T-Kit 1380 Kit Build: Part 2

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:

The full board

The full board

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.

schematic

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.

components

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.

inductor

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.

phase-2-complete

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.

 

T-Kit 1380 Kit Build: Part 1

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).

1380 Manual

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.

Phase 1 schematic

Phase 1 schematic

Here’s the board as assembled:

Phase 1 assembled

Phase 1 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.

The full board

The full board

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!

Surface-Mounted LEDs for LEGO & LED Inventing Camp

PlacingParts0270Rachel and Jim made up some very skinny surface mount LED/resistor strips that fit between Lego posts for a STEM camp Rachel is running.

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, ReadyToSlice0273then 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!

EllaHead180514Campers beta-tested Rachel’s Conducty Inventing Kit during a week-long Spring Break camp at Moore Toys and Gadgets in Wheaton. They built circuits Cooper134906581directly 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.

We’re Hackerspace Passport Ready!

PageWstamp3788Thanks to the laser cutter, we now have an official rubber stamp, and we’re ready to provide Workshop88 visit chops to all our visitors with Maker Passports!  OK, as soon as one shows up.

Stamp3787But we now have the capability to make our own precision rubber stamps!  Rubber stamps.  Yeah, like in the paper-based olden days.  Well, I thought it was cool.

Some more details here.

Introduction to W88’s Laser Cutter class

Workshop 88 is excited to have a laser cutter for members to make use of at our makerspace. For those interested in becoming certified to use the laser cutter, taking the Introduction to Laser Cutting class is a required first step. For those interested in learning about what our laser cutter can do, and how it works, this class will provide you with descriptions and demonstrations of the operation of our laser cutter. This class is open to all. Certification to use the laser cutter is only available to current Workshop 88 members.

Minecraft Extravaganza

IMG_20151023_002406We’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 IMG_20151023_012142657will 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.

Teknistas Inventing Lab program is now free!

We have some great news! Workshop 88 will be able to offer the Teknistas Inventing Lab programs free of charge in 2015–the $330 Tuition and the $100 materials fee will be covered by a grant from Cognizant Making the Future program. In addition, we have opened up the age range to include 8- and 9-year-olds due to the enthusiastic participation of some young but crafty and creative kids at our September preview workshop. The girls will start with a Halloween project and I can’t wait to see how they light up their costumes, make candy glow, decorate their front doors, and invent other things we haven’t thought of!

Just as a reminder, the LED Circuit Crafts program that will be held Wednesdays 4:30-6:30 Oct. 7-November 4. If you have a daughter age 8-12 who loves crafts, please encourage her to apply for one of the remaining four slots.

I’d love to see girls in our community take advantage of this great program while the cost is subsidized by a grant. We need your application by Monday or Tuesday of next week at the latest.

Click on this link to download the brochure & application (you can disregard the tuition & materals costs):

Updated information and application

P.S. Some parents have expressed interest in trading pick-up vs. drop-off duties so we can put families in touch with each other once we finalize the admissions.

W88 Laser Cutter First Steps

Cooling+Exhaust5838The dead laser cutter donated to us by Inventables after blowing one too many power supplies is running!  While not yet ready for prime time, a water cooling system in a bucket and a fume exhaust thru the flue from the old furnace allowed first tests.  The Shapeoko laptop hosts the RetinaEngrave software that makes it look like a Windows printer.

We’re still getting our feet wet with laser power, speed, number of passes, raster vs FirstCutWolfHead3529vector operations, but we’ve actually cut some paper, wood, and plastic.  This wolf head – courtesy of Google Images – DollGoggles6419adorning a circular saw push stick was the first actual cut.

Daniil had the honor of being the first to produce an actual useful object on the cutter.  We think his daughter will be thrilled with these laser cut, hot air station formed goggles for her skateboarding doll.  She’s been trying to get some for a whTripleSpiral1470ile now.

There’s still a lot of work to do making much more proper implementations of cooling and exhaust systems.  We need proper electrical connections to guarantee the cooling will be running if the laser is on, and a damper on the exhaust pipe to keep cold air out and the landlord happy.  Lots more Ts to cross and Is to dot.  But it’s actually cutting stuff and hasn’t blown up yet!

BlueTape4371Update 11/12/15:  The laser is coming along.  We now have “air assist”, and have done some more tests and cuts.  Here’s a test using painter’s tape to reduce smoke damage, and a nice W88 logo.

W88Logo3mmPly2334