Logic explaination... please...

Hiya..

Got a fairly simple request. I am trying to get my head around programming logic. I can sorta figure out how it works and can pretty much use it to switch multiple channels with one group address.

What i am asking is if someone could explain is the most laymenest of terms (for lack of a better word) logic to me. Particularly AND and OR functions and when to use them and what they mean....

Thanx mucho in advance...

Cheers

 

The AND function requires all the states to be true before the output will be true. Why would you use it, well cannot think of an example but sure there are 1000's of them.

The OR function only requires one of the input states to be true.

Not to confuse things even more, outside C-Bus but with logic there are many others logic funcions too. There is the exclusive or function (XOR) which needs one or the other inputs to be true, but not both, or if using more than two inputs not all. And then there are the negatives of all the above, which require the states to be the oposite before the output become true.

 

Logic functions in C-Bus output units allow you to control output channels a bit more intelligently. Without logic you can have every channel linked to its own group or multiple channels linked to a single group, but there is no way you can have single channel linked to multiple groups.

Using logic you can make single channel "listen" to states of two or more groups. For example, you may have a requirement to program 2 channels and 2 single key units to operate on lights in conference hall and its entrance. So you could have

Channel 1 = "Conference Hall Entrance lights"
Channel 2 = "Conference Hall lights"

Key 1 = "Conference Hall Entrance lights"
Key 2 = "Conference Hall lights"

Both lights operate independently in this set-up. Now imagine you had a rule in that requirement "make entrance lights be on, when conference hall lights are on". To implement this you go to Logic tab of the relay unit, tick one checkbox for Channel 1, select the logic group against it to be "Conference Hall lights" and set the logic function to OR, which emulates switches in parallel.

If you had 4 channels serving conference hall lights (i.e. Hall Centre lights, Hall Podium lights, etc), you would then need to use all 4 logic groups to implement that rule.

AND logic functions means that a channel will be on only when all groups participating in logic operation are on. Basically it emulates series connection of switches.

There is a small difference in how logic functions work in dimmer output units. If Max (which is OR or "greater of") is selected, then the channel level is set to the level highest in groups participating in logic operation.

If Min (which is AND or in other words "lesser of") is selected, then the channel level is set to the level lowest among levels in groups participating in logic operation.

Regards,
George

 

That's Illogical Captain

Another way to think of AND Logic is to think of a series of switches in a row with a light bulb hanging off the end (asume the supply and neutral). Now for that light to work ALL the switches must be closed if any one of them is open the light will be OFF. Now imagins group addresses insted of switches and there you have it - when you AND logic 2 or more group addresses they all need to be ON for that particular relay channel to come on.

With OR logic it is as if the switches are wired in parellel rather than in series so that if any one switch is ON the light will be ON - ALL the switches must be OFF to turn the load off.

If you are just turning Dimmer Channels ON and OFF then dimmer logic is the same as for relays with MIN logic giving you the equivalent of AND - and MAX logic giving you the equivalent of OR.

The difference comes where you have one (or more) of the group addresses that are logically associated set to a level other than 0 or 100%. If you have selected MIN logic then the load will be dimmed to what ever group address has the lowest level (including OFF if the lowest level is 0%).

If you have selected MAX logic then the load will be dimmed to what ever group address has the highest level (including full ON if the highest level is 100%).

For those of you old enough to remember the good old days of V1 software you will know that rather than use the terms AND, OR, MIN or MAX we used + for OR and - for AND (!) and never mentioned MIN and MAX even though you could program the function in dimmers, they were marked + and - just like in the relays - boy have we come a long way!

 

Example on this site

http://www.play-hookey.com/digital/basic_gates.html


Colin Smith

 

Logic Group

what happens when you run out Logic group space
there is only 4 rows on a Dimmer

 

That's a bit like asking what do you do when you come to the end of your drink, isn't it?

Seriously though, the DIN mounted dimmers and relays have 4 groups of logic. Once you've used these up there aren't any more.

If you need more complicated logical functions in your C-Bus installation then you can consider adding a device that has the C-Bus logic engine built-in, such as a PAC or a Touchscreen with logic. These devices allow you to perform just about any logical function you can dream up.