Quick and Simple LED Mason Jar

Introduction: Quick and Simple LED Mason Jar

About: I am an electrical repair tech by day and an engineer by night, after work or free time.

Mason jars and leds are almost made for eachother. They are eye appealing and just plain fun. I am going to show you how to make a very simple one that involves a few cheap componets you can find anywhere online! This could be considered an introductory project for those new to electronics but why set limits? You like it you make it :)  lets get started and embark on the simplicity!

This LED mason jar turns on by itself at night. 

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Step 1: Things Needed

You are going to need;

One mason jar
One 5mm led (color of your choice)
One 3volt button battery
One 82k resistor
One 2n3904 switching transistor
Some wire

Soldering iron
Hot glue gun
Helping hands 
Wire strippers/cutters

Step 2: Schematic(s)

I have included two schematics. One is the, I guess, offical schematic and one is a 'birds eye' view. The second one is intended to give you the feeling as if you were looking down at the circuit. I mainly included this for the NPN because I know that they can be tricky if you're new to them. I remember when I first saw one (roughly 6 years ago) I got the pins mixed up all the time and doing so can result in the transistor getting really hot or breaking or even both. 

(three pins are collector, emitter and pin.)

Step 3: The NPN

I will be walking you through how to make this small circuit without using a PCB (printed circuit board). Now if you want to use a PCB go right ahead and do so :) I figured it would be fun to do without. 

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

The LDR is what turns the led on and off! It senses the dark based and activates the NPN. The ldr is a resistor that changes value as soon as light hits it. 

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

The led! The famous diode that got its popularity because it can produce light! The leads of your led need to be bent at the bottom 90 degrees. This way the led is pointing towards the bottom of the jar once finished. 

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 resistor plays a huge role in this project. The higher the resistance the more darkness it takes to turn on the led meaning the more the light will keep the led off. I think an 82k resistor is perfect for well lit homes and the sun. You can go higher if you'd like. Now if you use a low value resistor (like 160ohm) the led will not turn off in the light or be dim. 

In short;
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

Use color coded wire to help with polarity. I used red and black. Red=+ and black= -

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!

 the circuit is done and now is a good time for a test! why? Because NPNs are heat sensitive and you want to make sure evrything works before moving on. hook up the battery and expose the LDR to light , if it doesn't turn on then that's good! Now cover the LDR with some black electrical tape (or turn off the light) and if it lights then it works!

Step 9: To the Jar!

We will be putting everything together on the lid of the jar (last step gave that away). 

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.

What is a circuit without a current? What is peanut butter without jelly? Not a Pb&J. 
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. 

Step 11: Finish Up

Now after everything is done, screw the lid back on and test it out! put it near the light and turn off the light and enjoy the fun! stay tuned as I am currently working on another version! :) I hope you enjoyed this ible! Thanks for viewing!

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    4 Discussions


    5 years ago on Introduction

    Whats the point of the NPN? If the LDR is a switch couldn't the NPN be eliminated?


    5 years ago on Introduction

    Whats the point of the NPN? If the LDR is a switch couldn't the NPN be eliminated?


    5 years ago on Introduction

    Whats the point of the NPN? If the LDR is a switch couldn't the NPN be eliminated?


    5 years ago on Introduction

    Already bought the components but they forgot to send the LDR :(. Gonna make one with a switch to test light intensity.

    These will be my kids night light :)