Due to travel (and actual, legitimate research), I've not been able to progress on these projects much in the last few weeks. Additionally, getting the boards from Seeed took a little while (though it was worth it, 10 boards for 15$ is nothing to sneeze at; they're shown immediately below).
Today, I got back into things by trying out a little hot skillet reflow. Going off of resources at SparkFun and this instructable, it seemed the cheapest method available to me. To apply the paste, I didn't have the time, money or patience to do solder paste stencilling (shown in the previous links); so, I applied the paste manually, as at this site. Unfortunately, I didn't realize that the paste formulations are different between stencil and syringe application; I loaded some stencil paste from Sparkfun (here) into a syringe and it was very tough to get it to come out.
One thing to be aware of with the stencil-type solder paste: it behaves a lot more like wet sand than any sort of easily-coaxed gel. Syringe-type paste might behave a little better/differently.
In any event, I was able to reflow the majority of the components on the (hastily thrown together) helmet flasher board, shown below (apologies for the poor picture quality). I have seen heating-element control boards for toaster ovens and skillets to get the perfect heat profile; in my case, cranking the thing up to max temp and waiting for the solder to turn shiny sufficed. Note the blue wire fix; I forgot to connect the enable line for the step-up to a free pin on the controller.
Debugging revealed only two small errors in the reflow; two of the pins on the stepup controller were bridged (easily separated) and one of the resistors in the current controller didn't reflow (also easily rectified). The step-up produces 'high voltage' (16.5V), the pots have all been manually set (one to set the high voltage level, the other two to set the maximum constant-current levels) and the controller talks to my programmer.
The next steps for this quick project are A) create a simple program for this thing, and B) assemble the in-helmet parts of the project (lights, switches and 2xAA battery pack installed, wiring routed). There's also the more pie-in-the-sky goal of implementing the EL drivers (but I haven't quite sourced the transformers yet; not enough of my CFL bulbs have gone out yet).
Of course, just because the project has barely started doesn't mean I'm not already thinking about version 2; specifically, I'd want to implement the following changes:
A: source smaller components, with specs sized more appropriately for this project.
B: add a LiPolymer battery and charger circuit to allow the controller module to be more monolithic and allow it to be charged over micro USB.
C: figure out a better connector solution between the helmet and the controller; the 0.1" headers I'm using were chosen for inventory convenience.
Debugging revealed only two small errors in the reflow; two of the pins on the stepup controller were bridged (easily separated) and one of the resistors in the current controller didn't reflow (also easily rectified). The step-up produces 'high voltage' (16.5V), the pots have all been manually set (one to set the high voltage level, the other two to set the maximum constant-current levels) and the controller talks to my programmer.
The next steps for this quick project are A) create a simple program for this thing, and B) assemble the in-helmet parts of the project (lights, switches and 2xAA battery pack installed, wiring routed). There's also the more pie-in-the-sky goal of implementing the EL drivers (but I haven't quite sourced the transformers yet; not enough of my CFL bulbs have gone out yet).
Of course, just because the project has barely started doesn't mean I'm not already thinking about version 2; specifically, I'd want to implement the following changes:
A: source smaller components, with specs sized more appropriately for this project.
B: add a LiPolymer battery and charger circuit to allow the controller module to be more monolithic and allow it to be charged over micro USB.
C: figure out a better connector solution between the helmet and the controller; the 0.1" headers I'm using were chosen for inventory convenience.
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