DMX decoder

[sunray]

I'm trying to control some 12V LED floodlamps with DMX and have tried this: http://www.ebay.co.uk/itm/DMX512-Decoder-15A-RGB-Controller-LED-Stage-Driver-Mini-Board-3-Channel-Part-Top/263123345513?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649 and another slightly larger version.

Both of them have an annoying flicker every 4 seconds or so.

Has any one tried them and found the same issue or a resolution? Or a suitable economical alternative? I only need single channel for each lamp but space is very limited.

This works well: http://www.ebay.co.uk/itm/4CH-DC12-24V-RGBW-DMX-512-Decoder-LED-Controller-RGB-LED-DMX512-Decoder-BX/122552065296?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649 is fine but far too big to fit in the available space.

[DrV]

Looking at the 'user manual' the chips are clearly the same as the ones used in some cheap LED par cans. Some flavours of these can't keep up with full rate DMX. If you can, you might try reducing the DMX rate. Whether you can do that depends on your controller/desk.

[p.k.roberts]

I'm sure I recall reading recently that this can be caused (on more 'bargain' kit') by RDM being enabled on the control desk - could this be the culprit in this case?

[timsabre]

That's a good point, rdm sends a non-standard packet every few seconds. If the receiver doesn't check for this it could display as a flicker or glitch.

[sunray]

This is only on a transension 816 so no RDM. I have also been able to try it on a chavvy 50 (and the 816) in an installed system and found it is more noticeable when there is more kit in the universe.

[timsabre]

What are the led units? Some have internal drivers which don't respond well to PWM (or some speeds of pwm)

[c0astman]

I have used these successfully to control multiple strands of LED tape http://www.ebay.co.uk/itm/30-Channel-DMX-RGB-LED-Strip-controller-DMX-512-Decoder-DMX-Dimmer-Driver-12V-UK-/152673264534

 

In a gig I did last week I had an annoying flicker off two mid-low end LED Flat PARS the client wanted me to use. Everything was terminated and while the cable run was within the recommended distances, the addition of a DMX splitter (and by its nature signal booster) was enough to remove the flicker. Just a thought..

[dbuckley]

I have used these successfully to control multiple strands of LED tape

 

As have I. And LED lamps, and relays... Handy boards.

[sunray]

 Everything was terminated and while the cable run was within the recommended distances, the addition of a DMX splitter (and by its nature signal booster) was enough to remove the flicker.  Just a thought..

And could explain why the flickering is worse when there are more units on the universe.

 

As have I.  And LED lamps, and relays...  Handy boards.

 

I've been looking at this for another project, thanks for the vote.

 

What are the led units? Some have internal drivers which don't respond well to PWM (or some speeds of pwm)

 

Totally plain chip with nothing else in the housing. They dim well on the larger controller, (well at least as good as the cheap unit performs anyway)

This project is for ambient lighting so does not need to be high quality smooth dimming but once set needs to be clean and stable, it's in a listed building with listed luminaires/shades which used to be gas and the more recent 12V 36W bulbs have now been replaced with LED floods during some building work. The cast iron enclosures (which used to be the old gas valves) where the dimmers have to fit are about 100x100x30mm internally and currently contain a dimmer consisting of an OC23 transistor and 2 resistors. Due to the listed status, new wiring etc is unlikely.

[Hilary Watts]

Be careful - the OC23 transistor may be of sufficient vintage to be included in the listing on the basis that it is of special historic interest!

[sunray]

Some of the resistors are even body, tip, dot too!

[alistermorton]

Waxed paper capacitors ...

[sunray]

not unless they have completely melted.