What I want to do
I'm trying to come up with a single-board prototype for Public Lab's Thermal Flashlight project. I'm trying to build on the great design ideas put forth in recent research notes -- the idea of adding a thermal flashlight shield to a Visuallight board, and the proposal to mash up the Sparkfun IR breakout board with a 32u4 processorand an RGB Led. I'm still rather new to designing boards, but I was inspired to do this mashup when I found Rui Wang's open source wearable computing project, which places an RGB, two rechargeable battery options (coin battery, or lipo via JST connector), and a piezo buzzer ('geiger counter' indications of temperature, whee!) all on a beautiful little board. Rui also added a light sensor, an ambient temperature sensor, a button, and has some nice large pin holes for attaching conductive thread. Those might be great things to include here, too, but I figured I'd drop them for now, for simplicity's sake.
My attempt and results
I've created a thermal flashlight board design github repo, where I'm working on an Eagle board. The basic layout idea was this:
Which, on the actual board, came out looking like this:
I've added four holes on the corners of the board -- I'm imagining that it can thus be attached to the end of a stick or cardboard tube, so that it feels like a 'flashlight' -- but then it occurred to me that it'd make a pretty cool "Iron Man"-style device, too:
Thermal fishing bob tie-in. I also figured that I should add a screw terminal to the board to allow for connecting a thermistor probe -- that way the same board could serve as a thermal fishing bob prototype (imagined here as simply sitting inside the translucent plastic 'powdered lemonade' container design, pioneered by Sara and Catherine):
Questions and next steps
Further work on layout and schematic. The design isn't finished yet -- still need to figure out the layout on the board, and I'm thinking that it might be a good idea to put breakout pins for a through-hole RGB LED for the thermal fishing bob case -- so that the LED could be bent at an angle and displaced away from the board, and would be more of a 'beacon' -- rather than being placed in the middle of the board. Also note: for the thermal fishing bob case, we could just opt not to place the IR sensor on the board, to make the design less expensive.
NOTE: in the github repo, the "32u4" design (which I think is where we should head) is the set of schematics / board designs that have "32u4" somewhere in the label.
Kit options. All of the board components are surface mount, except for the IR sensor and the screw terminal. So a good plan might be: have the board produced with only the surface mount components; then, when distributing a kit, include that board + a coin battery, and then additionally include a) the IR sensor, for a 'thermal flashlight' kit, or b) the screw terminal + a thermistor, for the 'thermal fishing bob' kit. Most folks could likely handle soldering those parts on themselves.
Anyone who knows something about Eagle design -- please feel free to download and tweak the board design and play around with the layout!
Why I'm interested
Seems like a single-sided, all-in-one thermal flashlight design would simplify production and reduce costs ... so here's my attempt at that ...
Do you have a link to the Visualight schematics? I should check them out, as Jeff was hoping to use their more powerful LED, and we might be able to incorporate that onto this board ...
I was just going to use one of the files from the Visualight Github page- https://github.com/lpercifield/visualight/tree/rcgreen/Hardware. But I haven't managed to get that far yet. Is there not a usable schematic in that repo?
The "Github for Hardware" (nice way of putting that!) is something that so many folks I've met have been interested in ... farmhack.net had something like that in their tools wiki ... and Upverter seems cool ... but one issue it seems is that there are so many design tools out there, and so many file formats -- and so many ideas for what would constitute a 'design' -- that it's hard to accomodate all of that in one platform. Frankly, I'm finding publiclab.org's research note + wiki approach to be a pretty good solution, in this regard -- it's a flexible and fast way of putting up notes around a design ... witnessed in this note and its comments! :) But it's great to think about what the ideal solution would be (and build it / or incorporate it into the publiclab.org platform) ...
I recently came to the conclusion that the, in the end, the "Github for Hardware" may in fact best be achieved by using...well...Github for Hardware. So I tend to agree with your conclusion. Unless you can convince everyone to agree on a common platform from the beginning, its probably best to emphasize flexibility and compatibility in a format. Despite its heavy developer-jargon orientation, Github continues to offer the most flexibility from my POV. The major weakness is in the wiki feature which remains buried underneath the main repo page. So I agree that the present research note format might be the best way to do it. I imagine it helps that comments are written in markdown too even if it requires me to brush up on my html.
Idea: Rui's Squarewear design uses a bootloader he wrote that allows one to use the Arduino IDE on an Atmega328 without requiring an additional chip to handle USB. This means that one could conceivably use a through-hole Atmega328p, a through-hole RGB LED, and a through-hole coin cell holder ... basically, I think the entire design could be a through-hole, easy to solder kit. Would that be a good idea? Or do we think it's more important to be able to assemble a lot of these easily (a surface mount design would be better in that case) ....
This is a tough one... I can see as many merits in such an approach as drawbacks. Concerning the "through-hole vs surface mount" question I could see a lot of space between the flexibility of a breadboard and the permanence of a PCB. For example, I just noticed Adafruit is selling something called a "Perma-Prota Breadboard PCB"- http://www.adafruit.com/products/1608 that could fill this gray area to a degree. This could be especially useful for working with LEDs as it allows you to arrange them in any form. However, once you start getting into High-Power LEDs like the Cree XLamps, I'd probably be less inclined to trust my own ability to wire it safely.
The other question in my mind is whether or not it would be worth continuing with an ATmega328 even if it does have the ability to handle USB. Again, I see as many merits as drawbacks in the 328 for which I outlined a few in the comment thread on this research note- http://publiclab.org/notes/code4maine/01-22-2014/thermal-flashlight-using-mlx90614-ir-evaluation-board-from-sparkfun
If one were to go with a through-hole soldering kit, the 328 seems to be a better choice, as in my experience the 328 has been much easier to program then the 32u4. On the other hand... a 328 might not be able to take advantage of some of the latest advances in cloud-sensor communications. The decisions of the Arduino manufacturers themselves might be a good indication of how these advances are unfolding. Not only has almost every new Arduino release since the Leonardo has been based on the 32u4, but when you look at their approach to the new Arduino "Yun" to their plans for the Beaglebone-like Arduino "Tre" to recent efforts towards making a web-based IDE, its not too difficult to see them moving in a more software-oriented direction. I don't think it would be a stretch to see the move from the 328 to the 32u4 as a first step in this direction.
So my oversimplified formula is that people from an electrical engineering background prefer the Arduino Uno while software developers tend to prefer the Leonardo. My decidedly indecisive position on the merits of each approach is based in the fact that I am neither an expert in hardware or software...
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