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Re-design of the circuit and board for single sided compoent load and the metal core PCB.
04/07/2017 at 16:56 • 0 commentsThis is the current state of the circuit board and schematic, complete and utter chaos:
All SMD components have been moved to the top layer and a second footprint for regular through hole tact switches has been added.
These are not as low profile as i would like them to be but, from the list of available parts this is the only one suitable.
All low profile replacements with a higher actuation force are too expensive, these Omron switches are withing the budget.
All solder connection have been moved to pads on the backside of the board, entirely as SMD pads and not through hole pads.
A jumper and resistor has been added to disable the temperature sensor of the battery charger.
The discrete LEDs have been replaced with RGB LEDs.
There is a rough draft of the metal core PCB as well, the current idea is to to have three footprints for LEDs to enable this to be either a single or dual head design.
At the moment they are spaced further apart to have enough room for lenses.
But this may change and be replaced by a custom reflector.
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The firmware, things to do, things to change.
04/07/2017 at 15:19 • 0 commentsWriting the firmware will take a bit of time, writing code is not a particularly enjoyable task for me.
The next steps will be:
- Routing a PCB with a single sided load
- Routing a custom metal core PCB
- Ordering these boards from a board manufacturer
- Redesigning the button mechanism
- Adding the temperature feedback to both LED and Battery
- Overhauling the design of the whole body
- Writing a proper firmware
- Experimenting with reflow soldering the board
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Prototype build
04/07/2017 at 15:16 • 0 commentsHow can i make this whole thing work with just 3D printed parts, i wanted to just use standard parts and no glue.
Threaded inserts and glue would have made the whole design much smaller and sleek.
There were many design iterations but in the end, this is what i settled on:
The next step was to print all the parts and see how well they fit together, luckily everything worked out on the first try.
The PCB was printed and heatsink were printed as well, to check for clearance, and minimize surprises:
From here the LED head and heatsink had to be constructed, the heatsink was build out of regular 1.5mm aluminium, test runs showed that this will stay cool enough for now, but ultimately thermal management will have to be implemented and a custom metal core PCB will have to be used.
After this was done there were a few test and trial with different lenses, reflectors and window designs.
Sadly there are no pictures of that.
A single 10mm Carclo lens was chosen, it is not build for this LED but does work well enough.
After this the electronics had to be build.
The PCB is double sided and etched at home, the bottom layer holds all the power circuitry and the top side holds the processor, buttons and LEDs, this reduces the need for many vias and keeps the work on a double layer board at a minimum.
Everything could have fitted on one side but i solder the parts by hand and do not use reflow soldering, except for the ICs, those are soldered with hot air.
Especially the LED driver has to be soldered with hot air, it will fail if soldered with an iron:
At this point i had to face the reality that the buttons design will not work as intended and had to design a solution that would work with the already printed parts, this was the rough draft after much thinking:
It took a few tried to get the thickness of the spring arms just right, this was the 4th try, which worked out in the end:
But, the whole thing came together and seems to work pretty well, all things considered:
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3D printers, Sketup and Fusion360
04/07/2017 at 15:01 • 0 commentsAfter the printer had been bought, i had to settle on a workflow, how to design, export and print the parts.
I started using Sketchup many, many moons ago to plan my builds so i used it and tried designing the whole thing in Sketchup.
This was a bad decision and after someone recommended Fusion360 to me i spend a week getting comfortable with Fusion360.
There was a lot of swearing, but it was the right choice.
Here are a few pictures of the design process:
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Building a proof of concept
04/07/2017 at 14:57 • 0 commentsUntil this point i had no idea if the boost regulator would even work with the LED, a proof of concept had to be build with a Ebay special charge controller and protection board.
At this point the whole project used WS2803 status LEDs but these had to be removed due to firmware size concerns.
I could have replaced the ATTiny44 with a ATTiny84 but i did not want to buy new parts, i kind of regret this decision but at this point i was dead set on keeping it simple and getting the whole thing to work.
KEEP IT SIMPLE STUPID!
Here are a few pictures of the first electronics build:
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Eletronics, too much features and downscaling
04/07/2017 at 14:50 • 0 commentsAs with every project, more and more features kept creeping in, battery gauges, OLED screens and big processors were thrown at it, until it was near collapse.
My first draft used a ATTiny85 and just the bare minimum, in the end there was a ATMega32U4 with build in USB, a OLED display, a battery gauge, multiple status LEDs, a rotary encoder and I2C temperature sensors.
The only feature that i regret axing is the USB bootloader but i could not settle on a simple way to make this possible,
From here everything had to be scaled way back, here are a few pictures of one of the later electronics prototypes that never were build: http://imgur.com/a/KjDoa
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Heatsink and temperature measurements
04/07/2017 at 14:47 • 0 commentsThe thermal management of the LED was a challenge, initially i intended to use two LEDs in series but that proved to be a bit too much heat at this point.
Here are a few pictures of the test assembly of the LED head and heatsink:
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First ideas
04/07/2017 at 14:44 • 0 comments