opinion request on 2 different comparator circuit designs

[earckens]

Here are two designs for a circuit that detects ambient light and reacts according to its level compared to a reference lighting level.

Both designs incorporate both a comparator and a delay circuit (RC based).

The 4 channel version incorporates the delay circuit in the comparator input. The 2-channel version uses a comparator to compare lighting levels, and a separate comparator with a RC delay on its input.

Which of these designs carries your preference (and maybe: why?)?

Thanks!
Erik

 

[alec_t]

Why the diodes in series with C1 and C2? They will prevent C1 discharging and C2 charging.
The MOSFETS need pull-up resistors so that they can turn off.
The comparators have no hysteresis, so they will act erratically at the switching threshold.

 

[earckens]

Hi Alec,
thank you for your reply. The first schematic will not work. The second works well for what it needs to do: detect light variation at low intervals (>1 second, up to minutes).

I made a new schematic, this time to compare the second circuit above with a design needing only one comparator.
I am in a bind however how to introduce a delay for the voltage on pin 9 (non-inverting) going up on the one-comparator design.

Downward voltage may be immediate; upward I would like to see an RC delay.

I have a gut feeling this will need an active component (mosfet)?

 

[earckens]

...
The comparators have no hysteresis, so they will act erratically at the switching threshold.

Output to inv input: add resistor? 10k?