If all you want is an adjustable DC voltage, just use a linear pot between +5V and -5V with the wiper connected to the ADC input (assuming dual polarity ADC)
The only thing to be careful of is the recommended maximum signal impedance for the ADC, which you can check in the datasheet. Make sure the maximum output impedance from the pot (which is 1/4 of the total impedance, e.g. for a 10K pot the maximum impedance is 2.5K) is lower than this
You could also add a simple opamp buffer if you wish to really mimimise any impedance effects.
EDIT - from reading the comments above I suspect you are planning to use a 12V battery to power this. If this is the case you will need to either:
- Setup a virtual ground as Wouter mentions.
- Connect battery between
ground and V+ of your circuit, then use an inverter to create your
- Use two batteries in series and take your circuit
ground from the middle of them.
If you are not too experienced with this stuff, then I think the two batteries option may be the easiest. 12V is a bit high for the 7805, it will work but waste a fair bit of power, and may need heatsinking if you are drawing a lot of current (see datasheet). I'd use 9V or lower. If efficiency is important then you may wish to use switching regulators.