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:
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.
So, here are pictures of the finished product: