A heavy duty flashlight for special occasions.
Due to a flaw in my schematic, I needed to rearrange the electronics and split the control system in two entities. Here's a simplified schematic showing the power management. Not drawn here is the 5V regulators for each of the two MCUs.
The sole purpose of the "Battery MCU" is to measure the voltage of the battery and disconnect it from the rest of the system when the voltage drops below 3.0V/cell. I might also use the MOSFET at the bottom as a shunt to calculate the voltage sag and compensate for that.
Wiring up the 12V DCDC converters. The enable wire gets its own ground return path for EMC reasons.
These power two fans each, and get really hot to touch. Therefore, I glued them to an aluminium length using thermal glue and thermal tape to insulate the converter from the aluminium.
Three of the LED drivers mounting on acrylic glass due to all the leads of the through hole components poking out on the back. These modules have mounting holes, but due to the heatsinks, there is no room for any screw head... I went for cable ties as a sturdy substitute.
Had to accomodate the wires running from the battery, by making the cradle broader and with a acrylic glass bottom.
Swiss-cheesing the frame.
There are a lot of legs from through hole components poking out on the backside of the LED drivers, so I will put these on acrylic glass, mounted in a fashion you can see underneath. The DC/DC converters for the fans get pretty hot, so they will be mounted on a aluminium length using thermal adhesive. The ruler is just a substitute ;)
There should be plenty of space for the control board.
For securing the battery I made a "bed" out of two lengths, drilled a hole for the positive wire that is soldered to the side of the battery and secured the whole thing with Velcro.
It's a snug fit, but I don't like this solution much. The positive wire is exposed close to the battery, and is in danger of touching the frame. I don't want the frame to be "energized", so I'll move the aluminium length further away and add a bottom of acrylic glass.
I'm using XT60 connectors for connecting the battery.
Power wire harness with fuseholder and MOSFET switches. Approx 20-25 amps will be drained from the battery at full load. The ON-resistance of the N-channel MOSFETs is 22 mOhm each at 5V, which turns into 7.3 mOhm with three in parallel. That's about 5W of heat in the transistors. They will be mounted to the aluminium frame, just behind the fans to have a chance to keep cool.
The controller board, not yet done. The MOSFETs to the left will be switching each LED individually. Do I need a snubber circuit to protect them?
I see no voltage spikes on the Vds of the MOSFET upon switching it off with 1A of current. Should be good without a snubber :)
MOSFETs are working as intended.
The front, laying on the side.
Hooking up the LEDs. Should have used screw terminals and longer wires, but oh well!
The mounting holes used to screw the heatsinks to the frame were drilled with a 3.5mm drill bit, and M4 screws were screwed in place with force.
The light feels pretty damn sturdy.
A thermistor soon to be buried with thermal paste in the ridge of a heatsink to monitor the temperature for fan control.
I didn't have a clear vision of how to build this thing until I saw DIY Perks' fine video of his Sun-Blaster.
I bought a couple of meters of angled aluminium lengths at Obs Bygg, actually the only suitable I could find in town, and measured, drew, hacksawed and drilled away. There was more gut feeling than careful planning involved, so it may look a bit rough on the edges, but feels pretty sturdy. One point about the aluminium is that it was too porous, as it never was intended for bending anyways, so the length would crack up and break off if I didn't bend it slowly enough. If any of you have any tip on where to get some proper aluminium lengths to work with, that would be superb!
The frame for my light is pretty much built like DIY Perks' light, but will have a control panel somewhere with some extra knobs and a battery indicator. As not seen on the photo above, there will be a gap of a centimeter or two between the heatsinks to allow for the hot air to escape between them, otherwise there would be little airflow in the middle.
Also, no front panel to hide the wires and heatsinks.