While I know that it is impossible to slow light down I was wanting to delay an electrical response from a diode using either a resistor or a capacitor but I could not remember, which does which. The idea for the product is to create an electric delay on a row of led lights after a flashlight turn on the photoresitors behind them on so we can see it turn on slowly like a light chaser. I was planning on using a led a diode and resistors in a row with appropriate delays. I'd like it to be compact so no mechanical delays. PS: This is behind a opto resistor and am wanting one diode to turn on the row of led's then go down the row as the delay is making them react as if slowly like a gradient.
A microcontroller is probably your best best For example, microcontroller senses change in resistor → interrupt → LEDs turning on in sequence. PWM could also be used for dimming the LEDs.
You also get programmable LED strips. A 555 timer delay circuit may also work. Not sure if a capacitor is the best way to go for a project like this
1Meg Ohm resistors and 0.1uF capacitor, into CMOS 74HC14 (hex schmitt inverters), may work.
I' d implement the dimming feature with Pulse_width_modulation into NAND gates and some logic to produce numerous duty cycles.
But the MU idea is more compact solution.
In either case, you need some high-current LED drivers with 33 ohm or 330 ohm current limiting resistors.
For an LED light chaser, have a look here:
It uses a one-hot counter https://electrosome.com/cd4017/ which does the chasing, and a 555 timer as a clock, with which you can set the chase speed.
In your case you might need to add another flip flop to reset the counter. The flop is SET when the opto sensor is hit by light, and RESET when the last LED is illuminated.