Tuesday, 25 June 2019

How to Mark Delrin (Acetal), Even Though Nothing Wants to Stick to it

Nothing sticks to Delrin (acetal), so it's not easy to paint or label.  Or is it?

One easy and reliable way to mark is to use a simple technique common to laser cutting. Shallow cuts or engravings are covered with paint, then the excess wiped away.

What happens is that any paint that got into the shallow cuts stays there, resulting in a mark the same color as the paint.

Acrylic paints tend to work best.  They are water-soluble (as long as it hasn't dried) and is a usually a bit on the goopy side which tends to help the process.

But to be successful, one must be able to cleanly wipe away ALL the excess from the surface.  It's no good if the paint leaves a smudge or a stain.  It needs to come away completely while leaving the filled spots behind.

The good news is that even though acrylic paint won't stick to acetal (also called Delrin), this technique works great for two reasons:

  1. The paint in the marks is being physically held there, inside the shallow cuts.  It doesn't depend on the paint "sticking" to the surface.
  2. Wiping away excess paint completely (the key to success with this method) is super easy to do.  Because paint doesn't want to stick to Delrin, the excess wipes off no problem.

Monday, 10 June 2019

Get Low-Power Mode Payoffs, From a $6 Board

Sparkfun has a new part, one that I almost can't believe didn't get made by someone sooner.  The Nano Power Timer is just under $6 and makes it easy to take just about any microcontroller project (Arduino or anything else) and effortlessly give it a hardware low power mode, all without needing to mess with any low-level microcontroller programming.

Here is how it works: the switches on the board set a time delay. During this time, the Nano Power Timer sips barely 35 nanoamps but the catch is that power to your circuit is completely cut off.

Once the timer is up, power is applied to your circuit and it will turn on to do its job (read a sensor to decide whether or not to do something more, for example.)  Once it is finished doing whatever it needs to do, a GPIO pin signal to the Nano Power Timer's DONE pin is all it takes to go back to sleep and reset the timer to do it all over again. It works on any voltage between 1.8 and 5 volts.

Low power operation is the difference between viable and non-viable for some projects. Not everything can be plugged into the wall all the time and not everyone can easily make low-power modes work.  A board like this is a great companion to a solar charger solution, as well.

Monday, 6 May 2019

How to Visualize 4D Objects

A 4th spatial dimension (meaning not "Time" but instead a 4th axis (W) in addition to X, Y, and Z) is completely non-intuitive and difficult to comprehend, but there are some amazing resources to help you do exactly that.

First is a short video from the maker of an in-development game. It does an excellent job of describing how 4D navigation might appear to a 3D entity (like ourselves.)

Trippy, isn't it?

There is also a somewhat more in-depth and detailed (but still very accessible) two-part video series. Here is part one, which covers some fascinating essentials and is all about Perspective:

And the follow up about visualizing 4D geometry:
If you're thinking you can't really wrap your head around it, don't worry because no one else can either. But it's fascinating nonetheless.

Thursday, 4 April 2019

Worldwide Hardware Design Contest for 2019 Opens

The Hackaday Prize has been running every year with a different spin, and this year it focuses on HARDWARE.

Anyone can make one of something, but making a hundred or a few thousands of a thing requires a different set of skills and represent the next step for "making something".  The good news is that those skills can be taught, learned, and there are resources available for making it happen.

The 2019 Hackaday Prize has almost $200,000 up for grabs, and all you need to get started is an idea, an image, and some documentation. So get started!

Thursday, 14 March 2019

How to Make a Lithophane (3D Printed Photo)


Lithophanes are solid plates of varying thickness, which show an image when lit from behind.  Think of them as a carving, where the thick parts are dark and the thin parts are light, so it can make a picture.

Today, it's possible to use 3D printing to crank them out fairly easily but there are a few easy tricks for getting the best results.

Wednesday, 13 February 2019

Can a Handheld Rechargeable "Ultrasonic" Scaler Be Turned Into a Cutter? (Spoiler: Nope)

I made a compact DIY ultrasonic knife by modifying an ultrasonic dental scaler I purchased from China for a little over $100. It worked great for fine detail work.

Well, someone showed me that there are also small, handheld, rechargeable "ultrasonic scalers" available for around $20. Could they also be made to work? I decided to purchase one to find out. It arrived today. The answer is no.
A roughly $20 "ultrasonic scaler" that -- spoiler alert -- is not ultrasonic.
So why not? Because the tool is not ultrasonic, meaning it does not vibrate at ultrasonic speeds (over 20,000 Hz) To do that, one requires an ultrasonic transducer. The transducer will vibrate the tip a tiny amount at super high frequencies. As a result of this motion, the tip gains some mild superpowers when it comes to breaking up different stuff, such as -- in the case of dental scalers -- breaking up hard calculus (tartar) on teeth without damaging the teeth themselves.

These tools may be advertised by sellers as "ultrasonic scalers" but they do not contain a transducer. In fact, the product packaging and manual themselves make no claims of being ultrasonic. It's just a vibe motor -- much like the one that vibrates your phone, or a cheap electric toothbrush. And that's all it is. A handheld vibe motor with a dental scaling tip on it.

I burned the $20 so you don't have to! eBay uses the magic word "ultrasonic" in the name and description of these tools but they are not. Maybe I can make a micro sanding tool out of it or something, but I won't be making an ultrasonic cutter out of it, that's for sure.

Friday, 8 February 2019

Early Hardware Test of Robotic Envelope Addressing

One of my big ideas involves a robotic system to address mail and stuff envelopes. Today I successfully had a robotic system pick up a blank envelope, have another robot write on it (with placeholder data), then move it when it was done.

At this stage, it's mostly playing around with the hardware and tools and getting familiar with the capabilities and limitations, and creating the "glue" parts that let everything work together. Integration work is the embodiment of the phrase "the devil is in the details."

I'm currently using a uArm Swift Pro from UFACTORY, and an AxiDraw from EMSL (which I happily purchased from a Canadian distributor, Solarbotics.) The support hardware and systems are all my own work so far, but it's nice not to re-invent the wheel with the rest of the robotics.

There is still a long ways to go (and I still need a name) but it's very gratifying to have something come together and do useful work, even just as a test.

UPDATE: I make and sell clever little clay target hangers and as of Feb 18th, I shipped by first robot-written order!  An important milestone! Buy one and get a robotically-addressed envelope!