hikerlt

Looking for a circuit to allow input of # fractional seconds, or # AC cycles, to control AC voltage to a small spot welder. This being used to do spot welds on sheet metal, welding pieces together. here is the spot welder I am using: http://www.harborfreight.com/115-volt-spot-welder-45689.html Right now am controlling the weld manually , but I would like more precise control with repeatable precision, to get the same weld every time. . Thinking some form of control for a zero-crossing turn on SSR or Triac that would pass 10-20 amps of AC 120v, for time periods ranging from 0.5 seconds up to 5 seconds...in precise steps. Any suggestions of circuits doing this is appreciated....this is for a home hobby project, not commercial... I am just getting started using the Digilent chipKit Arduino compatible and the Silican Labs toolstick - so would have either of those to work from. Also have a Renesas M16c starte kit evaluation platform, that has a small display built in - I'm thinking that may be the best approach as the display is already there. Other thoughts would be to have the timer AC voltage controller be between a PC ( rs232 or USB connection ? ) - so have the timer AC voltage contgroler interface to a program display to the PC, and get timing data via entry on the PC. Any thoughts or suggestions, or pointers to projects someone may have already done on this is appreciated