Chinese DMX dimmer - not connecting to Loxone?

[Clegger]

Hi all

I installed Loxone in our newbuild just over a year ago.

After agonising over lighting for several months, we eventually went with 10 of the ubiquitous Chinese 3-channel DMX dimmers (this sort of thing: http://www.yozop.com/index.php/dmx-triac-dimmer-led-controller-ac90v-240v-3-channels-dmx302.html) to dim Photonstar downlights.  I can't recall the drivers we used.  Dimming is reasonably good, although we get occasional low level flickering at times when the lights are dimmed down low.

We had some trouble a few months ago after turning things on again after our electrician had the power off for several hours.  One of the dimmers exhibited extreme random dimming on its channels every few seconds.  The randomness was per-channel rather than all channels in synch.

We were distracted by other things at the time, so put off doing anything about it.  A few weeks later, we needed to turn the power off for a while to do something else, and turning it back on seemed to fix the problem.

We had a power failure over the weekend which seems to have kicked off something similar.  This time, all channels on the dimmer have really serious random dimming fluctuations.  Having looked at it more closely this morning, it seems that the dimmer isn't under the control of the DMX extension.  The switches to those lights don't work, and nor is it possible to control them from the web interface or app.  They seem to have reverted to manual control at the dimmer unit itself.

Does anyone have a manual for these units?  I can't find one and the documentation they came with was scanty to say the least.  Failing that, does anyone have any idea about the best way of getting the dimmer to lock onto the Loxone DMX bus?  Maybe a turn-on sequence for the dimmers and Loxone?  I've tried both ways but nothing yet.

One other thing, which I don't think is related but should mention anyway: I noticed when looking at this that the starting address of the affected dimmer (basically, the address of channel 1 of the 3 channels) was wrong.  Instead of being channel 16, it was 15, meaning that it overlapped with the third channel of the previous dimmer.  I don't know whether one of my kids or my wife accidentally changed the channel when trying to manually turn the lights on/off, but could that have caused an issue?  I don't know much about DMX, but if it's just a bus protocol, I assume the worst this would have caused is for the output channels to be mapped wrongly. 

Many thanks for any help.

Kind regards

Jeff 

[Simon Still]

On Monday, 9 January 2017 11:37:38 UTC, Clegger wrote:

One other thing, which I don't think is related but should mention anyway: I noticed when looking at this that the starting address of the affected dimmer (basically, the address of channel 1 of the 3 channels) was wrong.  Instead of being channel 16, it was 15, meaning that it overlapped with the third channel of the previous dimmer.  

I don't think that should be a problem - if that was the case both of the lights on channel 15 should have received the same dim level from Loxone.

I've just got one of these running and mine has been reliable despite having been powered up and down on a good few occasions.   I'm using mine to run Gu10 bulbs.  

One Channel has 3 bulbs attached (c15W and it's fine - light level is stable whether full or dimmed).

One Channel is has 2 bulbs on an outside light attached to a movement sensor.  That seems to work reliably.

The third channel, with a single bulb attached, is the issue.  It used to give a flash some time after being dimmed to less than 100%.  It now seems to change dim level even when on 100%.   

[DavidL]

It is entirely possible that the triac inside the dimmer has failed.

Are you able to manually control the dimmers across their full range?

We replace triacs in some of our entertainment lighting equipment we own when they fail.

We can tell they've failed as they either stick on a particular level and can't be controlled, or they fail closed and again won't work via DMX control.

Here's a brief guide on how to test them: http://www.circuitstoday.com/how-to-test-a-triac

One option it to get your hands on a DMX tester. Again, we use these in the entertainment lighting industry, so I do have access to one, but it's not something your everyday electrician might have unless they undertake DMX installs regularly.

David

On Monday, 9 January 2017 11:37:38 UTC, Clegger wrote:

[Clegger]

On Monday, January 9, 2017 at 12:33:07 PM UTC, Simon Still wrote:

On Monday, 9 January 2017 11:37:38 UTC, Clegger wrote:

One other thing, which I don't think is related but should mention anyway: I noticed when looking at this that the starting address of the affected dimmer (basically, the address of channel 1 of the 3 channels) was wrong.  Instead of being channel 16, it was 15, meaning that it overlapped with the third channel of the previous dimmer.  

I don't think that should be a problem - if that was the case both of the lights on channel 15 should have received the same dim level from Loxone.

Yes, it didn't seem likely it would be a problem, but thought it safest to mention it.  Interesting you're having problems with dimmer level changing too.

thanks

Jeff

 

 

[Clegger]

On Tuesday, January 10, 2017 at 9:29:48 AM UTC, DavidL wrote:

It is entirely possible that the triac inside the dimmer has failed.

Are you able to manually control the dimmers across their full range?

Yes, I can manually dim them.  That's why I thought maybe there was a problem with the DMX side of things within the unit.

That said, I've just turned it on after leaving it off since yesterday and it seems to be working!  I don't know whether there's some component that's borderline out of spec that means the unit doesn't reliably lock onto the DMX signalling.  

Thanks all for you help.

Jeff

[Duncan]

these dimmers are trailing edge and use mosfets,, not triacs

they can fail usually in 2 ways:
1) the low voltage converter used to drive the electronics dies or
2) they are susceptible to glitches and power cycling which seems to kill them quite often

given that they cost around $40 i dont think its worth trying to repair them, and always keep a few spares around

[Clegger]

Thanks Duncan.  This behaviour matches my experience.  The same power cut that (re-)started the odd behaviour with this dimmer also killed another one stone dead.

I did have one spare, but will grab a couple more to put away.

thanks again

Jeff

[DavidL]

Ah I see. I saw the product page mention triacs, so made an assumption!

[Duncan]

yes you are right, this product is always advertised as being triac but they arenet - triacs dont work for trailing edge because they flow current from being triggered until the supply ac voltage reaches zero then they shut off - its just the way that particular type of semiconductor works so its ideal for leading edge dimming only

[Simon Still]

I'm glad I'm only using one (that could be swapped out for relays) and have a spare.  

On Tuesday, 10 January 2017 14:20:07 UTC, Clegger wrote:

Thanks Duncan.  This behaviour matches my experience.  The same power cut that (re-)started the odd behaviour with this dimmer also killed another one stone dead.

[Sander Van de Wiel]

Just to be sure, these dimmers are trailing edge right?

Btw, we have the same one and also experience flickering when on low level. Seems to happen only on LED-bulbs tough.

Op woensdag 11 januari 2017 11:15:41 UTC+1 schreef Simon Still:

[Duncan]

yes they are trailing edge, but many 240v dimmable led bulbs have difficulties with smooth dimming, particularly at low levels irrespective of which dimmer is used.

ive compared these dimmers to expensive knx trailing edge dimmers, and overall there isnt a lot to choose between them in terms of effective dimming, other than 2 things:

1) the apparent better reliability of the knx dimmers, but they cost £60-100 per channel against the £12-15 per channel for the chinese dmx

2) knx dimmers dont work with the loxone in-built perception correction, so you have to use whats built into the knx dimmer, or use a formula block with a log curve between the lighting block and the knx dimmer to create/change/modify the lighting curve if you arent happy with whats built in - when using dmx dimmers the loxone perspective correction is sent to the dmx extension which does the correction for you