FM Transmitter

I bought the Niigata NS73M FM transmitter module from Sparkfun.  I prototyped it with my AVR Butterfly module using the Nuts & Volts May 2008 article.  I reduced the code size by taking out the audio generator so it would compile with the Bascom-AVR demo software. 

I wrote a Basic program for an ATTINY13 to initialize the NS73M at a fixed frequency of 102.9 MHz.  The Bascom-AVR compiler I2C support made the program quite easy.  9 bytes of data is all that is required to program the NS73M.

The finished FM transmitter is very simple consisting of a 3V regulator, ATTINY13, NS73M, and a handful of passive components.  I get good coverage through the entire house with a 32" antenna.

DJB-FM transmitter schematics

DJB-FM transmitter Basic source code

Scrolling Car Display

This project is a follow-on from PSIM display work.  Since this VFD easily interfaces with 9600 baud serial I decided to build a scrolling message board. I chose the ATTINY13 processor because of it's small size.  I ported the Atmel AVR304 application note implementing a software uart to the ATTINY13 processor and used an additional pin to blank the display.

Vacuum fluorescent display software source code

I set the display to 50% brightness which limits the total power consumption to ~280 mA.  I used a LM2940 low dropout regulator to be able to power this from a 6 volt battery in my 1949 Chevy.  I assembled the display in a 1.5" clear plastic tube.  The ATTINY13 is the small DIP on the left at the end of the wires and the LM2940 regulator is on the right mounted to the 2 pin power connector.

Here is the display on the dashboard of my 1949 Chevy.  It slowly scrolls information on the car including the name, year, model number, mileage, original content, and owner.

6V  Car Battery Float Charger

I two 1949 Chevrolet cars with 6 volt car batteries.  I don't drive them during the winter so I am constantly having to keep the batteries charged.  Most automotive chargers are 12 volts and if they have a 6 volt setting they are manual charge only.  I wanted a continuous unit that would not overcharge the battery.  A lead acid battery can be maintained at full charge without overcharging with a constant voltage of 2.25 ~ 2.30 volts per cell so I designed a float charger using a 9VDC wall wart with a post regulator set to 6.75 volts and a 100 mA current limit.

6V float charger schematics

Reel Tape Box Display

I have a variety of reel tapes and some of the boxes have interesting covers.  I made a frame with a glass front with inside dimensions tight enough that the tape boxes simply press in from the rear.

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