Monthly Archives: December 2017


via Dangerous Prototypes


Angus Ainslie writes about an open source project a CHIP Pro TNC:

So I finally have a design of the TNC I’ve been working on that I think is ready for release. Initially this started with me wanting a replacement for my mobilinkd and AP510. With feature creep it has turned into much more.
The current board has a VHF radio module, a CHIP Pro computer module running Linux ( NTC calls it gadget OS ) and a Mikrobus slot. I’m currently using the Mikrobus for a GPS module but there are lots of variants.

See the full post on his blog.

The Great Ceramic 3D Printer Experiment, Part III

via SparkFun: Commerce Blog

Hello, friends. It has been a while since my last progress report on The Great Ceramic 3D Printer Experiment (catch up on parts I & II). Fear not, for this project is still very much alive.

As a quick reminder, I am following OS designs for a Delta 3D Printer by Jonathan Keep. He has generously posted everything one needs to build this project…except a step-by-step tutorial. This is a daunting project and is definitely beyond the limits of my comfort zone. Thus far the process can be described as “two steps forward, one step back,” but I am learning a ton along the way and that’s really what it’s all about.

Last time we left off, I had finished building the basic structure of my printer…

for the second time.

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My next step was to make the pulley system, for which I needed to build some parts and then put a few together, none of which made sense to me. Luckily I work with some very talented mechanical engineers, so I have all the help I need in figuring this out.

First, I set out to make the parts circled in the image below.

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I was deeply perplexed about how to make this part. Yes, the measurements are provided, but that shape is complex. I decided to enlist (Pearce) to help me figure it out. Pearce modeled the part and sent me a printable file, which took him maybe five minutes. I am not a modeling pro - heck I am not even a modeling novice - so I have no idea how it was modeled, but I can share the file with you! Let us all collectively thanks Pearce for his great contribution in this project. Thanks, Pearce!

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As soon as I finished printing these I realized that they attach to the linear bearings via zip-ties as you can see in this image from Keep’s website:

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At this point, I had two options:
1. Edit the model to accommodate the zip-ties and reprint.
2. Drill holes in the printed parts like a heathen.

As you can see in the image below, I went with option two.

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It was actually a perfectly fine solution, and I saved myself a few hours of extra printing.

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Next up was building the tension. Here is an image of what we are looking at from Keep’s site.

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He also provides some files that can be used to machine this part on the laser cutter, but I ended up designing my own based on the hardware we had lying around.

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I started by cutting this part out of Delrin for strength. I assumed this part would eventually be moving, and thought Delrin would be stronger than acrylic. Cutting the Delrin took forever, and in this design I did not account for the bulky nuts on the hardware I was using as you can see below.

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Unfortunately we only had (relatively) bulky hardware lying around so my part does not look quiet as elegant as Keep’s, but elegance was never the goal here so I’m OK with it (Edit: no I am not. My deep-seated need to make things look pretty is overwhelming and I will probably re-do this later to make it look better because I am who I am).

Elegant or not, the hardware was too close together and needed to be spread out.

Since I learned this part does not move, I decided to cut the second iteration out of acrylic because it’s cheaper and much easier to cut.

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You can see here that there are three screws. The two on either side hold this part in place against the rods. The center screw acts as the tension for the pulley. In order to (hopefully) make this work smoothly, I added a 3D-printed part around the middle screw to keep the belt from moving around too much. Our very own Evan helped me make this part.

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There is one more piece of hardware involved with the pulley system – the motor. The three motors sit snugly at the top of the printer structure.

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I added a pulley to each motor so they can effectively control the belt.

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The last step was adding the belt. There were two parts to this: First, the belt needed to be cut to size and clamped together into a loop. Second, I needed to somehow attach that point of connection to the moving linear bearings.

In order to make the belt a loop, I used 3D-printed clamps modeled by Evan.

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It was tough to get the belt in there. I ended up having to use tweezers to make enough space. I think that may have compromised the structural integrity of the part by stretching it out.

I also needed to attach this to the moving linear bearings. It was pretty awkward and I’m still not entirely sure what to do.

I attached the 3D-printed clamp object (the one that holds the belt) to the 3D-printed object attached to the linear bearing with a screw. Then, I started to move the linear bearings up and down. The first issue I found was that the motor moves with the pulley and ends up looking like this:

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No bueno. I added a zip-tie to hold the motor and that worked really well. (This would be a good time to note that Keep explicitly calls for zip-ties on the motors on his site. I just breezed right past that part and discovered it was necessary through testing. Paying attention to the documentation would obviously make this a much easier process, but again, I am who I am.)

Here is a video of my second test, this time with the zip-tie around the motor:

There was a little slack but I was confident I could make some adjustments and get everything nice and taut. That was until this happened:

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If you look closely, you can see that one end of my belt is NOT in the clamp as it should be. What did I learn? My 3D-printed clamp is not strong enough to hold the belt as it pulls the linear bearings up and down. I’m going to need to figure out a new clamping system, as well as a way to attach that to the linear bearings. I’m going to talk to a few folks who are more adept at mechanical engineering than myself to help come up with solutions, and that will be where we start the next installation of The Great Ceramic 3D Printer Experiment.

I sincerely thank all of you who are following along as I fumble around on this project. Please join the conversation in the comments below. I would love to hear everyone's ideas, suggestions, and thoughts!

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Monitor your sleep quality with Arduino

via Arduino Blog

While it can be difficult to get enough sleep, at least you can try to make it as restful as possible when you are in bed. That’s the idea behind this project by Julia Currie and Nicholas Sarkis, who developed an Arduino Nano-based sleep monitor for their final ECE 4760 project at Cornell.

The bulk of the monitoring device takes the form of a glove which measures heart rate using an IR sensor, along with movement via an accelerometer. Breathing is recorded using a conductive band wrapped around the user’s chest, which changes resistance depending on how it is stretched.

The Nano mounted to the glove collects this information, and transmits it wirelessly using an nRF24L01 chip to a PIC32 microprocessor on a base station. Data is then graphed nicely on a TFT display for further analysis.

You can read more about the project here and see the video below!

#FreePCB via Twitter to 2 random RTs

via Dangerous Prototypes


Every Tuesday we give away two coupons for the free PCB drawer via Twitter. This post was announced on Twitter, and in 24 hours we’ll send coupon codes to two random retweeters. Don’t forget there’s free PCBs three times a every week:

  • Hate Twitter and Facebook? Free PCB Sunday is the classic PCB giveaway. Catch it every Sunday, right here on the blog
  • Tweet-a-PCB Tuesday. Follow us and get boards in 144 characters or less
  • Facebook PCB Friday. Free PCBs will be your friend for the weekend

Some stuff:

  • Yes, we’ll mail it anywhere in the world!
  • Check out how we mail PCBs worldwide video.
  • We’ll contact you via Twitter with a coupon code for the PCB drawer.
  • Limit one PCB per address per month please.
  • Like everything else on this site, PCBs are offered without warranty.

We try to stagger free PCB posts so every time zone has a chance to participate, but the best way to see it first is to subscribe to the RSS feed, follow us on Twitter, or like us on Facebook.

BML USB 3.0 FPGA interface over PMOD

via Dangerous Prototypes


An open-source-hardware USB 3.0 to FPGA PMOD interface design from Black Mesa Labs:

Black Mesa Labs is presenting an open-source-hardware USB 3.0 to FPGA PMOD interface design.  First off, please lower your expectations. USB 3.0 physical layer is capable of 5 Gbps, or 640 MBytes/Sec. This project can’t provide that to your FPGA over 2 PMOD connectors – not even close. It does substantially improve PC to FPGA bandwidth however, 30x for Writes and 100x for Reads compared to a standard FTDI cable based on the FT232 ( ala RS232 like UART interface at 921,600 baud ). A standard FTDI cable is $20 and the FT600 chip is less than $10, so BML deemed it a project worth pursuing.

More details at Black Mesa Labs homepage.

Via the contact form.

Desk of an Engineer: the Pete Edition

via SparkFun: Commerce Blog

We’re back with more desk details! This is Part Five in a series where we barge in on our engineers while they’re working and kick them out so we can document their desks in all their chaotic glory. And because we know that just isn’t enough information, we ransom their offices back to them in exchange for some details on what they have on their desks and why. We do this for you!

Clicking the image will enlarge it, so you can experience the full resolution of each engineer’s home away from home.

Today’s victim: the one and only Pete Dokter. Let’s get right into it.

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Jeez, what a mess. About once every three months, I’ll get nuts and drop everything to clean and organize my workspace. Today’s clearly not that day.

This is one of three workable horizontal surfaces. The most obvious features here are the speakers and the Kenwood KA-4006. Music features prominently in pretty much everything I do, and I rarely work without it. Headphones? Nope, gotta be able to move around. My favored genre tends toward stoner/psychedelic (check out the channel “Stoned Meadow of Doom” on YouTube), but I’ve also been listening to the Delvon Lamarr Organ Trio a lot lately. The right music is critical.

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Upon closer inspection… needs more lights. There’s one small fluorescent on the shelf (center, poking up out of the pic) that does the job, but I could always use more. Instruments tend toward the left, with my laptop usually occupying the left-most corner of the bench. The scope is a Tektronix 2247A, the signal generator on top of it is a Tektronix AFG1022 (swiped from Alex last week, I’m gonna have to return that), and an Extech power supply on the shelf above. There’s also an Analog Discovery 2 USB scope in just about the dead center of the pic. That’s a super handy piece of gear, and it travels better than the big scope.

My iron and hand tools tend toward the right side (but they’re starting to creep over), and semi-random parts up the middle. In the very middle, in the back, is a segmented box of parts - caps and resistors of various useful values, all 0603, some regs and mosfets as well - with a roll of red wire-wrap wire on top of it, then another cardboard box on top of that filled with a bunch of other build parts, all through-hole. There’s another box peeking out from behind the scope that’s got screws, nuts, washers, standoffs… all the mechanical junk I’m likely to need to build something. And if it’s not there, there’s a stash of parts outside my office that I can raid. The coffee cup? More parts.

Last is the board vice, close to my iron. I use that thing pretty much every day. Back in the day, I used to just pin stuff down with a roll of solder or whatever other heavy thing I had lying around. That’s just one random element I can do without these days.

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Second horizontal work surface. From left to right, a small pile of docs and parts, a couple of coffee cups, computer, disused telephone, big box of granola bars and a plant that Feldi gave me that, apparently, I’m too self-absorbed to care for cuz it’s dead, dead, dead. I’m sorry Feldi, I have shamed myself. Under the box of Kleenex is a drawing my son made for me a bunch of years ago that I recently found. It says “I [heart] U” on one side, and on the other is a stick figure of me with a gold trophy that says “100” on it. I guess that’s me in a nutshell.

I split programming and layout duties between my desktop and my laptop, which is an Asus gaming laptop (so fast, big screen and a full-sized keyboard). But I tend to do documentation and other writing on the desktop.

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Last horizontal surface, and it’s mostly collecting junk right now. From left to right (generally, sorta), a broken power supply that works just enough to be useful, bunches of samples (including flexible solar panels, Invensense IMU’s, inductors, I think there’s a buck regulator in there too), one of Brian Benchoff’s boards (for Defcon?) that he gave me because it didn’t work, a keyboard and monitor from a Pi project I was doing, and… um… a glider. Sometimes I gotta go fly. That’s it!

Thanks, Pete! You can have your office back now.

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