Posted on Tuesday, April 15, 2008 • Category: MP3 Players
This MP3 player is similar to iPOD shuffle that is based on the latest innovative BU9432 chip from RHOM. It features USB 1.1 / 2.0 Controller, MP3 decoder, system controller for loading MP3 files from a USB flash drive, USB hard drive, USB CD-ROM or USB DVD-ROM drive all in one chip.
Once USB flash drive is connected, BU9432 automatically searches for MP3 files for playback. Audio is controlled by tactile buttons; Play, Stop, Previous Song and Next Song.
BU9432 can decode VBR MP3, MP2, MP1, Layer 1, 2, 3 files with Sampling rate: 8K - 48KHz and Bit rate: 8Kbps - 448Kbps. It can also recognize FAT16 and FAT32 USB flash drive / hard drive with capacity from 32MB to 2TBytes. Audio playback is exceptionally good with 93dB signal to noise ratio and 88dB dynamic range.
Posted on Tuesday, April 15, 2008 • Category: FM Transmitters
This is a high quality PLL Stereo FM Transmitter with build-in VHF amplifier for long transmission range. It is based on BH1417 chip that offers high quality crystal clear stereo transmission. Eight available frequencies are controlled by grounding 3 pins on header connector. This transmitter comes assembled and is ready to use.
- Two on-board transistors increase transmission range
- Uses 7.6MHz crystal for rock-solid PLL FM transmission
- Crystal based stereo encoder
- Very small size
Posted on Monday, April 14, 2008 • Category: PLL Circuits
PLL Synthesizer module is an add-on based on SA1057 and PIC16F84 that converts any existing FM Transmitter into stable rock-solid PLL transmitter. Frequency is selected through 8-DIP switch. PLL Synthesizer board will also require a 100K resistor and varicap diode such as MV2105 or MV2109 to control the frequency of the transmitter's oscillator.
Posted on Monday, April 14, 2008 • Category: FM Transmitters
Here is the latest and greatly improved TX200 VFO/VCO FM transmitter. The most versatile transmitter to date that can be turned into high fidelity stereo PLL based 200mW FM transmitter. It is a perfect circuit for transmitting your music around the house and yard. TX200 uses only two coils; one in the oscillator and the other one in the 200mW VHF amplifier so it should be fairly easy for anyone to build. It also includes built-in pre-emphasis and C5 for enhanced sound quality. While assembling the transmitter care must be taken to make sure that C1 is directly connected to L1 and C9 to L2. These caps eliminate the distortions form the DC supply and improve the sound quality greatly. 9V voltage supply is also very important because it provides the exact amount of current to Q1 to produce loud and clear sound quality.
Posted on Friday, April 11, 2008 • Category: Battery Chargers
Lithium Ion batteries pack a lot of power by weight compared to other types. There are 2 things that need to be handled differently than nicad on NiMH:
1. They cannot be used as a direct substitute (even if they look like other AA's) since they run at about 3.6 (or so) volts.
2. They cannot be charged in the same way as nicad or NiMH.
After a bit of research, I came up with this design.
Normally, you put in a specified current (about 0.2C) until 4.2 volts is reached. Then, you keep the voltage tightly regulated at 4.2 volts until the charge rate drops to 10 percent (about 0.02C).
This design uses a regulated supply for both parts of the charging. Only the charging current is monitored since the supply voltage is maintained at 4.2 volts. The charging current is controlled using variable pulse width of the voltage feed.
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