I will use the Sofirn SF22 as host for this flashlight mod. Sofirn sold some SF22 hosts a few years ago. The price was good so I got two of them. The original Sofirn SF22 has 16 XM-L2 leds and can use 2x or with the extension tube 4x 26650 batteries.
The first SF22 host which will be used for this mod arrived all in single parts. The following pictures are of the second SF22 host which came fully assembled. It shows better what the host looks like than all the parts.
Instead of the original reflector I will use nine single reflectors, nine XHP50.3 HI 4500K 90CRI and some copper as a spacer underneath. The driver will be a Sofirn SP70 driver.
Mon, 10/03/2022 - 13:06
This is my entry for the modified flashlight category of the 10th Annual BLF Old Lumens Contest.
As there is not much time left until the end of October I will keep the modding project rather simple and not as big and time consuming as my last entries.
I have quite a few flashlight hosts and the corresponding drivers, leds, copper and aluminium around so I will check my supplies for a suitable mod.
I will update this thread once I am sure what to mod.
I started with cutting the copper for the copper spacer. I cut six 9mm pieces from a 8mm copper rod to partially fill the groove underneath the leds. On top of that I will use pieces from a 3mm thick copper plate soldered together with a 60mm diameter 1mm thick copper disc.
In the gap between the two parts of the head I will insert a 30mm diameter 3mm thick copper disc. That is where the central led, whose reflector is a little higher, will sit.
Yes, indeed. I started with the three triangles and then I fitted the other irregular parts in. I used the remaining part of a 10x10cm copper plate where I previously cut out an 8cm circle.
The central reflector is a Convoy S11 reflector (28.5mm diameter, 20.7mm high) and the outer reflectors are 20mm diameter and 12mm high.
I reflowed the eight XHP50.3 HI to 16mm copper PCBs and retrieved the ninth led from a S21A where it was way too green.
After the reflow I tested the leds and they all work.
I drilled and filed a hole in the 60mm copper disc for the central reflector and the cables.
I soldered the copper disc to the six copper pieces. First, I aligned the copper pieces inside the head and pressed the copper disc with solder paste on them. Then, I carefully took the assembly out of the head and put it on the hotplate.
The copper spacer turned out nice. It fits inside the head with just 1-2mm space around.
In the next step I removed the anodisation from the contact surfaces and prepared the 30mm copper discs which will go between the two head pieces.
I decided to use two 30mm copper discs because after filing the edge of the lower one they have the right height to make a thermal connection between the two head pieces. Also, the central led will be placed on them and the heat has to be passed on to the host. The two copper discs sit on the tube and if the upper part of the head is screwed on they are pressed on the silver edge where I removed the anodisation. I will solder them together later and add thermal paste.
Yes, it would have worked without centering gaskets but I decided to add them for the outer leds because they made the height perfect for the glass lens. Also, the cables and the soldering were quite tall already.
Thanks, MascaratumB. The flashlight is finished now and I am updating my thread.
Well, builds with few leds are just as challenging as those with more leds. For multiple XHP50 or XHP70 you need good heatsinking, though.
I prepared the spacer which will go between the two head parts by drilling two holes in the two copper discs and soldering them together with a third 2x2cm and 1cm thick copper part.
I decided to solder the 16mm copper boards of the eight outer leds to the copper spacer. The leds are quite on the outer edge. Soldering improves the heatsinking, doesn’t dry out like thermal paste and prevents the leds from moving.
I replaced the wires on the SP70 driver with long 18AWG wires and instead of the two springs I used a single spring to make it fit the retaining ring.
Next, I connected the leds with 22AWG cables.
Instead of using the stock switch assembly I prepared my own with improved contact and less resistance. I soldered two silver-plated springs on a 6mm high copper piece. The copper piece lifts the springs above the retaining ring where there would be a brass contact piece. I didn’t have a spring which was long and stiff enough , they are all just thin steel springs or too big in diameter. Later, I had to add some solder to the outer contact ring of the switch PCB because it didn’t make contact with the retaining ring.
I did the final assembly of the head in several steps.
I screwed together the two head parts with thermal paste on important contact surfaces.
I inserted the little copper columns with thermal paste and thermal glue in the groove in the shelf. Then, I applied thermal paste on the deanodized parts for the big copper spacer.
I put in the copper spacer with the leds and the central led and connected them to the cables from the driver. I already had soldered the two cables of the new side switch to the driver. It is a simple side switch without leds because they would not be visible underneath the metal side switch cover.
The next photo shows all cables soldered and the GITD tape I added.
The driver needed a copper ring to fit well in the driver cavity which would be made for a 32mm driver and make contact with the retaining ring.
On the bottom of the reflectors I put kapton tape to prevent shorts.
Last, I inserted all the reflectors with retaining rings for the outer eight. The central reflector moved around too much because it is just 2mm below the glass lens. So I attached it to the MCPCB with some double sided transparent adhesive tape which you can see in the picture above if you look closely.
I was surprised how well the glass lens and the bezel fit. The glass lens presses the outer reflectors down with some but not too much pressure.
From left to right: SF22 modified flashlight, 7th OL contest modified L6 18x LH351D
From left to right: SF22 modified flashlight, Astrolux MF01S 4000K, Astrolux MF01 Nichia 5000K
Comparison with the Haikelite Q30 and the MT09R
The modified SF22 has a nice beam with big hotspot and lots of spill. The nine single reflectors blend together nicely and form a round beam. It is a bit greenish like most XHP50 and XHP70 with 90 CRI but it doesn’t disturb me. The MF01S is much rosier but the Q30 with 90CRI XHP70 is even slightly greener. The beam is between 4000K and 5000K and not too yellow.
The outdoor beamshots were taken with 2.5s, f7.1 ISO400. The tree in the background is 150m away.
Control
My modified flashlight from the 7th OL contest 18x LH351D
Haikelite MT09R 4000K
Haikelite Q30 5000K 90 CRI
Astrolux MF01S 4000K 95 CRI
Animated
Modes
Comparison
The beam of my modified flashlight has a nice mix of flood and throw. It is plenty bright and on High and Turbo it illuminates the tree at 150m. The batteries were not fully charged so it might not have reached the maximum brightness on Turbo. I had only one set of pointed 26650 which worked because all the other flat top 26650 were too short.
It was nice to be a part of this year’s contest. I’m glad that I managed to finish my flashlight without major difficulties and that it worked as expected.
Many thanks to the organisator Hoop, the judges and the sponsors.
And of course, thanks to all of you who followed the contest and read the build threads.
Nice going, getting this done Skylight. It’s a mean looking light!
Spacing and centering the LEDs is tricky with these kinds of builds, where the MCPCBs are soldered to the heatsink. I can think of a few ways to accomplish this, and surely there are more. One is to create a template, which can likely be made out of thick paper, divided by a compass, and with accurate holes cut for the LEDs or MCPCBs. If the template has holes cut for the LEDs rather than the MCPCBs, it might be more accurate, but there is the possibility of the LEDs being pulled out of position during reflow. Another method would be to position the MCPCBs and optics while everything is cold, then use a high temperature adhesive or potting compound to glue a paper or toothpick structure to the MCPCBs so that they can’t shift position during reflow, then remove it afterwards. Paper would allow the MCPCBs to move vertically, to sink down onto the heatsink when the solder melts, whereas toothpicks or a more rigid structure might not, but a toothpick structure would probably offer more security. Just a couple of small glue spots should be used per MCPCB, so that any remnants are inconsequential. Another method would be to use high temperature potting compound made to withstand reflows, to glue the perimeter of the MCPCBs down so that they can’t move when the solder goes liquid. Use ample solder so any minuscule gap is filled completely.
Something that is often neglected by modders and manufacturers is LED cleanliness. Any specs of dust or solder residue on the LEDs can combust and potentially damage the LED. Careful handling of the LEDs during assembly and reflow, and then cleaning with isopropyl alcohol after reflow to remove any residues, is the way to go. Dust and residues matter less if the LEDs are powered conservatively.
Thank you, Hoop, for your interesting explanation of the different methods. The positioning of the leds is more difficult with a multi-led reflector where every led has to be exactly in its place. I already looked for any debris on the leds but I may clean them again.
