Hey Nerdkits friends! I haven't been posting much in the forums lately, life and all that, but I still have been plugging away at various projects when I have an hour or two.

I recently made some more modifications to my 16x8 LED array PCB. I finally got ahold of a couple TQFP 328p MCUs and mounted one to the little breakout board you can see in the middle of the breadboard in the first photo. I tried to reduce the circuit size and the 16 array wires as much as possible.

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The plan next is to lay the circuit out in Eagle and use all SMD parts so I can make a really low profile board that attaches to the back of the array with headers. Once that is done I want to also add a mini-USB port so it can be powered off USB or battery and put it in a project case so it can be my portable "desktop" array and sit next to my computer spitting out RSS feeds or whatever. Should be fun if I can find the time and resources.

Ted

That looks sweet - really nice work!

It'd be nice to see a little vid of this bad boy in action if possible.

I would like to make a similar thing, (ie small led array) that can be embedded in a particular item of clothing for comedy reasons.

Steve-

Thanks! The youtube vids off the original thread are the same exact array, just in the earlier stages of the circuit with the spaghetti wiring, etc. Check it out:

YouTube link #1
YouTube link #2

Lately I've been putting it on the back of my daughter's bike trailer when we go riding at night with a message that reads "SLOW DOWN!! BABY ON BOARD!!!", heheh. I'll get a video of that later tonight if we go out riding.

Ted

So, I'm trying to design a controller board for this array. I have been playing with Eagle and have come up with a schematic for this.

I was wondering if anyone could give me any tips on this circuit. I know I have the USB connector hooked up wrong, I haven't researched that enough. I'd also like to add the PL-2303 chip if possible on the board so it can be directly plugged into any computer with just a mini-usb cable, as long as the Prolific driver is installed of course. The power supply incorporates a DC step up (NCP1400) so I can use a single AA battery to power it if I want to, but I think it will be mostly powered off the USB.

Anyway here's the schematic:

Larger Size

Ted

Also, just remembered that I didn't notate the value on some of the components. e.g. -the crystal I want to use is this one, which has a load capcitance of 12pf. I found a formula for figuring the value of the two decoupling capacitors but I'm not sure if it's right:

Cᴸ=((C¹xC²)/(C¹+C²))+Cˢ

Cᴸ is the load capacitance value and Cˢ is supposed to represent the "stray" capacitance in the circuit. I have no idea how to find this out but on the site where I found this formula it was stated that stray capacitance is usally 2-5pf. So, if I plug in 12pf for the load capacitance and add the stray capacitance of 3pf I get a suggested value for the decoupling caps of 18pf. So, would the standard 22pf caps be OK for this application?

Ted