Various sources of cheap imported components have started stocking a 100W chip-on-board LED module for quite a reasonable price. With a few extra off the shelf modules it’s possible create a 8500 lumens portable torch capable of setting paper on fire at close range. Fuck. Yeah.
This shot shows a side by side comparison of an unlit and lit scene with the camera settings kept the same between the photos.
Most of the parts can be found in a number of places. I used DealExtreme & HobbyKing to source the majority of mine. Not included in this list is the price for the case as the cost of laser cutting parts can vary and i probably wouldn’t recommend copying it directly as it could probably do with a few tweaks.
- 100W LED : £7.55
- 150W Step-Up Convertor : £4.21
- CPU Heatsink : £5.39
- High Current Toggle Switch : £2.40
- XT60 Battery Connectors : £1.76
- LiPo 5000mah Battery (3S 25~50C) : £26.21
- Battery Charger : £7.53
- 10KOhm Resistor : Free from parts box
Total : £55.05
The above choice of parts will give a run time of around 20mins. This can be extended by choosing a larger battery. I also chose a warm colored (3050K) LED, for photography or filming it might be better to go with one of the many 6500K 100W LED’s.
The circuit for this is very straight forward. It’s just a matter of wiring up a couple of modules. The following image shows the circuit diagram.
Before wiring everything up it is a good idea to preset the step-up converter to a safe voltage. To do this connect a bench-top powers supply to the input of the module and a voltmeter to the output. Adjust the potentiometers on the board until the voltmeter reads roughly 30V (or a couple of volts below the rated voltage of your LED).
When wiring up the rest of the circuit make sure to use heavy gage wire for all the high current carrying wires, and make sure to not power everything on until the LED is firmly attached to the heat-sink. To do this i drilled and tapped some holes into the heat-sink matching the LED’s mounting holes, making sure to apply thermal paste before firmly bolting the LED down.
When everything is wired up power the LED and check the following:
- No smoke/fire.
- Fan is running.
- Battery is not getting warm.
- Heat-sink is not too hot to touch.
If everything is running OK remove the battery and run the circuit from a bench-top power supply. Place a multimeter across the LED’s terminals and slowly increase the voltage from the boost converter to just below the rated voltage of the LED. As you do this keep an eye on the current and voltage readings from your bench-top supply making sure that the total power (voltage x current) doesn’t exceed 100W. I run mine at around 60W~70W total power usage as there seemed to be diminishing returns in brightness above this.
My usual work-flow is to design the flat parts to be laser-cut in LibreCAD then import them into OpenSCAD and model any other parts in the design to make sure they all fit together in 3 dimensions.
Aluminum angle was used to protect the edges of the case and a number of small 3D printed L shaped brackets were used to hold the rear of the case on. In the following photo a set of bolts with wing-nuts glued on to them can be seen which screw into the L shaped brackets. These bolts allow the rear of the torch to bee asily open-able for re-charging the battery..
The last notable feature of the case is an unusual bracket for holding the heat-sink & LED onto the front of the torch. I went with this strange string fixing because it was the simplest reusable attachment i could come up with for all the awkward angles of the heat-sink.
For the time spent building this and the use I’ve had out of it this has been one of the best projects I’ve worked on. It brings the sun with you wherever you go.