DALI Dimming - Page 1
Forum section: electronics / beginners

author: Harsh Chandola
author_rank: Contributor
timestamp: April 05, 2017, 05:05:14 am
content: Hello All,I am designing a Lighting system with DALI dimming. I am new to it,so been reading about it, I have done some research on it but am failing to understand a lot of things like how would individual lights be controlled differently. How is addressing done etc. I d be obliged if somebody can explain the whole concept and designing or direct me to a tutorial and/or a website that explains DALI from scratch and has a few design examples too.Thank You All.

author: clack
author_rank: Newbie
timestamp: April 05, 2017, 06:51:39 am
content: I have researched DALI before and it is difficult to find information. It is one of those systems that you need to fork out for the spec from the standards body (IEC 62386-101:2014 costs 300CHFhttps://webstore.iec.ch/publication/6954) which I can never afford to do! would be interesting if anyone has any information about it, this is my very obvious findings.I found very general information that skips over electrical and protocol informationhttp://www.artisticlicence.com/WebSiteMaster/User%20Guides/the%20dali%20guide.pdfhttps://web.archive.org/web/20130627012349/http://www.dali-ag.org:80/c/manual_gb.pdfThe line is a 2 core cable that is powered by a 16V PSUThe devices communicate by shorting the cables together.High Logic Value shall be 16V (9.5V to 22.5V DC)Low Logic Value shall be 0V (-4.5V to +4.5V DC)The protocol is Manchester encoded at 1200 baud (that is slow!)Serial Data: 8 bits, 1 start bit, 4 stop bitspacket is address:message:datalooking at the commands it is all plain text, I dont know if this is because its simplified for the reader of if it is actually sent ASCII which would be oddThere is a discovery system for setting up all the addresses and setting scenes but I have not seen the commandsI also don't know how it achieves the duplex communicationHere is a python script that works with DALI, could be possible to use it to see how it works?https://github.com/sde1000/python-dali

author: Harsh Chandola
author_rank: Contributor
timestamp: April 05, 2017, 07:25:53 am
content: I have gone through both the links, they were quite helpful in understanding the concept. What I am looking for is basically a tutorial for it. An analogy would be : like, for example; for micro-controllers we have blinking LED examples, something like that, so that I could grasp what all parts are required to implement DALI, for example, I want to know about ballasts and how they are integrated with DALI, how is dimming actually done, how are addresses assigned, how do I tell controller which luminaire to dim, turn on/off etc., what do we have exactly on the control side. On internet there are mostly block diagrams everywhere. However, some links are helpful but an exact image of this protocol is still not clear in my mind. At most places companies are selling their solutions so it's becoming a little too hard to grasp the concept.

author: clack
author_rank: Newbie
timestamp: April 05, 2017, 10:01:47 am
content: Ooh how about this, gives examples on a PIC and the interface circuitry, good one microchip!http://ww1.microchip.com/downloads/en/AppNotes/01465A.pdfedit: found the commands, so it is straight forware bytes in a packet type commandshttp://www.rayzig.com/manual/rayzig.html?DALIcommands.htmlhttp://www.nxp.com/documents/application_note/AN10760.pdfSorry I dont think there are any nice all together tutorialsSo I presume address discovery is done by polling all the addresses and see if you get a response, then to determine the physical location you flash the lamp on and off. I dont know what happens if 2 ballasts have the same address and you have a clash.

author: Kjelt
author_rank: Super Contributor
timestamp: April 05, 2017, 12:43:29 pm
content: You have a commisioning phase: you put the devices on the DALI bus in commisioning mode by broadcasting some special sequence, in that phase is where the devices assign themselves an unique id.Then you test if all devices have unique ids and which device has which number. You write this down in the lightplan and program the controllers to set the correct lighting setting for the correct id.To help installers do this work there are PC software programs with USB devices that you can connect to the DALI bus, they can handle the commisioning and help identifying the drivers.Each manufacturer has besides the standard DALI commands some proprietary commands where they can identify which driver it is (power and settings) and also update the driver firmware or program some settings like max. output current etc.It is a pretty old fashioned and stupid protocol with one master and many slaves (two masters don't work) but still heavily sold and in operation to this day.So devices out of the box do not have a DALI address, they only respond to broadcasts.If you want to learn DALI you need to get your hands on the specifications. With the specifications it is quite a large undertaking, without will be MI10.

author: clack
author_rank: Newbie
timestamp: April 05, 2017, 04:11:42 pm
content: Quote from: Kjelt on April 05, 2017, 12:43:29 pmYep I saw the randomize command, this is good to know, I am working on a DALI based system soon! but I think they will have the addresses mapped out already for the building.Quote from: Kjelt on April 05, 2017, 12:43:29 pmI have seen diagrams with 2 master switches but I guess they rely on the fact you are not going to touch both light switches at the same time?Yes it also seems a bit silly an unbalanced DC signal down a line I guess at the time it was cheaper than doing somthing like RS485

author: Vtile
author_rank: Super Contributor
timestamp: April 05, 2017, 04:22:11 pm
content: Quote from: clack on April 05, 2017, 06:51:39 amHeh, but how quick you need to be able to chance the dimming settings..What I have used Dali based dimmers it did work nicely.

author: Kjelt
author_rank: Super Contributor
timestamp: April 05, 2017, 08:23:02 pm
content: Quote from: clack on April 05, 2017, 04:11:42 pmI am not sure, I think it is undefined. The first standard DALI system can only handle one master at a time and sure you can use multiple independent of eachother but since the master always has the same address you must make sure that if one master requests data from the driver the other master also receives the answer and should not interfere although the data is sent also to his address. Not sure how and if that works with all DALI masters. Even multiple companies do not always work 100% together, the spec is good but it is not airtight and small deviations in timing and response have had severe consequences.Now since last year there is a new DALI standard called MultiMaster and that is specifically created for multiple DALI master devices such as sensors and control panels working together.QuoteDALI is very robust, I would guess even more robust than RS485, it was made so it could run parallel to high power lines.

author: clack
author_rank: Newbie
timestamp: April 05, 2017, 09:07:27 pm
content: Quote from: Kjelt on April 05, 2017, 08:23:02 pmOh right, yes I saw it can run down the same multicore cable with mains .. its just the maximum distance is 300m (compared with 1200 for RS485) made me think it was a bit susceptible. I guess combination of slow rate, the manchester encoding and the fact you can put the PSU in the middle of the line makes it reliable too.This is great, I found it a bit overwhelming to understand at first, sorry to hijack the thread!