DIY Web Chat Hack

Remotely Control Home Devices via Internet

By Lee von Kraus
MAKE Projects

dog Lee von Kraus hacked up this inexpensive and easy way to control motors, lights and other devices at home from another computer online, like the one at work. The system can be set up in minutes and requires no programming. All you need is a webcam, a flashlight, a standard computer running free software, and about $15 worth of analog electronics. This self-made control system works through a video chat connection between two computers. Instead of videoing people talking, the video stream activates a photosensor, which in turn powers a device. With the author's setup, a light shone in the upper left corner of the image powers a dog dish, and shining it in the lower right sounds a buzzer to signal dinnertime, and voilá! Happy dog!

Assembly Time: 1 hour
Skill Level: Beginner

Required Tools:
Soldering iron

Parts List:
Transistors, 2N2222 NPN
Wrapping wire, 30 AWG
Electrical Tape
Computers (2)
Power supply
Surge protector
Piezo buzzer
H-bridge motor controller IC
PIC microcontroller
Cardboard box
Dark, flat surface

Computer Schematic for Home Monitoring via Internet

Step 1: "Home" Computer Set Up

A. Have two separate email addresses prepared, one for your home computer and one for the remote computer. On each computer install Yahoo Messenge, and set-up two accounts with matching names, one ending in "home" and the other ending in "work."

B. Log into each account from the respective computers, add them as friends for each other, and configure the webcam preferences to "Allow everyone to view my webcam" and their Super Webcam preferences to "Start Super Webcam mode automatically."

C. You'll need one photoresistor for each device you want to control. Solder or wire-wrap a long length of wire to each of the two leads of the photoresistor. Following the schematic above, set up a power circuit for each device on a breadboard. Be sure that all of the power supplies are plugged into a surge protector.

Note: If you're using higher powered devices you may want to insert an additional transistor/relay (2N2222 transistor is ok up to about 1 amp).

D. It's a good idea to test the switching for each device by covering and uncovering the photoresistors with your hand. Use electrical tape to tape the photo-resistors, sensor-side down, on the computer screen, spaced apart. Adjust the screen brightness to a level such that the devices switch off when the screen is black.

Photoresistor Photoresistor Prepared to Tape to Screen


Lee found that sometimes he had to put a piece of paper between the photoresistor and the screen to reduce the light. He also recommends putting the computer screen in a box to exclude non-screen light that could interfere with the sensor readings. If possible, point your home computer webcam at the devices so you can remotely watch what's happening.

Home computer shown with photoresistors taped and hooked upHome Computer Shown with Photoresistors Taped and Hooked Up

Step 2: "Remote" Computer Set Up

A. At the location of your remote computer, connect a webcam and set it up so that it looks at a dark, flat surface. Lee used a PVC stand that he made for the camera and pointed it down onto a black T-shirt (below).

Remote ?controller? set up Remote "Controller" Set Up

Step 3: Establish the Connection

A. On your remote computer, open Yahoo Messenger. Next to your home username, select "View My Webcam" to open a webcam fee, and leave it running.

B. On your home computer, click to view your work video feed. Change the window size so it fills your home computer's screen or at least covers the area around all the sensors.

At the remote computer, shine a flashlight into the camera's field of view at different locations to activate the devices controlled by your home computer screen (demonstrated in picture above).

Step 4: Recommendations

Test your system for a full day before you put it to use while you're away. Because it's based on analog sensors taped to a screen, there are little ways in which the "real world" might interfere with it. For instance, the photoresistors might fall off, or be triggered by changes in daylight coming through the windows.

Step 5: Taking It Further

For more complex control, you can connect the sensor signals to a microcontroller. The author connected the transistor outputs to a PIC microcontroller and H-bridge motor controller IC that run a simple motorized dog food feeder with a piezo buzzer. Both could be connected directly, as shown in the diagram in Step 1, but he put a PIC in the loop to allow more complex outputs in the future.

Remotely controlled puppy feeder
Remotely Controlled Puppy Feeder

Where's the MORE button?
"Where's the MORE button?"

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