Archive for May, 2011

Sunday, May 29th, 2011

Just wow…

Via popsci

Grimsvotn Volcanic Eruption

Tuesday, May 24th, 2011

Group import LED matrices?

Friday, May 20th, 2011

If you love LEDs as much as I do, you might find this blog post interesting. From the comments:

The P4 (the 64*32 indoor one, 4mm pitch made of 8*8 elements) costs around 160 dollars and the p6 (32*16 outdoor one, 6mm pitch made of SMD leds) around 40 , and it is just for fun! Note that I’m also able to get 32*32 6mm pitch SMD led matrices for around 70

Oooooh, seriously tempting :D I’ve been wanting these things for years, but always stayed away due to the high pricetag. But this thing changes that. Here’s a quick comparison. You might have heard of those 8×8 LEDsee RGB modules for 7 euro (or 10 dollar or so). Those are the cheapest RGB modules I’ve run across available to mere mortals. Now imagine a 128×64 matrix. That’s 128 modules aka 896 euro! With the group import you’d need 4 panels to get the same resolution. Smaller dimensions, but at roughly 460 euro. And a crapload less work because the factory has already done all the LED soldering for you :D

1 day remaining

Tuesday, May 17th, 2011

As long as can remember Microsoft has never gotten anywhere near a decent file copy remaining time. A day for a 5GB copy (on a SSD!)…. how on Earth do they come up with these numbers!? Fascinating :)


Thursday, May 12th, 2011

Whoa, looking forward to giving these big ass LEDs a testdrive. 10mm diffused RGB and the first testcase for the LED drivers. The 3mm red one and 5mm strawhat are a quick size comparison to give you an idea how big 10mm actually is (personally I never saw 10mm ones before irl).  Gotta love Chinese manufacturers :D

TLC5940 driver boards

Wednesday, May 11th, 2011

So with all those LED drivers lying around it’s time to do something fun with them. Given the amount of chips a PCB certainly wouldn’t be overkill so I whipped one up. It’s the max size Eagle freeware allows, but everything fits nicely. Of course using SMT would enable a smaller PCB, but since the drivers are already present, that’s not an option. The TLC5940 comes in 3 packages; SPDIP, SSOP with PowerPAD and QFN.  Soldering PowerPAD packages is a pain because you need to put solder underneat and adapt the PCB to lead away heat. QFN packages have no leads, which is also a pain for a hobbyist. SPDIP is the only one easily used.

Each board has 3 TLC5040 chips and data is clocked in as 8x8x8 (aka RR…RGG…GBB…B). The board is designed to be Daisy chained, including a return path. The return path may offer possibilities to automatically detect the size of the array via the status information bits. It would be nice to have RGB…RGB, but 16 channels per chip isn’t really dividable by 3. Same problem arose when I thought up smaller PCBs, e.g. use 1 driver per PCB.

A potential problem with these big boards is that they’re harder to build into a system which has small dots. The jury is still out on what to use as a light source. Options are (large) regular LED’s, LED strips cut up into smaller pieces, etc. The TLC5940 can drive up to 120 mA, so that allows for a range of options. Using separate LEDs requires a huge amount of hole drilling, so for the time being I much prefer using LED strips. By cutting it into pieces holding 3 LEDs, oval shapes (in milk coloured acrylic) should be easy to accomplish.

One thing I greatly underestimated was the cost of connectors. Usually only a couple are needed, but in this case I’ve got enough drivers to make 15 boards. Each board has 16 RGB channels, which makes a grand total of 240 connectors. The initial idea was to use polarised connectors, but even low cost connectors from Thailand or China drove up the price too much for my taste. To give you an idea, the male part alone costs $140 at Mouser’s! So I settled on using standard angled pin headers and cheap Molex C-grid like connectors. Should work fine, just have to make sure that during hookup the connection is not reversed.

To be continued….

Making popcorn with style

Tuesday, May 10th, 2011

Btw, also worth checking out is this video by the same author!

What to do with these?

Sunday, May 8th, 2011

Imagine you’ve got a bunch of  TLC5940 ICs lying in front of you and you’re thinking “What can I possibly make with these….”.

Ooooooh the possibilities >:-)