David Barrett has taken TTL logic to the extreme! No his logic isn’t controlling a photocopier, printer or some obscure computer equipment. David’s TTL handywork is controlling a 180 Amp TIG Welder.

“Many modern welder front panel’s were looked at and many dozens of spec sheets studied to gain a list of requirements, then it was simply a case of reproducing those function’s simply and cheaply.
The descision was made early on to build using descrete I/C’s for three main reasons. Firstly they are easy and cheap to obtain for anyone wanting to copy the design.
Secondly Microprocessors are great and simplify things a geat deal but one has to have programming knowledge and the equipment neccesary to actually get the firmware into the chip….not everyone has either.
And thirdly if fault finding is required descrete TTL and CMOS is far easier to troubleshoot with average home type test equipment (VOM, Freguency Counter, Oscilloscope etc)”

Source: Hackaday