Here I am with a new tutorial of redstone. It is based on an automatic portal to the nether and it is an automatic door for your house, here are some examples of when it is on and when it is of (NOTE: make sure you don't have any blocks on the top of the sand)
For this door you will need:
-A redstone block
-8 sticky pistons
-2 redstone repeaters
-9 items of redstone
-6 blocks (that have no gravity)
-A redstone torch.
-And a button
First you have to put 2 blocks and the button
Then you have to put a block, a redstone repeater on the block, Then a sticky piston and on the sitcky piston a sand block or a gravel block.
After that you will have to put a sticky piston and next to it a redstone block, to wich you will connect a redstone signal and a redstone repeater next to a block.
Next you will have to put a redstone item two blocks in front of the redstone repeater, a redstone torch next to it and a bloack next and up of the redstone torch.(on the block next to the redstone torch goes a redstone item)
At the end you have to put 4 blocks of redstone in front of the blocks an the redstone and on one side you put two blocks of sticky pistons
Now you only have to put two blocks next on the sticky pistons (NOTE: look at he left side of the sand block and make sure you have that block with a redstone repeater on it)
And thats all guys now you have a semi-automatic door that can be used in your house. Bye!