Drawbacks Of Laser Cut Delrin–and How To Slip Around Them

September 22, 2015 by Sonya Vasquez 34 Comments

Welcome back to part II in this ensemble of techniques with laser-cut Delrin. Thanks for many of the great insights along the way in the comments. In this guide, I’d like to go over some of the more immediate kinks that come to mind when getting started with this material.

Sourcing Delrin Sheets

When it comes to shopping, there are a variety of suppliers to choose from, but there are a few key words and thoughts to keep in mind.

Names

First, Delrin, is the “brand name” that refers to the Acetal homopolymer. Variants may also be labeled, acetal or acetal homopolymer. Delrin’s natural color is a soft white, but dyes can take it into a range of other colors. Black and white are, by far, the most common, though.

Tolerances

In the previous guide, all of the examples were cut from a small range of sheet thicknesses (0.0625[in], 0.09375[in], and .125[in]) sourced from OnlineMetals. As the thickness of the sheet increases, the tolerances on the thickness rating will also become more loose. You might buy a .125[in] plate and find it to be .124[in] in some places and .126[in] in others. If you purchase a .250[in] sheet, however, you’ll find that it may vary as much as .126[in] oversize though!

Buy it Flat

Despite McMaster-Carr being my go-to solution for one-off prototypes where rapid build iterations trump BOM cost, I don’t recommend purchasing Delrin from them as their sheets don’t have a flatness rating and often gets shipped bent in (oddly sized) boxes. (Seriously, has anyone else gotten a few oddly-sized parts in a gigantic McMaster-box before?)

Internal Stresses

Extruded Delrin has internal stresses built up inside of the sheet. There are a variety of reasons why this could be the case, but my biggest hunch is that the extrusion process at the factory results in different parts of the sheets solidifying at different times as the sheet cools, possibly causing some parts of the sheet to tighten from the cooling before other gooier sections have yet to finish cooling. What this means for you is that as your part gets lased out of the sheet, you’re, in a sense, relieving that stress. As a result, the part that you cut–especially for thin sheets–may come out of the laser cutter slightly warped.

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A Better Spectrum Analyzer For Your Rigol Scope

September 22, 2015 by Eric Evenchick 11 Comments

The Rigol DS1000 series of oscilloscopes are popular with hobbyists for good reason: they provide decent specs at a low price. However, their spectrum analysis abilities are lacking. While these scopes do have a Fast Fourier Transform (FFT) function, it’s limited and nearly useless for RF.

[Rich] wanted a spectrum analyzer for amateur radio purposes, but didn’t want to build his own sampling hardware for it. Instead, he wrote PyDSA, a software spectrum analyzer for Rigol DS1000 oscilloscopes. This tool uses the USB connection on the scope to fetch samples, and does the number crunching on a far more powerful PC. It’s able to plot a 16,000 point FFT at two sweeps per second when run on a decent computer.

PyDSA is a Python script that makes use of the Virtual Instrument Software Architecture (VISA) interface to control the scope and fetch the sample data. Fortunately there’s some Python libraries that take care of the protocol.

[Rich] is now able to use his scope to measure amateur radio signals, which makes a nice companion to his existing Teensy based SDR project. If you have a Rigol, you can grab the source on Github and try it out.

HC-SR04 Isn’t The Same As Parallax PING))) But It Can Pretend To Be!

September 22, 2015 by Rud Merriam 8 Comments

“It’s only software!” A sentence that strikes terror in the heart of an embedded systems software developer. That sentence is often uttered when the software person finds a bug in the hardware and others assume it’s going to be easier for fix in software rather than spin a new hardware revision. No wonder software is always late.

[Clint Stevenson] is his own hardware and software guy, as are most of us. He wanted to use the less expensive HC-SR04 ultrasonic rangefinder in a prototype. Longer term he wanted to have the choice of either a Parallax PING or MaxBotix ultrasonic sensor for their better performance outdoors. His hardware hack of the SR04 made this a software problem which he also managed to solve!

[Clint] was working with the Arduino library, based on the Parallax PING, which uses a single pin for trigger and echo. The HC-SR04 uses separate pins. Originally he modified the Arduino library to accept the two pin approach. But with his long term goal in mind, he also modified the HC-SR04 sensor by removing the on-board pull-up resistor and adding a new one on the connector side to combine the signals. That gave him an SR04 that worked with the single-pin based library.

We’ve seen Parallax PING projects for sensing water depth and to generate music. These could be hacked to use the HC-SR04 using [Clint’s] techniques.

[Arduino and HC-SR04 photo from Blax Lab]

Quick Marty! We Have To Go Back, With The Golf Cart!

September 22, 2015 by James Hobson 16 Comments

Talk about an awesome project. [Lucas Evanochko] was commissioned to build this totally rad Delorean style golf Cart for Red Deer College’s 30^th annual Golf Tournament.

According to him, it’s been about 600 hours in the making – and they only started building it in July. This past week was its big unveiling, and it has had an overwhelmingly positive response so far!

They started with one of the club’s golf carts and modified it heavily, relying on the automotive expertise of [David Keykants] and [John Perrin] to turn it into the aw-worthy time machine it is today. It has a 7” tablet built right into the dash to play music and use the Fluxy88 Time Circuits app. A big array of arcade buttons hooked up to an Adafruit Audio FX board play various sound bites from the movie, including the theme music!

All the accessories are powered off of a separate 12V system from the main 48V drive line. Oh and the Flux Capacitor? It’s controlled by a Trinket Pro. Check it out after the break. We love the detail that went into this!

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Reach Out And Touch Your Computer

September 21, 2015 by Will Sweatman 22 Comments

[Carter Yagemann] found himself in a bit of a pickle. He uses his computer mostly for gaming, but would like to access it remotely from time to time to do a littler server work on the side. The problem is gaming computers eat up a lot of electrons and he didn’t want to waste them by leaving it on all the time. The obvious solution was to use the Wake on Lan function. Unfortunately, his motherboard did not support this technology.

Like any good hacker would do, [Carter] used an IoT board to connect the power button of his PC to the internet. He achieved this goal with a Particle Core board. His motherboard was an ATX variety, so wiring up two of the IoT board’s I/O pins to the power on pins on the motherboard was a simple task accomplished with the help of an inline resistor.

This hack is so easy that it’s a great alternative to the blinky LED first program we all know so well. Want to get started in the hacking community? This is a great way to get going.

Omaha Mini Maker Faire: Recycle All The Things

September 21, 2015 by Kristina Panos 13 Comments

A young maker named [Allie] drew a lot of attention at the 2nd annual Omaha Mini Maker Faire. Her booth was full of the various creations she has designed and built herself throughout the course of her short life. The biggest draw was her green design dollhouse, which focuses on environmentally friendly living. With the exception of the LEDs lighting the interior, some tape, and the requisite bit of hot glue, the entire structure and its contents were made from recycled materials.

The cardboard structure features a kitchen, living room, bedroom, bathroom, and attic. Every piece of furniture and all the decorations are made from salvaged materials and packaging. One side of the roof holds a Snap Circuits board with a solar panel that powers some blue LEDs on the bedroom wall. [Allie] poured water down the other side of the roof to demonstrate the rain water collection system. The house’s rain barrel was made from a grated parmesan cheese container, which is perfectly designed for the airline tubing running into it from the recycled plastic guttering.

One of [Allie]’s other projects is a disagreeable owl fashioned from cardboard and a salvaged canister. Hidden away beneath the owl’s platform lies a simple gear system attached to a key on the front. Turning the key causes the owl’s head to swivel back and forth. We tried to make it spin all the way around, but the full range of motion is about 270 degrees. She also brought Mountain Dew, a hummingbird model made from a spark plug and other metal bits and bobs, including a pair of soda can wings.

In addition to her crafty skills, [Allie] is one well-spoken tween. She was more than happy to discuss her creations in detail to anyone who would listen, which included at least two local journalists and this impressed reporter. We learned through a bit of light research that a robot [Allie] built a few years ago inspired a British toy company to produce a new doll, the Robot Girl Lottie. She’s an inspiration to makers of all ages.