Digging into the vault of never fully documented projects, I found this and decided to make an Instructable on it. Doing this mostly by memory, I might have missed some things. Let me know if you see any errors. This is a project that displays how many unread email messages you have. It also displays the temperature. It wirelessly transmits your unread message count to a small acrylic cube. There is a piezo transducer on the lid of the box that allows you to switch between temperature and email by tapping on the lid. If you could vote for me in the epilog
and battery powered contests
, that would be great!
Paso 1: Transmitter Electronics
The transmitter is basically a FT232RL USB to UART bridge and the RCT-418-AS transmitter. The UART signal from the FT232 must be inverted before going to the transmitter because the UART "no data" state is high. If a high signal were going to the transmitter constantly, it would violate FCC rules because the RCT-418 would be transmitting constantly. This circuit is powered directly off the USB port of your computer. For correct VSWR the antenna MUST be 17cm. This is a 1/4 wavelength antenna for 418MHz.