Triac Suggestion

[lightsoncallaway]

Correct me if I'm wrong, but I think that the triac on the BoM could be replaced with this one from mouser:  You are not allowed to view links. Register or Login and effectively allow for up to 6 amps per channel.  It's only $0.40 more per triac, but may be worth the cost if you are still using incandescent C-7 or C-9 lights in your display.  I still have a set that uses about 4.5 amps.

Just a thought, let me know what you think.

-Curt

[rrowan]

Bad idea

Are you planning on increasing the paths on the pcb to handle the extra current?

The parts on the board were chosen for a reason. Like safety for you and the board along with other parts on it.

Of course you can shorten c7/c9 light strings to reduce the current requirements.

Rick R.

[KeithTarpley]

Greetings,,,

Part of the problem is feature creep.  If you keep adding a few cost upping features here and there, it soon adds up to much more of a cost per unit.  A constant question as to what to add or leave be.  A more heavy duty SSR4 unit for a few channels here and there might be a suggestion.  But, as mentioned, the extra current needs to be within range of whatever unit you use.

And the total current for a LE is 40 amps max, due to input issues.  6 amps per channel * 16 channels = 96 amps.  Ouch.  It's always a tradeoff, and it's hard to please everyone.

Keith

[bmsgaffer86]

For me, since it seems everyone is going LED, I think 4 amps is plenty per channel. If you are going to do more than that, you will want that current off of your control board (like seperate SSR boards).

As for the C-7/9's since they are all 120V lights, you can just clip and split the string with some wire and plug from the hardware store.

Just my thoughts.

[RJ]

Just so you know 4.5 amps on a single express channel will not hurt it. 4 amps is conservative. but if I say 5 amps then people do 6 amps...... you know how it goes.

Stay at 4 amps per channel and 40 amps max but if you have a single string with 4.5 amp pull use it and smile. It is all about the smiles. The ones you get and the ones those who watch your show get. 

RJ

[lightsoncallaway]

Thanks everyone for the feedback.  Although I'm entering my 3rd year for this stuff, I still consider myself to be pretty much a newbie in the game.  I did do my own build of two of the d-light silver edition boards, and the reason I raised this question is that the d-light board is rated for up to 8 amps on a channel when using the heavy duty heatsinks.

I also understand Keith's post about 96 amps, so before anything gets plugged, every channels amp draw is measured with the P3 Kill-a-watt, then the values are loaded into a spreadsheet and my channels calculated to balance draw across the boards.  In fact, my draw per 8 channels is actually lower this year than it was last year, this is because I added 16 more channels and was able to switch out some of my incandescent strings to LED's.

From a design perspective, it appears that yes this triac can be substituted as a mod to the express, however one must still be mindful of the total amp draw on the bank of 8 and not exceed 16 amps (80% of your 20 amp circuit)

This mod would allow for 1 or 2 channels of a higher amp draw (e.g. 5 amps) and 6 or 7 of low draw (e.g. 1 amp or less)

-Curt

[n1ist]

The thing to watch out for is that the maximum current per channel is limited by multiple things:


- The triac itself
- Heat sinking and ventilation
- Current capacity of the PCB traces
- Operating temperature
- Current capacity of connectors, terminal blocks, and wiring
- Total current rating for that side of the LE.
- Probably other things I am not thinking of right now

As long as you verify (or properly work around) all of this, I'd keep to RJ's spec'ed limits.
/mike


/mike