I am attempting to make a circuit which triggers a 555 astable. The input is one of those IR beam break sensors with the output of the phototransistor going to a NOT gate and the output of that is connected to the gate of the thyristor through a 1k resistor. That thyristor is then powering the 555. The idea is that, when the beam is broken, the 555 will be triggered.
The only way that I can get it to work is by adding an LED in parallel with the 555, but it is quite unreliable. I think the problem is that the drain-source current is less than the holding and latching current, which are specified as 5 mA and 6 mA respectively. When I measured it, the current drawn by the 555 dropped as low as 3 mA, so this seems plausible.
Does anyone know of a "low current thyristor" or something else that would get this working reliably?
Any help is greatly appreciated.