hello!
currently designing 2 handheld devices, 1 on burner , 1 active platform various projects.
consisting of main pcb mcu, voltage regulator, display, human interface, storage , rtc wich has header "expansion board" hold circuitry specific task.
the pcbs not routed yet, schematic done.
i thought longest time had sorted out, prototype has been build , right working on case.
but forgot something...
it designed work of 2 aa cells in series , drain them until power fails, startup voltage of regulator 0.9v , work down 0.3v.
now thought using rechargeable cells , problem, not that.
a simple undervoltage lockout take care of on discharge prevent squeezing every last drop out of primary cells.
but below 1v alkaline cell have not charge left , nimh well, cut off @ 1.8v 2v mean primary cell gets discharged reasonably low , nimh not damaged.
would right assumption? in case have put sort of low power device (supervisor, reset ic, comparator) @ enable input of boost converter , can call done.
additionaly decidet use polyfuse , big tvs diode reverse battery protection since possible put batteries in unit have been discharged low enough gate-source voltage of p-channel fet not high enough disable it.
at least datasheet predicted , test have shown.
if ask yourself, why not want use more cells or lithium cell...
ease of use, swapable cells, readily available replacements, size/case restrictions , "big brother" uses lithium cell integrated charger.
so little brother low cost possible
greetings,
peter
currently designing 2 handheld devices, 1 on burner , 1 active platform various projects.
consisting of main pcb mcu, voltage regulator, display, human interface, storage , rtc wich has header "expansion board" hold circuitry specific task.
the pcbs not routed yet, schematic done.
i thought longest time had sorted out, prototype has been build , right working on case.
but forgot something...
it designed work of 2 aa cells in series , drain them until power fails, startup voltage of regulator 0.9v , work down 0.3v.
now thought using rechargeable cells , problem, not that.
a simple undervoltage lockout take care of on discharge prevent squeezing every last drop out of primary cells.
but below 1v alkaline cell have not charge left , nimh well, cut off @ 1.8v 2v mean primary cell gets discharged reasonably low , nimh not damaged.
would right assumption? in case have put sort of low power device (supervisor, reset ic, comparator) @ enable input of boost converter , can call done.
additionaly decidet use polyfuse , big tvs diode reverse battery protection since possible put batteries in unit have been discharged low enough gate-source voltage of p-channel fet not high enough disable it.
at least datasheet predicted , test have shown.
if ask yourself, why not want use more cells or lithium cell...
ease of use, swapable cells, readily available replacements, size/case restrictions , "big brother" uses lithium cell integrated charger.
so little brother low cost possible
greetings,
peter
Arduino Forum > Using Arduino > Project Guidance > Primary and rechargeable cells in handheld application
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