How to keep an entry gate operating during a power outage

It sounds like you're using keypads to control sets of lights. Two important things:

Label the buttons well and Keep it simple and consistent.

For example, if you're using scenes, have the buttons say the name of a scene that makes sense, depending on the location. If there's a keypad in the hallway outside the kitchen in the living room, make sure it's clear which scenes control the kitchen, and which control the living room. Also, if you're using scenes, avoid mixing button types; eg, having "dim" and "bright" buttons in addition to scenes is confusing.

I'd also echo @Rob Napier's point that reliability is a huge factor. If you press a button and it "sometimes" works, it will just lead to frustration (in effect: don't use X10).

Also along the lines of being consistent, pick one or two different types of switches, and stick to those. If you have a mix of toggle switches, rocker dimmers, 6-button and 8-button keypads, it's just going to be confusing. Standardize on a manufacturer and style, and stick to it.

The other obvious thing is really talk to your users. Make sure you know what they typically do, and adjust the system appropriately. Maybe they always go into a room and want a certain light on at a certain level, but you never do .. make sure you talk to that person so you know to set it up so it works they way they expect.

In an attempt to answer some of the questions raised in your posting let me respond in answer format.

1) It can be advantageous in some situations to affix a timber post to the brick or concrete posts/walls in either side of the gate opening. This post can then serve as a better medium into which to attach hinges and latches.

2) A 3.8 meter wide gate will develop a huge amount of lever arm out at the latch end of the gate and this needs to be taken into account when developing the gate design.

3) The size of wood used can play a big part in how heavy the gate will end up being. The type of wood can play a role as well. This is one reason that boards are often used for gate facing instead of thicker planks. Cedar wood is also much lighter than hard wood like oak and thus becomes a popular choice for gates.

4) Adding appropriate bracing into the design of the gate will keep the gate from sagging.

5) Successful wide gates can often benefit from making the aforementioned side posts much higher than the gate opening and then using a cable from the top down to the end of the gate away from the hinges to help support the weight of the gate. Sometimes you can see the tops of the two higher posts connected across by a horizontal member. This provides support from post to post to keep the weight of the gates from pulling the posts to the sides.