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

-A door(obviously)
-An old RC car (I used an old batman one)
-Wire
-Paper clip
-Aluminum foil
-Scotch tape
-Electrical tape
-Batteries
-Alligator clips/Nine volt battery clip(useful to connect to nine volt battery, if that's what you're using.)
-Wire Strippers
-Scissors
-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.

Step 4: Make the Key/Access Card

To make the key/access card you need your old credit card and magnets. Tape the magnets onto the bottom middle of the old credit card with the polarities all facing the same directions. Then, cover it with paper so that it looks good. Add a label or drawing on the side opposite the magnet side, and cover it with clear tape to preserve it. When you put the card over the switch, the magnets will attract the paper clip, which will touch the foil and complete your circuit!

Step 5: Attatch the Motor

To attach the motor, I used electrical tape. I put tape on the door above the motor and then onto the motor and under the door. I did this twice because I wanted it to be strong. You also need a spacer of some sort in-between the door and the motor so that you can easily push it open without the wheels jamming against the door. (This is kind of unclear until it actually happens to you). I used a dead AA battery because it was laying on the floor of my room and it was the right size.Tape this spacer in place from the top and the bottom and go crazy with the taping so it doesn't fall out all the time like mine did, which was very annoying.

Step 6: Add the Battery

To add the battery, first you need to know what the voltage of your toy car was. Mine was 4.5 volts, but I bumped it up to 9 volts to keep things simple and to make it stronger. I know this might burn out the motor, but it has worked for a while and will work longer. To attach a battery, just electrical tape it onto the door, and then secure the ends with a piece of tape perpendicular to the first. You can repeat this as many times as it takes for you to think that it won't fall. Then, for a nine volt battery, use the connector clip or alligator clips to attach some wires to it.

Step 7: Hook Everything Up

Now you need to connect the wires. To make a connection, just twist the wires together. I usually cover it in electrical tape too. The first connection should be the battery to the motor. Then you should connect the other wire of the motor to the switch. The connect the other wire of the switch to the battery. There is a diagram for the step's picture as well to make it easier. In many places on the door, it is good to tape the wires in place so that they don't pull on the switch and possibly damage it.

Step 8: Test It!

Try putting the access card over the switch. The door should open. If it moves the wrong direction, then reverse the polarity of the battery. I once tried to make another switch to make the door shut, but ended up shorting out the battery,(which then made a sizzling sound) so I haven't tried again yet for fear of starting a fire.

Step 9: Trouble-Shooting

My door is going the wrong way!:
You need to reverse the polarity of the battery
The door won't move!:
The first thing to do is test the battery. Try hooking up a new one or testing the old one with a battery tester. Another possible problem is a loose connection. Make sure your wires are connected well. Also, you motor may not be strong enough to push the door.