Digital System for 730nm trigger

I designed a crude digital system for timing the 730nm trigger pulses after lights out.

The "lights" signal will have to detect to see if ac line voltage is detected on the main lights circuit. I'm thinking an optoisolator would be okay for providing a 5V signal that can be used as a cmos input. Theoretically you should be able to feed that signal using a 5V wall wart for USB chargers...

Anywhere, here's the design.. I'm not exactly sure on all the details, but right now it pulses for 15 seconds after lights out. To get it to pulse longer, either the timer period needs to be lengthened, or another divider counter needs to be added. The timings won't be perfect, nor do they need to be. It just needs to pulse for a "few minutes".

I was thinking of using a 555 timer for the clock since it doesn't need to be perfect, and might allow for crude adjustment.

(NOTE: DVIEW10 isn't actually part of the circuit, it's used to output the digital signals to the simulator so they don't all overlap)

Long story short, it's supposed to turn the 730nm lights on for a configurable amount of time after the main lights turn off, then turn off until the main lights turn on and off again.

It works because the clock for the counter is disabled when the count reaches 15, but the light being on resets the count to 0 and holds it there, which allows the clock on the counter to start again. Once the lights turn off, the counter stops clearing, and can finally count to 15 again, where the clock is disabled... etc.

One caveat about this design (shown in the simulation) is that if you turn on the system for the first time while the lights are already out, it will pulse the 730nm signal for 15 seconds immediately. To prevent this, you can either physically switch off those 730nm leds for the duration, or only turn it on for the first time while the lights are on. (or design something to handle the system's reset condition more gracefully).

Chances are this won't matter as most people only work on their plants when the lights are on, but it's good to know about the edge case that they will come on on first startup if the main lights are off.

I like the idea of 730nm not being on a separate timer and I think the IG pontoon has the best idea with the battery powered initiator at lights out. If I knew how to build a circuit to charge the battery during lights on and then run off the battery during lights out I would definitely build one to try out. I imagine it would just need some relays, a proper sized battery for desired light and duration and charger but I don't really know.