Ever get up in the middle of the night and go stumbling towards the hallway light only to trip over your cat and fall down your stairway and bash your head on the wall at the bottom? Neither have I! But if you're afraid of this happening, or you just want to make your friends jealous of your awesome electronics prowess, you can build this IR light trip sensor to light up your stairway (or any room in the house you'd like) when you walk past it so that you'll see that pesky cat waiting for you to trip on it.
The sensor uses a directional infrared LED beamed at a sensor that shoots past where you'll walk. When you interrupt the light from the LED, the LEDs turn on for a period of time that you can adjust. There are a lot of advantages to using IR LEDs over lasers; they're safer to work with since lasers can damage your retina if you stare at them, they're a lot easier to aim since you're pointing them at a small sensor usually across a hallway, they use really low power, and of course they emit no visible light which makes them stealthy and therefore cooler. The biggest drawback? Sunlight or incandescent lights generate infrared light, so if you put them in an area where they get hit by this light they won't turn on. I actually feel that this is an advantage as well, since it keeps them off during the day when you don't need them.
Please note: this project is designed to assume that you have at least a basic knowledge of electronics, electronic schematics, and know how to handle and mount static sensitive devices. You need to know how to solder, and more importantly how to solder on tiny chip leads that can only handle a brief hit of heat before they fry and turn into slingshot ammo.
Play the high def video. I'm a terrible cameraman so sorry if it's shaky!
The sensor uses a directional infrared LED beamed at a sensor that shoots past where you'll walk. When you interrupt the light from the LED, the LEDs turn on for a period of time that you can adjust. There are a lot of advantages to using IR LEDs over lasers; they're safer to work with since lasers can damage your retina if you stare at them, they're a lot easier to aim since you're pointing them at a small sensor usually across a hallway, they use really low power, and of course they emit no visible light which makes them stealthy and therefore cooler. The biggest drawback? Sunlight or incandescent lights generate infrared light, so if you put them in an area where they get hit by this light they won't turn on. I actually feel that this is an advantage as well, since it keeps them off during the day when you don't need them.
Please note: this project is designed to assume that you have at least a basic knowledge of electronics, electronic schematics, and know how to handle and mount static sensitive devices. You need to know how to solder, and more importantly how to solder on tiny chip leads that can only handle a brief hit of heat before they fry and turn into slingshot ammo.
Play the high def video. I'm a terrible cameraman so sorry if it's shaky!
Remove these ads by
Signing UpStep 1: Tools, parts, and supplies
You'll need a variety of stuff to do this project. The less tools you have for working with electronics, the more you'll have to spend to make it, so either buy all the tools, or find someone that has them and buy them a nice lunch at Applebees then ask nicely if you can use their tools.
Tools you really should have:
-A soldering iron with a small point tip
-A small pair of wire cutters
-A small needle nose pliers
-Wire strippers (You'll be stripping really small gauge wire, 26 or less)
-A Dremel motor tool with a carbide cutter (for cutting the perf board and drilling holes)
Most of the electronic parts can be bought from Mouser Electronics. I'll list the supplier that I got various other supplies from for other parts. Feel free to innovate if you can find a better/cheaper place to get something, and post it here for all of us!
Supplies/parts:
-Plastic Leg Tips (Home Depot, 89105)
-1/4" coaxial cable staples (home depot psw-1650)
-Solder Wire
-Pre-punched perfboard ( Radio Shack 276-1396 A)
-50 ft PS/2 extender cable ( Monoprice p/n 2540)
-White electrical tape (Frys)
-A 5 volt power supply capable of handling at least 700 mA, or more depending on the power requirements of your light LEDs. I used a power brick from an old zip 250 drive, that puts out 1 amp at 5v.
For electronic parts, you can download the excel spreadsheet of the components I used by clicking the excel spreadsheet I linked here. To make your life really easy, create a mouser account, click here, select the second and third columns of the spreadsheet and copy and paste them into the BOM importer.
2x 940nm IR LEDs: you can get these at mouser as well, but I found the best directional LEDs I could get came from Newark Electronics. If you want to sub in another LED for these, you'll need something that operates at 940nm and is fairly directional (to prevent it from dissipating over the distance to the sensor).
You'll also need a bunch of LEDs for your stairs or whatever room you want to light up. Once you choose your LEDs, you can plug in the specs for them here to calculate what resistors you'll need and how to configure them.
Overall, you should be able to do this project for about $60 as long as you don't destroy components while building it. If you're prone to soldering chips to kingdom come, make sure to buy spares.
Tools you really should have:
-A soldering iron with a small point tip
-A small pair of wire cutters
-A small needle nose pliers
-Wire strippers (You'll be stripping really small gauge wire, 26 or less)
-A Dremel motor tool with a carbide cutter (for cutting the perf board and drilling holes)
Most of the electronic parts can be bought from Mouser Electronics. I'll list the supplier that I got various other supplies from for other parts. Feel free to innovate if you can find a better/cheaper place to get something, and post it here for all of us!
Supplies/parts:
-Plastic Leg Tips (Home Depot, 89105)
-1/4" coaxial cable staples (home depot psw-1650)
-Solder Wire
-Pre-punched perfboard ( Radio Shack 276-1396 A)
-50 ft PS/2 extender cable ( Monoprice p/n 2540)
-White electrical tape (Frys)
-A 5 volt power supply capable of handling at least 700 mA, or more depending on the power requirements of your light LEDs. I used a power brick from an old zip 250 drive, that puts out 1 amp at 5v.
For electronic parts, you can download the excel spreadsheet of the components I used by clicking the excel spreadsheet I linked here. To make your life really easy, create a mouser account, click here, select the second and third columns of the spreadsheet and copy and paste them into the BOM importer.
2x 940nm IR LEDs: you can get these at mouser as well, but I found the best directional LEDs I could get came from Newark Electronics. If you want to sub in another LED for these, you'll need something that operates at 940nm and is fairly directional (to prevent it from dissipating over the distance to the sensor).
You'll also need a bunch of LEDs for your stairs or whatever room you want to light up. Once you choose your LEDs, you can plug in the specs for them here to calculate what resistors you'll need and how to configure them.
Overall, you should be able to do this project for about $60 as long as you don't destroy components while building it. If you're prone to soldering chips to kingdom come, make sure to buy spares.
Visit Our Store »
Go Pro Today »
if you're considering doing this project, beware that 7 and 14 on the HEF4071B are flipped. if you follow the schematic included in this instructable to the letter, you'll have a fried chip.