portable chromatic tuner solar mod

some ney anban from iran. note the double chanter.

i have a portable chromatic tuner i carry with me all the time. it came with some basic lead batteries, and they eventually ran out. so i modded it for solar energy. an interesting side effect is that since the current is very low, we can actually charge the lead batteries. while some batteries do explode or leak, most can be recharged slowly. this is a risk we can take, since my cells are 75mA only.

materials

  1. any chromatic tuner that runs on batteries
  2. solar cells (i have a bunch of 1V/75mA cells that came from recycled toys, check ebay for that kind of stuff)
  3. a diode that can handle 75mA (almost any diode you find on any scrap electronics from the trash can)
  4. wire, soldering iron, voltmeter and diode meter (if you don’t know which one is the plus and minus)

schematic and pictures

schematic

pic 1

pic 2

pic 3

results

it works. you can see the led lighting up in the last pic. looks a bit ugly because the cells aren’t a perfect fit to the tuner’s size, plus i made a board out of newspaper and glue layers to hold it, making it look even worse. that’s about it. considering lead batteries do not have memory, they can be recharged indefinitely. this might sound a bit strange, but as long as they aren’t completely drained, they can be reused over and over again. the main advantage of lithium is that it can be completely drained and still work, plus energy density and weight, but there’s no particular reason not to use these as the chargeable cells in this case. also, the charge voltage is very near the operating voltage (3.3V versus 3V) which means it could work only with sunlight. however, it’s always better to have batteries between the two as they stabilize the voltage.