There have been a few posts recently from people new to the delights of DIY light building looking for guidance, so I thought I would put together a very simple project that would introduce anyone to the techniques involved in creating a simple DIY LED light. The design utilises only the most basic of components and the construction requires only common hand tools and simple workshop skills.
The design of this light uses a single XP-G R5 LED being driven at 1A by a cheap, Deal Extreme, single-mode driver. This will give around 350 lumens and will run for around 2 hours 20 minutes on a single 18650 2500 mAh Lithium-ion cell when fully charged. As it uses a single mode driver, I have kept the construction as simple as possible, so no switch is deemed necessary, the light being turned on and off by plugging and unplugging the battery lead.
I stumbled across this design after purchasing some Ledil LXP optics and wondering what sort of tube they would best fit in. I had some 22mm copper pipe fittings in the garage and it turned out that at 21.6mm diameter, the optic fits quite nicely into the couplings. These are known as end feed couplings in the UK because when used for their proper purpose the pipes are joined together by heating them up and feeding solder into the ends. Apologies to those outside of the UK if you cannot obtain similar sized plumbing fittings but I am sure it shouldn’t be too difficult to fashion a suitable case somehow.
Pic 1 - Basic Components
From the above picture the component list is as follows:
Ledil LXP-RS optic
22mm copper straight coupler
XP-G R5 LED on 16mm round MCPCB
5mm Aluminium slug
22mm copper pipe
DX SKU26110 3V-18V 1A Driver (Kaidomain SKU S002982 is a similar alternative)
DC Power socket (2.1mm 5.5mm)
22mm copper end cap
Equipment wire (not shown)
One thing I should point out before we start is that the Ledil LXP optic is supplied with a thin layer of double-sided tape on the base of the optic holder for fixing the optic to the LED MCPCB. I have removed this to make handling of the optic easier when locating the LED. The optic is going to be sealed into the pipe casing anyway so the tape is redundant in these circumstances.
You will also need a suitable battery pack for running the light equipped with the right DC connector if you are using the DC power socket that I have included in this design.
1. Cut a piece of 22mm pipe around about 25mm in length. Clean up any burrs at both ends internally and externally and make sure at least one end is square to take the slug.
2. I created the slug out of a piece of 5mm thick aluminium which I filed by hand to a tight fit to one end of the 22mm pipe. Interestingly a UK penny is exactly the right interference fit so I used one as a template for the slug. If you are feeling lazy you could always AA 3 or 4 together and use them instead!
Pic 2 - God Save the Queen!
Pic 3 - Slug with attached LED and Modified Optic Detail
3. Fix the slug into one end of the 22mm pipe with Arctic Alumina adhesive and leave to set.
4. To accurately fix the LED to the centre of the slug I have found the following method works reasonably well. Push the pipe, slug end first, into the straight coupler until it reaches the crimped section halfway down the coupler. Coat the back face of the LED’s MCPCB with a thin layer of AA adhesive and locate carefully, LED face down, onto the inverted optic holder, seating the LED correctly in the cut-out in the optic holder. Carefully slide the coupler with the pipe containing the slug over the optic and gently push down until the LED makes contact with the slug and the adhesive spreads (you will need to push the optic up slightly into the coupler for this to happen). Invert the whole assembly so that the optic is now uppermost and put aside for the AA adhesive to harden. (You could tackle steps 8 & 9 whilst waiting for this to happen.)
5. Remove the optic from the coupler and pull the pipe out of the coupler as well. Drill two small holes either side of the LED MCPCB through the slug to run the connection wires through to the driver.
6. Solder two suitable wires onto the LED tabs and run them through the holes in the slug.
7. I think if you use the 20mm round MCPCB you won’t have to follow this next step. I have used a 16mm round MCPCB (because it’s what I had available) you will need to drill a couple of small holes in the optic carrier to clear the solder tabs and wires on the LED. If you don’t do this the optic holder will not sit flush with the MCPCB and the beam pattern will probably be adversely affected.
8. Drill an 8mm hole centrally in the copper end cap to take the DC power socket.
Pic 4 - DC Power Socket & Driver
9. This next step is optional but is a good way to connect the driver to the DC power socket and fix it in place at the same time. The back of the driver has a central copper disc for the +ve battery connection and an outer copper ring for the –ve battery connection. Bend the contacts on the back of the DC power socket so that the positive contact will sit somewhere in the centre of the central disc on the driver. Bend the –ve contact on the DC power socket so that this lines up with the outer ring on the driver.
Now carefully solder the +ve and -ve contacts to the driver. Test with a digital multi-meter that you haven’t got a solder bridge at this point. If you are not confident with your soldering skills then I would advise using wires to create the contacts between the DC power socket and the driver. The last thing you want is a short circuit here when you connect the battery. If you do use wires then you will need to select a method for mounting the driver board in the housing. I would suggest some silicone at the point of final assembly. Note: It is usual for the DC power socket to be wired centre positive so make sure you test the contacts before you solder them up so you know which is positive and which is negative.
Pic 5 - Pipe and End Cap Detail
10. Solder the LED wires to the relevant connection points on the driver.
11. Assuming that you are happy with all your connections I would suggest connecting up a suitable power source to test that everything is working okay before final assembly. The driver I am using can accept between 3V-18V so a battery pack or DC mains adapter outputting voltages in this range will do. Assuming that you have light (a very satisfying experience that I never seem to tire of), are still around and all the pieces haven’t disappeared in a Lithium core meltdown, we should be ready for final assembly.
12. Remove the locknut from the DC power socket and pass the socket through the copper end cap. If waterproofing then use a small layer of silicone around the socket boss as you push it into place and fix with the locknut on the outside of the endcap.
One other small precaution I took was to put a blob of silicone around each wire as it came through the slug, just to provide a little cushioning for the wires and also second level waterproofing.
13. The Ledil LXP optic is held inside a holder which if you are not too fussed about waterproofing then you can just leave as is. If you want your light to be waterproof then I suggest sealing the optic to the holder using a suitable adhesive like an epoxy be definitely NOT Superglue as this may cloud the optic. I would use a clear epoxy or maybe just some clear silicone but be careful not to smear it all over the optic. If in doubt I would just leave it.
14. The next step is to fix the optic into the straight coupler. This is a fairly loose fit so I would suggest smearing the inside of the coupler with a suitable epoxy such as JB Weld or even silicone and sliding the optic in. Do not use too much adhesive as you will tend to push it back down the coupler towards the LED and you don’t want adhesive all over that! You will need to twist the optic at the end to make sure it is seated on the LED correctly. I also connect up the power supply briefly at this point once again just to make sure that the optic is located correctly and I am getting a nice round beam pattern.
15. The 22mm copper pipe is quite a tight fit for the end cap so if you would prefer you could probably get away without fixing the end cap on permanently or maybe just wrap a length a of electrical tape around to hold it in place. If you are happy with the build and would prefer sealing the whole light then use some more JB Weld or similar to fix the end cap in place. Once the JB Weld has set, preferably overnight, then your light is ready for use.
As it is made of copper I polished up the casing with some metal polish and it came up really nice. I also left the manufacturer’s stampings in full view deliberately to proudly display its industrial heritage!
Pic 6 - The Completed CuLite
As this is a Dinotte style light then I would suggest the simplest mounting for the bars would be to use a suitably sized o-ring to hold it in place for the size of bar you have. You will need to fashion some kind of rubber pad to accommodate the perpendicular curvatures of the bars and the light. In the picture I have just used a rubber band with no pad just to give an idea of how the finished light looks.
I personally think that makes a killer headlight so I have utilised a Hope helmet mounting bracket that I have and have made a piece of aluminium which I fixed to the bottom of the light with JB Weld. I’m sure many of you could come up with suitable alternatives of how to mount the light and I leave that up to you.
Using the driver I have specified (or similar) and driving the XP-G R5 LED at 1A should yield around 350 lumens. I have specified a Real Spot Ledil LXP optic which is rated at +/-5.5 degrees FWHM for the XP-G giving an overall beam angle of 11 degrees. This gives a very useable spot light and is in my opinion particularly suited for use as a headlight. If the user would prefer a wider beam then I suggest referring to the relevant Ledil datasheet and selecting one of the LXP optics with a wider angle.
I personally use this light with a single 18650 battery mounted on the helmet. This gives a run time of around 2 hours 20 minutes. The DX driver used here however is quite flexible about voltage and therefore could easily use larger battery packs which will achieve much longer run times to suit the user.
I ran the light indoors with an ambient temperature of 21 degrees C and it started to get uncomfortable to hold after 8 minutes or so. With normal outside use with air moving over the case it doesn’t really get hot at all. Just remember if you stop for any length of time to disconnect the light to prevent overheating.
My light came out at a respectable 62 grams (for just the light head without any mounting) even though copper is more than three times as dense as aluminium. The copper body also actually gives it a nice solid feel in the hand. According to their website, the Dinotte light engine weighs in at 68 grams so the DIY effort comes out top trumps on that score as well.
If you have made it this far then congratulations - nearly over!
If you have a go at making one of these then please post your finished light for the benefit of others especially if you have come up with a good idea for mounting the light or modifying it in some way. Any feedback about the whole project will of course be welcomed as well.
I hope that this article has been easy to follow and that it demonstrates that building a powerful, affordable DIY LED light is not as difficult as first might seem. Hopefully it will encourage a few people to have a go at building their own light and maybe inspire yet others to come up with other designs.
p.s. I’ll try and post some beam shots if the weather improves here in the UK any time soon!
p.p.s. Merry Christmas and a Happy New Year to all.
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Thread: CuLite - Easy DIY Dinotte