Since the case already had a power and reset switch (for the tape counter), I wanted to utilize those buttons for the computer power and reset buttons. The original power switch was a single-pole/double-throw switch, so I had to replace it with a momentary pushbutton switch. I got a switch from RadioShack and cut out an aluminum mounting plate so I could attach it to the original case. I measured the lengths, and cut down the original switch to fit, then epoxied it to the pushbutton switch as shown. Toothpicks and tape held it while gluing. Afterwards I mounted it as shown in the correct location. The glue didn't hold the first time, but I reglued it later and it's stayed strong since.
For the reset switch, I used a momentary contact switch I salvaged from the tape deck. The original switch was mechanical, so I had to attach this switch so the plastic arm made the connection. I wanted to leave the original tape counter in place for looks, but also intact so I can use this down the road should I want to add a counter of some sort to the machine (possibly showing hours running?). I drilled a hole in the plastic for a tab on the switch for rigidity, and after I failed to screw the switch on I ended up epoxying it in place (see photo below).
Moving on to the dynamic parts, the LED backlighting and fan controls! I needed a good use for the buttons on the front, so after a couple hours late at night I found some low-profile SPST (single-pole/single-throw) switches online from Digikey that would fit well into the case. In order to mount the switches as close as possible to avoid interfering with the motherboard I filed down the mounting threads and fit the switches partially inside the front of the case. To hold them in place I epoxied bolts to the plastic and made an aluminum bracket to hold the switches in.
Iâ€™m missing some photos here, I guess I got too wrapped up to take any. But you can see here the rest of the electronics on the back of the case. I mounted two low-profile microphone inputs to match the front of the case (originals were too big to fit), and also enlarged the knob hole so I could fit a multiple-position rotary switch large enough to handle all the current from my large fan (19W max). Originally I wanted to control the fan with a potentiometer but I wasnâ€™t able to find one small enough to fit in the case that could handle that much current. Instead, I placed resistors in series around 5 positions on the rotary switch. At the lowest speed the fan gets approximately 4volts after ~50ohms resistance, and at full speed there is minimal resistance so it gets the full 12 volts. The fan I bought is a very high powered fan, so itâ€™s too loud to run at full speed all the time. The front panel gets 12v/5v power via a molex connector from the PSU, then passes on the controlled power to the fan molex. The fourth switch on the front turns this case fan on and off.
After mounting the rotary switch and pushbutton switches in position, I started assembling the LED backlighting. As you can see in the above photo, there were originally two green lamp bulbs that backlit the glass panel with the VU meters on the front. I replaced these with various LED lights mounted on a strip of aluminum:
To construct this I marked the position of each bulb on the aluminum and drilled out the holes with a drill press. The LEDs almost stayed in the hole by themselves, but I helped them with a few drops of super glue. While I originally planned on wiring all the LEDs in series to be more efficient, I decided to wire them in parallel to make less of a mess of wiring. This way I could use a common ground for all 18 bulbs, and a single wire running across for each color of lights.
I soldered each wire, pulled back the coating a bit, soldered the next, cutting out sections of coating so that there was no way the wires would short. Lots of bare wires would be asking for trouble.
I calculated the resistance I needed to drop 12v to the 3.6v and 2.2v level required for the different colors, and made a stop at the store for 1W resistors (I required about 0.8W). After grinding the tops of the LEDs and the plastic case a bit to make things fit, I tested the look out and attached the bar. The switches were then wired. They used to tell the deck what kind of tape was in use, but now they control the backlight colors:
LH is green
CrO2 is red
METAL is now UV blacklight! (I can tan while gaming! Just donâ€™t stare at it.)
And they can be combined to form a bright purplish-bluish light as well.
Now I ran into a slight problem, the bolts holding the switches in place were a tad too long. I cut them down to size using a Dremel and metal cutting blade. This worked just fineâ€¦ until I later realized this fine metal dust collected inside my VU meters, despite being sealed away in the front of the case! I mostly remedied this with a whole can of compressed air, so it doesnâ€™t seem to be a problem now.
And for another really cool part.. the VU displays! I intend for the first one to show the fan speed, and the second to show volume or case temperature. While I originally wanted to design a circuit to utilize the tachometer (yellow wire) signal from the case fan, I later realized this was really unnecessary since it is unlikely Iâ€™ll use a PWM fan later (not to mention Iâ€™m not an Electrical Engineer
). Rather, I connected the VU (Volume Unit) meter in parallel with the fan voltage (controlled by my rotary switch). Through a small resistor the VU meter shows the voltage of the fan, such that at 12v (100%) it reads 0dB (100%) on the meter and 40% at the lowest speed). So you know when itâ€™s on and what speed itâ€™s running! Check out the video in the final Section 3 to see it in action.
Wow, this is a lot of work! But things are starting to shape upâ€¦ and Iâ€™m getting excited for the final product! I now had to make use of the microphone inputs I mounted, the original phono (headphone) jack, and remaining potentiometer on the front of the case. I found the pinout for my ACâ€™97 front panel connector
on the Asus motherboard online (common layout) and started looking for a 5x2 pin plug to connect to the motherboardâ€¦ no luck at my local source. Luckily I snagged some 4pin connectors from an old computer recently, so I started hacking away. I cut one end in half and glued it to the other 4 pin connector, creating a 6 pin custom connector.
I soldered and shrink-wrapped the wires and cable, then cut it to length and attached all the wires to the front panel connectors, using the potentiometer to control the headphone volume. At this point I still havenâ€™t tested any of this (because my mobo hasnâ€™t been back in the case), but hopefully the pinout and all my connections were correct! Weâ€™ll find out later.
Hereâ€™s the inside of the front panel:
Not much room, is there? I cut off part of the 24pin mobo power connector to make it fit with that aluminum mounting plate there (no problem with that). I soon used black cable loop spool stuff to organize all the wiring and give it a cleaner look (and hopefully better airflow through this cramped case).
The final (mess of) wiring can be seen at the end of this log.
And finally we get to the case temperature sensor. The second VU meter was unused, until I was able to get my temperature sensor to power the meter. This required a long time testing circuits on a breadboard, until I finally got one that worked thanks to my electrical engineering buddy Khalil. Using two standard op-amps, a LM335A analog temperature sensor and lots of resistors, we came up with this circuit, which initially used a test VU meter to avoid frying the important one:
This takes the 1.4-1.5 volt range output from the temperature sensor and converts it to 0 to 0.6V, the correct range for driving the VU meter. Once I got the circuit working on the breadboard I mounted it on a PCB and installed it inside the case behind the VU meter:
Here is a video of the meter in action, heating it up quickly with a blowdryer:
YouTube- OtterPopJunkie's Cassette Deck Temp SensorEdited by otterpopjunkie - 7/1/10 at 8:53pm