Ben’s Blog

For about two months now, I’ve been spending most of my spare time reading and doing experiments out of Make: Electronics. My spare time has dwindled now that I’m back to teaching and taking classes. It’ll dwindle even more as I get into semester projects.

I’m now up to Experiment #16 in Make: Electronics; about half way through. I’ve learned a good bit, even though the book is definitely aimed at newbies. I have skipped a couple of experiments that didn’t seem like they offered enough new experience for the amount of effort they would require.

I would recommend the book to anyone with one disclaimer: be prepared to spend a lot on tools and supplies. I’m also not terribly fond of the author’s recurring intruder alarm example. I feel like he could have come up with a better project. On the other hand, I don’t know of a better hands-on, beginner’s guide to electronics.

For now, I’m suspending my efforts on the book to finish up my DDS-60 card. More on that soon.

I started playing around with electronics about a year ago. You can make do with a breadboard for a while, but if you stick with electronics long enough you’ll eventually get around to soldering. I actually started soldering kits right off the bat, but I agonized over what gear to buy. I agonize over any major purchasing decision (and most non-major ones), so this isn’t new for me. I’ve been very happy with my gear, so I thought I’d share it to make the decision-making process a little easier for others. I’ve been meaning to post about my gear for a while now, but actually tinkering with electronics has taken priority. Last week a friend of mine mentioned he was looking at buying a soldering iron and related gear, so I thought it was time to finally get around to it.

I got a Circuit Specialists Soldering Station for $45. It’s a 40 watt temperature-controlled station. I have the one with the digital temperature display, but they have an analog version for $5 less. The analog one is more than accurate enough, but I like the digital look. It comes recommended by others, and I have no complaints. The grip on the iron gets a little hot, but not to the point of being uncomfortable. I’ll probably upgrade eventually, but I expect it’ll be several years. You could probably get by with a non-temperature-controlled iron, but I think this one is definitely the best bang for buck.

For through hole work I use a 1.2mm chisel tip. Most people would probably use the next size up, but I enjoy the extra control the smaller tip gives you. For surface mount work I use a 0.8mm conical tip.

I decided on 63/37 Kester 285 solder, in 0.031″ diameter for through hole and 0.015″ diameter for surface mount. The 63/37 refers to the percentages of tin and lead in the solder. The 285 refers to the type of flux. Flux helps the solder stick to the objects you’re trying to solder. While solder sticks to metals like copper very well, it doesn’t stick to oxides very well. Unfortunately, the high temperatures involved in soldering cause accelerated oxidation. Flux helps prevent oxidation and also serves as a wetting agent, causing the solder to flow. Some fluxes must be cleaned off the board after soldering. I don’t have time for that, so I settled on Kester’s 285, the most active flux I feel comfortable leaving on a board. There are also “no clean” fluxes, but they tend to not perform as well. Especially while you’re learning to solder, stick with something like Kester 285. You can also get lead-free solder, but it’s not beginner friendly either.

I bought my solder from Digikey in 1lb. spools. It runs $20-30 per spool.  It’s hard to find good solder in small amounts. Radio Shack has small quantities of solder, but I have no idea if it’s any good. If you’re just getting started in this hobby I’d be glad to give you some solder. There’s no way I can use it all before it goes bad. (This type of solder has a shelf life of three years or so.)

I also have a flux pen, but I’ve only used it a couple of times when hand soldering surface mount ICs.

You need a way to clean your soldering iron’s tip. Most irons come with a cheap sponge that you wet. I use a Hakko 599B tip cleaner. It looks like a pot scrubber, but it has flux on it that cleans your tip. It also doesn’t drop the temperature of your tip like a wet sponge.

Sometimes you need to remove solder. There are two basic ways to do this: a desoldering pump or desoldering wick. The pump seems to be the old standby, but I’ve had way more luck with wick. I never use the pump these days. I use TechSpray wick and it does a good job. I use size #3 for through hole components and size #2 for surface mount.

I use Xcelite 378M pliers and 170M shear cutters. Amazon has them for $14 as a pair. You can make do with a small pair of regular pliers, but cutters like this are virtually essential. Home Depot carries an identical set under the Cresent brand.

Good lighting is essential for this sort of thing. While not ideal, I use a Petzl headlamp when soldering. Magnification is also important. I have a 10x jeweler’s loupe that I use for checking joints after the fact. I’d love to have a lamp/magnifier combo that clamps to my desk, but they’re expensive, and I’m sure my kids would find a way to break it. One of those magnifier visors would be nice too.

So, yes, getting setup to solder is a little on the expensive side, but it’s not bad compared to a lot of hobbies, you don’t have to buy it all at once, and it’s a good skill to acquire. Let me know if you have any questions.

I started building electronic kits about this time last year. (My grandmother got me a soldering iron for Christmas.) At this point I’ve built several kits, but I’ve only gotten around to posting about a couple of them. This kit, the NorCal Dummy Load was my third project, the first being the MintyBoost, and the second being a AVR microcontroller programmer that I haven’t had a chance to post about yet. More on that one later. I built this kit back in February of 2009. You can see all the photos here.

Dummy load in vise, on desktop.

So, what the heck is a dummy load? When you’re testing a transmitter, you can’t just transmit without anything connected to the output. You could fry your final amplifier. So you need a dummy load that presents the correct impedance, 50 ohms in most cases. As it just so happens, I’m getting ready to build a transceiver, and will need a dummy load for testing. Also, this particular dummy load involves several surface mount (SMT) parts, and I wanted a little practice with those before beginning my next project, the Softrock Lite II 30m software-defined receiver.

This kit was designed and sold by NorCal QRP, a low-power (QRP) ham radio club based in Northern California. They have put together several kits over the years. They actually retired this kit a couple of years ago, but I inquired on the qrp-l list and someone had one they weren’t planning on building.

Some hams are intimidated by surface mount (SMT) components, and rightly so; they’re pretty small. Have a look below. The small black thing to the right of the penny is a 2.2 kOhm SMT resistor. SMT components come in different sizes. This size is referred to as 1206, which means it’s 0.126″ × 0.063″. It’s one of the larger sizes of SMT components.

As it turns out, soldering SMT components isn’t too bad. I used a small tip on my soldering iron and small solder (0.015″ diameter) and had no problems. There were no SMT integrated circuits on this project, but there would be on my next project.

Tonight I started on another SMT project, but using solder paste, a griddle, and an embossing gun instead of solder and a soldering iron. More on that later.

I’ve got too many electronics projects going, but I’ve already got my next one picked out. It’s KD1JV’s ATS-3B, billed as “the world’s smallest, lightest, six band HF CW rig.” Steve Weber, KD1JV, is a serial designer of QRP radios and accessories. The whole thing fits in an Altoids tin and puts out four watts on all bands. (My SW-40+ only puts out 2-2.5W.) It also has a DDS VFO and a built-in keyer. Band switching is done using removable band filter modules. The whole thing is controlled by a PIC microcontroller, which some people have reprogrammed for additional capabilities. It seems to be very well though of by those that have one.

The ATS-3B was designed by Steve to be the ideal radio for backpacking. He lives in New Hampshire and backpacks the Appalachian Trail often.  (ATS stands for Appalachian Trail Sprint.) I haven’t done much backpacking lately, but I’m looking to get back into it soon.

Most ham kits use through hole parts, which are easier for some people to handle. The ATS-3B uses lots of surface mount parts, allowing it to be very small. I’ve used surface mount parts on a couple of projects and actually prefer them. I’ve always soldered them by hand. Steve seems to prefer the solder paste/warming plate/embossing gun method. I’m not sure if I’d give that a try or stick with soldering by hand. Here’s a YouTube video of Steve doing it both ways.

Steve only offers ATS-3B kits periodically. I believe he’s offered them about three different times now. He’ll be offering them again sometime in late fall, and I’ll be ready. This will also be the last time Steve will offer this kit, as some of the parts he uses are being phased out. He’s already working on the ATS-4, which looks to be a very nice (though somewhat larger) radio.

As most of you know, I’m currently afflicted with the ham radio bug. I have a VHF radio I can use to talk locally, but nothing I can talk around the world on. For Christmas last year, Cassie got me (at my request) a Small Wonder Labs SW-40+ 40m QRP CW transceiver kit.

The 40m ham band is a good all-purpose band. It’s open to somewhere pretty much any time, day or night, even at this point in the solar cycle. QRP means it’s low-power. In this case, around 2.5 watts. Most commerical radios put out around 100W. CW means it only does Morse code, no voice, which means I’ll finally have to learn Morse code.

The SW+ series is well-regarded in the QRP community. There are models available for the 20m, 30m, 40m, and 80m bands. The kits are put together by a guy in New Hampshire. There’s a waiting list of around two months to get a SW+ kit.

The SW-40+ board with 8 of the 16 sections installed. I've added a couple of sections since this photo was taken.

A few weeks ago I finally got a chance to start putting mine together. The instructions that come with it basically say to build the whole thing, then test it. I’ve built some smaller kits before, but this is definitely my largest undertaking thus far, so I wanted some assurance things were going right as I built it. So, I’ve been using Chuck Adams’s, K7QO, guide to building the SW-40+. By following his guide, you build a section, then test it. He has it broken down into 16 sections, more or less. Some of the previous kits that I’ve built are used for testing.

You can see all the pictures from the construction process here. I’ll continue to add photos as I go along. I’ll post an update here occasionally too. So far I’ve installed the power supply, audio amplifier, keying, muting, audio preamplifier, receiver mixer/detector, IF crystal filter, receiver mixer, VFO, and transmitter mixer sections. That’s 10 of the 16 sections.

Testing the transmitter mixer section by feeding the output of the transmitter mixer into the receiver.

A few months ago I bought a VE3DNL Marker Generator kit, but had never put it together. Chuck suggested using it to test the receiver mixer/detector section. It was a quick build, and the receiver mixer/detector section passed the test.

VE3DNL Marker Generator board is on left of SW-40+ board. The VE3DNL transmits tones every 5kHz that can be picked up in the SW-40+ receiver.

After building the VFO section I wanted to have a look at the waveform. Chuck’s guide shows a nice sine wave. A friend had loaned me an oscilloscope for another project a few months ago, so I drug it out and set it up. To make a long story short, I was never able to view the VFO’s waveform on the oscilloscope. Something is wrong with either the probe or the oscilloscope itself. However, I was able to confirm that the VFO is running at around the correct frequency with the FCC-1 frequency counter I built a while back.

I have also built a K1EL K12 keyer to put in the SW-40+. As designed, the SW-40+ can only use a straight key. I wanted to be able to use iambic paddles, so I found the K12 keyer. It handles the input from the key and outputs perfectly spaced Morse Code. It sounds beautiful. It’s a pretty cool little device in its own right. I may do a post on it at some point.

The K1EL K12 keyer assembled.

More on the SW-40+ when I get a chance to work on it.