Need some help with regards to connecting two PIR sensors to one LED strip for my staircase.

Thread Starter

renaldoie24

Joined Aug 2, 2020
1
Hey guys,
I need some help on my home project. I wanted to attach a LED strip to my stair railing and use two PIR sensors. So that when someone comes down or goes up the stairs the LED lights will automatically turn on.
 

dendad

Joined Feb 20, 2016
3,591
I think you will need to supply a lot more detail info.
A "PIR sensor" is a pretty loose definition.
What is it powered from and what output does it have?

If the sensors use a relay output, just put both sensor's relay make contacts in parallel to switch the power to the LED strips.
But you probably need a delay timer too as the LEDs will turn when you move away from the sensor.
A board with a 555 timer could do it, but I would use an Arduino to keep the time adjustment easy and maybe add extra functions like a light sensor so it does not turn on during the day.
 

AnalogKid

Joined Aug 1, 2013
8,534
PIR sensor part number / mfr / vendor web page ?
LED strip datasheet / web page ?
LED strip length / power requirements ?
Power source ?

ak
 
In home automation or building management that is typically called a corridor switch/circuit.
In a typical two way lighting circuit switch arrangement each switch is a single pole changeover.
your load connects to the common of one switch, the NO and NC contacts of each switch connect together and L/Hot is connected to the common of the other switch...
you can add any number of double pole changeovers between the two switches and if any switch changes state the load will change state...
Any yes I know that inst much help, directly, but it serves to illustrate an issue.
I am guessing you need to have an ability to control this thing, overriding both on and off as well as leaving it in 'auto as it were.

You could get creative with relays and timers, it may even work well in some circumstances but picking a very cheap MCU board, switching the load with a single output and then processing all other inputs, including any and all PIR's and switches will be quicker easier and more flexible.
You will also find many properly rated modules that are pre-built to handle the mains voltage and isolate your control circuit not to mention the opportunity to use IR / RF / WIFI ... 'O' and wires of course.

Hope that set you looking in the right places...
Happy to help with specific questions if I can.
 

Martin_R

Joined Aug 28, 2019
5
In home automation or building management that is typically called a corridor switch/circuit.
In a typical two way lighting circuit switch arrangement each switch is a single pole changeover.
your load connects to the common of one switch, the NO and NC contacts of each switch connect together and L/Hot is connected to the common of the other switch...
you can add any number of double pole changeovers between the two switches and if any switch changes state the load will change state...
Any yes I know that inst much help, directly, but it serves to illustrate an issue.
I am guessing you need to have an ability to control this thing, overriding both on and off as well as leaving it in 'auto as it were.

You could get creative with relays and timers, it may even work well in some circumstances but picking a very cheap MCU board, switching the load with a single output and then processing all other inputs, including any and all PIR's and switches will be quicker easier and more flexible.
You will also find many properly rated modules that are pre-built to handle the mains voltage and isolate your control circuit not to mention the opportunity to use IR / RF / WIFI ... 'O' and wires of course.

Hope that set you looking in the right places...
Happy to help with specific questions if I can.
This is an overly complicated answer to the problem. You don't need to use changeover switches, as the PIR only a tivates for a timed period.
All that needs to be done here is to parallel up the PIR outputs and connect the LED strip to them.
 

PhilTilson

Joined Nov 29, 2009
85
In home automation or building management that is typically called a corridor switch/circuit.
In a typical two way lighting circuit switch arrangement each switch is a single pole changeover.
your load connects to the common of one switch, the NO and NC contacts of each switch connect together and L/Hot is connected to the common of the other switch...
you can add any number of double pole changeovers between the two switches and if any switch changes state the load will change state...
....
This would not work here! Even assuming the PIR sensors had the equivalent of single-pole, two-way switching outputs, this would mean that as soon as you came into range of the second sensor, the lights would turn off. Not much help if you are half way down the stairs!

The answer is above - simple PIR sensor modules in parallel - either module turns on the lights for a fixed amount of time. Job done!
 

Hemi

Joined Mar 17, 2012
14
Guessing you're only using a white LED strip, so it will have a positive and negative connection at both ends.
You'll probably need a couple relays or logic-level n-channel MOSFETs rated to sink the current of the LED strip unless the PIRs have them built in. Connect those to the negative at each end on the LED strip. Then run a wire along side the LED strip for common ground. Use the positive on the LED strip and common ground wire to power the PIR sensors. When either PIR senses motion, it will pull the LED strips negative to the common ground and the LED strip will turn on. Like dendad suggested, a 555 timer or Arduino/microcontroller will be need to extend the time the LEDs are powered on as the PIRs normally only stay active for a few seconds when motion is sensed. You'd need a 555 at each end to accomplish this. If using an Arduino/PICAXE/etc, you'd only need one at one of the ends. You could use a digital input on the uC to monitor the negative line on the LED strip to sense when it's on and control timing.
 

sghioto

Joined Dec 31, 2017
1,313
You'll probably need a couple relays or logic-level n-channel MOSFETs rated to sink the current of the LED strip unless the PIRs have them built in.
The units I linked to in post #4 have all that plus the timer is adjustable from 2 to 360 seconds. Connect in parallel as mentioned.
Steve G.
 
Multiple PIR's with changover contacts.... Obviously not.
My point was that the circuit probably needed a manual overide and would, pratically, need to be constructed from equipment, on the mains side at least, that conforms to whatever electrical standard is applicable in that location.
I dont disagree with most of what is being suggested, I was simply trying to point out that there are many established ways to do this type of lighting circuit.
 

Martin_R

Joined Aug 28, 2019
5
No one has twigged yet - if 2 way switching is used on a DC supply feed, the polarity will change to the LEDS , so the LED strip would need to be fed via a full wave bridge rectifier or the magic smoke will be released from the LED strip. Definitely not a great idea. Paralleling the output of the PIRS is the only way forward in my opinion.
 

Hemi

Joined Mar 17, 2012
14
The units I linked to in post #4 have all that plus the timer is adjustable from 2 to 360 seconds. Connect in parallel as mentioned.
Steve G.
I'm probably not understanding how you'd use two of those. Wouldn't you need two AC adapters, one at each end? Seems a bit excessive and also require outlets at the top and bottom of the staircase.
 

sghioto

Joined Dec 31, 2017
1,313
I'm probably not understanding how you'd use two of those.
Would depend on the staircase design. A straight staircase may only require one. "L" shaped possibly two, again depending on the design. If the "L" shape has only a few steps to a landing then probably needs just one located at the landing. As far has power is concerned that's always an issue. That will be up to the TS to figure out what works best.
Steve G
 
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