This LED mason jar turns on by itself at night.
Step 1: Things needed
One mason jar
One 5mm led (color of your choice)
One 3volt button battery
One 82k resistor
One 2n3904 switching transistor
Hot glue gun
Step 2: Schematic(s)
(three pins are collector, emitter and pin.)
Step 3: The NPN
First you're goint to take your pliers and bend the left leg and right leg as shown in the picture. Then tin all three legs.
Bending them this way ensures no shorts.
Step 4: The LDR and NPN
Make sure your LDR has long leads. We need the long leads for a later step. Simply tin the leads and solder one lead to the base pin of the NPN and the other to the emitter.
Step 5: The LED
Use your pliers to bend the leads (as shown in pictures) then tin both. Then solder the negative lead to the collector of the NPN. (see pictures for better understanding.
Step 6: The 82k resistor
The higher resistance the more the light works at keeping the led off. The lower the resistance the more the light doesn't work at keeping it off. Meaning it will stay lit or dim when exposed to light.
Tin the leads of the led and bend the leads as shown in picture and solder it to the positive lead of the lead and to the base of the NPN.
Step 7: Some wire for a battery connector
Cut a red wire about 3 inches long and strip both sides. Do the same for the black wire. Tin one side of the red and one side of the black.
now solder the red wire to the positive lead of the led and the black wire to the emitter. these two wires are now are what we will use for the battery
Step 8: Quick test!
Step 9: To the jar!
Lay some electrical tape down (if your lid is metal) on your lid so you can insulate it.
Then hot glue the NPN down. Use a little bit of hot glue. once everything is secure, bend your LDR 90 degrees as shown in the picture
Step 10: The battery.
We are using a coin battery. They are small and can run an led for a decent time. Now You can add a solar cell and some rechargeable batteries if you want, I wanted to keep things simple. We will be making our own battery holder out of the wire. We have to strip more of the insulation of the wires.
First strip an inch or so of insulation off the black wire then wrap the wire around your pliers to create a nice circle or spiral. This helps create surface area for the negative side of the battery. Then hot glue the wire down. (as seen in picture)
Second, strip an ince of wire from the red, just like you did the black. Now wrap it around your pliers aswell. Again this creates more surface area which will help hold the battery in place and keep strong connections.