Inverting SCR Action?
I think the problem with both proposed circuits is that the hold-current through the SCR is not met. Probably not the most elegant solution, but the easiest way to fix your circuit is with the lower one. Basically make sure there is a current flowing through the SRC (5mA minimum according to the datasheet), and limit the base current of the transistor.







simulate this circuit &ndash; Schematic created using CircuitLab