Device that blocks signal, 200426

Hello Makerspace,
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

System Requirements:
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?

Thanks

Allen Pitts
Dallas Texas

2 Likes

Sounds like you need to look up some logic gates. You should be able to throw a few 7400 series gates in the mix and get what you need.

2 Likes

What @michaelb said.

This is an interesting little problem to solve.

I think it’s just going to be a bunch of AND gates chained together.

Hello MichaelB, MD Redmond and the MakerSpace forum,

Part of the following was stated above in the first post and is repeated herewith
below for some one who might start reading here.

Have designed a circuit and a PCB that sends the 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. This the schematic.
schematic
The plan is to use several P5Ls to, instead of turning all lights on a 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. it is quite pleasing and very cool.

A colleague who is an EE and has much experience was asked about how to make the lights below come on
when approaching from above and lights above come on when approaching from below. He said the
two methods that came to mind were an Arduino and 4013 flip flops. To avoid the programming overhead
and to learn about a new IC the 4013 was chosen.

Research on the 4013 Flip Flop led to
4013 Flip F;lops
staircase_design_200423
The system should work differently depending on whether the walker is going up the stairs
or down the stairs. Or stated more formally:

System Requirements:
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.

NOTE: ‘Q2’ is used as a substitute for Q with a hyphen above it because there is
no way of putting a hyphen above a Q using the characters on a standard keyboard.)

In Use Case One (going up)
S1 is triggered and the PIR

  • Sends a signal to the P5L operating LEDs L1 and turns L1 LEDs on

S2 is then triggered

  • Sends a signal to 4013.1 pin 4 ® which makes Q1 = 1 and Q2 = 0. Q1 sends a high signal to L2 LEDs and a low or no signal to L1 LEDs

S3 is then triggered

  • Sends a signal to 4013.2 pin 4 ® which makes Q1 = 1 and Q2 = 0. Q1 sends a high signal to L3 LEDs and a low or no signal to L2 LEDs

S4 is then triggered …

In Use Case Two (going down)
S8 is triggered and the PIR

  • Sends a signal to the P5L operating LEDs L7 and turns L7 LEDs on

S7 is then triggered

  • Sends a signal to 4013.6 pin 4 ® which makes Q1 = 1 and Q2 = 0. Q1 sends a high signal to L6 LEDs and a low or no signal to L7 LEDs

S6 is then triggered

  • Sends a signal to 4013.5 pin 4 ® which makes Q1 = 1 and Q2 = 0. Q1 sends a high signal to L5 LEDs and a low or no signal to L6 LEDs

S5 is then triggered …

Three questions:

  1. Is this the best way to use the flip flops?

  2. Is the clock an oscilator like a 555 timer? If there are six 4013s can they all be run from one 555?

  3. I am familiar with a positive signal coming from, say, the PIR sensor which sends a 3 volt
    signal. And at the Arduino send a HIGH signal with the statement ‘lc.setLed(0,0,0,true)’.
    And it is assumed that the three volt signal from the PIR to a pin on the 4013 would be
    interpreted as value of 1. But how does one send a signal to the pin of value zero?

Thanks.

Allen in Dallas