Hello All,
This system is designed to light 5 LED's around the mailbox depending on the sunlight. The issue I'm having is getting the system to light up when it gets dark out and to turn off when it's sunny out. I've tried a couple of configurations for the switching part. This included using two NPN transistors as shown below, and also using a single PNP transistor, also shown below. I looked into using a SSR-NC but decided the price wasn't justified. I am currently using the NPN config but the system seems to act as an amplifier, meaning that when the solar panel is seeing sun the lights get brighter instead of dimmer. I believe I have the system wired correctly but I'm more than happy to test other designs out.

Thanks in advance

Parts List
Ground Transistor=2N3904 Link
Main Switch Transistor=TIP31C Link
Resistor=1 kOhm
2 7V, 3W SP in series
4 CRP2 6V 1400mAh batteries in series plus parallel=12 V w/ 2800 mAh
Radioshack Switch
Various LED's

*I noticed that the resistor value by the transistors is showing 100 Ohm, it is in fact 1 kOhm.

 

Edit: In the cutout file I wrote that the SPR will act as an open circuit when the solar panel is turned on. It should say that it will act as a short circuit.

 

You need a 10k resistor in series from the solar panel to the NPN base.
Otherwise there's nothing to limit the base-emitter current.

The pnp circuit is more efficient since the collector-base voltage is small (less than a tenth of a volt) when ON.
The NPN circuit is a emitter -follower so the minimum collector-emitter voltage is about 0.7V

Here's an LTspice simulation of the PNP circuit.
You need to add a resistor to ground (R3) from the PNP base to turn it on when the solar voltage falls, since the solar panel looks like a reverse biased diode (simulated by D1).
I use a Schottky diode for D1 to slightly improve charging efficiency.
I lumped all the LEDs into one load for simulation purposes.

You can see that the LEDs turn on when the solar voltage drops below the battery voltage.

 

crutschow, thank you very much for the help. I rewired the diagram as you instructed for the PNP transistor and it worked. My issue from before is that I didn't have that grounding resistor. Is that there as a voltage divider? I'm just trying to understand its importance to the circuit to make it work since it didn't before, and thats basically the only thing different. My thought process is that the base is more negative than the collector so the current wants to flow that way and since the SP has its own diode it won't back flow through there so in order to allow the current to flow I need a resistor to "ground" the circuit. If thats the case then if I modify the 100 ohm resistor that will effect the current to the PNP and allow me to tune the time the circuit will turn on.

Thanks again for your help. It's the little details that catch me everytime.

Here's a picture of the finished product for you!

 

then if I modify the 100 ohm resistor that will effect the current to the PNP and allow me to tune the time the circuit will turn on.

That's a neat mailbox.

The LEDs basically turn on when the solar panel voltage drops below the battery voltage.
Modifying the 100 ohm resistor value will change that some, but not much.
If you want to not have the LEDS come on until the panel voltage has dropped more than that, then you will need to add some additional circuitry, such as some diodes in series with the base.
Each added diode will reduce the panel voltage it turns on by about 0.6V.
You could also add a zener in series to get more voltage change.

Is that something you want to do?
If so, you need to experimentally determine at what panel voltage you want the LEDs to come on.