iPAQ USB Solar Charger

Having a means to charge my FT-817 while out in the field is nice.  Since I also use a iPAQ rz1715 with my FT-817, it is only logical to use solar energy to charge this unit as well.

My favorite "geek shopping site" recently had Coleman Solar Powered Trickle Charger for $10 each.  These are not quite powerful enough to charge the FT-817 at one watt output, but this is more than enough power to charge the iPAQ.

The charging circuit is extremely simple.  A one-watt, Zener diode (1N4733A) limits the USB charging voltage to 5.1 volts.  There is no need to use a current limiting resistor as the maximum current from the panel is around 80 mA.  Even at the maximum current, the Zener diode will dissipate less than one-half of a watt.

The output from the panel is supplied to the iPAQ via a USB type A jack connector.  This was salvaged from the female (jack) end of a USB extension cord.  This connector has four pins, but only pins 1 (+5 VDC) and 4 (ground) are used.  These pins are normally connected to a red and black wire respectively.

In theory, this could also be used to charge other smaller electronic devices as long as they are capable of being charged via a USB connector.  It seems to charge my Nuvi 200 GPS without any problem, with the exception that a standard USB cable places the Nuvi into the data mode.