DavidEF HandMade - 4th Annual BLF / Old Lumens Scratch Made Light Contest

Giveaways and Contests
92

fritz,

I used vias, but I wanted them covered with solder mask, especially on the back. I wanted nothing but the ground ‘ring’ exposed on the back, because it is going flat against metal, which I’m hoping will help with heat. Of course, the solder mask is another layer on top of the copper, which means that the ground traces will be lower and won’t contact the metal directly. I’m hoping to help that by putting a bit of solder over those traces so they stick out further. In fact, what I might do is glop it on thick, then sand it, so that it is a uniform layer, smooth and even over the traces. That way, the board will still sit flat, and there will be good electrical and heat conductivity. This is my dream anyway. Whether it will work is yet to be seen. I had also thought about putting some holes so the board could be screwed down. But, I have so far forgotten to do that. I may try to add them for the next version of the board.

I think turning the AMC’s sideways wouldn’t help, because then the traces would still need to cross somehow. But, I’ll take a look at it when I get a chance. Anything that would simplify the traces would be great. I really like to KISS. :stuck_out_tongue:

The trace you see from the AMC to the LED was put there by the auto-router. I added all the wide traces you see on the board, then hit the auto-router to fill in the rest. Since my center LED pad is grounded and the center pin of the AMC chips are also grounded, I guess the auto-router thought a trace there would be nice. :smiley:

The middle pad of the LEDs is as wide as it can be on the bottom, but on top I was just using the same size for all the traces I ran. If you look closely, you’ll see that I put wide traces both top and bottom for all three LED traces, and joined them with vias. I wanted to make sure this board had the least resistance possible to the emitters. But I’ll look at possibly making those thermal traces wider when I make the next version. I have seen people use vias under the thermal pad for boards made for LEDs. I just didn’t do it. Maybe I’ll add those. That would definitely help with heat management. For this light, it won’t need it. But, if you count the AMC chips, there is potential for a total of 7.98A on this board (or more, if stacked). Divided by six LEDs, that is over Cree’s current rating for XP-E2 emitters by one third. So, better thermal management might be needed in order to maximize the potential of the board.

I was planning to order the 0.8mm board, for the 2oz copper. I want the best conductivity I can get, both electrically and thermally. I don’t need physical strength, since the board will be sitting flat against a metal base.

This board will support ATTiny25 (and 85 with bent pins) but My UI is going to be super simple, so nothing more than the 13 is needed. In this light, I will be using an e-switch, but OSH Park gives you three boards. I might need a clicky in the future with one of these. I want to leave the board flexible. However, the resistors don’t have to be populated if they’re not being used. And the capacitors could be bridged if not being used. At least this is how I understand it. My concern with the components is their positions relative to each other, especially to the MCU. I remember reading that some of these need to be close to the MCU, but I can’t remember which ones. And I don’t know if mine qualify as close, especially with some of the traces I have there.

I’m already using three pins for output. This board is meant for triple channel support. It is divided into one chip, four chips, and sixteen chips. The sixteen chips are on pin three with no PWM. I won’t be using those at all in this build. I’ll use two channels - one chip plus probably either two or three, not even four on the other channel.

Since it’s been brought up now, I could use some advice on mode spread. I was thinking of using four modes (maybe five) as: 1) 10% of one 7135 chip 2) 33% of one chip 3) 100% of one chip 4) 100% of three chips and possibly 5) Moonlight mode (but I’m not sure if I want that in this light or not). Anybody have a better idea for mode spread? I’ve seen people use thirds like this, but I’ve also seen people use quarters. My board is actually designed for quarters. But, which is better visually?

Edit: I just remembered that I still need to add some e-switch solder pads somewhere.

93

Oh, sorry my fault, well now I learned something. I didn’t know that OSHpark could do those covered vias :person_facepalming: How do you do that in eagle? I can’t prevent eagle from creating a t/bStop circle where the via is and also can’t delete it.

I think it should be possible. I just drew a quick sketch:

The LED- traces are on the outside and the VDD traces are on the inside and the GND in the middle. Then you should be able to make the bottom one big ground pad. And if you use the first few AMCs for the first and second channel you don’t even need traces going around the LEDs.

If you want to and like the Novatac/HDS UI you are welcome to try my firmware, it’ll support three channel output as well, is programmable, has a beacon feature included and if I have time have a thermal regulation as well as a battery protection.

94

I also just thought it actually could be cool if you wouldn’t connect all the LEDs. For example you connect five LEDs and then leave one with one ACM7135 connected so you could install a red LED for example.

95

Thanks fritz! I’ll definitely have to take a look at my board and see if I can get that kind of a layout to work. I do like the idea of making the bottom a huge ground. Then, I wouldn’t have to paint any of it. It could all be exposed on the bottom for better heat conduction.

I don’t know if OSH Park can do covered vias or not. I didn’t think to ask. :stuck_out_tongue: However, it didn’t give me any errors when I uploaded it. I’ll have to look at their design rules again to be sure. You’re right about Eagle not ‘allowing’ covered vias. It automatically exposes around them according to the internal Design Rule setting for solder masks. That rule states that vias over a certain size will automatically be left exposed. The default setting is zero. Change it to something larger than the actual vias on your board, and they will all be magically covered over as soon as you click ‘Apply’ (the vias will disappear from your tstop and bstop layers).

Thanks also for offering your firmware to me. But, I have no way to flash the MCU. I was going to buy pre-flashed Tiny13 chips from Mountain Electronics with a simple 4-mode (or 5 with Moonlight) firmware. I’ve already made this light more fancy than ever intended by creating a driver PCB with integral LED pads. I was planning on putting it together much more crudely. Now that I let you talk me into learning how to design my own driver board, I will probably have to learn to reflow as well. Please don’t make me learn to flash firmware too! :open_mouth:

96

Yes, they’re called tented vias.

97

Thanks to vestureofblood there is a great tutorial here in the blf. Although I wouldn’t leave the part as long as he did on the frying pan, since you actually saw the mcpcb getting a little brown. But I guess it was just for the tutorial. You also can do it with normal solder but then I’d recommend to first cover the contacts of the star as well as the contacts of the led with some solder. That’s how I always did it. I don’t think it makes sense to buy solder paste for just a few leds. And you also don’t need to reflow the rest, you can just solder them on with a soldering iron.

Regarding the firmware - there is a tutorial here in the budge…. :stuck_out_tongue: OK, I guess you can also just buy a pre-flashed one. If you give me your address I could also send you one although I couldn’t promise that it would arrive in time for the competition.

98

fritz,

Thanks again for all your helpful advice and tips. I started version 2.0 of the driver board, with the AMC7135 chips turned sideways like you suggested. In the first few minutes of it, I actually began to think it would not only work, but be a lot easier and look a lot better (neater traces and all that). After trying to actually run traces around the board, I’m reverting back to thinking it won’t work. There’s just too much going on at the MCU and not enough room to get it all in on one side of the board. I still may finish the 2.0 board (since it will still look better) but I’m going to have to have multiple vias and traces running around on the bottom.

I just can’t get away with using only the top for traces and making the bottom one big ground plane. I even ripped up all my wires, vias, traces, etc. and hit the autorouter to see if it would give me a clue. It couldn’t figure it out either. It would just leave the pins disconnected on the MCU that it couldn’t get to. If all my LEDs were on the same circuit, it would work just like you drew it, with the traces going around the board in one big loop. But, with three channels, it just doesn’t work. At least, it hasn’t worked for me yet. I’ve got another trick or two to try with arrangement of components. But, it’s not looking good.

Edit: I just looked again at my version 1.0 board, and realized the autorouter left out the PWM traces to some of the AMC7135 chips there, too! So, it already had issues reaching everything. This driver board stuff is ‘challenging’ to say the least! :person_facepalming:

Edit II: Well, looked again! at the V1.0 board. There are traces there for all the AMC7135 chips. Some of them just run in weird ways. Still gonna be a challenge to get a nice board out of all this.

99

Excuse my crude drawing, the black squares are 7135’s, the gold are the emitters. This is basically what fritz said. David you wanted the bottom to be one big ground plane, right? Then wherever you need a ground (like for your 7135’s) just drop some vias to “bring up the ground”. All of the 7135’s are oriented with their 3 pins pointing to the left.

Of course make your powerpath as wide as possible, and give yourself a lot of copper connected to the LED thermal pads

100

Thanks PD68! Looks like you’re drawing a two-channel layout. That would work fine for this light, but I was hoping for a triple channel, with the non-PWM channel being the largest group of 7135’s. That channel will not be used in this light (7135 pads won’t be populated), but OSH Park gives you three boards when you order. So, I’m trying to throw everything in that I might eventually want on the next light or the one after that. I’m still hoping that it’s possible and that I’m just not getting it.

101

I was thinking two channel, but really it makes no difference. Just run Pin3 instead of Pin6 to the 7135’s on the bottom of the picture.

102

Yeah, I think that’s where my problem is though. Pin 3 is on the other side of the MCU from pins 5 and 6. I think if I squeeze my LEDs in toward the center like your drawing, giving more clearance on the ends, all the traces can get to where they need to go. It’s all the criss-cross stuff that is holding me back. I’m going to work on it some more tonight, if I can get the chance.

103

Remember you can run traces under the mcu and between other pins. You definitely need to have traces outside of the last emitters as I have drawn, but you don’t need that much clearance. Just remove the vias on the outside of the emitters and you’re fine.

Just orient the MCU with Pins 5678 to the right, in my head I think that should work fine… right?

104

Thanks! I didn’t get to work on this at all last evening. I was having computer mouse trouble. Actually, the mouse quit working while I was trying to work on the driver. Then, I finally got one to work, but my wife needed the computer. Then, by the time she was done with it, I had given up on doing any driver design, and had found something else to do. So I never got back to it. Maybe tonight.

105

Maybe some ideas from this bad sketch(pleading bad hand) I suggest you don’t use autoroute as it cannot intuit your ideas. Note the use of components as trace jumpers.

106

Another thing, you want to leave as much copper on the board as possible. Think of the board as a solid copper surface that you are separating into different signals.

107

I’m starting to think there’s a bit of misunderstanding about the board size. You guys are drawing pictures that are a lot taller than the board I’m trying to make. My constraints are 16.5mm x 64.5mm, roughly the size of a 16650 cell. I know the picture in the OP doesn’t look like that, so maybe that’s where the confusion is coming from. It’s a lot of stuff to pack into such a small space.

I worked on the board a little more last night. I still haven’t figured out how to get all the signal traces to where they need to go without crossing each other. If I’m not going to use the bottom for traces, then NONE of the traces can cross each other at all. They each need a dedicated amount of space on the top of the board to get to where they’re going. I’m using all but a couple of the pins on the Tiny13 chip, since my design is for three channels. I also have six LED pads on the same board with the driver components. These things combined make it extremely complex and challenging for me, being the newbie that I am. I still haven’t given up, but I’m getting frustrated.

Edit: I also haven’t yet tried out all the suggestions given so far. So, it’s far from over. Just venting here. :stuck_out_tongue:

108

How big of a physical keepout do you need around the emitters for the optics/reflectors?

109

Mattaus wasn’t a newbie and it took a few months to hammer out the design of the tiny 10. Don’t sweat it. There’s no scale on my drawing and no reason it can’t be made the size you want, specifically the LEDs and their traces and can also be made narrower and folding R1/R2 and moving the OTC. I mainly just did it to show how to route signal traces under components which auto route won’t do. What you want to do is possible, it’s just a matter of trying different ideas and seeing which works best. Just a suggestion but most of the difficulty is working around the mcu, the LEDs and 7135’s are mostly rubber stamped so start with the mcu and auxiliary parts layout and don’t bother with the rest until you have that sorted to your liking. I agree that daisy chaining the 7135’s is the way to go as it allows the LEDs and 7135’s to share the same trace width on the - side. You can adjust the size of the annular rings on vias to be able to cram more of them together without overlap and the ones in the center pads need to be untented to fill with solder.

110

I don’t need physical keepout at all for reflectors on this light. One big lens/cover will be over the top of the whole board. But, OSH Park gives you three copies of your board. So, I’m designing also for the future possible use of boards two and three. I’d want to keep at least 3-5 mm away from the flat sides of the LEDs, I’m guessing. Someone who’s done lots of modding would know better.

111

Thanks, RBD!