I have a brand new automatic litter box for sale- if you type Petjc into Taobao you should find it and can see how it works. It detects your cat's weight when they go in and automatically spins/cycles the used litter into a bottom compartment after every use, so you just change the trash bag whenever it tells you the bottom compartment is full and don't have to scoop. It stops spinning if it detects weight so it's very safe even if your cat jumps in mid-spin. It's pretty similar to the Litter Robot in the US which I had before and works just as well.
But it's about 20-30% smaller than the Litter Robot especially in terms of height and it's too small for my giant American sized cats (12lb) to use comfortably. If your cats are normal sized HK cats it will work.