Have designed a circuit and a PCB that sends a signal from a PIR sensor (motion detector) and
triggers a 555 timer to turn on some LEDS for about a minute. I call the circuit P5L (PIR to 555 to LEDs).
It has taken about month to design the schematic, prove the circuit logic with a breadboard, and design and order the PCBs.
The plan is to use several P5Ls to, instead of turning all lights on stairway at once, light up the
staircase two or three treads at a time so that the system reacts to the movement of the walker. I saw
something similar at a staircase at the Perot Museum in downtown Dallas.
This the URL to a diagram which shows the idea.
The plan is to have the system work differently depending on whether the walker is going up the stairs
or down the stairs. Or stated more formally
Use Case One (going up): When sensor S6 is triggered the LEDS above (LED L7.1 and L7.2) are turned on
if LEDs below (L5.1 and L5.2) are on.
Use Case Two (going down): When sensor S6 is triggered the LEDS below (LED L5.1 and L5.2) are turned on
if LEDs above (L7.1 and L7.2) are on.
Sensor S6 is used in the requirements as an example to illustrate that the lights below a sensor would
be activated by movement down the stairs and lights above a sensor would be activated by movement up
the staircase. The exception is sensors S1 and S8. There are no lights below S1 or above S8 and so S1
has no sensitivity to another set of lights. S1 simply turns on LEDs L1.1, L1.2 and L1.3. And similar for S8.
In Use Case One (going up) S6 is triggered and sends signals to the transistors operating both LEDS L7 and L5.
But a device is needed to detect the signal from the S6 PIR to the L5 lights, and if L5 is on,
the device blocks the PIR signal from going to the transistor operating the L5 LEDs.
In Use Case Two (going down) S6 is triggered and sends signals to the transistors operating both LEDS L7 and L5.
But a device is needed to detect the signal from the S6 PIR to the L7 lights, and if L7 is on,
the device blocks the PIR signal from going to the transistor operating the L7 LEDs.
So the device is like transistor in reverse. That is, a transistor uses a signal at the base to allow current to flow.
What is needed that, instead of closing a circuit and allowing current to flow, the device opens a trace
and prevents a current from flowing.
Is there such a device?