After building the abacus bracelet last year, I wanted to explore the idea of archaic wearable computing a little more. An abacus wristwatch seemed like a good way to do so, and the project would challenge me to learn 3D modeling. Pebble or the rumored iWatch would have nothing on the computing power I had in mind!
I’ve long been attracted to nixie tubes with their warm, glowing numbers, and wanted to build a clock with them. Not experienced in the high voltage circuitry required, I ordered a kit from TubeHobby. There’s still some DIY in it, but not as much chance of burning down the house as if I tacked it by myself. It took a few years of off and on work (mostly off) to finish the clock, and I didn’t start the project thinking I’d write it up, so please forgive the lack of in-progress photos. I did take a few pictures before I put it together, though, so you could get an idea how it came together.
After my son saw me troubleshooting a circuit with my multimeter, he wanted to use it himself. Now while I strongly believe that kids should have access to real tools, that doesn’t mean they have to be my tools (you should see what he did to my dial indicator).
Having real tools doesn’t mean that thought can’t be given to how a five-year-old might use them differently than an adult. In a multimeter, the features I thought would be most useful included
- Auto-ranging. The kiddo isn’t reading resistor values yet, so plug and play is the way to go.
- Auto-shutoff. I guarantee it will be left on after use.
- Durability. It has to withstand the bumps and drops that it’s more likely to get from small hands than large ones.
- Affordability. In case it’s not durable enough.
The Equus 3320 multimeter fits the bill on all counts, ringing up at right around $20. Considering that it’s not a toy and can continue to be used for decades, it seemed worth it.
Most of my son’s electronic projects are with his Snap Circuits kit, and he doesn’t have the dexterity to hold the two regular probes on the circuits while at the same time manipulating switches and shining flashlights into photoresistors. Heck, I couldn’t do it either. The multimeter would need snaps for probes. Not surprisingly, these are not standard equipment for electronic testing. So, with a set of sheathed banana plugs and a pair of replacement jumper wires from Snap Circuits, I made my own.
This hardly needs instructions, but I’ll write up the steps anyway.
First, disassemble the banana plugs.
Cut off one end of each Snap Circuits jumper wire and strip half an inch of wire from the long wire remaining. Instead of cutting the wire as close as possible to the snap, you might want to cut it with about an inch of wire remaining on the short end. This way those snaps can be spliced to something else (alligator clips?) and re-used.
Insert the stripped end of the wire into the housing for the banana plug, into the plug itself, and then tighten with the included Allen wrench to clamp it in place. Assemble and snap the back into place.
That’s it. Put the original probes aside to use later, and start testing! Some fun things to do include seeing how precise the marked values on the resistors are, testing continuity, measuring the resistance of different chains of components, and measuring the current draw of various circuits. Seeing the numbers on the meter change as he turns a potentiometer or adds a light bulb to a circuit really makes concepts come to life.
Another great thing about the snap probes is that they’re a lot harder to misuse when a budding engineer decides he wants measure the voltage of a wall outlet or the resistance of an iPhone charging port. They just won’t fit!
Officer, it’s not what it looks like! I did not steal this car; that’s my key! Why are you getting out your taser?!
For no practical purpose at all, I wanted to see if I could make a screwdriver into a car key. What fun it would be to impersonate the look of a stolen car with a screwdriver jammed into the ignition! And maybe I could empty my glove box all over the seat so it looks like I was scrounging for spare change and prescription drugs too!
Read on to make your own.
Every year I throw an Oscar party with my friends, with lots of drinking, yelling at the TV, and low-stakes wagering. Everybody puts in a dollar as each category is announced, then that pot is split among everyone that made the right pick. After almost 20 years of doing it the same way, I finally got tired of counting out the change after each win. $1.65 times nine winners equals clinking coins for minutes.
So why not do what grocery stores and fast food restaurants figured out long ago and automate the change dispensing so any middle-school dropout can do it? I present to you the Change-O-Matic.
My Counting Box article in MAKE magazine was meant as a short “How I Made This” story, not a detailed “How You Can Make This Yourself” guide. Because people might want some instructions to follow in order to make their own counting box, I built a new version and documented it.
But first, an update on Counting Box Version 1. It’s been in service for 17 months and is showing a count of 121,860. This is three less than the highest number it’s reached. My son doesn’t seem to be a fan of negative numbers because -93 is the lowest the box has counted. The increment button has been pushed 18,422 times and the decrement button 4227. It’s only been recharged twice that I know of, so that giant battery was total overkill.
Now here’s how to build your own.
As is the case with so many celebrities, the meteoric rise of Pumpktris was followed by an equally swift and brutal decline. Unable to cope with the twin pressures of fame and fungus, he was last seen passed out in the alley. A spokesman claims Pumpktris is merely suffering from “exhaustion.”
What do you get when you combine a pumpkin with the classic video game Tetris? Pumpktris! Fully playable, embedded in a pumpkin, and with the stem serving as a controller. Watch the video below to see it in action, then read on for the development story.