Surprise Secret Of This PIR Sensor

Well.. Well... Well ... what do we have here?

This is a wildly popular PIR sensor which is awesome at detecting motion pretty reliably. 
 

It uses a Fresnel lens which sits in front of a heat based sensor to detect objects about 7 feet away.

It also has the ability to delay firing by 2-4 seconds approximately. Great for filtering out unwanted movements from retriggering the sensor.

BUT! It has another trick up it's sleeve.

Ready, Ready?

These sensors normally trigger when it see's any type of motion, doesn't matter if the lights are on or off, it will trigger.

But what if you want to build something where you only want to trigger when the lights are off?

Something like this under bed lighting system perfect for those midnight runs to the loo. It will only go on when it sees motion in the dark!

 

 

Fun side story...

I almost bought this exact model myself, but I wanted to add another sensor for my dog...

Yeah, long story here but he can't see the pet stairs and needs his own light. 

So I have one for my girlfriend, myself and my pup of course, I can control all the colors!

Ok, back to this little sensors super power!

In order to make this sensor only trigger when its dark, all you have to do is add a simple electric eye to the circuit like these

 
 

Best part? It's pre-configured for this, so just pick up an electric eye like this one, and solder it in.

All you need to do is pop off the lense, and look for the 2 pins directly under the heat sensor.

See picture below for location.

 

Cool right?

I thought so too!

Happy Sensor-ing...!!

Let me know what you think by commenting on this post!

 

 


6 comments

  • I can’t wait to try it out with my 9 yr old Son. Cool project. Thanks!

    Alex
  • Great idea! …. and easy too!

    Jimmie Fouts
  • Great idea going to tear one now and play around with it.

    Roger Bingler
  • Great little secret! I’ve got these parts in my collection…can’t wait to try this!

    Tony Verduga
  • Those electric eyes, or ones similar , are used in motion sensing spotlights. I have dissected a few over the years so I may have some sensors in storage. Thanks for sharing!

    Timothy Savage

Leave a comment

Please note, comments must be approved before they are published