Deal Extreme

2 Articles

Speaker Cabinet Boom Box Build

November 21, 2014 by 8 Comments

When you get that itch to build something, it’s difficult to stop unless you achieve a feeling of accomplishment. And that’s how it was with [Rohit’s] boombox build.

He started out with a failing stereo. He figured he could build a replacement himself that played digital media but his attempts at mating microcontrollers and SD cards was thwarted. His backup plan was to hit DX for a cheap player and he was not disappointed. The faceplate he found has slots for USB and SD card, 7-segment displays for feedback, and both buttons and a remote for control. But this little player is meant to feed an amplifier. Why buy one when you can build one?

[Rohit] chose ST Micro’s little AMP called the TDA2030 in a Pentawatt package (this name for a zig-zag in-line package is new to us). We couldn’t find stocked chips from the usual suspects but there are distributors with singles in the $3.50-5 range. [Rohit] tried running it without a heat sink and it gets hot fast! If anyone has opinions on this choice of chip (or alternatives) we’d love to hear them.

But we digress. With an amp taken care of he moved onto sourcing speakers. A bit of repair work on an upright set got them working again. The bulky speaker box has more than enough room for the amp and front-end, both of which are pretty tiny. The result is a standalone music player that he can be proud of having hacked it together himself.

Turning An $8 RFID Reader Into Something Useful

February 16, 2013 by 37 Comments

[Fabien] ran across a very, very inexpensive RFID reader on Deal Extreme a while ago and with money to burn, added it to his cart. When the USB RFID reader arrived, he noticed something fairly odd about it (French, Traduction). The RFID reader presented itself to his computer as a USB HID device that spit out characters into a text editor whenever an RFID card was waved above the coil. The only problem was these characters weren’t the hex values recorded on the RFID card. So what’s going on here?

As it turns out (Anglais), this random piece of Chinese electronica sends 10 bytes of data to the computer, just like this well-documented RFID reader. Apparently, both these RFID readers take the hex value of an RFID card, convert those bytes to base 10, and pass each digit through a lookup table. Exactly why it does this is anyone’s guess, but since [Fabien] figured out how it worked, he could also figure out how to reverse the process.

Unfortunately, the RFID reader in question is currently out of stock at Deal Extreme. Seeing as how most of the electronics available there are remarkably similar and differ only in the name printed on the enclosure, though, we wouldn’t be surprised if a nearly identical RFID reader was available elsewhere.