With a puppy and a full grown dog, both of whom prefer the garden to the house, it is a never ending job letting them in and out. As the weather is cold at the moment leaving the door open is not an option and I need to be able to be elsewhere in the house.

A tech solution was required, the remit is:-

A door opening and closing device that will also hold the door ajar if required.
The door must be capable of normal use.
I must be able to operate it from another room (using a web cam to monitor).
Once dogs are shown how, they need to be able to open door themselves.

Step 1: Design Time - Parts

The obvious operating device would be a 12volt jack, similar to the ones used to move a satellite dish.

The one I found was from a mobility bath lift.
A power supply to run it

Some extra odd and ends

Some microswitches to limit the movement..
High strength magnet for the catch.
Some diodes For restarting in the oposite direction.
Door latch catch.
and something to control it with.

Step 2: Design Time - Drawings

Once I knew what the parts looked like it was time to design the hardware and electronics.

The drawing of the hardware may not mean much to people looking at this but took a number of hours to get right. :)
A GA shows what it would look like.....

The electrics drawing shows 2 microswitches at the top, each has a diode wired between the normaly open and normaly closed contacts, the diodes allow the motor to restart when the direction of the ram is reversed.

The second wiring diagram shows the addition of a manual..or dog operated... switch to the existing wireless remote setup.

Step 3: Build It! 01

Lots of metal cutting and welding then ensued, starting with the pivot and magnetic catch.

Once the small catch plate was built the parts were test fitted on the door, it is very inportant that the centre line of the door closing pivot is on the centre line of the door hinges or none of this will work correctly.

Step 4: Build It! 02

The limit switches were mounted on a piece of scrap bath panel. The other parts, brackets and rod to make it work come from the scrap box....
All held in place with jubilee clips which makes it nice and easy to adjust once in situ..

Step 5: Instal It!

Once it was assembled onto the door a rain cover was made from twinwall plastic sheet and a piece of electrical ducting, this too was installed.

A quick bit of wiring up to a 12v battery had the ram going in and out and the limit swiches were adjusted.

Step 6: Latch Catch :)

For the door opener/closer to work the existing door catch needs to be held back so that it will not latch the door closed.
The UPVC door frame has a couple of handy grooves down the side that are ideal for a sliding catch catch, a little bit of work with a craft knife at the top of the door allows the catch catch to slide into place.

I popped in a catch catch catch (little piece of bent plastic :) to prevent the catch catch from sliding too far down the door.
At night the catch can be locked in the normal way.