Hi, I was trying to design a small circuit that integrates a battery solar charger and a decent night lamp. The charger part works fine. However, the lamp part doesn't. I'm not sure what is going on, but I get strange voltage in the ground pin of LDO (U4)— if I measure between the battery ground and the LDO ground, I see the battery voltage. If I measure the common ground and the LDO positive input, it shows about 0.6V. I would appreciate your help with this. Thank you.

 

That's a pretty unintelligible diagram, sorry. Too hard for me to unravel.

You don't have Q1A Q1B upside down do you?

 

Fortunately (or otherwise) bipolar transistors still work when the emitter and collector are swapped. Swapping them means that a transistor will usually breakdown when the emitter rather than the collector avalanches and gain (Ic/Ib) is lower.

It doesn't have to be complicated:

 

Yeah diagram does not make sense.

The arrangement of upside-down transistors is supposed to shut the light off in the day?
PWR_FLAG? what?

 

Switching ground to disable a circuit is a bad idea. You can switch the battery plus to the regulator using a PNP transistor or P-channel MOSFET. Or, better yet, use a regulator that has an enable input.

 

Yes, the arrangement of transistors is supposed to shut the light off in the day.
PWR-FLAG doesn't mean anything in this schematic, just a way to mitigate the KiCad validation warning.

Thank you for the suggestions.

 

Tracing out that collection of circuit snippets is rather tedious, and having to guess at the meaning of the labels leaves me wondering. And for a solar powered Nite Lite it seems quite complex.