This summer has been quite good here on the south coast of England. Got the grass cut, rained destruction on some hideously overgrown plants, the garden looked more like a garden and less like a small wildlife preserve. More Alan Titchmarsh and less Bill Oddie. Plenty of BBQ's sat out until the early hours of the morning. Good times.

Now I love candles, and there were plenty. I made sure of that! There was enough light for general chit-chat and it was very atmospheric, but it wasn't really enough. I had seen various commercial patio umbrella light offerings in the garden centres and supermarkets, but none of them seemed worth what they were asking for them.

I knew I could do better, brighter... cheaper? Probably not to be honest, but more flexible? More satisfing? Definitely.

So now I'm done rambling, let's make some LED Jar Lights!

Step 1: Prerequisites

Skills

You need to know how to solder electronic components. That is a whole other topic that I'm not going to go into here.

You also need to know how to splice wires together, specifically, an inline splice. Those are the best kind and once you've done it a coupe of times, it's easy and quick. Not to mention strong and convenient.

There are many videos and tutorials on the net about how to solder and splice wires. I'd suggest that you search this site and YouTube/Vimeo for more information on that.

Tools

- Soldering Iron.I have a 40 watt "pencil" type iron with a fine point tip.
- Solder.I used ∅0.7mm lead-free solder.
- Helping Hands.You know, those weighted base thingies with crocodile clips on it. If you don't have one, get one. It will make your life so much easier, you'll see why.

A note on solder: I've seen a number of places online where people have been complaining about lead free solder. They say it makes for unreliable joints and have all recommended "60/40" solder, meaning 60% tin and 40% lead.

Personally, I've had better results using lead free solder comprised of Tin, Copper and Silver than I have with the "good old" Tin and Lead stuff. So my recommendation is to get a roll of ∅0.7mm lead-free solder with silver. I find there is a massive difference between using ∅1mm and ∅0.7mm solder. For me it just makes it that little bit easier and gives me greater control over the amount of solder going into the joint, and lead-free because we've only got one planet.

Supplies

- Jars.The ones I got were labeled "cosmetic jars", they're ∅25mm and 30mm tall. They turned out to be the perfect size.
- LEDs.The technique I use here somewhat relies on the package type of the Superflux Piranha LED. So get plenty of those or similar.
- Resistors.Anything between 100Ω and 150Ω is fine for Warm White Superflux Piranha LEDs. I used 100Ω.
-Single core wire.If there's insulation, you'll want to remove it, just to make things less fiddly.
- Multi core wire.This will power the whole string. I used 7/0.2mm.
- DC Sockets.I used standard 2.1mm "barrel" type panel-mount sockets.
- DC Plugs.Just need to compliment the sockets.
- Heat-shrink tubing.Magical stuff. I used 3:1 shrink ratio. ∅3mm unshrunk.

Quantities

Each individual light will require:
- 1x Jar
- 1x DC Socket
- 1x DC Plug
- 3x Resistors
- 9x LEDs

You'll need one extra DC Plug for the end of the light string to plug into your 12vdc power source.

As for the length of the multicore wire, I allowed ≈10 metres from the first light to the end plug for the power supply. It's more than enough for me to get from the power supply to the patio umbrella. Anything more than that would just be a nightmare to untangle!

I was unable to find multicore wire where there were two insulated strands fused together, like they use on commercial strings of lights. Instead I used a drill to twist two seperate lengths together tightly.

Step 2: The Circuit

There really isn't much to this circuit, it's a very simple LED array. Each jar contains an array of 9 LEDs arranged in three strings of three LEDs and their resistor. See the screenshot of the LED array calculator* for a diagram. Each light is then connected in parallel to the power supply. Simples!

Since the forward voltage of these LEDs is 3.2v each, and we want to group them into threes, that's a total of 9.6v that needs to be dropped. I could have gone with a supply of 10v but I decided to go for 12v instead since it's a more common supply voltage.

* The LED array calculator can be found at http://led.linear1.org/led.wiz

Step 3: Assemble the Lights

Now this is what you want the Helping Hands for. You need to solder the LEDs directly together. To do this, put an LED in either of the two crocodile clips, then position them so the legs are overlapping each other and the LEDs are right up against each other. What you end up with is a kind of arc of LEDs which works out really well in terms of light distribution.

Take special care with the orientation of the LEDs, there is a little notch on one of the corners indicating polarity. Or, looking into the side of the LED, the legs attached to the larger piece of metal inside the package are the cathode or "negative". The pins attached to the smaller piece is the anode or "positive". See the picture of the LEDs in the clips to really see what I'm getting at.

Once you've got your LEDs soldered into arcs of three, clip one lead of a resistor so it's just a little longer than the leg of the LED and solder the clipped leg to the free cathode of the LED arc. Also cut a length of single core wire so it's about the same length as the total length of the cut resistor and solder that to the free anode of the LED arc so you end up with the arc and resistor on two long legs.

I tested them all at this point. I had a 12vdc source to hand so I put them all into my breadboard's power rails and flipped the switch. Five minutes later when I fully regained my vision, I returned to work!

Now you need to identify which tab on the DC socket is the positive and which is the negative. I did this by inserting a plug that I knew was wired properly (a 2.1mm barrel plug with integrated screw terminals. Very useful things!), set my multimeter to measure resistance and just tested each tab on the socket.

The sockets I used have a third tab positioned opposite the negative tab. After having identified the positive and negative, I assumed that the opposite one was also negative... wrong. Not sure what's going on there, there was a smidgen of voltage on it so... yeah. Don't make that mistake.

Once you've identified the tabs, you need to take three LED arcs and feed all their anode wires through the positive tab. Then feed all the free resistor legs through the negative tab. This is a bit fiddly. My single core wire was thicker than the resistor legs making it harder to bend, so I did those first. The resistor wires were significantly easier to bend into place. Make sure that all the arcs are arranged as you want them before you solder those connections.

All that remains now is to drill an appropriately sized hole for your socket into the jar lid, mount the whole thing in the lid then ease the leds through the neck of the jar and screw on.

When that's done, give it a final test.

Step 4: Wiring Them Together

This is a great opportunity for you to practice your cable splicing!

The lengths of cable between the lights is up to you, whatever you need. I didn't even bother to measure anything. I just fed some wire between the spokes of the umbrella at the point that I wanted them to hang from, cut the wire, then just measured out lengths against that.

So, you want two lengths of ≈10m for connection to the power supply (power wires), and two leads of whatever length you need to go between each light (link wires). I also cut two shorter lengths for each light so they'd hang down from the umbrella a bit (hang wires).

Solder the hang wires to the 2.1mm DC barrel plugs, I stripped the insulation off the positive wire so I'd know which was which. All my wire is black. The positive wire is the one you connect to the centre of the barrel plug, the negative should be the exterior of the barrel.

Inline splice the link and power wires together into two long chains of wire, don't solder them just yet. Once you've done all the inline splices, start seperating out the cores of the positive hang wires into two and wrap them around the inline splices thoroughly. Solder it. Then do the negative ones. Positive or negative first, doesn't matter, just don't mix them up!

Remember to cut some small lengths of heatshrink tubing, enough to cover your splices, and feed the power/link wire chain through them before attaching the hang wires. It is a monumental pain in the arse having to desolder and undo the splices to get the heatshrink on, so don't forget it!

Keep doing this until you've got all your DC barrel plugs connected in parallel to eachother.

Step 5: Powering the Lights

Given that 12vdc is already a well established standard supply voltage. Finding a source that supplies it isn't too hard.

"Wall Wart" Transformer: You'll probably have a couple of these kicking around in the spares box. Just remember that almost all of them lie to you about what they output so be sure to check the output voltage. The majority of them only have a transformer (to step down the voltage), a rectifier (to make it DC) and a capacitor (to "smooth" the DC). Because the regulation is often done outside the transformer, they allow a couple of extra volts to drop when it gets regulated further down the line.

I found one of my "9v" transformers actually putting out ≈11vdc, which is ok for running these lights with. I would discourage using an unregulated power source as a long-term solution, but it'll do in a pinch. If you plan to only use these lights occasionally, it's probably fine.

A simple voltage regulator: There are many voltage regulator ICs available that are fixed at a 12v output keeping the component count and complexity down. You can build a simple 7812 based regulator on good-old stripboard with minimal fuss. Mine required only one break in the copper strips and one jumper! It even includes it's own rectification and smoothing stages!

12v batteries: These are easy to find and if you really can't find them then you can just string up ten 1.2v rechargable cells to get a 12v battery. Personally I use one stonking big 12v battery that gets charged by a 20w solar panel.

There's something about running lights from a solar-charged battery that I like, I think it's the pretending the battery is full of sunlight! It appeals to my inner treehugger.

Step 6: Future Changes and Improvements

Securing the lights

Now there is one... I don't want to say "design flaw". But definitely a bit of room for improvement.

Hanging them from the power connecter isn't the greatest idea in the world. The lights aren't particularly heavy and they do hang from their connecters perfectly fine... as long as they're still. But if you knock one and cause a light to bob up and down on the string, then odds are it'll fall off and break.

Oddly enough when one of mine fell to the patio, the glass jar was fine and it was the plastic lid that shattered! Which wasn't that bad since I had accidentially drilled one too many lids anyway!

Another option would be to get some locking DC barrel sockets and plugs. They're exactly the same as the usual panel mount sockets except that there's some extra thread on it that is matched on the plug. I did consider getting these, but I couldn't find them at a non-hideous price. Seriously, we're talking ≈£2.50 per plug and ≈£3.50 per socket! Sod that! Of course if you have a different kind of locking socket, that'd do fine, just make sure it's ok to carry 12vdc.

I'm thinking of using some small hooks in the lid and short lengths of small, fine chain to hang them from. That would give plenty of support and I reckon would have a nice finish to it.

Weatherproofing for permanent installation

This could be achieved by either paying a little more for weatherproof connecters, which would probably be bulkier and I think would ruin the asthetics of the lights a bit. Another option would be to omit the connectors completely, feed the wires in through the hole and solder directly to the LED arcs. Don't forget to use a bit of hot glue or mastic in the hole for the wires. This would be a little more fiddly in construction I reckon. But it would also allow you to save a bit of cash on the connectors.

Colours

The Superflux Piranha LEDs come in many colours, including Red, Green, Blue, Yellow, Ultra-Violet, "Cool" White and "Warm" white. So the obvious thing would be just to make them in a variety of different colours with those. You can also get them in a single RGB LED package, both common-anode and common-cathode varieties are available.

I have plans to build some RGB Jars. The particular construction method used in these lights is only really suitable for single-colour LEDs. So my RGB jars will have the LEDs mounted on custom PCBs and as a result will need a 4-way connector on the top and probably larger jars too.

Dimming with PWM

This isn't strictly an improvement to be made to the lights themselves, but I'll mention it because it's relevant. You could dim these lights by reducing the supply voltage going to the LED arrays. A few resistors could do this, provided they're powerful enough. Or you could use an adjustable voltage regulator circuit with a potentiometer to alter the output voltage. Neither of these are ideal though. A much better plan would be to use a method called PWM (Pulse Width Modulation). This basically means flashing the lights so fast that you can't see it, then you can dim them by varying the ratio between off-time and on-time.

You could build a PWM controller for these LEDs using a simple 555 timer astable circuit. The common "LED Blinker" circuit, you just want it to go much faster. You'll also need to use a power-transistor on the 555 output to drive the LEDs with just to avoid damage the 555 chip. As the LED Array Wizard tells us, each light will pull 75mA from the power supply, making 600mA for the whole string. The 555 can only handle up to 200mA output. A relay would not be suitable since it can't switch fast enough. There are many PWM circuit examples out there since this technique is also commonly used to control motor speed.

Motion Activitated

Again, this is more about controlling them than improving them directly, but using a PIR (Passive InfraRed) sensor and a couple of other components you could make them turn on when somebody walks by and fade out over time. Similar to security lights. I don't have many details on this since I haven't done it fully yet but I will, and when I've come up with something, I'll post the details of the build.

Alternative uses

- Emergency lights.Consuming very little power, they would run on batteries for ages. I won't suggest a timescale, that really depends how big your battery is! On my battery, at least a couple of days!
- Night lights.Used in conjunction with a PWM dimmer, these would make great nightlights!
- Torch light.Get a bit of PVC pipe, shove batteries down it, stick one of these on top and you've got yourself a modern-day Indiana Jones-style torch! Except that this one won't go out as easily or burn you! Add a microcontroller to give it a real flame effect!
- Table lamp.Really just need to make a weighted base with a DC plug on a stick, a shade too, pop the jar in like a lightbulb!

In closing
These lights have been well worth it to me. They put all the commercial equivalents I've seen to shame and aren't limited to one use! If you have any questions regarding these lights then please leave a comment below and I'll do my best to answer. Thanks for reading and remember, if you liked this instructable then please rate it accordingly!