RE: Re: [Development] Lights functions required

["Keith Doxey" <ukha@xxxxxxx>]

Hi John

I had a lighting controller that was fitted with 8A triacs.
They were protected by Quick Blow fuses, 2A externally and a 5A internally.
When bulbs went the triacs would blow.

I upgraded to 16A triacs but more inportantly used HI-SPEED CERAMIC fuses.
The fuses were actually more expensive than the triacs but I NEVER blew a
triac after that.

The main reason for keeping the rating down is the cost of the chokes. They
will cost as much as the Relay+Triac+Opto. The higher the rating the more
the choke will cost. Also Isolated tab triacs >16A rating are VERY
expensive.

Some commercial controllers have the triac legs connected via cageclamp
terminal blocks. Self tapper into the heatsink. Triac change is a two
minute
job involving 4 screws.

The reason for detecting the output of the dimmer is to know if the triac
has blown. Agreed the relay will always cut the power but when the relay is
closed you check to see if there is an output BEFORE the triac is fired, if
there is then the triac is blown so no dimming

Alert service personnel :-)

The Lutron example for power rating was not intended to indicat my lighting
load. Anyway their dimmers are rated at 16A (downrated to 10A for CE
approval). the system I used to look after had 50kW of lighting spread over
32 channels.

Keith

> -----Original Message-----
> From: Dr John Tankard [mailto:john@xxxxxxx]
> Sent: 12 June 2001 22:10
> To: ukha_d@xxxxxxx
> Subject: [ukha_d] Re: [Development] Lights functions required
>
>
> --- In ukha_d@y..., "Keith Doxey" <ukha@d...> wrote:
> > Here I go, answering many questions in one go.
> >
> > Channels Per Dimmer Pack/Packs Per Room...
> > 8 channels per pack, possibly 2x4 channel boards each with one
PIC
> per
> > board. That allows a 4 channel pack to be built and also makes
the
> PCB
> > cheaper. Granted you would need 2 PCB's but you are buying more
so
> the price
> > per board comes down. Also limits failure.
>
> Keith, are you thinking that the dimmers are on the channel boards? I
> was thinking we would have a motherboard which the rabbit plugs into.
> The pic and optos on the same board. then upto 8 small drive boards
> which would connect to the motherboard.
>
> I have no problem with either route, its up to you. At the moment I
> have been running the pic at 10Mhz and 8 channels are no problem. But
> if we go down your route we might be able to drop down to 4mhz if you
> are talking two pics.
> >
> > Channel Assignment.
> > Some form of Dimmer/Address mapping. Lutron assign dimmers to
> channels. This
> > allows several dimmers to have the same identity so you can
handle
> a 20A
> > load as 4x5A.
>
> Thats an idea. how bright do you want your lights !! or is ths to run
> the pizza oven :-)
> >
> > Dimming Curve/Dipless Crossfade....
> > I dont believe anyone would notice the difference unless it was
> pointed out
> > to them. For dipless fading my idea is this. If the level is 0 to
> 100 and
> > you have 2 channels that require to do the following
> > A 25 > 75
> > B 100 > 0
> > with a fade time of 10 seconds you need to do the following.
> Increase A by
> > 50 steps and decrease B by 100 steps. You have 10 seconds to
> complete this
> > so that gives A needing to step 50 times in 10 second = increase
1
> step
> > every 200mS, B needing to step 100 times in 10 seconds = decrease
1
> step
> > every 100mS. The only calculation needed it to work out how many
> steps in
> > the time period.
>
> Yep, at the moment the prototype fades at a constant rate across all
> channels, which i agree is not good enough, so if one channel needs
> to go one step and the second channel needs to go 50 steps, the fi4st
> channel will get there in the first time period. I will fix it.
>
> >
> > Fault detection.
> > Subject to having spare pins available on the PIC you can detect
> > No Output - fuse or relay blown
> > Continuous Output - Triac blown
> > No Load - All lamps disconnected (NOT INDIVIDUAL BULBS unless 1
> bulb per
> > dimmer)
>
> In my case i have wired every lamp back to the packs so it is
> possible to check each bulb. (sorry my LV units are in groups),
> however i suspect most people will not have every lamp isolated so
> thats not a option.
>
> Since we have a protection relay so if the triac goes short circuit
> it will still go off when we go to off mode.
>
> I dont realy know which would be best. Do you know what the comercial
> systems do ?
> >
> > Cost.
> > Prices quoted by others seem reasonable at about £15 per channel,
> possibly
> > £20 with fault monitoring but that can be optional. The expensive
> bit is the
> > choke. By keeping the dimmer rating low - say 3A per channel
~720W
> the
> > chokes are cheaper. for heavy loads you use more than one channel
> as per
> > channel assignment above.
>
> I like that idea, perhaps if the drive boards were seperate we could
> do different triacs. From my personal view we need to go over the top
> on triac size, pain in the ass to swap when a bulb goes. As a side
> note i have some channels on ssr's where i dont need dimming and out
> of 10 channels I have had two go in the last three years even though
> the are 5 amp rated
>
> John
>
>
>
>
>
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> http://www.automatedhome.co.uk
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