Introduction
After reading through BLF topics for some days and searching for information related to high power LED’s, drivers etc. I have now decided to create my own topic where I hope to document in detail the process of prototyping a functioning helmet mounted light that one can use in high speed sports, E.g. enduro (bikes without pedals).
I have no experience in designing high power lights so I hope to share thoughts with more experienced flashlight tinkerers. Especially the component selection is something where I could definitely benefit from second, third and fourth opinion.
Specification
There are some interesting lights in the market:
Olight H67
Hyper 8500 Arctic
Lumonite Leader
Judging by these factory made lights I have made couple of assumptions:
-Battery has to big in order to keep the light running on high power for 1-2 hours.
-Cooling is critical as the light will be constantly running on high (highest) power
-Light has to be powerful enough to light up the forest, especially in the autumn it gets really dark. When the snow falls, things get a lot easier. Speeds can reach about 100kph, so light has to have decent throw and “enough” flood.
-Light has to be mounted on the helmet. Bike will bounce all the time, so it’s not an option to mount it on the bike.
Hardware
To reduce the costs I have decided to forget the battery pack and take the power from the bikes electrical system (4S lifepo battery, 14,8V charging voltage when bike running).
My current idea is to build the helmet light with 2 high power LED’s, where one is used for throw and second for flood. I did order 2 pairs of SFT70 LED’s (3000K and 5000K), some reflectors and TIR’s to experiment with. I believe they will arrive in the next couple of days and I can then experiment with them myself. I’ll use copper flat iron as heat sink on my first tests and lab power supply to drive the led’s. I’m interested to see how much heat is generated and if they can provide enough light.
For the electronics part I’m a bit lost. I did start by disassembling old (cheap) LED auxiliary light to see how these are done by proper manufacturer. There are 2 LED’s on the PCB and they seem to be in series. Here is a picture of the PCB.
I haven’t yet decided what kind of user interface I need, most probably power button and maybe possibility to switch between couple power settings. Most probably it’s easiest to use MCU for switching between power levels, but I’m just wondering could and should I try to manage without…
I did scroll through TI’s selection of LED driver IC’s and found LM3409 which seems relatively simple to use. Is there similar IC’s that I should take a look at?