now, and [Kerry]’s hack provides an inexpensive and fun way to get started. It’s the perfect companion to a computer-controlled supply. (Or two!.)

Tiny Hotplate Isn’t Overkill

April 1, 2016 by Bryan Cockfield 31 Comments

When working on a new project, it’s common to let feature creep set in and bloat the project. Or to over-design a project well beyond what it would need to accomplish its task. Over at Black Mesa Labs, their problem wasn’t with one of their projects, it was with one of their tools: their hot plate. For smaller projects, an 800W hot plate was wasteful in many ways: energy, space, and safety. Since a lot of their reflow solder jobs are on boards that are one square inch, they set out to solve this problem with a tiny hot plate.

The new hot plate is perfectly sized for the job. Including control circuitry, it’s around the size of a credit card. The hot plate is powered from a small surplus 20V 5A laptop power supply and does a nice 4 minute reflow profile and cools off completely in under a minute. Compared to their full-sized hot plate, this is approximately 29 minutes faster, not to mention the smaller workspace footprint that this provides. The entire setup cost about $20 from the heating element to the transistors and small circuit board, and assuming that you have an Arduino Pro sitting in your junk bin.

It’s a good idea to have a reflow oven or a hot plate at your disposal, especially if you plan to do any surface mount work. There are lots of options available, from re-purposed toaster ovens to other custom hot plates of a more standard size. Overkill isn’t always a bad thing!

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DIY Active Sub-GHz Differential Scope Probe

March 31, 2016 by Elliot Williams 31 Comments

Fancy measurement gear is often expensive to buy, but some bits of kit are entirely DIY’able if you’re willing to put a little work into the project. [Christer Weinigel] needed to get some measurements of a differential clock signal that was ticking away around 500 MHz. El-cheapo probes aren’t going to cut it here. They won’t have the bandwidth and most off-the-rack probes are single-ended, that is they’re referenced to ground. [Christer] needed the difference between two balanced signals, neither of which is grounded. In short, [Christer] needed a high-frequency active differential oscilloscope probe, and they’re not cheap. So he built one himself.

The circuit in the probe is really just an instrumentation amplifier design with a modified input stage and a 50 ohm output impedance. (See this article on in-amps if you need to brush up.) With higher frequencies like this, it’s going to be demanding on the op-amp, so [Christer] spent some time simulating the circuit to make sure it would work with his chosen part. Then he made up a bunch of PCB designs and had them made. Actual results matched fairly well with the simulation.

With some minor tweaking on the input damping resistors, he got a tool that’s dead flat up to 300 MHz, and totally usable up to 850 MHz. If you tried to buy one of these, it’d set you back the cost of a few hundred lattes, but this one can be made for the price of one or two if you get the PCBs done cheaply. Of course, the design files are available for your own use. Kudos [Christer].

Edit: By total coincidence, Bil Herd just posted a video intro to differential signals. Go check it out.

And thanks to [nebk] for the tip!

Nanocounter: Frequency Counter With An Android UI

March 29, 2016 by Eric Evenchick 9 Comments

Have you ever started a project, run into an issue, started a new project to solve the issue, and completely forgot about the original project? [Andy] went down a rabbit hole of needing a tool to calibrate an MCU oscillator, but not having an accurate way to measure frequency. Most people would just buy a frequency counter and be done with it, but [Andy] decided to build his own.

The Nanocounter is an accurate, open source frequency counter that uses an Android phone as its display. It’s based on a high accuracy temperature compensated crystal oscillator (TCXO) fed into a phase locked loop (PLL) to create a high frequency, accurate reference clock.

This reference clock, along with the signal to be measured, are sent into a Xilinx FPGA which uses a method called equal precision measurement to determine the frequency. A STM32F072 microcontroller uses a SPI interface to get this data out of the FPGA, and controls the whole system. Finally, a cheap HC-06 Bluetooth module facilitates communication with an Android device.

The project achieves the goal of frequency counting, though [Andy] doesn’t remember what project sparked the idea to build it. (Classic yak shaving!) But the result is a great read of a detailed writeup, and you can watch a video of the Nanocounter in action after the break. That’s a win in our book.

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You Speak, Your Scope Obeys

March 29, 2016 by Elliot Williams 17 Comments

We’ve been scratching our heads about the various voice-recognition solutions out there. What would you really want to use one for? Turning off the lights in your bedroom without getting up? Sure, it has some 2001: A Space Odyssey ~~flare~~ flair, but frankly we’ve already got a remote control for that. The best justification for voice control, in our mind, is controlling something while your hands or eyes are already busy.

[Patrick Sébastien Coulombe] clearly has both of his hands on his oscilloscope probes. That’s why he developed Speech2SCPI, a quick mash-up of voice recognition and an oscilloscope control protocol. It combines the Julius open-source speech recognizer project with the Standard Commands for Programmable Instruments (SCPI) syntax to make his scope obey his every command. You’ve got to watch the video below the break to believe how well it works. It even handles his French accent.

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Handy Power Supply With 3D Printed Case

March 26, 2016 by Al Williams 12 Comments

You can never have too many power supplies around your workbench. It is easy to buy them or cobble something together for most purposes. But once in a while you see one that is simple and also looks good, like this one from [RegisHsu].

The project is simple since it uses off-the-shelf DC-to-DC converter modules, and good-looking LED meters to measure voltage and current. The dual supply can accept 5 to 16 V in (presumably from a wall transformer) and deliver 1.3 V to 15.5 V out at 2 amps. [RegisHsu] removed an adjustment pot from the converter board and replaced it with a 10-turn pot to allow voltage adjustment.

Given the parts, you probably don’t even need a wiring diagram. However, the part that brings it together is the 3D-printed case, which [RegisHsu] has on Thingiverse. We’ve looked at muti-turn pot replacements before, and this is hardly the first power supply project we’ve posted.