The Case LED v. 2.0: Completed

After much pain and work…(ok, I had a great time; let’s be honest now)…I have finished the case LEDs!

Pursuant to the V-USB licence, I am releasing my hardware schematics and the software (which can be found here). However, it isn’t because of the licence that I feel like releasing them…it is because it was quite fun to build and I would recommend it to anyone with a lot of time on their hands. So, to start off let us list the parts:

  • 1 ATMega48A (Digi-key: ATMEGA48A-PU-ND)
  • 1 28 pin socket (Digi-key: 3M5480-ND)
  • 2 3.6V Zener diodes (Digi-key: 568-5907-1-ND)
  • 2 47Ω resistors (Digi-key: 47QBK-ND)
  • 1 39Ω resistor (Digi-key: 39QTR-ND)
  • 1 15Ω resistor (Digi-key: 15H-ND)
  • 3 100V 300mA TO-92 P-Channel MOSFETs (Digi-key: ZVP2110A-ND)
  • 3 2N7000 TO-92 N-Channel MOSFETs (Digi-key: 2N7000TACT-ND)
  • 1 10 Position 2×5, 0.1″ pitch connector housing (Digi-key: WM2522-ND)
  • 10 Female terminals for said housing (Digi-key: WM2510CT-ND)
  • 1 4-pin male header, 0.1″ pitch for the diskette connector from your power supply (You can find these on digikey pretty easily as well..there are a lot)
  • 2 RGB LEDs (Digi-key: CLVBA-FKA-CAEDH8BBB7A363CT-ND, but you can you whatever you may find)
  • 4 White LEDs like in my last case mod
  • 1 Prototyping board, 24×17 holes

The schematic is as follows:

Schematic (click to open full size)

The parts designations are as follows:

  • R1: 15Ω
  • R2: 39Ω for the Red channel
  • R3: 47Ω for the Green channel
  • R4: 47Ω for the Blue channel
  • LED1-4: White LEDs of your choosing. Make sure to re-calculate the correct value for R1, taking into account that there are 4 LEDs
  • LED5-6: The RGB LEDs. The resistor values here are based on the part I listed above, so if you decide to change it, re-calculate these values.
  • Q1-Q3: The P-Channel MOSFETs
  • Q4-Q6: The N-Channel MOSFETs
  • Z1-Z2: The zener diodes
  • U1: 16Mhz Crystal
  • C1-2: Capacitors to match the crystal. In my circuit, I think they were 33pF or something
  • CONN-PWR: The 4-pin connector for the diskette
  • CONN-USB: The USB connector. You will have to figure out the wiring for this for your own computer. I used this site for mine. Don’t forget to twist the DATA+ and DATA- wires if you aren’t using a real USB cable (like me).
  • C3: Very important decoupling capacitor. Place this close to the microcontroller.

As I was building this I did run into a few issues which are easy to solve, but took me some time:

  • If the USB doesn’t connect, check the connections, check to make sure the pullups are in the right spot, and check to make sure the DECOUPLING CAPACITOR is there. I got stuck on the decoupling capacitor part, added it, and voila! It connected.
  • If the LEDs don’t light up, check the connections, then make sure you have it connected to the right power rails. My schematic is a low-side switch since the LEDs I got were common anode. I connected both ends to negative when I first assembled the board and it caused me quite a headache before I realized what I had done
  • Double and triple check all the wiring when soldering. It is pain to re-route connections (trust me…I know). Measure twice, cut once.
Although I already have a link above, the software can be found here: Case LEDs Software

So, here are pictures of the finished product:

LEDs shining magenta

LEDs shining orange

LEDs shining green

With its guts hanging out

The mounting viewed from the outside

Mounted onto the front fan grille

13 thoughts on “The Case LED v. 2.0: Completed

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    1. admin Post author

      Are you using the V-USB driver? USB in general is very finicky about exactly what voltage levels you use and such. I believe my schematic above shows how I managed to get it working (a combination of zeners and resistor dividers). I also haven’t had much luck changing the pins from the defaults using V-USB, so you may want to try using the default pins first. I have gotten it to work on an Atmega328P before, so it does work. I just used a different controller in this project because it was cheaper :p.

      Reply
      1. Kristoffer

        hmmm, ill keep trying, cant seem to find the error thought, using 500mW 3.6 zeners and everything seems to be connected right and at the right voltage, and i am using an external 16MHz crystal.

        Reply

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