Limit Switch

How can I connect a limit sensor switch to crane

What does it limit, the hydraulic system or electrical.
Need a lot more details.
If this is an important safety feature, then it needs to be done with a great deal of attention to detail. For example, does it need multiple redundancy.
Usually this sort of system has to be mechanically very robust, use high quality connectors, immune from getting scraped off, and any wiring or hydraulic lines need to be mechanically protected as well.
We have logging machines in the area, they are always having to do on site repairs of limit switches.
Cheers,
Richard

A stopper in between the boom and the chain block
To prevent the chain block from touching the boom

A stopper in between the boom and the chain block
To prevent the chain block from touching the boom when lifting up an object

Do you know anything about electrics, and do you have access to a mechanical workshop. To do this work you will need both. I can't tell you how to do it, since I have no idea of the specifics. I would say that a mechanical switch would probably be the best, but the mechanics of how that is arranged I cannot comment on. The switch will have to turn off the power in the up direction, but when you lower the block, the switch has to be bypassed, so you have a bit of logic to work out around the up/down switching.
Cheers,
Richard