Tiny RGB Stick - converting to string lighting?

[pfriedel]

So to keep my iron hot and to give me something to keep practicing working with SMD devices, I'm about to order a run of about 30 tiny little 14x50mm stick blinkenlights. I figure as I finish them they'll end up hanging over my desk or end up being used as some form of artificial dawn alarm clock over my bed. The first OSH prototype looks like the one on the right of this picture:



(While I like the one on the left, it ends up being a bit more prohibitively expensive in LEDs. "Scrap" 5050 RGB LEDs are ridiculously cheap and enabling.)

The question I have is if there's an easy way to just run drops off to them from a single pair of wire using crimps or wire splices or something along those lines? The prototype (to the prototype) involves a bunch of cut wire and soldered splices and heat shrink and JST connectors and.. Well, it works, but it has approximately zero wife-acceptance factor. And it's fiddly as hell. And it isn't particularly friendly to piece-by-piece extensions.

My current leading consideration would be to use a pair of JST connector leads, one male and one female, so I could plug them in as I want. That way if I need them to be 6" apart I just use the JST leads I get and if I want them to be a couple of feet apart I use 24 gauge speaker wire to extend the lead. The advantage is that I can get JST connectors for RC BEC circuits on the order of USD$0.10 per off of ebay, which is appealing enough considering the current per board cost.

But are there other options for easily making easily extensible string-style lighting? The boards all draw a peak of 25mA, so even weedy little USB adaptors can light up a fair number of them, although I hate to think of what that's doing to the power line.

Although this doesn't show the milling to panelize them, this is the current board I'm thinking about submitting. There are VCC and GND SMD panels on the back of the board for power flexibility. (I figure a couple of boards won't get depanelized and just have 15 LEDs running 3 independent programs. Having those panels makes it a lot easier to convert it to a single supply feed.)

[Sjaak]

Having two power connections on each board would help to avoid splicing cables and makes it easy to chain the boards.

[rwinscot]

I'm thinking these would make great turn signals!

[pfriedel]

Having two power connections on each board would help to avoid splicing cables and makes it easy to chain the boards.

Yeah, that's in line with the JST connector thinking - one of the leads would get the strain relief holes & through hole pads and the other gender would get the surface mount pads and end up with a relief zip tie buddying them to the through hole lead. They shouldn't be under significant loading on the surface mount pad at that point, I wouldn't think. Or possibly the other way around - the leads on the surface mount pads get the strain holes & the through holes get zipped to the surface mounted leads.

I'm thinking these would make great turn signals!

That's actually something I'd considered - strap a pair to the seat stays or rear rack stays on my bike after suitably waterproofing them. I'd probably want to go to something sturdier like a Deans connector for the battery then, but they're bright enough to be visible without blinding my riding partner. (I have a taillight that I love but that I can only use when riding solo because it's just too bright - it kills my wife's night vision.)

[kizzap]

could you not just use some of those connectors with screw or push terminals to make it easier to utilise?

[pfriedel]

could you not just use some of those connectors with screw or push terminals to make it easier to utilise?

I'm not sure if its just the ones that I got in my last order from Digikey, but I haven't been impressed with the structural stability with those. Admittedly I got the 2.54mm spacing ones to try using them with normal protoboards, so maybe the normally-spaced ones are more stable?

[pfriedel]

And a short 16 days after I submitted the gerbers to Seeed, the boards are back!



3 boards per 5x5cm panel, 14x50mm per board with 2mm of milling between each sub-board. The end slots are 10mm long and the mid slot is 18mm long. 10 0.6mm drills per tab tangential to the board with a 2mm tRestrict and bRestrict keeping the ground planes from bleeding. The middle slot was drawn on the dimension layer and it also exists on the milling layer, so I submitted the GML that their cam processor generates for whatever it was worth.

I did the basic board as a single unit, smashing all the components and deleting the part names and replacing them with manually laid up text. Once I was happy with the single board I opened a new blank board and imported the single board into it 3 times and drew up the perforations and mills by hand. If I didn't smash out the part names, R1 would become R7 on the 2nd board and R14 on the 3rd board - which isn't a game stopper, but it looks funny. Manually placed holes were funny after importing, so they were added after the panel was combined.

I drew the initial square-edged outline in the dimension layer and then hit all the internal corners with a 1mm radius to give the milling tool a break. The panels are sturdy enough that I used my bench vise to break them apart, but my angle cutters are strong enough to snip through the remaining perforations on the tabs. A cleanup with a sanding block and they're golden.

Judging by the density I've seen on matseng's panels I'm probably losing more space than I need to to the milling, but these seemed much easier to break apart soooooo. Eh.

The silkscreen is particularly misaligned on this run, but it's not going to kill me.

A quick pass with the continuity meter and a netlist tells me that at least the few boards I checked are all working as I designed, which is a relief. Now I just have to wait for the rest of the components to show up and I have a stack of 30 blinkenlights to make!

[Sjaak]

There is a standard script that helps for panalizing pcbs. It is an ulp and called paneluze.ulp

Copy the pcb to a new file, open it, run the script, copy the board all over et voila!

[pfriedel]

There is a standard script that helps for panalizing pcbs. It is an ulp and called paneluze.ulp

Copy the pcb to a new file, open it, run the script, copy the board all over et voila!

Aaah, so that's what that's doing. Yeah, that's more convenient than manually smashing out all the part names. I was confused when it just sort of ran without changing anything.

...although I tend to smash out part names on stuff that isn't destined for a kit anyway - if I get confused later on, I have my schematic to refer to. But good to know there's a ulp for it.