10 Channel Light Bulb Sequencer

[Nigel Goodwin]

I doubt if that would happen ! When bulb fails, it becomes open circuit ! How will that affect the TRIAC ??

As bulbs fail they commonly go S/C before they go O/C, this kills the TRIAC's - it's a VERY, VERY common fault on light units. I've made a lot of money over the years repairing light units damaged in this way

 

[shokjok]

May I suggest a safer circuit, built 20 years ago and still functions.

 

[iflymyhelishigh]

Thats pretty dang cool! Its next on my boredom list.

 

[Warrant2000]

Hi folks,
First time poster. I'm looking for help on a light sequencer. But since I'm electronically inept, I was hoping someone could point me in the direction of where to purchase one.

I am setting up my lighting effects for Halloween and have several lights (light bulbs and floods) I need to manage.

Thanks!

 

[Ubergeek63]

I doubt if that would happen ! When bulb fails, it becomes open circuit ! How will that affect the TRIAC ??
I have been using this circuit for years now with quite a lot bulb failures, never had to replace a TRIAC or 4017 yet!
Can you explain ?

You undoubtedly have properly rated triacs in your own circuit. Nigel is a repair shop guy who sees primarily consumer crap that undoubtedly has under rated triacs.

Another way to look at it would be that you have a military type of design and what Nigel sees is cut rate crap manufactured in China.

While the bulbs do tend to short before they open, triacs have a tremendous surge rating that handles it fine. Were it not so there would be no market for triac lamp dimmers.

 

[Nigel Goodwin]

You undoubtedly have properly rated triacs in your own circuit. Nigel is a repair shop guy who sees primarily consumer crap that undoubtedly has under rated triacs.

Certainly not military grade, but certainly professional and semi-professional grade, used for light shows in clubs and disco's. You don't really get anything similar in consumer electronics?.

 

[Ubergeek63]

Certainly not military grade, but certainly professional and semi-professional grade, used for light shows in clubs and disco's. You don't really get anything similar in consumer electronics?.

I have never heard of one blow.

It is more likely in that case to be frayed wires shorting out or under rated triacs in that case. Clubs are likely to be moving things around or putting in over size bulbs bulbs for effect.

 

[Nigel Goodwin]

I have never heard of one blow.

It is more likely in that case to be frayed wires shorting out or under rated triacs in that case. Clubs are likely to be moving things around or putting in over size bulbs bulbs for effect.

I don't know where you're from?, but you've obviously never been involved in disco or clubs, or in any service work

This is an EXTREMELY common and well known problem, with fuse manufacturers even bringing out special highly expensive fuses to try and reduce the problem.

Do you have MCB's rather than fuses at home?, it's commonplace for the MCB to trip out if a bulb blows, same thing - high current surge takes it out.

 

[Ubergeek63]

US ... Almost everything here is circuit breakers, but they don't blow either. How often do you hear of wall lamp dimmers blowing out? That would be the real difference between an overloaded or crappilly designed triac circuit blowing and what you are seeing.

If it was that properly designed and rated triac circuits were blowing out all the time you would be hearing of people replacing their wall dimmers all the time.

 

[Nigel Goodwin]

If it was that properly designed and rated triac circuits were blowing out all the time you would be hearing of people replacing their wall dimmers all the time.

So you've no experience of light effect units at all, and you're basing your idea on domestic light dimmers

Completely different things, and the lamp failure rate is massively different.

Incidently, if it's of any help to you?, TRIAC's used are generally TO220 rated at 8A continuous, with a maximum 4A load per channel (1000W per channel) for a 3 channel unit, correspondingly less as you get more channels (as there's a 3000W total capability).

 

[Ubergeek63]

So you've no experience of light effect units at all, and you're basing your idea on domestic light dimmers

No I am calling out the least common denominator for a reliability example.

My FACTS are based on a typical triac, say a MAC8N.

At 4A you dissipate 4W per triac min. The die temperature has to be between 40C and 280C with a max of 125C (2.2C/W j-c or 62.5C/W j-a times 4W plus 30C max ambient) meaning you need heat sinking of 20C/W with proper ventilation.

"And you're basing your idea" entirely on untested theory of a single app that is notorious for abuse. The fact is that for your theory to be correct the single bulb would have to conduct 100A for 2.6mS in a properly designed unit in order to have a chance of blowing the triac. (26A²S fusing per the mentioned spec sheet)

Completely different things, and the lamp failure rate is massively different.

Incidently, if it's of any help to you?, TRIAC's used are generally TO220 rated at 8A continuous, with a maximum 4A load per channel (1000W per channel) for a 3 channel unit, correspondingly less as you get more channels (as there's a 3000W total capability).

It does not matter the application. It is either properly speced or it isn't. It is either properly heat sunk or it isn't.

It would be much more common failure in an app like that to be either overloaded, which a club is likely to do, or the have design corners cut in the heat sinking, which substandard engineers are likely to do. If properly designed and loaded, I would still not put it past a club to prevent air circulation past the heat sink.

You should probably clarify to the less knowledgeable that the 3000W is the circuit capability and not the unit capability.

 

[Nigel Goodwin]

No I am calling out the least common denominator for a reliability example.

My FACTS are based on a typical triac, say a MAC8N.

Your 'facts' have no relevance to the thread at all - I'm not posting an opinion, I'm posting what happens, and what everyone who's ever been involved in effects lighting systems knows - when a bulb goes it commonly takes the TRIAC out with it. Most go S/C (so that channel is permanently ON), but occasionally they go O/C instead.

I've done disco's, I've done PA and lights for bands - replacing failed lamps and TRIAC's is a regular part of doing so.

 

[Ubergeek63]

Your 'facts' have no relevance to the thread at all - I'm not posting an opinion, I'm posting what happens, and what everyone who's ever been involved in effects lighting systems knows - when a bulb goes it commonly takes the TRIAC out with it. Most go S/C (so that channel is permanently ON), but occasionally they go O/C instead.

I've done disco's, I've done PA and lights for bands - replacing failed lamps and TRIAC's is a regular part of doing so.

Yes and that is called FUSING, and my facts are quite relevant.

It is highly doubtful that all things being proper even a single 1KW bulb could draw 22KW for 2.6mS before going open circuit. It follows, therefore, that you're blaming the failure of the triacs entirely on the triacs is unfounded.

It is FAR more likely that the triacs are overloaded and overheated when the bulb blows. Come to think of it, another DESIGN issue is trying to flash a cold filament from peak line voltage, bad for the bulb and would not sit well with an overheated triac.

 

[Nigel Goodwin]

It follows, therefore, that you're blaming the failure of the triacs entirely on the triacs is unfounded.

Sorry?, I've never blamed the TRIAC's for anything.

It is FAR more likely that the triacs are overloaded and overheated when the bulb blows.

Which is what I've been saying all along - the bulb blowing often takes the TRIAC out.

 

[Ubergeek63]

Sorry?, I've never blamed the TRIAC's for anything.



Which is what I've been saying all along - the bulb blowing often takes the TRIAC out.

Yes... which you proceeded to blame on the triacs to the extent of recommending that poor guy not use them.

How is that not blaming the triacs?

 

[Nigel Goodwin]

Yes... which you proceeded to blame on the triacs to the extent of recommending that poor guy not use them.

How is that not blaming the triacs?

The exact quote is below - perhaps you might read it again in context?.

Quote:
Originally Posted by kinjalgp
To avoid triac failure, never connect load beyond its rated capacity.

And never use them to feed bulbs, because when the bulb fails it almost always takes out the triac at the same time.

Bit difficult for a light sequencer though?.

 

[Ubergeek63]

The exact quote is below - perhaps you might read it again in context?.

Was not really needed... the context of my reply to that was then the triacs are not being used properly.

The old computer saying: "garbage in, garbage out" ... or in your case "garbage out, cash in" ... if they were properly designed and utilized the triacs would not be blowing. Period. Which is what I said in the beginning.

 

[Nigel Goodwin]

Was not really needed... the context of my reply to that was then the triacs are not being used properly.

The old computer saying: "garbage in, garbage out" ... or in your case "garbage out, cash in" ... if they were properly designed and utilized the triacs would not be blowing. Period. Which is what I said in the beginning.

So almost all professional and semi-professional light units are poorly designed?, interesting idea

 

[Ubergeek63]

So almost all professional and semi-professional light units are poorly designed?, interesting idea

I wouldn't know... I do know that it is my experience there are many wanna be engineers in niche markets that are less than well qualified, and that your experience supports mine, though you might not like admitting it.

 

[Disco Elephant]

So almost all professional and semi-professional light units are poorly designed?, interesting idea

Ok, I'm new here, and this is my first post, so I don't want to step on anyone's toes, but I've read this thread, and have a few points I'd like to make.

1. I'd say any piece of equipment that takes out a triac (and possible other components) because a light globe fails is poorly designed. Light globes are user-serviceable pieces of equipment with a limited life expectancy, and are expected to fail. If they take out semiconductors when they do, then it says to me that the designer didn't take this into account.

2. I can't see why a light globe would go short circuit when the filament breaks. How can there be a low impedance between the 2 contacts if the only part that could possibly cause a short is the filament, which is resistive. Nigel, if you could explain the mechanism that causes the light globe to become a short circuit, it could well clear up a lot of confusion.

3. Is it possible that the reason you see a lot of professional lighting equipment with a blown globe and a dead triac is because the globe failed and was never replace, and sometime later the triac, which is driving several other globes, failed for a completely unrelated reason? From what I've seen, as the number of lights in a lighting system increases, so too does the probability of having a blown globe, so I think this is possibly the reason why you see lots of dead triacs connected to blown globes. But that's really nothing more than an educated guess.

4. If this thread is any kind of measuring stick, I'm gonna like this forum, A LOT