In my spare time I like to make stuff. One of my best devices is my automatic door opener. It opens your door when you put the access card over the switch. Your door still can be pushed open or closed, so this won't cause any problems.
(clip-art used was from free clip-art sites)
Step 1: Materials
-An old RC car (I used an old batman one)
-Alligator clips/Nine volt battery clip(useful to connect to nine volt battery, if that's what you're using.)
-Strong, thin magnets (neodymium work well)
-Old Credit Card
-Poster board (paper could be used, but isn't as strong)
Step 2: Take apart the RC car
First thing to do is to take apart the old toy car and get the motor with the wheels still attached . You need a big and strong motor so that it can push the door.
Step 3: Make the Switch
To make the switch you need to get a piece of poster board. You should cut out a piece that is 4"x2". Tape a piece of aluminum foil onto the poster board so that the middle is not covered by tape. Next, roll up a piece of tape sticky-side out. Cover the sticky part with more tape. Now, test if it is springy, or pops up when you squish it. It only needs to spring back a little. Next, take your paper clip and bend it into the shape in the pictures. It basically is straight with bends on each end. You should tape it down, like in the picture. It is hard to put into words, so follow the picture when in doubt. After this, strip a wire and tape it onto the end of the foil opposite the paper clip, as in the picture. Twist another wire around the paper clip and tape it in place. Now your switch is done.