small trigger circuit

Micro controllers are so cheap now that they are the best choice for doing jobs like this, especially when the requirements are as nebulous as what you have described. Easy to change if your first attempt does not fit the need.

I would suggest the Microchip 16F series. IDE Development system is a free download.

Zum, Lead is right. Left over from my kidhood are thousands of individual parts such as resistors, capacitors, transistors, inductors, connectors with which I usta construct such devices

Does anyone in my neighborhood of Victorville, Ca know of a young kid interested in electronics who might benefit from such a collection which at 85 I never expect to tap again