We’d suggest using a control system for this to simplify the cabling and improve the dimming.
One of the challenges here will be dimming a small number of low power LED lights. We’d suggest using the 0-10v protocol for the best dimming performance and the kind of fixures we might use would include LD64 and the LD42 family. All of these perform well as staircase accent lighting with the LD64 being a versatile floor washing fitting as seen lighting this curved London staircase. These wouldn’t work however if the treads rather than the balustrades were glass.
The complication with “conventionally” wiring the setup you’ve been asked to look at is the interaction of the 3 different switching locations and the PIR. One way to bypass those issues is to use a control system to give independent control to each location and the PIR. One way to achieve this would be to use Rako which is a flexible lighting control system that can be used to control a small number of circuits without the need for a central control processor. A lighting control system could be employed to control this particular circuit of lights but a lot of the benefits come from wider control across the property. This article is an introduction to lighting control.
You would need a Rako 0-10v dimming module, a Rako relay module (to take an input from the PIR) and three Rako wall switches – they are available in a number of keypad configurations to suit the number of different lighting scenes you want to achieve.
If you’d like any more details on Rako please give us a call.