[aprssig] Solar charging again

Scott Miller scott at opentrac.org
Thu May 5 18:18:46 EDT 2005

Slightly different topic this time - I'm interested in solar charging for 
small systems, probably with NiMH batteries.  I suppose a very small SLA 
might work, too.  I want to put 1-wire weather station OpenTrackers in 
mast-mounted boxes with small PV panels.

The average power consumption of the system can be kept to under 50 mW.  The 
tracker (with an LDO regulator installed) maybe 6 mA at 5 volts, including 
the weather sensors.  I figure a 6" by 6" or smaller panel should be able to 
do it, but I'm not sure about the efficiency of small charging circuits. 
Does anyone have any good example circuits?  I think I saw a Maxim appnote a 
while back that did something similar - I'll have to check.  I figure the 
battery pack will probably be 6 or 7.2 volts.

It'd be nice to use something like the PocketTracker transmitter, but I 
think it'll be cheaper and simpler to use a DJ-S11T or something similar. 
They're cheap and readily available on eBay.  Though the lack of an antenna 
connector is annoying...



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