Custom 3.5" multifunction panel (several 640x480 pics)

T

Teancum

Limp Gawd
Joined
Dec 12, 2003
Messages
275
I've wanted to add front USB and audio ports to my computer for a while now, but I've never been satisfied with what I can buy online. Frontx is too expensive, so, I decided to make my own. Here's what it will have:

-fit in 3.5" bay. No big stuff here
-two channel fan controller that varies from ~5-6 V to 11-12V. Who really needs to control six fans independently anyway? It will be a PWM controller, so I don't have to worry about dissipating all sorts of heat
-front USB port (or more) with enough current capacity to run my laptop hard drive in an enclosure
-headphone jack, possibly with an internal amplifier, since the output from my motherboard is too wimpy to drive headphones.

I've built the fan controller circuit. And I've tested it. And I found out that even though it should be optional, you HAVE to connect the control voltage to a capacitor and tie the reset pin to Vcc in order to get the two sides of the 556 timer to work without interfering with eachother. Thank goodness for being a TA for a circuit design class--I have unrestricted access to the analog circuit lab on campus!

So, here are a few pics. I'm hoping to get a whole lot more done over this Thanksgiving holiday. First up, the panel as it now stands:
IMG_0148.JPG

And here's the plan:
3_5%20panel.jpg

here's the current backside (not much to look at, yet):
IMG_0147.JPG

And here is the PWM circuit, without the power transistors that I will use to drive fans (or whatever else) in the case.
IMG_0146.JPG

The red wire will be +12V, the black is ground, the white and blue wires will attach to the pots that will connect to +12V. The yellow wires are the outputs of the two timers. Since I've heard about problems with PWM fan controllers making a "growling" sort of noise, I made sure that this one operated well above human hearing. When it is driving the fans at slowest speed, the output will have a frequency of about 100KHz, and when driving the fans at max, it will be running at just under 20KHz. Yeah, 19KHz might technically be within the realm of human hearing, but with the fans running at full blast, it's unlikely I'd be able to hear any 19KHz signal anyway.

I'm also seriously considering adding an amplifier (just a simple non-inverting opamp) to the remainder of the board--I certainly have enough room left there. The board will have some sort of floppy or molex connector to get power, so you can kiss the USB's 500mA rating goodbye. :D

Questions, comments, suggestions, derogatory remarks, let me hear 'em.
 
Oh, drat, I forgot to put the nice machined aluminum knobs on the pots before taking the picture--they are why everything is so far from the pots.

If anybody wants a schematic for the timer/PWM circuit, I'd be happy to whip one up and post it.
 
Yeah, it's been a while since I did any work on this. However, there is progress! I find myself very easily distracted. I've completed most of the more intricate circuit work, and actually made a sort of enclosure. The bottom panel I dremeled out of an old busted PSU, and the sides are spare chunks of 1/4" acrylic. I haven't soldered everything yet--my "To Do" list is below, but I have done the hardest part.

Here's a shot of the backside of the panel, with the circuits in place. The group of stuff closer to the face of the panel is the PWM fan controller circuitry, and the stuff closer to the camera is the headphone amplifier/attenuator for the headphone jack. Since this will be running off of a motherboard header, the sound comes from the motherboard through the circuit to the headphone jack. If no headphones are present, the signal goes back to the motherboard and out to the back speaker jacks. Since I wanted the headphone jack to have an amplified signal but wanted to retain the normal signal level to my speakers, I had to amplify the signal for the headphones and attenuate it on its way back to the MB.
IMG_0169a.jpg

And here's a shot of the front. I still haven't done anything as far as the CF slot is concerned, but that's on its way. Eventually.
IMG_0170a.jpg

And now, the To Do list:
-figure out which way the PWM circuit hooks up to the pots
-get power transistors so I can drive LOTS of fans
-figure out how to fit the power transistors on the PCB
-add 3-pin headers for fans (still figuring that one out)
-get power into the circuit from PSU
-add USB ports and CF slot <- that's a big one.
^a note about the USB ports. I don't like the 500mA limit, so I'll hook up the 5V line of the USB ports directly to the PSU. No, it's not dangerous, but it will allow me to draw a whole lot more power than normal.
-add cables for the amplifier/attenuator to connect to the MB header
 
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