Battery Graph

After three weeks of operation I have produced the following graph, showing our battery discharge cycle. We are getting 8 days per battery charge, which is quite impressive (at least to me).

Neighborly WiFi

We live in a rural part of southwest Wisconsin. It is very pretty, but broadband Internet is scarce.

Most people around here get to choose between dial-up Internet or satellite Internet.

Because I work full-time from a home office, my company provides a T1 circuit for my use, a whopping 1.544Mb/s. Not that fast compared to the 6Mb/s fiber that is available to some homes or even the 2-4Mb/s available via cable, but a far cry from dial-up or satellite.

As a result of telco upgrades that happened due to my T1 circuit order, some of my neighbors are now eligible for DSL.

Unfortunately, our next door neighbors live on the other side of an imaginary line that divides the territories of two different telephone companies. My phone company now offers inexpensive DSL, but our neighbors are still stuck on dial-up.

I proposed to them that we might be able to provide Internet via a wireless link, and they were immediately interested.

Even though they are only .3 miles away, this was not going to be easy due to the hills between our homes.

I set up my GPS and laptop in the car and drove around, performing an elevation survey and marking possible relay tower locations.

The initial plan was for two towers- one next to my house and another mounted to their silo or machine shed- since we were trying to choose locations near existing electrical service for powering our relays.

It soon became apparent the two 40' towers I had scavenged would not be tall enough to overcome the hill between us unless a tower was placed on top of the hill.


Since the hilltop directly between us was occupied by a field, we looked around for an alternate hilltop which would meet our needs. The hill we found was a bit out of the way, but it offered a good view of both houses and a good site for the tower. There was no nearby electrical service to power the tower, so we would have to use a deep-cycle battery for power. However, we would only need one short 25' tower in order to see both houses.

We set to work digging the hole for the tower base, and made it down about three feet before hitting rock. The following weekend, we hauled 30 bags of Sackrete (1800lbs) to the tower site, and set the bottom section of the tower in the hole. We temporarily supported the tower using fence posts and ratchet-straps as guy wires, while we mixed cement 5 bags at a time in a plastic kiddie pool from which we shoveled the cement into the hole. This went surprisingly quick, and in a short time we could stand back and look at our fledgling tower with pride. ;-)

We waited a week, then attempted to add the additional tower sections to the base section. I'm glad we were not erecting all 40'! It was every bit as difficult as we expected, but a short time later our tower was 25' tall and ready to host our new wireless relay.

For our link, I had decided to use wireless routers running the OpenWRT open-source firmware. I checked the OpenWRT supported hardware page and, after reading numerous support forum posts and documentation, decided to use Buffalo WHR-HP-G54 routers for our project, in addition to the Linksys WRT54GS which was already in use at my home.

I flashed the routers with the OpenWRT firmware ( a little scary since this can sometimes "brick" the router, leaving it unresponsive and worthless) and configured them to mesh with one another via WDS. I tested them in my office and they appeared to work correctly: the three wireless LANs were bridged together and I was able to get to the Internet no matter which access point I connected to.

I shopped around a bit and was unable to find inexpensive weather-proof enclosures for the router on the tower and the one which was planned to be mounted to a TV antenna mast at the neighbor's house. My router was to be mounted in my garage, with just vinyl siding and a layer of OSB between it and the tower. I hoped that the OSB was sufficiently RF-transparent. I covered the router with a large clear Rubbermaid container to keep pests out of it.

I finally found what I hope to be a suitable outdoor enclosure! A Coleman lunch cooler. Just the right size, and a nice lid that seals all the way around, unlike hinged-lid coolers that are difficult to seal along one edge. A bonus is that it will keep the router warm in the winter, but I was concerned about over-heating in the summer. I ran a test for two days, the router sealed in the cooler while my laptop continuously downloaded large files via the wireless link. The router never locked up, and when I opened the cooler it was not noticeably warm. :-) Since the cooler worked so well for the router, I decided to use a larger cooler to house the battery and other electronics at the bottom of the tower.

The Buffalo router requires 5VDC to power it, and our power source is a 12VDC deep-cycle battery, so we needed to build a power supply. We decided to use a switching 5VDC regulator module because they are very efficient. This is especially important because we are running on battery power. We used the 78SR105 module from Texas Instruments. It converts input voltage ranging from 7-30VDC into nice stable 5VDC. We bought it here for $18.05 plus shipping. We mounted the module and two capacitors to a small piece of perf-board and mounted it inside the cooler with the router. Also planned, but not installed yet, is a low-voltage disconnect circuit to keep the battery from becoming over-discharged, which would damage it. We are using this circuit, which will be mounted in the battery box cooler. We have two 120aH RV/Marine deep-cycle batteries, and one of them will always be on the charger ready to replace the one in service. So far, we are getting five to six days of operation on a fully-charged battery.

Now, with the routers in my garage and on the tower operational, it was time to install the router at the neighbor's house. On a lark, we decided to check for link with the router sitting in an upstairs window. It worked! So, no one had to climb on the roof and we did not need a cooler-enclosure for the third router. After running CAT-5 cable down the upstairs hall, we hooked up a PC and tried it out. Unbelievably, it seemed to work as well as it would have if we were sitting in my house, three wireless routers and .42 miles away.

The project is operational now and working very well indeed! I added a ZoneCD content-filter and firewall, which should help keep some of the less-pleasant online material offscreen.

As I mentioned, we plan to add a low-voltage disconnect circuit immediately. In addition, we will add reverse-polarity protection at the battery as is shown here. Finally, the addition of a solar panel and charge-controller circuit would allow the relay to run indefinitely without weekly battery swaps. Time will tell if the current inconvenience justifies the expense of the solar panel and charge-controller.

Much thanks to Fred, Andrew, Don, Katherine and Nathan who helped with the construction, and Lisa, whose constant inquiries kept the project on schedule. Also a big thank you to my wife Emily for supporting this project even though it meant more time in the office researching stuff and getting everything working. Much thanks to Ron S. who provided useful information for the next phase of the project, when we will add the solar battery charger.

Here are some pictures of the tower and from the tower:

The tower from my house.

The tower from the neighbor's house.
(can you see it?)

The view from the top of the tower towards my house.

The view from the top of the tower towards the neighbor's house.

Emily and Henry posing with the tower.