It looks like it might work (in fact it's rather clever), but a few things:
* I don't understand the Optoisolator in this context. What is it isolating? Both sides of the isolator are connected to the same circuit (i.e. supplied by the same supply).
* When the Opto's transistor is on, it causes quite a large reverse voltage across the gate and anode of the SCR. Not sure what will happen there.
* Because all but one of the outputs of the 4017 will be sinking maximum current, not sure if the device can take that. CMOS is not really designed to provide much in the way of driving capability. You might need to limit the current with a resistor in series with the opto's LED. BUT, then, will that be enough current to drive the opto's LED, (such that the opto's transistor turns on enough). OR, buffer the 4017 outputs with transistors (unless you can do away with the optoisolators, in which case replace them with transistors).
* The 4017 spec sheet gives a typical Maximum IOL--not sure if that means the device will limit to that current, or if external limiting is needed.
* Hopefully you're running the 4017 at 9 volts.
* Will a 100uf deliver enough energy to do the weld?
* I don't understand the Optoisolator in this context. What is it isolating? Both sides of the isolator are connected to the same circuit (i.e. supplied by the same supply).
* When the Opto's transistor is on, it causes quite a large reverse voltage across the gate and anode of the SCR. Not sure what will happen there.
* Because all but one of the outputs of the 4017 will be sinking maximum current, not sure if the device can take that. CMOS is not really designed to provide much in the way of driving capability. You might need to limit the current with a resistor in series with the opto's LED. BUT, then, will that be enough current to drive the opto's LED, (such that the opto's transistor turns on enough). OR, buffer the 4017 outputs with transistors (unless you can do away with the optoisolators, in which case replace them with transistors).
* The 4017 spec sheet gives a typical Maximum IOL--not sure if that means the device will limit to that current, or if external limiting is needed.
* Hopefully you're running the 4017 at 9 volts.
* Will a 100uf deliver enough energy to do the weld?
(I've only been fiddling with electronics for a few months )
)