This DIY solar flameless candle is a great beginner electronics project.
(In fact, it was the first project I made after teaching myself the basics of electronics.)
The circuit is also a simple DIY solar light circuit that you can reuse for many more solar light projects.
Let’s get started!
Materials & Tools
- 1.2V rechargeable AAA battery
- 1 AAA battery holder
- Container (I used a small cosmetics tin. You can also use an empty glass or plastic jar.)
- 22 AWG stranded wire
- 2V solar panel
- Candle flicker LED
- 220 uH inductor
- 1N5819 diode
- QX5252F IC
- 0.1 uF ceramic capacitor
- Plastic cap of some sort for covering the LED (I salvaged mine from an old LED candle)
- Jumper wires
- Tape (optional)
- Utility knife
- Drill & drill bits
- Soldering iron
- Hot glue gun (or just a tube of glue)
- Wire cutter
- Wire stripper
Step 1: Understand the Circuit Diagram
The QX5252F IC is the heart of the circuit. It regulates the charging and lighting based on how much light the solar panel receives.
When the solar panel receives enough sunlight, the circuit stores it in the rechargeable AAA battery.
Once it gets dark enough, the circuit automatically turns the LED on using the battery.
The IC’s pins are as follows:
- Solar input
- Battery input
This is a fairly simple solar light circuit, one that can be used from many DIY solar light projects.
Step 2: Prototype the Circuit on a Breadboard
First, connect the QX5252F IC. Make sure it’s facing the right way. The side with the numbering on it is the front.
Connect the 220 uH inductor to the same rows as pins 2 and 4 of the IC.
Connect the 1N5819 diode after the inductor to the same row as pin 4. Make sure it’s facing the right way. The silver band indicates the negative terminal.
Connect one leg of the 0.1 uF ceramic capacitor after the diode in the same row as pin 4. Connect the other leg to the same row as pin 3. Ceramic capacitors aren’t polarized, so it doesn’t matter which pin goes in which row.
Connect the anode (positive lead) of the candle flicker LED after the capacitor in the same row as pin 4. Connect the cathode (negative lead) after the capacitor in the same row as pin 3. You can tell which side is the anode and cathode by looking at the LED’s pins. The longer pin is the anode, the shorter is the cathode.
Connect the switch from the positive power rail to the same row as pin 2. (You may have to solder leads to your switch first.)
Connect the solar panel’s positive lead to the same row as pin 1. Connect its negative lead to the ground power rail. (Once again, you may have to solder leads to your solar panel first — just remember to desolder them before you start building the actual circuit.)
Connect the AAA battery holder to the positive and ground power rails.
Use breadboard jumper cables (or regular wire) to connect the terminal strips that are disconnected by the board’s center divider and connect the row with pin 3 to the ground power rail.
Your breadboard circuit is now complete! Now for the moment of truth.
Place the AAA battery in the battery holder.
Turn the switch ON and place your hand over the solar panel to block incoming light. The LED should turn on and flicker like a candle.
If your LED doesn’t turn on, try blocking even more incoming light to the solar panel. In daylight you need to really cover it up.
If that still doesn’t work, double check your circuit.
Step 3: Prepare the PCB
If your container is small like mine, a full-sized piece of PCB won’t fit inside.
To fix that, we’ll have to cut it down to size.
Grab a piece of PCB and place it inside your container the way you want it to sit when done.
Mark the row where you need to cut for it to fit inside.
Using a utility knife, make a cut at that row. Go back and forth a few times to deepen the groove. The deeper it is, the better.
Channel your inner Hulk and break the PCB in half at the groove.
Step 4: Solder the Circuit to the PCB
Solder the QX5252F IC to your PCB. Because I’m a soldering beginner, I wanted to limit my chance of bridging solder joints. So I bent the pins to leave an empty row in between each.
Solder the inductor to the same rows as pins 2 and 4.
Solder the diode to the same row as pin 4 after the inductor.
Solder the capacitor to the same rows as pins 3 and 4 after the diode.
Solder the LED to the same rows as pins 3 and 4 after the capacitor. I bent mine sideways so that when I stick the PCB in my container it will be pointing upward.
Solder the switch’s positive lead to the same row as pin 2, leaving an empty hole beside it for the battery’s positive lead. Solder its negative lead to the same row as pin 2 also, closer to the IC.
Once again, I bent my switch sideways to it will be pointing upward when I place it in the container.
Solder the battery holder’s positive lead to the same pin as row 2, in the empty hole before the switch’s positive lead. Solder the battery holder’s negative lead to the same row as pin 3.
Cut and strip some wire for the solar panel’s positive and negative leads. DO NOT solder the leads to the solar panel yet.
Solder the solar panel’s positive lead to the same row as pin 1.
Solder the solar panel’s negative lead to the same row as pin 3.
I repeat: DON’T SOLDER THE LEADS TO THE SOLAR PANEL YET.
Trim off any excess component leads with a wire cutter to make the connections as flush as possible. Finally, complete the circuit with solder.
Step 5: Prepare Your Container
Wash and dry your container, if necessary.
Place your solar panel on your container’s top where you want to attach it, leaving room for the LED. (I had to place the solar panel to the side to make room.)
Mark where to drill the LED’s hole with a marker.
Using a 7/32″ drill bit, drill a hole for the LED. (I started with a smaller drill bit and worked my way up until I found a good size.)
My hole had sharp ridges sticking up after drilling. I used some wire cutters to trim them down a bit.
Now its time to mark the holes for your solar panel leads. Flip your solar panel upside down and use its + and – markings as guidance. Mark the spots with a marker.
I recommend making a separate hole for each lead. This allows the solar panel to lay a little more flush on your container’s top.
Using a 5/64″ drill bit, drill the holes for your solar leads. (I used 22 AWG wire. Your holes might end up being smaller or larger depending on your wire.)
Step 6: Attach the Solar Panel
Feed your solar panel’s positive and negative leads through the appropriate hole in the container’s top.
Solder the leads to their appropriate terminal. For aesthetic reasons, make sure no wire strands are sticking out from the sides of the solar panel.
(This step took me a while because I made a lot of adjustments so the solar panel could sit as flush as possible on the container top.)
Slide the top to the end of the wires, then glue the solar panel to the top, pressing it down so it’s as flush as possible.
Glue your LED cap to the container, too. Make sure not to fill the LED’s hole with glue!
Wait for the glue to dry. While you do, get excited — you’re almost done!
Step 7: Finish & Test Your DIY Flameless Candle
We’re in the home stretch now. Just a few finishing touches.
Place the battery in the battery holder, and place the battery holder inside your container. (If you want, you can tape it down.)
Turn the switch ON, then place the PCB inside your container. (You may have to coil some wires to get everything to fit.)
Feed the LED through the hole in the top then close your container.
Test the circuit like you did on the breadboard by placing your hand over the solar panel to block incoming light. The LED should turn on!
Do a little jig because you’ve just made your own solar candle!
How to Use Your Homemade Flameless Candle
To charge your solar candle, make sure the switch is ON, then place it outside under direct sunlight. (This is similar to how solar tea light candles work.)
The LED will light up automatically once it gets dark enough. You can also force the LED to turn on by blocking the solar panel with something like tape or paper.
Bonus: Discover More DIY Solar Light Projects
If you want more DIY solar light ideas, here are some of my favorites.
These solar mason jars are very easy to make by comparison. They also look great. No electronics skills required!
Here’s another solar light that anyone can make. Upcycle your empty wine bottles into decorative, eco-friendly lighting!
This isn’t a solar light project, rather a simple solar electronics project. The circuit on this solar charger is even easier than the candle’s. It’s a portable 5V charger that can charge phones and other USB devices.