View Single Post
Old 11th Jul 2018, 11:29 pm   #11
McMurdo
Dekatron
 
McMurdo's Avatar
 
Join Date: Jun 2009
Location: Staffordshire Moorlands, UK.
Posts: 5,263
Default Re: Battery tag spot welder.

I've repaired quite a few commercial spot welders over the years and for repeatable results, they generally use a phase-angle controlled triac on the primary of the transformer and a timer which is based on counting mains cycles. The ones we used to get were programmed with thumbwheel switches and used a postcard-sized CMOS board.

The sequence was Jaws Shut>Preheat Current On, time off. Fusing Current on, time off. Cooling period, release jaws.

Just in case anyone wants to make on with an arduino etc!
__________________
Kevin
McMurdo is offline