I just recently learned how to use Eagle to design driver PCBs. I never thought I could do such a thing, so I just never tried. But, my contest light isn’t gonna make itself, ya know! So, fritz15 talked me into trying Eagle board design. And I’ve had lots of help along the way from pilotdog68 and Rufusbduck. My driver board is fairly large compared to the drivers we normally use around here. It’s 64.5mm x 16.5mm rectangular. When I uploaded it to OSH Park, I found out that it costs about three to four times as much to order my board compared to regular sized driver PCBs there, since OSH Park charges a flat rate of $5USD per square inch. I also found out that they charge according to the square that it would take to make the board. So, a 17mm round driver board has a total area of ~227mm² but OSH Park charges you for a 17mm x 17mm square, which is 289mm² total.
I don’t know if anybody has ever thought of this before (surely I’m not the first). For most of the drivers we use, and the way we use them, we could save a little money by squaring up the board just a tiny bit. For instance, taking 0.5mm from each of four sides, flattening them out, can save $0.26 on a 17mm board. Bigger boards, and bigger cuts will save even more. I know OSH Park is already considered to be pretty cheap, but if you’re heavily involved in either driver design or just plain ole modding, and you buy lots of boards, you will probably see a significant difference. And the money you save can go right back in to another order for more boards! Think of it like a buy five or six and get one free deal!
I know some of the members here try to push their lights to the extreme, and might be worried about heat and/or electrical resistance if the board isn’t round all the way. I don’t think that would be a problem for most of the drivers we use and most of the lights we use them in. Remember that the majority of the heat is at the back of the LED, not at the driver. And, if only a tiny bit of the driver edge is cut away, most of it then is still there and will conduct both heat and batt- current plenty well enough. I’m sure there are some builds that need a perfectly round, well-fit driver in order to perform optimally, but most of the time I don’t think that’s the case.
I always wondered why they are round, then figured that a round shape would have the best physical appeal? They just “look” best this way? But I agree that every cent does make a difference since we order quite a few boards.
If the boards are more rectangular - are they (potentially) less able to withstand the compression power of two springs?
Is that .26 per board or per 3 boards? Sounds like a nice way to save. I’m getting ready to upload some of my own eagle projects.
I’ll have to test out the difference. I just learned some of eagle as well. Since texasadvenger brought it up. I’ve designed some boards but I don’t realy know how to handle the settings and uploading to oshpark. I haven’t figured out how the silkscreen and solder mask layers work. Does it automatically build the soldermask or do I have to tell it what I want it to do?
I guess a not-round driver wouldn’t seal the pill (which is round mostly). I don’t like the possibility of something falling into the pill, for instance a tiny wire of a spring bypass.
Could be, but not necessarily. If it is in the battery compartment, it might only melt if it makes contact. But probably it will fall out when changing batteries. Touching the driver it could do more harm.
Surely any foreign object is better detectable in the battery compartment than in the pill.
It was 0.26 per three, since you get three boards for the $5USD per square inch. But, on bigger boards, it would be more. Do the math yourself. No need to do πr² for a circle, because OSH Park charges for a square, no matter what shape you upload. So just do 17 x 17 = 289 for a 17mm board and 16 x 16 = 256 if you only trim 0.5mm off each side, still leaving most of the round shape intact. Then, since OSH Park charges per square inch, you have to convert your metric measurement by dividing by 25.4 in each direction, so divide 289 / 645.16 is about 0.448 in² and 256 / 645.16 is ~0.397 in² for a difference of ~0.051 in². Then, multiply that by $5USD for a savings of $0.26 for one set of three 17mm boards. Seems cheap until you talk about people who buy many different driver boards, or bigger boards, like SRK size.
As for the issue of non-round boards not filling the pill, and possibly allowing wires, components, etc. to float by, I think there’s an easy solution. Make sure the amount you shave off the board is small enough that the ledge in the pill that the driver sits against still fills that void. In other words, if your pill has an internal diameter of 15.5mm with a shelf cut out to 17mm for the driver and your driver PCB measures 16mm from flat to flat , then you have nothing to worry about.
Eagle library parts (the driver components) have the solder mask already, as well as some silk screen text. But, if you want to do solder mask or silk screen anywhere else, you have to do it yourself. Have you watched the Mattaus Eagle tutorial videos? He shows a little about how to work with different layers of the board, such as the copper, the stop mask, and the silk screen. I recommend that you watch the tutorial videos if you haven’t yet.
There’s one thing that I learned that he apparently didn’t know about when he made those tutorial videos. The square that you start with on the board layout page is the default driver board edge. It is in a layer of its own, called the Dimension layer. It can be resized to the size of the PCB you’re making. Mattaus just deleted it and doesn’t say anything in the video about what it is. Since my driver board is rectangular, I used the Dimension lines to define my board size. Instead of drawing new borders in the Milling layer, I just resized the Dimension lines until they were the right size. Mattaus said he could never get Eagle .brd uploads to work at OSH Park. Well, I think it’s because he deleted the Dimension lines, and OSH Park expects them to be there. My Eagle .brd files upload fine.
If you need any help using Eagle, send me a PM and I’ll help you all I can. I had to get lots of help to get started with Eagle myself and I appreciate every bit of help I received. But it’s a very logical program, so I also picked up a lot just by poking around. And I learned how to do some of the things that I really wanted to accomplish on my driver board by simply searching Google for how to do it. I’d say it’s an extremely easy program to learn and use, once you begin to wrap your mind around it.
I’m only talking about shaving a tiny bit from the sides. Most of the board edge will still be supported by the driver ledge in the pill. Squaring up just a little should be a pretty insignificant change for most of the driver boards we use, but fairly significant money savings because of the way OSH Park charges for the PCB.
I’ll pay 9cents extra per board to have it be round. Aesthetics matter to me, and the driver is the only aesthetic component I really have any control over.
And I don’t mean round drivers look better, I’m saying round drivers look better in a round pill. If I had a square pill, I’d be using a square driver.
Also, the way I use Eagle, “shaving” some off the sides would cause significant headaches for me. A circle is a really easy shape. It really only has one dimension.
