Just wanting to share one of my latest projects, made possible by DirtyPCBs. I got a lot of good boards (actually 2 designs) and saved 25$ using this service. Very nice.
It's a simple thing, just a micro (ATmega168) + a bunch of WS2812B LEDs. Main purpose: more colours :-)
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It's meant to fit nicely into IKEA Samtid lamps, runs with 5V DC and takes up to 2.75A. The control module is removable, so one doesn't have to rip the lamp apart every time you change code. I used microMaTch connectors, as they're somewhat low profile, at least compared to standard headers, and provide quite good mechanical support.
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The most intricate part of the circuit is a 1-ch level-shifter / bus isolator (google AN97055). I felt I needed it to avoid feeding parasitic power via input clamping diodes of the WS2812B when the whole board is powered by the programming adapter only (main 5V power supply disconnected).
Does anybody know what the heck is wrong with their forum admins? 10.000 spam posts and no reaction to emails, not even using their shop to contact them works.
Heck, I've even sent them pointers to a few simple to implement patches for phpbb3 to cut down the spam posters.
So far I haven't seen any sloppiness concerning order fulfillment (mostly PCBs), but to me the state of their 'support' forum is a bad omen. If that doesn't change I'm thinking about redirecting future orders to other shops.
as everybody else I've had issues with floating input channels picking up noise or signals from adjacent channels. Grounding unused channels does the trick, but these probes like to slip and it can get a bad mess of wires ;-)
To solve this problem (for me at least) permanently I made a little board:
It supports selectable pull-up and pull-down resistors in two groups with selectable pull-up voltage (2.5V, 3.3V, 5.0V). The pull-down resistors are 10k, which seems to work reliably so far. The size of the pull-up resistors that work reliably depends on the selected voltage. 5.0V and 3.3V works OK with 10k, 2.5V needs something close to 4k to suppress picking up signals.
Please don't ask me what this board does to signal integrity or relative channel delays, I don't know.
Once the forum allows me to post images and links, I will do so.
