I have completed a MOT spot-weld unit, but I am further refining it. I am primarily spot-welding sub c ni-cad battery tabs, and am implementing a timer to control weld duration. The welder is 120V and works well.
I intend to use an Allen-Bradley 700-HX digital unit (octal socket) along with an Omron G3NA-240B 120V solid state relay. I am not sure if these are the optimum parts, but they are what I have. I will also be using a generic style momentary contact switch or micro switch for a trigger. Approx .3 seconds spot time will be needed, which is within the timer capability. I would like to utilize "one-shot" logic.
I am looking for wiring schematic information for the timer in conjunction with the relay.
I have reviewed the 5bears.com site, but the timer differences are confusing. The user manual for the timer is also a bit overwhelming for me.
Thanks for the advice!

 

A relay with a high coil resistance activated thru a capacitor charge, could work. The
relay could have an extra contact to discharge the capacitor thru a resistor, between cycles.

 

The Omron SSR is designed for switching resistive "heater" loads. The spot welder is an inductive load. Look for relays that can safely switch motor-type loads.

I think Crydom had an app note on de-rating their SSR's for inductive loads.

Ken