Night Light gone bad. . .

[skorekaj]

Hi All,

Im a total noobe when it comes to this stuff but here we go.
I got the idea to create a night light for my 2 children that would turn itself on at night and off when daylight is detected.
So far so good, that all works fine with what i got. But i thought, wouldn’t it be awesome if we had a solar panel to charade the batteries up during the day?
The solar panel charges the battery just fine, but only when i break the circuit to on the right hand side of the battery.

So the question is, how can i break the circuit so that current doesn't flow around the circuit and just charge the battery ?

I have the attached ciruit:

1: LDR
2: Variable resistor
3: LED
4: NPN transistor
5: Battery, 3 x 1,2 v rechargeable batteries
6: solar cell, producing some 22 mah at around 4 v

 

[ClydeCrashKop]

Post deleted. Someone will find a better way.

 

[skorekaj]

Hi p, i did have a look at the ic, but i think that your solution will make the LED light up during the day and not at night .
Thanks for your effort though .

 

[ronv]

Can't say for sure this will work. It assumes you have an LDR that is about 10K ohms in the light and 200K ohms in the dark. Many are like this.
Also assumes a white LED. It may glow a bit when charging.

 

[cowboybob]

Welcome, skorekaj!

This works nicely. Since it appears you're using a lithium style battery and if your confident of the max current the solar cell(s) can produce, I think you'll be safe with this circuit:

FR1 (the SIM LDR) is set for "Moonlight", or approx 2 Mohms. Circuit draws approximately 23mA when LED on (night time) and <200uA during daylight (LED off). You may have to adjust R2 to suit your LDR.

LED operation is unaffected by output of solar cell(s).

 

[ronv]

Hmmm. Red night light. How romantic.

 

[cowboybob]

USN hangover. Doesn't ruin night vision. And was not meant to be romantic... .

 

[dr pepper]

Your old circuit was quite clumsy, it would have burned more energy when the led was off.
Bobs circuit is a lot better.
Monitor the batteries and see if they warm up, as theres a possibility the solar cell will overcharge them, if so cover up some of the cell or put it more in the shade.