Solar Powered SM Fox Blinky LED Jewelry



About: We’re life-long tinkerers, siblings, and fourth generation engineers. We’re not quite sure which of us had the idea of putting LED’s on jewelry and powering them with solar cells, but once Marty proved it c...

Ready to up your soldering game and try some surface mount components? Disappointed with the boring "learn to surface mount solder" kits that do nothing and look lame?

Well we've got your answer, our advanced blinky Fox surface mount soldering kit. She don't say noth'n, she's too cool for that nonsense.

Not only will your nerdy skills improve, you'll have something to show for your efforts at the end. Win-win! Foxy Fox makes a great geeky jewelry gift for yourself or a friend.

She has two alternating amber LED eyes powered by 4 solar cells in her tail. There is also a micro USB connector on the bottom if you want to quick charge her or are someplace dark. The board comes with a hole through the top making hanging easy. Watch Foxy in action above.


  • Size: 1.6″ wide by 1.72″ tall
  • Solar Charge Time: 15 minutes
  • Optional USB Charge Time: 2 minutes
  • Lifespan in Darkness: 90 minutes.

We have a whole range of soldering kits from beginner to advanced, check out our store.

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Step 1: Tools

This instructable gives step by step instructions on how to assemble the surface mount LED eyed fox. If you have some soldering experience don't be intimidated by they tiny surface mount components. With good lighting and a pair of tweezers you can do it. That being said, surface mount soldering is NOT for a beginner. If you are new to soldering check out our beginner or intermediate soldering kits. Come back to this beauty later.

Sparkfun also has some great tutorials for the fine details of surface mount soldering. Honest, with the right tools it is as easy as they make it look.

The schematic and parts list are included. You are welcome to wire up your own, copying is the sincerest form of flattery. But why would you want to when we also have the kit available in our store? I mean, its a FOX, how cool is that?

Here are the tools we recommend:

1. Good lighting, period. A flashlight can help too.

2. A Magnifying glass. These parts are tiny, and unless you have go-go-gadget eyes you'll need one.


1. One of those combination magnifying lights. Solves two problems with one gadget.

Oops, now the numbering may be messed up. Oh well, you get the idea.

3. A static free or dissipative surface. Surface mount soldering components can be sensitive to stray electric shocks, especially the chips.

4. Tweezers, self explanatory.

5. A good quality soldering iron. Like Sparkfun says, spend the money on a $50 one with decent temperature control. It will prevent you from frying the tiny components.

6. Small solder (0.032" or smaller) with a rosin core. We prefer water soluble flux, it makes cleanup easier

7. Solder wick, 1/8" wide or less. 1/16" works best for this project.

8. Liquid flux, water soluble preferred.

9. Exacto knife. Can be useful to fix mistakes

10. Your handy dandy diagonal cutters

Step 2: Parts List

To help keep everything straight we put the smaller pieces into a weekly pill organizer. Some of these parts look exactly alike, so staying organized is important. We also include a detailed pictures of each component. The kit comes with one extra of everything in the pill organizer, just in case you loose one. So don't worry if you have one left over.

Below is the parts list, in order of instructable assembly. They are written QuantityxPart (day in pill box). If there isn't a day listed next to a part, it is loose in the bag.

  • 1XWhite Fox circuit board
  • 3X1uF 0805, C5 and C6 (Wednesday)
  • 3X10uF 0805, C2 and C3 (Thursday)
  • 2X74LVC2G14, U1 (Sunday)
  • 3X300ohm resistor, R2 and R3 (Friday)
  • 3XD3 and D4, SM red LED (Monday)
  • 3XSchottky diode, D1 and D2 (Tuesday)
  • 4XSC1-SC4, BPW34 solar cell
  • 1XMicro-usb-b connector
  • 1XSwitch
  • 1X C1, 0.33F black Super cap
  • 2X2.0Meg 0805, R1 (Saturday)

Step 3: Capacitors C6, C5, C2 and C3

We'll start with capacitors C5 and C6 from the Wednesday compartment. The orientation doesn't matter on these parts.

The basic steps for surface mount soldering go like this:

  1. Tin one of the pads (melt solder onto it)
  2. Grab the part with tweezers
  3. Place the part correctly onto the board. Hold it with the tweezers while melting solder onto one end of the part.
  4. Remove soldering iron from melted solder but continue to hold the part with tweezers until the solder has solidified.
  5. Rotate the board and solder on the other end of the component. It's best to be quick when soldering the second end so the first pad doesn't melt as well. Don't worry if that happens, SMD components are so small that the solder surface tension should keep it in place when you remove the soldering iron.

A video of soldering the first cap is shown above.

I prefer not to use a helping hands or clamp when surface mount soldering. This allows me to rotate the board for easy access regardless of which hand holds the soldering iron or solder.

Next capacitors C2 and C3 in the Thursday compartment. Use the tweezers to lift the edge of the plastic covering the components. Repeat the same steps listed above: solder a pad, solder one side of SMD component, solder remaining pad.

Congratulations, you have learned to surface mount solder!

Step 4: Brains! I Mean, the Chip.

And now the hardest part, soldering on the chip. They're in compartment for Sunday, and we included an extra one just in case it goes flying out of your tweezers. It happens.

The correct orientation is shown above. Make sure its 6 legs are on the table and the lettering H14 is right side up. If you can't see the label use a flashlight at an acute angle and a magnifying glass.

Solder the chip as follows:

  1. Tin one or two of the pads. Don't worry if you solder them together, we'll fix that later.
  2. Using the tweezers, hold the chip in the correct location and orientation, lining all 6 legs up with their pads.
  3. Melt the tinned pads onto a leg, soldering the chip in place. Keep holding it in place until the solder is solidified when you remove the soldering iron.
  4. Solder the remaining pads. A little dab of solder is all you need.

You may have some bridged leads on the chip as shown. DON'T PANIC! This is easy to fix with our handy dandy liquid flux and solder wick. This method is called the smash and grab by spark fun, but I'm sure there are other names.

  1. Add solder flux to the bridged pads. You don't need much, but its ok if you accidentally add a lot. We will clean it off later.
  2. Place the solder wick on one side of the chip with the bridged pads.
  3. Press the soldering iron onto the wick, melting the solder underneath the iron as shown. Don't leave it on too long, the wick is very absorbent and may suck up ALL the solder.
  4. Using a new part of the solder wick, repeat steps 2 and 3 on the other side of the chip if it is also bridged.
  5. Double check there is still solder connecting the legs of the chip to the pad. Sometimes the wick removes all of it. Add a bit more as needed.


Step 5: Yellow LED Eyes

And now the blinky bits! The amber LEDs are in the compartment for Monday.

The orientation of the LED's is also important. As shown in the pictures, there is a green 'T' on the back of the LED. The top of the T goes TOWARDS the A end of the LED pad on the board. There is also a tiny green dot on top of the LED. This dot faces AWAY from the A on the board. Again, a magnifying glass is very helpful. Solder as usual.

Step 6: Schottky Diodes

Next the Schottky Diodes in the Tuesday compartment. Again, the orientation is important. The three parallel lines are the easiest to see, they face TOWARDS the C of the AC label on D1 and D2. Good lighting and a magnifying glass will help you see the detail.

Double check the orientation after soldering. If you mess up, the first few steps of this Sparkfun Tutorial show you how to remove components.

Step 7: Resistor R3

R3 on the nose is the 270 ohm resistor from the Friday compartment. Use the tweezers to lift the edge of the plastic covering the components.

By now you should have the rhythm of surface mount soldering down, so I won't repeat myself.

Step 8: Tiny Solar Cells

Next are the mini solar cells, or photo-diodes. They are loose in the bag, you should have 4 of them.

There is a small silver dot on one end that indicates the + positive end of the pad. Double check with our pictures if you are unsure. Solder them onto S1 through S4 on the fox's tail.

Step 9: Micro USB and Switch

The micro USB is mostly through hole, making it a little easier.

  1. Start by tinning the thin pads in the center of the USB. These carry the power.
  2. Add a small dab of solder paste to the tinned pads and the gold pins on the back of the USB. This will help the solder wick onto them.
  3. Hold the USB with the tweezers and line up the gold pins on the bottom. The outermost pins align with the thin pads.
  4. Next carefully melt the thin rectangular tinned pad onto the gold USB pins as shown. Double check the solder has melted onto the gold USB pins, you should see a change in color from gold to sliver.
  5. Repeat step 4 for the other USB pin, using only a small dab of solder onto the iron.
  6. Finally, you want the USB to be very securely attached to the board. Solder the 4 through hole legs of the USB from the back.

Next the switch. It has two plastic pins on the backside that fit into the holes in the board. This makes soldering super simple, it holds itself in place. Solder all 7 pins as usual.

Step 10: Main Power Cap and Final Resistors.

Next we'll solder the main power storage, the large black cap.

  1. Insert it through the two holes, oriented as shown. The metal lead on top of the cap labeled - (negative) should be facing towards the fox's head.
  2. Flip the board over and rest it on the table. This will hold the cap in place while soldering. Double check the legs are still sticking out of the holes.
  3. Solder on the back side as usual and trim the leads with the diagonal cutter.

And finally the two tiny resistors above the USB. We left these till the end to make soldering the USB easier. R1 is 2.0 MegaOhm resistor from the Saturday compartment and R2 is another 300 Ohm resistor from the Friday compartment.


Step 11: Operation and Extra Credit

Regardless of how you display your fabulous fox, we recommend cleaning it first. We used water soluble flux, so a rinse and maybe a scrub under the faucet is all it needs to be squeaky clean. Leave it to dry overnight before plugging it in.

Fox operation is super simple. It has two modes of behaving controlled by the switch, we call them Store and Direct. The switch connects and disconnects the power storage capacitor. When on the Store side, the power storage is connected. On the Direct side the fox runs directly off the ambient light in the room. No light, no blinky. For more details see step by step instructions below. A video of it charging is shown above.

How to store power

1. Switch into “Store” mode.

a. USB – plug it in. Wait 2 minutes till its really, really bright. If the LED's are constant, its full.


b. Solar – find a light source it likes and leave it under for 10-15 minutes. How do you know if it likes a light source? Switch it to Direct and see if the eyes blink.

2. Enjoy the blinky awesomeness now!


3. Store the charge for later by flipping the switch to Direct.

The first time you charge your skull we recommend conditioning the super cap. What does this mean? Charge it for longer than it takes to reach full capacity and store this for a few hours. It keeps the cap from having a memory and undercharging.


  • Size: 1.6″ wide by 1.72″ tall
  • Solar Charge Time: 15 minutes
  • Optional USB Charge Time: 2 minutes
  • Lifespan in Darkness: 90 minutes.

And don't forget to check out the other geeky soldering kits in our store.

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