A member of the Workshop 88 mailing list posted a review of a new sewing machine she recently acquired. With her permission, we’re posting it here:
Last night (9/8/16) at Workshop 88 Scott showed us how to do Schlieren photography. See the video for Schlieren images of a hot soldering iron.
Also, Cameron showed the development of his laser harp project:
Hope to see you next Thursday!
Andrew and Jim represented Workshop 88 at the Southland Mini Maker Faire in Mokena August 27th. That Faire is run by Jay Margalus, one of Workshop 88’s founders.
Andrew’s workshop for kids to create their own hand-dipped paint-film artworks was a big hit, with dozens of delighted artists taking home their masterpieces. Foam balls were the canvas; a bucket of water was the studio.
The technique, invented by Andrew using a film of spray paint on a tub of water, was inspired by a similar approach he’d seen using nail polish. Less-than-perfect results with the polish caused him to test and perfect the paint approach. Results were spectacular.
The laser toys box was there, as usual, and its Escher lizards provided entertainment and education for many little (and not-so little!) hands. Having the back sides of the laser-cut pieces engraved with three different patterns provided an additional level of challenge based on the 3-way tessellation as a 3 color map problem. The laser engraved wording on what used to be the bottom of the tray used to be obscured by the toys. With the addition of the new slightly smaller lower box, that old tray is now both a useful top cover and a convenient display card!
Jim’s UV-lit fluorescent non-round gears caused lots of folks to stop and take a look. Their graceful turning, speeding up, slowing down, reversing and repeating mesmerized a few visitors. Their stepper controller and Tiny85 processor mostly worked, but required some discreet wiggling several times to keep it all going. The flaky solderless breadboard that hosted them has since been replaced by a much more reliable dedicated PCB.
His hexagonal WS2812 individually addressable RGB LED wall display made its debut as an actual interactive device at this Faire. Controlled by a 16-button app on an Android tablet, connected via Bluetooth to a cheap radio on the Arduino that runs the display, the display was fun to make dancing patterns with to music from a small sound system on the table. Next upgrade will be a better drum pad app with velocity and aftertouch, and lots more controls.
Thanks and a tip of the W88 hat to Drew Fustini for some of these pictures!
Today, I’ll be continuing my 80m transceiver build that I started in T-Kit 1380 Kit Build: Part 1.
At the end of the last post, the board looked like this:
Today I’ll be moving on to the VFO section of the board. A VFO, or variable frequency oscillator, is the circuit that allows you to tune a radio. This particular VFO is based on a Collpits oscillator, and can tune over a 50-70 kHz range centered on a frequency determined by the component values. The frequency range shown in the image may seem a bit strange. This transceiver can be built to cover that 50-70 kHz range somewhere near 3.5 MHz to about 3.75 MHz. The short explanation is that the frequency we’re interested in is shifted by the frequency of the VFO to an intermediate frequency of 8 MHz, where we can do filtering and amplification at a single fixed frequency. Since a lot of circuit characteristics are frequency-dependent, performance is much better if the components can be selected for just one frequency.
The majority of the components are supplied with the kit, so their values are fixed. One of them, an inductor, I had to wind myself. Since this phase required quite a few components, I decided I’d lay them out before I started.
Rather than start building immediately, I decided to wind the inductor first, so I could get that out of the way. The instructions specified 28 turns of the green #28 enameled wire on the red toroid core. I had to count the turns several times to be sure.
The inductance of the coil is dependent on a lot of things, including the material the core is made of, the diameter of the core, the number of windings, and the spacing between the windings. Later on in the build, I tweak the range covered by the transceiver by adjusting the coil spacing.
From this point on, it was simply a matter of stuffing the board and soldering, as per the instructions. The one thing I would have changed was the process for doing initial testing of the inductor. They have you tack a couple leads to the pads you’re going to use, and then tack the inductor to those. Unless your inductor is wildly off, you’re not going to be rewinding it, so I would have skipped that step and just soldered it in directly at the beginning.
The testing of phase 2 was relatively simple, because I’m using a frequency counter. I just hooked up the frequency counter, and adjusted the spacing of the turns on the coil I mentioned before until the VFO covered the range between 4.470 MHz and 4.391 MHz.
I’ll talk more about it in the next post about the transmit mixer and filter, but that provides an actual range of 3.530 MHz to 3.609 MHz. This includes the QRP CW calling frequency at 3.560 as well as W1AW’s code practice sessions transmitted on 3.5815. It does not include the main CW DX window between 3.500 and 3.525 MHz, but I’m still working on getting my Amateur Extra license, so I’m not authorized for that part of the band anyway.
I won a T-Kit 1380 80m 3 watt CW transceiver kit at the WCRA Hamfest back in 2014, and it’s been sitting on my bench unopened since then. I didn’t have my license at the time, but I got my General license about a week later. I decided that this summer was a good time to start building it. Here’s a link to one you can pick up if you’re interested : http://www.rkrdesignsllc.com/-13/
I have quite a lot of kit-building experience, but most of it is digital electronics, so this is probably the most complex kit I’ve ever built, both in number of components and circuit complexity.
If you’re not familiar with amateur radio, this kit will let you transmit and receive on the 80m band (between 3.5 and 3.75 MHz) using CW (morse code).
The schematics in the manual are a bit low-res, but the instructions for assembly are very good. My biggest complaint with the manual so far is that errata are supplied as a stack of papers inside the manual. Some of them referenced parts this kit doesn’t use, so it was a bit of a chore to go through and update the instructions and update the steps by hand.
The assembly process is documented in phases, with testing procedures at the end of each phase.
Phase 1 is construction of the DC input circuitry as well as the keying circuit. The keying circuit is connected to the code key, and disables the receive circuitry while transmitting. Here’s the diagram for phase 1.
Here’s the board as assembled:
This is a pretty densely packed board, and the silkscreen suffers for it. The manual gives pretty decent drawings of the section of the board each phase is concerned with, and this helps quite a lot. You can usually locate a component by finding a nearby component you’ve already installed, or one whose silkscreen isn’t broken up by a pad.
Once this phase was assembled, there was a short test procedure to verify that it is operating correctly. Essentially, I had to apply 12v to the 12v input, and then verify that R13 (the resistor in the center of the board, just between the two beige ceramic capacitors) read 0v while the key wires were disconnected (the white and black wires just under ‘J1’), and 12v while they were touched together.
I misread the directions and it took me a while to figure out what I was doing wrong (I was measuring voltage drop across the resistor, not between the resistor terminal and ground), but in the end, everything checked out.
As you can see, there’s quite a lot of work still to do, so come back next time, when I move on to assembly and testing of the VFO section!
A simple pattern was etched on flexible copperclad Kapton film, using vinyl from the vinyl cutter as resist. Solder paste blobs and the tiny 0805 components were hand placed, then reflow soldered on the hot plate. Here are some ready to be sliced apart. The resulting glowing Gummi bears were a big hit with the kids!
Campers beta-tested Rachel’s Conducty Inventing Kit during a week-long Spring Break camp at Moore Toys and Gadgets in Wheaton. They built circuits directly on LEGO baseplates using conductive tape and components designed to fit between the LEGO studs. Kids lit up everything from Minecraft torches to outdoor campfires made of LEGO. Here, Cooper and Ella show off their creations. The Conducty LED Inventing Kit will be launching on Kickstarter later this Spring.
Some more details here.
Who says gears have to be round? Here’s a clip of some gears we just made.
And tesselating lizards!
We’ve mapped out a wiring diagram and rough layout for an Arduino-controlled Minecraft landscape. Bill has graciously agreed to write the code. Rachel roped in a bunch of newcomers to build part of the set and brainstorm Minecraft “events.”
We settled on a line of light-up Redstone dust (red LEDs in perforated boxes) leading up to a tree which catches on fire (LEGO flames will stick out of the tree). Then a second tree will catch on fire. We’ll be working on it at Workshop 88 the next couple of Thursday evenings if you’d like to stop by and contribute your Minecraft, LEGO, and/or Arduino expertise. Come play!
We’re gearing up to display this at the Barnes & Noble Mini Maker Faire, along with some other projects. Scott Wojton from the Naperville store has been out to the space a couple of times and has been very helpful to us,so we’re happy to be showing stuff at his Faire Nov 6-8.