I want this project to have one power supply, but the motors run on 115Vac and the arduino and relay board run on low voltage DC power. Is something like this the best option? Or is there a better way to do it?
Your links are broken but I managed to decode them.
Whoever wrote the datasheet for that pump doesn't know the difference between AC and DC, or even Watts and Amps. That doesn't fill me with confidence.
Assuming those pumps work, and your "relay board" needs 12V DC with less than 2.5A, then, yes, that power supply will do it.
(On the other hand the page clearly says "Out of stock", so....)
why three voltages ?
if you plan on running the motor on line voltage, fine.
then all you need to do is to create a DC power for the rest of the project.
http://yourduino.com/sunshop2/index.php?l=product_detail&p=123
then use a 5v relay
or
put the power to the relay and then jump it to the Arduino.
the Arduino will only need to control the opto so the output current will not be very great.
I don't need three voltages, I only need two. The whole thing is I don't want to have to run two different power plugs, thats precious real estate. Anyway, I ordered that product, I must have gotten the last one because it wasn't sold out before. I'm using a sparkcore and spark relay shield for this project so I have everything I need but the power converter.