Tuesday, January 10, 2012

lm386 headphone amp.

Just another amp build. nothing special about the circuit. the Power supply on the other hand is a different story. I picked up a little iphone speaker box from the dollar store that took only one aa battery. after tearing it apart i found a little opamp and a buckboost converter. the converter takes 1.5volts from the battery and turns it into 5volts that the op amp requires. So for 1 dollar I got a switch, battery snaps, and a dc-dc converter.

For a better write up on this type of amp go here

Taming those charging cables with a usb breakout board.

I'm sure there are those out there like me, that have a ton of usb charging cables. In my case theres my phone, my girlfriend's iphone, my tablet, her nook, and my camera. Thats 5 different devices using 3 different types of cables. On top of that the iphone wont respond to all usb chargers.It seems Apple will take every step to try and insure that you only use their chargers if your not using a computer.

So I put together a box that contains five usb sockets including one for the iphone. its a pretty easy thing to put together just paralleling the connection from one port to the other and attaching that to a usb cable.

Now the iphone port took a little more effort. With the iphone expect to see some voltage on the data lines of the usb port. So a couple of voltage dividers are required to trick the iphone into charging.
Heres the schematic:

Now we have all the ports we need. Everything is tucked in a nice wooden box that looks a whole lot better than a mess of wires.
I will write up the box build soon.

Monday, January 2, 2012

360 VGA output with 3.5mm audio jack

I recently had an xbox given to me. The only problem no video cable. I decided to see If I could hook it up to a computer monitor.

The older 360s have the capability to output rgb vga video signals. One simply has to connect the correct pins on the video connector to a db15 connector. I used some old hard drive ribbon cable to make the connections.

I added a pin socket to the cable to so I could unconnect the setup if necessary. the arrow in the picture is pointing to the solder bridging the two pins together. this tells the xbox that the cable is connected and to use vga mode

on the other end is a db15 video connector and headphone jack.

The setup works great. I can enjoy 360 game at 1080p and it looks amazing. If you would like to try the same thing here are some links to get you started


LM386 Noise

After some experiments I concluded that the radioshacks version of the lm386 is extreamly noisy. lm386 .7watt and 1 watt versions from digikey are far better sounding and seem to eliminate the white noise that can be heard from the radio shack equivelent.

Getting android 2.3.3 on the cobe kyros 7015a

Getting this working on the device seemed to be alot bigger of a problem then I would of liked. After trying to follow the guide layed out here. I ended up formating the flash and not writting the new data. The nand patch file provided by the megaupload link at the bottom didnt match the internal nand found in my tablet. Knowing that if I powered off the device with an empty flash would leave me with a brick I did all I could to get this working until I found just the file I needed.  http://www.szltp.com/download/download36.html The page is in chinese so I recommend using google to translate it. simply use the files in the Download as outlined in the tutorial above and it should work. DONOT use the megaupload link.

Another tip for those that had trouble. If your tablet enters fastboot mode after resetting, you can get it back into fwdn mode by holding down the home key and pressing the reset button.