Baluns & Ununs

Anyone building antennas will come across designs that either recommend or require the use of a balun or unun. The design and construction of these components can get quite complex and are beyond the scope of this blog and my own knowledge. In short these devices act as impedance transformers from balanced loads to unbalanced loads (balun) or from unbalanced loads to unbalanced loads (unun). They can also be used as a common mode choke to eliminate any RF on a coax feed line’s shield. That said, it is actually quite easy to construct your own baluns and ununs and to learn something in the process. You can also save a considerable amount of money.

1-1 Balun (2)1-1 Balun (1)Amidon sells a good starter kit for building baluns and ununs. It includes everything you need including a book with dozens of designs with various impedance transforming characteristics. 1-1 Balun (6)1-1 Balun (3)I used this kit to make a 1:1 balun. Since the kit uses 14AWG wire, it should be capable of handling 2KW of power continuously. This is overkill for me since I will never be putting more than 100W through the balun. The 1:1 balun is essentially a choke that blocks current flow on the shield of the coax feed line. It is constructed using 10 bifilar wraps on the toroid core using approximately 4 feet of wire.

For other projects I decided to use the same FT-240-K core with 18AWG wire covered in 16AWG PTFE insulation. While the 18AWG has less power handling capability, it should be more than adequate for 100W usage as well as being cheaper and easier to work with.

4-1 Balun (2)4-1 Balun (1)The first balun I made using these materials was a 4:1 current balun. This balun is intended to transform a 200 Ohm load for use with a 50 Ohm coax feed line. This type of balun is commonly used in 4-1 Balun (3)Off-Center-Fed dipole antennas because the feed-point is placed at the location on the antenna where the impedance is approximately 200 Ohms on multiple bands. I intend to use this balun as part of a 6 meter collinear antenna that I am building. The balun is constructed using two sets of 8 bifilar wraps on the toroid using approximately 8 feet of wire. Each pair of windings is then wired in series with the other pair. This design can be thought of as two 1:1 baluns wired in series and in fact an alternate design of this balun uses two separate 1:1 balun cores wired in series to achieve the same affect.

9-1 Unun (2)9-1 Unun (1)Next I made a 9:1 unun for use with an end-fed antenna I am building. End-fed antennas exhibit very large impedances and consequently require considerable impedance transformation to 9-1 Unun (3)get the feed point within the range of an antenna tuner. Unlike a dipole, an end-fed antenna is unbalanced and therefore an unun is used instead of a balun. This design uses 8 trifilar wraps on the toroid using approximately 6 feet of wire. Each wrap is then wired in series to create the desired impedance transformation.

1-1 Line Isolator (2)1-1 Line Isolator (1)I also made another 1:1 balun. The main difference here is that I constructed it using two SO-239 connectors because I intend it to act as a coaxial feed line isolator. My plan is to use this in conjunction 1-1 Line Isolator (3)1-1 Line Isolator (4)with the 9:1 unun as part of my end-fed antenna project. The idea here is that a section of coax from the 9:1 unun acts as the counterpoise for the end-fed antenna and the line isolator is used to choke the RF current in the shield of the coax and allow the remainder of the feed line to continue to the antenna tuner without risk of radiating RF.

For all of these projects you can see that I used colored electrical tape to mark the various windings. This is essential to keeping track of the wiring and assuring that the windings are wired together correctly. For all of these I also used standard NEMA 4X 4″x4″x2″ plastic electrical boxes which are cheap and commonly available. I also used 10-32 stainless steel hardware for the antenna connections and silver-teflon SO-239 connectors.

Ham Radio EMCOMM Go Kit – Battery Box

Battery Box (1)Battery Box (2)A portable battery system is a very handy item to have for ham radio in general (think field day, special event stations, etc.) and is essential for an EMCOMM kit. I based my battery box around a deep cycle lead acid battery and I ended up choosing a group 27 battery with a reserve capacity of 160 (66.7 Ah). Reserve capacity refers to the number of minutes a fully charged battery is discharged at 25 amps before the voltage drops below 10.5 volts. This figure can be converted to amp-hours by multiplying the reserve capacity by 0.4167. According the Battery School within a BCI group size, the battery with higher ampere-hours (or RC) will tend to have longer lives and weigh more because of thicker plates and more lead. While lead acid batteries are heavy, they are also versatile and can be continuously trickle charged to keep them at full charge until they are needed. A deep cycle battery is appropriate for this application since their power level can be drained very low without damaging the battery, unlike a typical car battery.

Battery Box (3)For ease of transport and to keep the wiring organized and neat I store my battery in a plastic battery box and hardwired it to a Rigrunner 4005 power distribution block mounted on the box. I went with a small Rigrunner since this system will only be used with a few items at a time (1 or 2 radios, inverter for laptop power, low voltage lighting, etc.). I keep the battery charged using a NOCO Genius G3500 charger which is smart enough to not overcharge the battery and powerful enough to recharge the battery at a decent rate. After years of thinking about it I finally got around to standardizing all of my power connections with Anderson Powerpoles which make 12V power connections very modular and interchangeable.

This is a very useful and simple project that performs well for my purposes. I could easily parallel another battery with this one for increased capacity if the need arises in the future. You could buy a premade battery box with a Rigrunner, but doing it yourself is a lot cheaper.

Ham Radio EMCOMM Go Kit – VHF/UHF

VHF Go Kit (7)Recently myself and others in my ham radio club have been getting more involved in emergency communications (EMCOMM) training and activities. As part of this effort to be better prepared for emergencies I decided to build a go kit or “station in a box” that could be used as a portable communications system.

VHF Go Kit (2)VHF Go Kit (1)Since VHF and UHF are the most used bands for EMCOMM I started with that. I already had a Kenwood TM-V71a dual band (2 Meter and 70cm) transceiver which is an ideal radio for this application. At full power it can output 50 watts and unlike many transceivers of this kind it features a data port on the back for easy connection to an external sound card (I use the SignaLink USB) for digital communications. It also has a detachable faceplate which allows for a lot of flexibility regarding where and how the transceiver body is mounted.

To house the electronics I chose the Monoprice 14″ x 16″ x 8″ weatherproof hard case which is similar to Pelican cases at a fraction of the price.

VHF Go Kit (4)VHF Go Kit (3)For power, I chose to include a 10 amp switching power supply in the go kit. I used the Astron SS-12 since its dimensions were such that it fit perfectly in the case when mounted next to the transceiver. In case 120V is not available, I can simply unplug the transceiver’s powerpole connection from the power supply and plug it into my battery box.

In order to mount all of the equipment in the case I built a base of 1/2″ plywood. The base consists of a single sheet cut to fit in the case glued on top of a four 1/2″ spacer blocks which raise the sheet above the bottom of the case. This serves two purposes:  first it negates the need to round the bottom edges of the sheet to match the curve of the case and second it doubles the thickness of wood that the mounting screws have to grip when screwed in through the bottom of the case. An added bonus of raising the sheet is that it provides space to store excess cable from the faceplate separation kit in an out of the way location.

VHF Go Kit (6)VHF Go Kit (9)Mounting the transceiver to the plywood is done using the mobile mounting bracket for the radio. The power supply is mounted by removing the rubber feet from the bottom of the power supply and replacing them with spacers and screws for a strong connection to the plywood. The microphone mount is also simply screwed to the plywood. The faceplate is mounted to the lid of the case using the separation kit mount which uses very strong double stick tape. The SignaLink is mounted to the top of the power supply using industrial strength velcro which allows for easy removal of the unit if I want to use it in a different configuration while holding it very secure when I want to leave it in the case.

VHF Go Kit (5)Before I mounted anything to the plywood I applied a coat of clear polyurethane. This not only makes the oak veneer look a lot better, it also seals the wood and provides some protection. The equipment was then mounted to the board and it was mounted in the case using 4 wood screws driven through the bottom of the case. In order to help restore the weatherproofing of the case I used silicone caulking to seal around the screw heads.

Overall I am very pleased with how this go kit turned out. To get on the air all I have to do is open the case, hook up power (either 120V or 12V), hook up the coax to the antenna and plug in the USB cable to my laptop if I need to run digital. In all it’s a very capable VHF/UHF station that weighs about 17 lbs and isn’t much bigger than a shoe box.

Core i7 Skylake PC Build

It’s been 4 and a half years since I built my Sandybridge based workstation and it while it isn’t a terrible performer, I do more video and photo editing than I did in the past and wanted a machine with more power. Since Intel finally came out with the Skylake line of processors and the next upgrade won’t come out for a while I decided to do a new build now. In order to keep costs down I reused the case, power supply, storage devices and video card from my previous workstation. This limited my costs to $520 for a new motherboard, processor, and RAM.

Parts List

This build is essentially a motherboard, CPU, and RAM swap from the previous system.  Since this case is old enough to not support USB 3.0 I decided to add a USB 3.0 expansion panel to one of the front drive bays for convenient access. I also stuck with the stock CPU cooler for this build since they are actually pretty quiet and this CPU generates considerably less heat then the Sandybridge it replaces.

Software

Windows 10 installed perfectly and runs great on this machine, as expected.

Power Usage

  • Idle – 42W
  • 1080i MPEG2 to 720p MP4 H.264 Compression (Freemake Video Converter) – 85W
  • Bluray Ripping (MakeMKV) – 54W
  • MKV Bluray Rip to MKV 1080p Compression (Freemake Video Converter) – 95W
  • Adobe Lightroom RAW to JPG Conversion – 94W

Update-New Graphics Card & CPU Cooler (August, 2016)

OLYMPUS DIGITAL CAMERA

After upgrading the graphics card in my Gaming PC to a GTX 1060, I rolled the GTX 960 that I took out into my main desktop. This will be a substantial upgrade over my old GTX 750 Ti and be much more suited to my 1440p monitor when performing graphics oriented tasks.

While I had the case open I also installed a much more substantial CPU cooler, the Cooler Master Hyper 212 EVO. Intel’s stock cooler is not bad at all, however, when performing intensive video compression I definitely noticed the fan working a lot harder and decided to upgrade to a more capable cooling system. The new cooler has lower pitched fan noise and is quieter overall as well.

Update-New Case (July 2017)

In today’s world PCs rarely need optical drives, many new cases forgo the 5.25″ drive bays required for them, which reduces the case size and allows for a much cleaner case layout. My old case was getting long in the tooth and I wanted a more modern setup with USB 3.0 ports native to the case so I re-cased this PC build using a Fractal Design Define C case. It’s a few inches smaller in height and depth than the old Antec case while providing tons of room for everything I need. The 3.5″ drive bays are in front of the power supply at the bottom of the case and there are SSD mounts on the back of the motherboard mounting panel. Taken together the case is very well laid out and results in a very clean build.

Since I still use my Blu-ray drive from time to time I needed an external enclosure to mount it in. I went with the Vantec NST-536S3-BK and it works very well. It uses USB 3.0 and is plug and play with Windows 10. I have noticed no difference in performance between using the drive in this enclosure compared to being installed in the PC and plugged straight into the motherboard.

Update-Gaming PC Parts (September 2017)

I have come full circle on my gaming PC idea I had a couple of years ago. I like the idea of having a dedicated PC connected to my big television but it also has some drawbacks, especially if you want to play a mouse and keyboard game on the couch. It is also kind of silly to maintain two high powered PCs in my house at the same time, not to mention the space the extra PC takes up. The end result of all this is that I rolled the key parts of my gaming PC build into my main workstation: the GeForce GTX 1060 graphics card and the Crucial 750GB SSD (my Steam drive). The swap went very smoothly thanks to how robust Steam is at finding games already installed on a drive and I didn’t have to re-download anything.

In the end this makes the most sense for me since all of my most powerful components are now together in one machine and I have one less Windows box to maintain. I can also take better advantage of my 27″ 1440p monitor’s higher resolution vs my 1080p television, one of the main advantages of PC gaming in the first place. This change should be a good continuation of my trend of simplifying my technology which should save some money and a lot of time.

Loop Skywire Antenna & Remote Tuner

Now that I’ve had this antenna setup for a few years now I have come to recognize the drawbacks. The biggest of these is a lack of tuning bandwidth. This resulted in having to retune the system even when changing frequency by only a few kilohertz, very annoying. After playing with a MFJ 926B remote automatic antenna tuner at Field Day this year I decided to modify my antenna to make use of one of these units and see if it improved my operation. The 926B is actually pretty similar in design to my LDG tuner except it is mounted in an enclosure suitable for use outside and can be powered via coaxial cable using a BiasTee power injector so no extra cables are needed. It automatically initiates tuning when a mismatch over 2:1 SWR is detected while transmitting and it saves the match settings to memory.

The idea of a remote antenna tuner is that it allows the tuner to be located at the feed point of the antenna. This means that the tuner is matching the impedance mismatch of the antenna only; not the antenna, plus feedline combination that it was dealing with previously. This allows the tuner to find a match much more easily and also results in a much better tuned bandwith because the only variable changing is the impedance of the antenna not the impedance of the antenna and feedline combined.

A side benefit of this new setup is that in order to reach the tuner as it is mounted on the side of my house I had to add some wire to my antenna which now contains approximately 270 feet of wire. The antenna is now solidly resonant in the 80 meter band. In addition to adding wire I separated the feed point in the air by about 10 feet. This allows the wires to drop to the tuner at an angle in order to keep the shape of the loop as intact as possible and prevents the two ends from contacting or crossing one another. I also installed an Alpha Delta TT3G50 surge protector in the coax line from the tuner.

In the short time that I’ve had this setup on the air I have been very pleased with its operation. To tune the system I switch to CW mode on my Icom 7200 and transmit a tone (with the power turned down to 10W). The tuner then initiates its tuning cycle and matches the antenna. This generally only takes 2-3 seconds, much faster than before. It also tends to find much better matches and regularly achieves close to 1:1 SWR. As hoped, the tuning bandwidth is greatly improved as well and I am no longer required to retune every time I move around a band. This new setup is also much cleaner looking on the house with no ladder line or balun, just wires going to the low profile tuner and a coax run along the brick.

Loop Skywire Antenna – Update

After reevaluating the trees in my yard I realized that I could rework the layout of my loop skywire antenna. This would allow me increase the size of the loop, improve the feed point arrangement, and increase the height of the antenna.

After adding a fifth anchor point the loop is now a distorted pentagon instead of trapezoidal in shape (see the sketch for the rough layouts). The new arrangement is not only larger, but also higher than before, which should help its performance. With a new circumference of approximately 244 feet of wire the loop is much closer to resonance on the 80 meter band than it was previously.

Due to the repositioning of the feed point I had to shorten the feedline. I decided on 37 feet of 300 Ohm ladder line as an acceptable non-resonant length for the feedline. This is a good length since it keeps it well off the ground while still providing some slack for movement. So far the performance has been at least as good as the previous version.

Mini Home Theater PC

In order to fill my need to endlessly tinker and upgrade my HTPC, I decided to build a new system using one of Intel’s Haswell CPUs. These are not only faster and more power efficient than past models, they also feature much improved graphics capability. I also decided to switch to external hard drive storage since USB 3.0 is not only well supported in Linux, it also performs nearly as well as internal hard drives. This allows me to more easily swap or add drives while keeping the size and noise of the HTPC to a minimum.

Parts List

The key to this build is the effectiveness of the USB 3.0 external hard drives. By moving to external storage I can use a much smaller case with an external power supply, all of which reduces the cooling requirements and consequently the noise of the PC. The only internal drive is the SSD which generates no noise and little heat. The only sound from this configuration comes from the CPU cooler which is somewhat oversized for the 35W CPU and therefore never runs at a high speed. The result is a versatile, snappy, power efficient, and very quiet HTPC.

Software

For this build I decided to go with Linux Mint as I have grown progressively tired with Ubuntu‘s UI tinkering. Otherwise my software choices are similar to past builds.

Network Sharing

For network sharing I use the Samba utility (repository package:  system-config-samba) which makes it easy to setup and manage shares with other computers on my network.

Backup

For backups I use the Scheduled Tasks utility (repository package:  gnome-schedule). With this I run various RSYNC scripts every night which synchronize my local hard drives with my FreeNAS server.

I am currently using a backup tool called Back In Time in place of my RSYNC scripts. I like it a lot and it provides significantly more functionality than a simple backup sync.  Back In Time creates snapshot style backups which allow for recovery of deleted files from past backups. It also has a lot of configuration options regarding how often backups occur, the exclusion of certain files, and the removal of old deleted files to save space.

Media Playback

  • VLC – media player
  • XBMC – media player and streamer (using plug-ins)
  • PLEX – media transcoder (works great through its Roku channel)

Bittorrent

  • Deluge – my favorite torrent client

Performance

Here’s an informal comparison between this build (bold) and my old HTPC (in parenthesis):

  • Time to import 227MB, 128kbps MP3 into Audacity – 0:53 (2:16)
  • Time to re-compress 227MB, 128kbps MP3 at 64kbps with Audacity – 6:40 (10:08)

While this is a sizable improvement these numbers don’t show how much snappier the system is in general, especially when multitasking.

Power Usage

While I anticipated a significant power consumption drop due to the lack of a video card, I was pleasantly surprised at how much of a drop I actually measured.

  • Old HTPC – 43W
  • Current Configuration (including external hard drives) – 30W

That’s quite a significant drop. From past experience I believe the video card used about 10W of power, therefore the Haswell CPU uses 3W less power on average than the Sandybridge model I was using previously.

Noise

This was another area of significant improvement. The combination of reducing the number of fans from 4 to 1 and swapping the stock cooler for a more efficient one results in this build being nearly silent.

HTPC – Case & SSD Upgrade

My home theater setup has changed somewhat over the last year since I moved into my house and my HTPC tower ended up being tucked away in the corner of my dining room. Needless to say this was not an ideal location. I decided to look for a more traditional HTPC case that would allow it to fit on my TV stand with the rest of my gear. I also wanted to take this opportunity to swap out the boot drive for an SSD.

New Parts

I hadn’t planned on getting a new power supply or CPU cooler, however, after reassembling my HTPC with my Antec Earthwatts 380 power supply and a stock Intel CPU cooler the system was just too loud, not to mention all of the excess cables. The new modular power supply is not only quieter, it allows for a much cleaner installation with no unnecessary cables. I like this Arctic CPU cooler a lot, it installs with a combination of push-pin clips and screws that doesn’t require you to take the motherboard out to install. It was a tight fit though, due to the close proximity of the RAM slots on my motherboad.

This Silverstone case is not only a great value, it is surprisingly versatile. It supports several different hardware configurations both with and without an optical drive. I chose not to reinstall the DVD burner from my previous build because it has seen little use of late and eliminating it frees up enough space for both 3.5 inch hard drives to use the included silicone mounts which greatly reduce hard drive noise. If I absolutely need an optical drive in the future I have an external USB model that I can plug in on those occasions.

The only other modifications I had to make to my existing hardware were due to the slim profile of the case. I made a new bracket for my coaxial SPDIF connection and switched to the low profile bracket that came with my video card.

SSD Setup

Using an SSD with Ubuntu has been one of the most dramatic performance improvements that I have had with an SSD. The system now boots in about 10 seconds once it clears the BIOS, a huge improvement.

While current Linux kernels support the Trim function for SSDs, it is not enabled by default in Ubuntu. I found these posts very helpful in setting up my SSD.

Power Usage

With the replacement of my boot drive with an SSD and the elimination of the optical drive, I expected the power usage of my HTPC to go down a few watts but I was pleasantly surprised by the end result.

  • Previous Configuration – 53W
  • Current Configuration – 43W

Not bad for a hard drive swap.

Noise & Heat

My previous build helped keep the noise down by using silicone hard drive mounts, large slow moving fans, and fanless CPU & GPU coolers. This new design uses a much quieter power supply (the 120mm fan is a big improvement over the old 80mm), similar hard drive mounts (with one less drive), a nearly silent CPU cooler (the fan barely has to run due to the 35 Watt CPU), and two 80mm Antec Tricool Fans set to very low speeds. This new arrangement is significantly quieter than my old one. A good thing since it is now closer to my seating position. You can only notice the slight fan noise when the room is very quiet.

In addition to keeping the noise down, this build also keeps the component temperatures under control. The CPU temperature doesn’t fluctuate nearly as much as it did with the stock cooler, generally staying around 40 degrees C, and the hard drives don’t go much over 30 degrees C despite the tight space.

FreeNAS Server

After two hard drives in my Home Theater PC failed this summer, almost resulting in some significant data loss, I decided to move toward a better local backup solution. My previous backup strategy involved syncing hard drives on my HTPC. Although this was a simple and effective solution, it wasn’t the most efficient use of my hard drive space and it doesn’t provide much redundancy. After looking at my options I decided that a FreeNAS Server was the way to go.

Parts List

Hardware

For my server build I not only wanted to keep the cost down, I also wanted it to be as quiet and power efficient as possible. I chose the case because of its noise reduction features in addition to its build quality and 6 hard drive bays. The motherboard offers 8 SATA ports and 4 RAM slots for future expansion. I was planning on using an Intel Celeron processor, but the Pentium G630T is more efficient, generates less heat, and doesn’t cost much more. I considered reusing some of my 2TB Western Digital Green drives from my HTPC, but in the end I decided to get 3TB Red Drives instead. Besides their larger capacity, they are specifically designed for this application as well as offering a better warranty and support from the manufacturer.

Software

FreeNAS has a lot of useful documentation, but I found Engadget’s tutorial to be a better starting point for basic setup. This got me started with basic CIFS sharing that I can access with both my Windows & Linux PCs. I set up my 4 hard drives as a RAID Z2 array which should be able to survive one hard drive failure without affecting performance and two hard drive failures without data loss. After creating the array, I ended up with about 5.5TB of space available for storage. This should be more than enough for the forseeable future, but I can aways get two more hard drives and recreate the array to increase my storage capacity. Another key part of this setup is the recognition that my server will be used for backups only, never as the sole repository of data.

I ran into some issues, however, when I tried to RSYNC from my HTPC to the FreeNAS box. Using a scheduled RSYNC every night is how I plan to backup my media files and is critical to my local backup strategy. After a lot of Googling and experimenting I discovered how to properly setup the permissions on both the FreeNAS server and my HTPC in order to be able to RSYNC properly.

For my purposes I only have a Guest account on the FreeNAS server. This account does not require a password and has full access to all of the files in the share. On the HTPC side I setup Ubuntu to mount the remote share every time it boots by modifying the “/etc/fstab” file with the following line:

//192.168.10.200/Archive     /mnt/Server cifs guest,uid=joe,gid=joe 0 0

In this application 192.168.10.200 is the IP Address of the server as perminently assigned by my router. “Archive” is the name of the CIFS share I created on the FreeNAS server. The directory “/mnt/Server” is the local directory on my HTPC that I created to mount the server’s share to. CIFS (Common Internet File System) is the file sharing standard. The next three additions are key to getting the permissions correct:  “guest” is the user ID on the FreeNAS server, “uid=joe” designates my user ID on my HTPC, and “gid=joe” designates my group ID on my HTPC. When the server’s share is properly mounted I then had to make sure that the files I planned to share gave full read/write access to both my user and group.

With these set properly I can now RSYNC my media files from my HTPC to the server with the following command:

rsync -avru –delete –progress /local_directory/ /mnt/Server/remote_directory

Conclusion

Now that I have my permissions and RSYNC issues resolved, I am very pleased with my FreeNAS server. With the fan speeds set low it is very quiet and over a week of use it had an average power usage of 48 Watts. File transfer speeds are also pretty good over my newly installed Gigabit network. FreeNAS is a versatile platform and I look forward to learning more about it in the future.

Update – More Hard Drives & RAM (June 2013)

I took advantage of a price drop and bought two additional 3TB WD Red drives and two more sticks of 8GB RAM. This brings my total storage capacity to almost 11TB. In this current configuration the server uses 54 Watts on average.

Solar Chargeable Portable Battery Pack

There are a lot of rechargeable lithium battery packs available. Some have a lot of capacity and others can be used with solar panels, however, I could never find one that fits my requirements. The solar models that I’ve seen generally don’t have much capacity and use such small solar panels that they don’t charge very fast. Then I came across Adafruit’s USB/Solar Lithium Ion Charger board and it solves all of my problems. This board has a lot of cool features: it can charge a battery via a solar panel or any other 5V input and it can deliver power to the MintyBoost from both the input and the battery simultaneously. In this way you could charge a device on a not so sunny day by drawing some power from the solar panel and the rest from the battery.

My main goal for this project is to have a versatile power pack for use when I go camping/backpacking. I have a fair amount of devices that I typically bring with me that can be charged via USB: camera, headlamp, UV water purifier, cell phone, mp3 player, etc. The 6600mAh battery can charge any of these devices multiple times, providing many days of capacity before needing to be recharged. On sunny days the 3.4W solar panel can recharge the battery if I am away from power for a long period of time. At full power the solar panel will take about 12 hours to fully charge the battery. While this is a long time, for my use case this should be fine as I will most likely be topping off the battery with the solar panel not charging it from zero. I like this solar panel for its combination of size and capacity. A larger panel could charge the battery faster, but would be a lot less portable.

Parts List

Adafruit has a detailed tutorial that explains how the charger board works and shows how to wire it to the other components. Basically the charger board is connected to both the battery and the MintyBoost and uses either a USB or solar panel input to provide input power when you want to charge the battery. The charger also has the option to output the charging status (charging, charging complete) to external LEDs.

For this project I used a red LED to indicate that the unit was charging and a green LED to indicate that the battery was fully charged. I also isolated the battery from the remainder of the system using a power switch. This prevents the small self drain inherent to the MintyBoost from discharging the battery when I am not using the unit. You just have to remember to turn it on when you want to charge the battery. In addition I used a coaxial power jack for the power input and modified both the solar panel and a USB cable with matching coaxial power plugs of the same size. The final piece was using a scavenged panel mount usb port for the MintyBoost’s output.

I have to say that I really like this setup. I can charge all of my devices and when placed in the sun, the solar panel started charging the battery with no problem.