Jump to content
Light-O-Rama Forums

Traics continue to FAIL, why?


Jerry Ludy

Recommended Posts

Right a ruptured case and carbon trails is usually when a electronic part fails open like a fuse. When something fails in a closed manner, it is more like a melt down not an arc or explosion.

Link to comment
Share on other sites

A little more food for thought.  Please note that we are talking simplistically here.  Any/All/None of these things may apply to a particular triac failure, nor does any of this speak to the fitness of one product over another.  I am not an electronic engineer.  

 

Triacs are little more than gates for electrons.  They really are nothing more than miniature relays except they are 100% solid state and can be switched on/off, opened/closed if we stick with the gate analogy, VERY quickly.  

 

99% of the time, a Triac blows because it has been over-heated.  All electronics generate some heat since there are no 'perfect conductors' (or at least ones you could afford!).  Being VERY simplistic here:  Triacs have a 'max amperage' because they need to be able to dissipate that amount of heat without damage.  Overloading a Triac, by trying to pass more current through the device than it is rated for, generates more heat than the device can dissipate, and kaboom - blown triac.

 

The amount of current a Triac can handle is usually predicated on using a proper heat sink.  The object of the heat sink is to drain away (see?  sink) the heat from the Triac.  That's why an 8A triac can be blown with only a couple of amps --> IF you don't use a proper heat sink.

 

So why does a Traic normally fail at around 50%?  A Triac is actually 2 thyristors back to back.  As you know, AC is 'Alternating' current.  That means for 1/2 the cycle electrons flow in 1 direction, and then flow in the opposite direction for the other half.  A thyristor can only conduct in 1 direction, so we use 2:  one for the positive direction, one for the negative direction.  When a Triac blows, it usually does so with only 1 of the thyristors going bad.  Since the Triac is now conducting at all times on 1/2 the cycle, you see the typical 50% brightness fail.

 

Can you blow a Triac with a correct or even undersized load?  Yes you can, and very easily.  Take for example controlling a motor or transformer.  Each motor will have a different 'starting' value, but that value can be quite high.  Sometimes 7 or even MORE times the running current of  a motor.  In that case, a 5A motor would actually draw 35A at startup.  That inrush current should only last for a a few hundred milliseconds (more correctly:  however long it takes the motor to start up), so you won't blow a fuse or breaker.  However that much current could cause enough sudden heat within the Triac to blow it.

 

Rarely, a short can blow up a triac, even under the rated current.  Let's say you have a string of Mini lights that shorts out.  The fuse in the string is rated for 3A and should protect your Triac.  However, fuses are 'slow' to blow.  It takes time for the small piece of metal in the fuse to heat up and melt.  That time could be just long enough to kill a Triac.

 

So heat, generally by overloading, causes 99% of the Triac failures we see overall.  Ah, but there is that other 1%......

 

There was a case several years back where a major manufacturer of Triacs (ST Micro) made several bad batches at a plant in China.  Those should all have made their way through the supply chain by now.

 

Since these are semi conductors we are talking about, they are subject to damage by ESD - Electro-Static Discharge.  I suppose some could be damaged this way.  Nearby thunderstorms can produce HUGE static charges and inductive loads.  Long extension cords, and long light strings make for excellent antennas to pick up these loads and transmit them back to the poor Triac.

 

.....But I'll bet the greater majority of this 1% you would never find a reason.  It's the same for the 1% of people who blow a fuse on something.  There's no overload, it's been working for quite and while, and then POOF.  Fuse goes bad.  The best thing you can do is be prepared.  It isn't so much a question of 'if', it is a question of 'when'.

 

 

Did you know (I learned this today too!) -->

Triac is actually a now generic trade name, much like we refer to tissues as 'Kleenex' or adhesive bandages as 'Band-Aid's?  They are really called "bidirectional triode thyristors"

  • Like 1
Link to comment
Share on other sites

Great examples.  LOVE the real world example rather than the techno geek.  Helped me understand what these things do and how.

 

 

WOW  GREAT JOB !!!!

Link to comment
Share on other sites

There was a case several years back where a major manufacturer of Triacs (ST Micro) made several bad batches at a plant in China.  Those should all have made their way through the supply chain by now.

 

Hmmm... the two controllers I'm having problems with are my newest.  One bought last year and one bought this year.  I wonder if this is could be my issue?

 

I lost another channel last night so that makes 5 for me this year(which is 5 more than I've had the previous 5 years).  All on these two controllers and all loaded with 100ct incandescent lights or less.

 

Note, when the channels die I move them to a controller I bought 6-7 years ago and so far so good.

Link to comment
Share on other sites

From what I remember there was a fair amount of chatter about this about 3 years ago.  Good lesson to have an extra controller on hand to swap out if you need to while fixing the other.  

 

As my dad always told me.  "If you are go to play, be ready to pay".  Of course he was talking about other matters, it applies here as well.

Link to comment
Share on other sites

It's been a while for this post, but I thought I'd throw in my experiences.  Right now I have 76 LOR 1602's, old generation, G3's etc.  I keep 10 extra LOR units (86 total) on hand for spares, as I typically lose a unit for some reason about every 4 days or so.  My display is completely LED, by the way.

 

1. Most failures (I'd guess 80%) are blown triacs, and are usually on parts of the display that have no more than 4 strings connected together.  They fail in the 'always on' state.

2. In ALL cases, the failure occurred sometime between the show shut down and startup the next day.  That is, it was working fine right as the show ended (midnight), and the triac was blown when the show started up at 6:00 PM the next day.

3. I fix many of the triacs myself, but I send some back to LOR for repair.  Kinda depends on my mood.

4. I'd LOVE a socketed triac implementation, if that is ever possible in the future.

5. For some reason, my G3 units have a much higher incidence of triac failures than the older units.  I have about 8 G3 units, and all others are the older versions.  So far this year (since Nov 28th), I've had 17 triacs blown/replaced, and all but one were in the G3 units.

Link to comment
Share on other sites

What can be really frustrating is that most of the people here on the forums know what they are doing -- That is they know how NOT to overload a triac.  Since we (board members) only seem to hear from people who know what they are doing, that 1% of failures sounds more like the norm.

 

You guys don't get to see the help desk where we get them every day.  We had one the other day where the user melted both of the fuse holders.  Those fuse holders are rated for more than 20A, so melting them is pretty difficult.  He had no clue what his loads were.  I'm 100% sure when that controller comes in for repair it's going to need triacs as well.  

 

On the other hand, I can NOT discount that other 1%:

  • I have personally seen 8A triacs fail with a .16A load.  
  • I have personally seen triacs that can fully turn OFF the load, but for some reason flicker ON and OFF for no good reason.  
  • I have personally seen triacs that have no issue with full off, or full on.  Trying something inbetween just turns them on solid.
  • I have even seen a triac work BACKWARDS - telling it to turn on turned it off.  Turning it off turned it ON (at around 50%)

I'd also like to point out it's not a question of cost or quality.  Triac problems like this span every mfg and every end user.  There is (at least IMHO) no one company that makes better triacs than another.  The triacs used in LOR controllers are well over-specified for what they should handle.  

 

I know it sounds like a cop-out, but sometimes triacs just die.

Link to comment
Share on other sites

I just noticed one of mine isn't quite shutting off. There's still a lot of ice out there so all I can do is wait and see after the ice is gone.


Its just a single channel and only two small strings of LED's on that channel so current draw is probably next to nothing.

Link to comment
Share on other sites

just my two cents, few dozen LOR boards in my display count, only have two bad channels over the years, and yes I push some of my channels to the max of the ratings.

Link to comment
Share on other sites

I have found over the years that "ANYTHING MADE BY MAN, CAN AND WILL EVENTUALLY FAIL!"  So a few triacs needing to be replaced is not a big deal to me.  BUT, it would be great if they were socketed :D

 

Tom Straub

Link to comment
Share on other sites

A quick question... is there any output protection on the triacs (true RC snubber for example)?  From what I remember in the older 1602's, there wasn't really anything like that.  You wouldn't think there's much of an inductive load with (in my case) LED strings, but I've never really set out to measure it either.

Link to comment
Share on other sites

Does LOR or someone else, sell the actual triacs that we can purchase? Since some boards are 30Amps and others are 40Amps, are the triacs different as I would imagine they are?

Link to comment
Share on other sites

Several links exist.

Before Gen3, all used 16A parts. Now all use 24A parts, and these can be installed on the prior boards as well.

Link to comment
Share on other sites

I've lost between 1 and 3 every year. I'm all LED so I'm not overloading them and I doubt I'm shorting them out because when I move them to a new channel all works great for weeks (shorts don't heal themselves). I've just come to think it is a fact of life and live with it. Having LOR come up with an automated routine that would change a channel assignment to all my sequences would at least take the big pain in the butt out of it anyway

Lost one on the first night this year already.

Jim.  This tool http://forums.lightorama.com/index.php?/topic/30005-lor-cc-dmx-lets-you-use-cc-in-the-visualizer-and-dmx-in-the-show/ should do that.  Just make both the source and destination LOR and make the start channel the same as the max channel:

{
    sourceDirectory: "s:\\Light-O-Rama\\Sequences\\Christmas\\2013",
    destDirectory: "s:\\Light-O-Rama\\Sequences\\Christmas",
    mappings:[
        {
            name: "bad channel",
            From: {
                protocol: LOR,
                network: D,
                units: [1],
                startChannel: 5,
                maxChannel: 5
            },
            To: {
                protocol: LOR,
                network: D,
                units: [1],
                startChannel: 8,
                maxChannel: 8
 
            }
        }
    ]
}
Link to comment
Share on other sites

I got your PM with the ticket number, and you are absolutely correct -- rather than offer to send you some, we only gave you some links to buy them.  We really dropped the ball, I apologize for that.

 

I'm going to re-open your ticket and get some sent to you.  

Dropped the ball on my request too, however I've already gotten my replacement and don't need/want you to send me replacements.  Just wanted to provide another data point.

 

Jim.  This tool 

http://forums.lightorama.com/index.php?/topic/30005-lor-cc-dmx-lets-you-use-cc-in-the-visualizer-and-dmx-in-the-show/

should do that for you...  Just make both the source and destination LOR and make the start channel the same as the max channel:

{
    sourceDirectory: "s:\\Light-O-Rama\\Sequences\\Christmas\\2013",
    destDirectory: "s:\\Light-O-Rama\\Sequences\\Christmas",
    mappings:[
        {
            name: "bad channel",
            From: {
                protocol: LOR,
                network: D,
                units: [1],
                startChannel: 5,
                maxChannel: 5
            },
            To: {
                protocol: LOR,
                network: D,
                units: [1],
                startChannel: 8,
                maxChannel: 8
 
            }
        }
    ]
}

 

Darn bleeding link and lack of edit.   It's fixed in the above quote.

Link to comment
Share on other sites

So is there a way I could put a meter on a triac to test if it is good or not!\?

 

Yes. Triac tester here: http://www.ebay.com/itm/Atlas-SCR100-Thyristor-and-Triac-Tester-/161061126371?pt=LH_DefaultDomain_0&hash=item257ffdc0e3

 

I have one and it works very well.

 

This triac is about the biggest you can get at 24 amps without outgrowing the circuit board.

 

Keep spares if you need to.

 

I have theatre type of dimmers that can use the bigger 40 amp versions.

But they have a bigger spread on the terminals and won't fit into LOR devices.

  • Like 1
Link to comment
Share on other sites

Guest
This topic is now closed to further replies.
×
×
  • Create New...