The wire I am using is standard temp. nitinol wire which needs to be heated up to 45 degrees Celsius in order to be effective (move). What voltage do I need to achieve this?
I don't believe you can do this with any degree of precision : it depends too much on the wire and its environment which determines its rate of cooling.
This 450 page book would give you a brief introduction to the difficulty; the TL/DR version is: Don't.
Which leaves you with the alternative problems of:
- determine the wire's temperature and control the voltage to achieve the correct temperature. You could measure the drive current and voltage, to determine its resistance, and compute the temperature from that
- measure the actual motion and control the voltage accordingly (programming a PID controller is the best way, but the response time of the wire makes this tricky)
- Experimenting to determine what voltage is "good enough" in your environment. This is by far the simplest and may be good enough for your application; you haven't told us enough to tell.
Your vendor does not seem to have good information on resistance and current values for your wire. Here is a table from a different place that can help:
The numbers you want if you are using their -super heavy- 0.02" wire are
resistance per inch = 0.11 ohm / inch
apx current to actuate = 5 Amps
That gives you a starting point for your own testing. A 1.5V D cell battery, and a 3 inch length of the wire is a good place to start.
Their table is for 150 degree (F) wire, and yours is lower, so plan on a bit lower currents needed. On the other hand, the D cell probably will sag pretty much at 5A, so its a start.