Oregon Trail Should Have Prepared Me For This

DIY $7 Night Vision Baby Monitor

Checking the kid on my iPod Touch.  See sample video at bottom!

The Problem

This project had simple motivation: I wanted a video baby monitor, and I didn’t have a lot of money.  I didn’t need sound, as the baby’s room is right next to ours, but I didn’t want to have to get up every time I heard him cry to see if he’s okay.  There are great products out there if you’re willing to throw down $100, but I’m a grad student with a budget.

 

 Thinking of a solution

My first thought was just to train a webcam on him, but I didn’t want to have to shine lights in his face all night.  So, I needed a way to see in the dark.  In my brief research, I found two basic ways people do night vision.  One is to use photomultipliers, which basically just shine 10 photons of light at you for every one its sensors see.  Good for military night vision, bad for us.  The other is to flood the area with IR light and use an IR sensitive camera to detect it.  This is easy enough, but where do you find an IR sensitive camera?  Well, between your phone, webcams, etc. you already have a lot of them. 

The IR Webcam You Already Own

The light sensors on digital cameras are sensitive to a huge range of light, ranging from the IR spectrum through the visible and a bit into UV.  To achieve their goal of only capturing visible light, digital cameras put IR filters somewhere between the lens and detector.  These aren’t perfect (you can test your remote control by pointing it at a webcam and you should see a faint white light), but they block out most of the IR.  Basically, to make an IR-sensitive camera you can just take an average webcam and remove the IR filter.

The Big Picture

So what we’re going to do here is remove the IR filter from our webcam, make some USB-powered IR lights, and broadcast the webcam feed over our local network.  By the end, you should be able to view your night-vision webcam on any computer, smartphone, iPad, iPod Touch, PS3, or anything else on your network with a web browser.

Parts List

3 IR LEDs ($0.60, 20 pcs for $4)

1 25 ohm (or greater) resistor ($0.01, 1000 for $7.50 on eBay)

1 USB Cord ($1 at any dollar store.  Get an A/A (Male/Male) one and you can use it twice!)

1 old useless CD (come on, you know you have one)

OPTION A:

1 Super Cheap Webcam ($5, I used a Creative Live! Cam Vista Webcam.  Works fine, easy to remove filter, does NOT work with Mac OS).

1 Old computer (Everyone has an old laptop around, right? If not, you could just not use your laptop when baby is sleeping.)

OPTION B:

1 Wireless Wifi IP Webcam ($50ish on eBay.  I haven’t used them, so good luck.)

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Total Cost = about $7 with an old computer.

                   = about $50 with an IP webcam

Step-By-Step

Step 1:  Remove your webcam’s IR filter.  There are a few good sites describing how to do this.  For the webcam I used the hardest part was opening the case, and that wasn’t bad.  After that, I just unscrewed the lens until it came off and the IR filter popped right out.  Try here for help, or just google it!  http://www.hoagieshouse.com/IR/

The ridiculously simple LED light circuit diagram in poorly-focused picture form!

Step 2: Weld together the IR lights.  As with my flashing alarm clock demo, I like to set LEDs in old CDs because they are rigid, easy to work with, and you probably have a bunch lying around.  They also have a hole in the middle convenient for putting the lens of a webcam through.  For the power, just take scissors and cut your USB cord in half.  There should be 4 wires inside.   Red is +5V and black is 0V/ground.   The white and green wires are for data: we won’t be using these. 

The CD happens to have a convenient lens-sized hole right in the middle!

View from the back.  I used electrical tape to hold it together before I bought a glue gun, so forgive the black junk.

(Note: I really like using USB power supply for all sorts of electronics projects.  One is because years of cameras, cell phones, etc. have left me with a handful of ACàUSB converters.  The other is that if I utterly destroy the USB cord, they’re cheap and easy to replace.)

Step 3: (Note: If you’re using the Wifi IP Webcam approach, you don’t need this). Get some software that lets you broadcast your webcam on your local network.  I found Yawcam to be super convenient and easy to use.  In Yawcam, it’s the “Stream” option that you’re looking for. 

Step 4: Fire up your Kindle, iPhone, Laptop, or whatever and point it to whatever address Yawcam tells you.  For sanity’s sake, try not to be too compulsive checking it!

Video feed during an afternoon nap

Video taken at night.  The blanket at the bottom is actually 

blue with white dots, but in the IR it all looks the same.

$5 Flashing LED Light Alarm Clock

Don't mind the crying kid in the background

I had two basic problems that led me to this project:

1. I needed something to wake me up without waking up my wife.  (Headphones fall out of my ears overnight.  I thought of that.)

2.  I hate the sound of alarm clocks.

My answer: the LED light alarm clock! LEDs are problematic for normal lighting because the light is only bright within a narrow range.  For us, this is perfect as it lets us focus the light on just one person, letting the co-sleeper snooze on.

Parts and Cost:

1 Cheap Alarm Clock ($1.99, eBay)

5 White LEDs ($0.35, 50 for $3.29, eBay)

1 2N3904 (or other NPN) Transistor ($0.20, 15 for $2.99, RadioShack)

1 8 ohm Resistor ($0.01, 1000 for $7.50, eBay)

1 2 x AA Battery Holder ($1.99, RadioShack.  abt. $0.50 on eBay)

2 AA Batteries (You probably have some around)

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Total = About 4 or 5 bucks

Warning:  Some of this goes against good electronics practice.  Just so you know (see step 3).

The basic concept here is that somewhere in your average alarm clock is something that makes sound.  For it to make sound, it needs pulses of current.  Using a transistor, you can use that current to switch on current for whatever you want!

The left circuit is the part built into the clock.  The right circuit is the new part.
The question marks stand for whatever is going on inside the clock.  We don't need
 to know how the left part works, just that when the alarm goes off we get current. 

Step-By-Step:

Step 1: Open your alarm clock, find something that looks it makes sound.  Use your multimeter to figure out which side is giving it positive current and which side is negative.  Cut out the sound part

Step 2: Connect the positive side to the base of the transistor.  Connect the negative side to the emitter.

Step 3: Connect the LED circuit as shown in the diagram.  The positive end goes to the collector, and the negative to the emitter.  I use old CDs to set the LEDs because they're rigid, easy to put holes in, and I have a stack of 50 CD-Rs that I'll probably never use in the thumb drive/MP3 age.

 

(Note: Using just one current-limiting resistor for the whole LED array isn’t really a great idea.  Here, the 8 ohm resistor limits the current to (3 V – 2.2 V) / 8 ohms = 100 milliamps.  We just assume that the current will divide evenly giving us 20 milliamps per LED.  With variation among LEDs, it might not be evenly split.  Also, a bigger problem is that if one of the LEDs goes out we still have 100 milliamps, but only divided 4 ways. This gives us 25 milliamps each, which is more than the LEDs are rated for.  It would be better to use a resistor in series with every single LED.  I just didn’t feel like it at the time.)

Step 4: Enjoy!

Just a normal everyday alarm clock

The LEDs.  Get some use out of that stack of CD-Rs you'll never use!

Don't try to take this on a plane, it might look awfully suspicious.