Summer has seen few posts, but not because of lack of activity. I have been busy researching for the upcoming urban interface oslo exhibition. One of my challenges has been to find a setup with a short-range fm sender, a mp3 player and a solarcell/battery solution that would make it possible to place this unit anywhere and leave it running. This has proven a lot harder than I would have imagined.
First, there are now so many fm senders available, and it is really hard to distinguish good from bad (90 % bad), and the reviews out there are not trustworthy. There also seems to be so many factors affecting signal strength so the same sender might appear to have a strong signal one day and a really weak one the next day. Frustrating and time consuming, and I am still checking out different modules.
I guess I should ask Raghav Mahato in India, who claims to have built a radio sender for just over 1 usd.
I knew very little about solar power solutions before this summer, and the options range from build it yourself solutions to “how to survive after a nuclear attack” systems. I looked first at relatively new products advertised as solar chargers for mobile devices like ipods, cellphones and pdas.
Most of these mobile solar chargers combines small solar panels with an internal rechargeble battery with different types of breakout plugs.
Not all of them are able to provide power while charging, which was necessary for my setup. I gave the freeloader a try as it sounded like the perfect companion for a fm sender and mp3 player, it has a 2100 mAh battery, but the results were very disappointing. I guess the current from the solar panels is just too weak to provide enough power to keep the battery charged while in use.
There are not so many other ready-made solutions, either they have a smaller capacity than the freeloader or they are just chargers (so the batteries can´t be used while they are being charged).
I am now looking at more heavy-duty solutions, 6-15W solar panels in combination with a charge controller and a lead battery, but this becomes quite expensive and heavy. And all I need is about 100-150mAh. I am still hoping for the perfect solution to pop up.
This research will also be useful when looking for selfpowered xbee solutions. They seem to have had success with a solar powered xbee system at ITP.
I managed to do a little bit of work with the Xbees a few weeks ago, finally getting the directmode (connect a input of one xbee to the output of another xbee, without using an external microcontroller) to work, and also exploring the sleep options, which means being able to keep the power used to a minimum.
I have discovered lots of interesting alternative energy websites, here are a few of them: