cupoftea
Advanced Member level 6
Hi,
We all know DALI comms can do a bus wire length of up to 300m.
Also, that any ballast at say the end of that wire, if it wants to communicate back to the controller, then it does so
by sending a stream of bits, the zero of which , is literally gotten by
crudely shorting the cable to its own ground return with a transistor!
The main terminal has an 80mA (can be as high as 250mA!) current clamp at its connection to the DALI bus, so the short circuit current
is limited to 80mA.
However, thats a pretty high current to be pulsing on and off in a 300m wire cable!
There tends to be no rise time reduction in the DALI circuitry, So how does DALI get away with being such a noisy
comms protocol?
We all know DALI comms can do a bus wire length of up to 300m.
Also, that any ballast at say the end of that wire, if it wants to communicate back to the controller, then it does so
by sending a stream of bits, the zero of which , is literally gotten by
crudely shorting the cable to its own ground return with a transistor!
The main terminal has an 80mA (can be as high as 250mA!) current clamp at its connection to the DALI bus, so the short circuit current
is limited to 80mA.
However, thats a pretty high current to be pulsing on and off in a 300m wire cable!
There tends to be no rise time reduction in the DALI circuitry, So how does DALI get away with being such a noisy
comms protocol?
