Tiny Hotplate Isn’t Overkill

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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KiCAD BOM Management

KiCAD remains a popular tool for designing PCBs and other circuits, and with good reason: it’s versatile and it’s got pretty much everything needed to build any type of circuit board you’d want. It also comes with a pretty steep learning curve, though, and [Jeff] was especially frustrated with the bill of materials (BOM) features in KiCAD. After applying some Python and Kivy, [Jeff] now has a BOM manager that makes up for some of KiCAD’s shortcomings.

Currently, the tool handles schematic import, like-component consolidation, and a user-managed parts database that can be used to store and retrieve commonly used parts for the future. All of the changes can be saved back to the original schematic. [Jeff] hopes that his tool will save some time for anyone who makes more than one PCB a year and has to deal with the lack of BOM features native to KiCAD.

[Jeff] still has some features he’d like to add such as unit tests, a user guide, and a cleaner user interface. What other features are you anxious to see added to KiCAD?

This script is a great tool for anyone who has had similar frustrations. KiCAD is popular to modify and expand, too: there have been tools for mechanical CAD export, a parts-generator and cost-tracker, and an Eagle to KiCAD converter if you’re thinking of making the switch.

3D Printer Tool: Set Your Extruder Steps With Ease

My printer has other issues that i'm still tuning out, but the warping in PLA and excessive surface roughness has all the signs of over extrusion.
My printer has other issues that I’m still tuning out, but the warping in PLA and excessive surface roughness has all the signs of over extrusion.

I have an old Prusa i2 that, like an old car, has been getting some major part replacements lately after many many hours of service. Recently both the extruder and the extruder motor died. The extruder died of brass fill filament sintering to the inside of the nozzle (always flush your extruder of exotic filaments). The motor died at the wires of constant flexing. Regardless, I replaced the motors and found myself with an issue; the new motor and hotend (junk motor from the junk bin, and an E3D v6, which is fantastic) worked way better and was pushing out too much filament.

The hotend, driver gear, extruder mechanics, back pressure, motor, and plastic type all work together to set how much plastic you can push through the nozzle at once. Even the speed at which the plastic is going through the nozzle can change how much friction that plastic experiences. Most of these effects are somewhat negligible. The printer does, however, have a sort of baseline steps per mm of plastic you can set.

The goal is to have a steps per mm that is exactly matched to how much plastic the printer pushes out. If you say 10mm, 10mm of filament should be eaten by the extruder. This setting is the “steps per mm” in the firmware configuration. This number should be close to perfect. Once it is, you can tune it by setting the “extrusion multiplier” setting in most slicers when you switch materials, or have environmental differences to compensate for.

This little guy lets you tune the steps per mm exactly.
This little guy lets you tune the steps per mm exactly.

The problem comes in measuring the filament that is extruded. Filament comes off a spool and is pulled through an imprecisely held nozzle in an imprecisely made extruder assembly. On top of all that, the filament twists and curves. This makes it difficult to hold against a ruler or caliper and get a trustworthy measurement.

I have come up with a little measuring device you can make with some brass tubing, sandpaper, a saw (or pipe cutter), a pencil torch, solder, and some calipers. To start with, find two pieces of tubing. The first’s ID must fit closely with the filament size you use. The second tube must allow the inside tubing to slide inside of it closely. A close fit is essential.

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Link Trucker is a Tiny Networking Giant

If you’re a networking professional, there are professional tools for verifying that everything’s as it should be on the business end of an Ethernet cable. These professional tools often come along with a professional pricetag. If you’re just trying to wire up a single office, the pro gear can be overkill. Unless you make it yourself on the cheap! And now you can.

[Kristopher Marciniak] designed and built an inexpensive device that verifies the basics:

  • Is the link up? Is this cable connected?
  • Can it get a DHCP address?
  • Can it perform a DNS lookup?
  • Can it open a webpage?

What’s going on under the hood? A Raspberry Pi, you’d think. A BeagleBoard? Our hearts were warmed to see a throwback to a more civilized age: an ENC28J60 breakout board and an Arduino Uno. That’s right, [Kristopher] replicated a couple-hundred dollar network tester for the price of a few lattes. And by using a pre-made housing, [Kristopher]’s version looks great too. Watch it work in the video just below the break.

Building an embedded network device used to be a lot more work, but it could be done. One of our favorites is still [Ian Lesnet’s] webserver on a business card from way back in 2008 which also used the ENC28J60 Ethernet chip.
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uController Code Profiler Debugs Your Microcontroller

When working on digital circuits that operate at high frequencies it helps to have some special tools on hand. Things like oscilloscopes and logic analyzers are priceless when something isn’t working right. Another great tool would be this hardware-based profiler that [Mike] came up with while he was working on another project.

The profiler connects to USB and shows up as a serial port. Normally [Mike] used a set of LEDs to get information about how his microcontrollers work, but for this project that wasn’t enough. The uController Code Profiler can provide the main loop running time, time functions and sections of code, keep track of variables, and a few other tasks as well, all with nanosecond resolution.

The source code isn’t provided but a hex file is available, along with a schematic and an include file, if you want to try this one out on your next project. Like this homemade logic analyzer, this could be a powerful tool in your microcontroller arsenal. Simply include the file with various pieces of your code to get it up and running!

Exploding Multimeter Battle Royale

If you check out eBay, Amazon, or the other kinda-shady online retailers out there, you’ll quickly find you can buy a CAT III (600V) rated multimeter for under $50. If you think about it, this is incredible. There’s a lot of engineering that needs to go into a meter that is able to measure junction boxes, and factories in China are pushing these things out for an amazing price.

Over on the EEVBlog, these meters are being pushed to the limits. Last month, [joeqsmith] started a thread testing the theory that these cheap meters can handle extremely high voltages. A proper CAT III test requires a surge of electrons with a 6kV peak and a 2 ohm source. With a bunch of caps, bailing wire, JB Weld and zip ties, anyone can test if these meters are rated at what they say they are. Get a few people on the EEVBlog sending [joeqsmith] some cheapo meters, and you can have some real fun figuring out how these meters stack up.

The real experiments began with [joe smith]’s low energy surge generator, a beast of a machine that can be measured with an even beastlier high voltage scope probe. This is a machine that will send a voltage spike through anything to short out traces on poorly designed multimeters.

How did the cheapo meters fare? Not well, for the most part. There was, however, one exception: the Fluke 101. This is Fluke’s My First Multimeter, stuffed into a pocketable package. This meter is able to survive 12kV pulses when all but two of the other brands of meters would fail at 3kV.

What’s the secret to Fluke’s success? You only need to look at what the Fluke 101 can’t do. Fluke’s budget meter doesn’t measure current. If you ever look inside a meter, you’ll usually find two fuses, one for measuring Amps and the other for all the other functions on the scope. There’s quite a bit of engineering that goes into the current measurement of a meter, and when it goes wrong you have a bomb on your hands. Fluke engineers rather intelligently dropped current measurement from this budget meter, allowing them to save that much on their BOM.

There’s an impressive amount of data collected by [joeqsmith] and the other contributors in this thread, but don’t use this to decide on your next budget meter; This is more of an interesting discovery of how to make a product that meets specs: just cut out what can’t be done with the given budget.

2D Printed Tachometer For A Lathe

If you ever wanted a reason to have DC lighting pointed at the spinny part of your mill and lathe, [Bill] tells a great story. One day, he noticed the teeth on his lathe chuck would change color – red, then blue, then red. His conclusion was the fluorescent lights above his workbench was flashing, as fluorescent lights normally do.

Imagine if the teeth on [Bill]’s chuck weren’t painted. They would appear stationary. That’s usually a bad thing when one of the risks of using a lathe is ‘descalping.’ Buy an LED or incandescent work light for your shop.

This unique effect of blinking lights got [Bill] thinking, though. Could these fluorescent lights be used as a strobe light? Could it measure the RPM of the lathe?

And so began [Bill]’s quest for a 2D printed lathe tachometer. The first attempt was to wrap a piece of paper printed with evenly space numbers around the chuck. This did not work. The flash from his fluorescent bulb was too long, and the numbers were just a blur. He moved on to a maximum-contrast pattern those of us who had a ‘DJ phase’ might recognize immediately.

By printing out a piece of paper with alternating black and white bands, [Bill] was able to read off the RPM of his chuck with ease. That’s after he realized fluorescent lights blink twice per cycle, or 120 times a second. If you have a 3″ mini-lathe, [Bill] put the relevant files up, ready to be taped to a chuck.