Good grief I've just noticed that I have been made a 'senior member' (so hopefully I know what I am talking about!). Thanks to the forum pixies for recognising my contribution to the World of C-bus. We have just finished being involved with a job where the 5753PIRL unit is being used to switch on (PIR function) then control the LUX (LL Function) of rooms and open areas of an office block. The Fluro Lights are being controlled by DALI ballasts and getting the system to work correctly was not as straight forward as it might have first appeared. 1. The 5753PIRL issues 'ramp up' or 'ramp down' commands in response to the ambient light level being measured by the 5753PIRL as being lower or higher respectivly than the target level programmed in to the 5753PIRL. 2. The ramp rate set in the PIRL (and the 5031PE) is of the order of 60sec from 0-100% or 100-0% 3. The PIRL has a 4 second buffer (slug factor) built in to that it ignores any change in measured light level for less that period of time (ie a cars headlights sweeping across the room or a worker in a white shirt walking under the sensor and reflecting up more light than the, say, gray carpet does etc) 4. The DALI ballast can be programmed (using WINDIM or equivalent from Tridonic of other DALI manfacturers) to either turn on/off or ramp up/down not both and the default ramp rate is 8secs. If you want to control the brightness of the load you need to select the ramp option and note that it doesn't matter that the ramp rate from the PIRL is 60sec the DALI sees the initial 'on' command and ignores the 'over 60secs' bit. Think about that little lot for a moment. So the situation is, you walk in the PIR detects you sends out an on command but the DALI ballast can only have been set to ramp (see 4) the light ramps to 100% over 8 seconds but probably will pass the target set in the LL. But the 4sec delay means that the LL will not react until the light level is way above the target so a ramp down command is issued and the light gets dimmed down and again shoots past the target - it finally settles down after a few excursions. Well there are two options: reduce the 4 sec 'slug time' in the PIRL (not currently available as a variable) but this would mean that the loads would dim up and down as people in white shirts walked around the room/office. So not a real option or increase the DALI ballast ramp time so that the 4sec slug becomes less significant (ie set the ramp rate to ~60sec and everything is sweet. But (!) because the DALI can only be set to switch on/off OR ramp up down this would mean that as you walk in to the room the PIR send out an on command and the DALI can only then ramp up from 0% to the target (or 100% - which ever is the lower) over the 60secs so you are left standing there as the lights slowly come up around you (in fact you could walk in and out of the office a couple of times and the lights may still not have reached the target brightness) this is not only inconvenient but also may have Ocupational, Health and Safety implications. There is no happy ending. Untill the DALI guys allow their Ballasts to be turned on and then dimmed down to a target level (which is what a totally C-bus sollution would allow if you were using incandescent lights or fluros run by DSI or 0-10Vdc ballasts) to give you a bright room that then goes to the set level making the room conveniently bright as you walk in and safe so you won't trip over the wast paper basket the only option is to use as short a DALI ramp time as is possible (given the over and under shoot issue) while still bringing the lights up quick enough to met any OH&S issues. If anyone has any better solutions (ie if there is some way of setting the DALI ballast to on/off then ramp up/down) please post it here.