R-2R D to A Converter

Description
Having recently started playing with µControllers, I wanted to experiment with converting a digital signal into an analog voltage. The easiest way to accomplish this is by using an R-2R resistor ladder.

This simple project is really just a PCB board layout for a R-2R breadboard adapter I made to experiment with Digital to Analog Converters (DACs). For my breadboard adapter, I used 10K and 20K 0.5% 0805 SMD resistors. These were reasonably priced from Digikey, but you can use any values you like as long as one is R and the other is 2xR.

To save real estate on my breadboard, I prefer to have my adapters stand up as in the photos. However, you can also make this board in a horizontal configuration on 0.500" centers that should easily fit in any breadboard as well. One thing you will notice that is a little different about my board is that you can use it as anything from a 2-bit DAC to an 8-bit DAC.

If you would like to experiment with a 4-bit DAC, connect the input bits 1 (LSB) through 4, and leave the input bits 5 through 8 (MSB) floating. Then read from the 4bit DAC output pin. For a full 8-bit DAC, connect all the input pins to your µController and read from the 8bit DAC output pin. In general, connect up to n input bits and leave all others floating. Do not connect the other input pins to ground or to Vcc. Read the output of the DAC from the n-bit output pin.

This is a very simple single sided board made using the toner-transfer method.