511-BTA08-400B vs. 511-BTA04-700T

[WakeFan]

I am using the 400B in the SSR's I built last year(Ren 64). Should I stay with the same on the Ren 24's building now. I want them to dim as close together as possible, but I also would like to go with led's eventually (none now). I'm sure there may not be a correct answer, but opinions are what I'm looking for.
Thanks!!!

[Macrosill]

Besides the obvious difference in the current and voltage specs the 700T has a lower trigger current of 5ma vs 100ma on the 400B.

If you are interested in dimming leds then I would go with the more sensitive triac, 700T.

[Elmo2resc]

Besides the obvious difference in the current and voltage specs the 700T has a lower trigger current of 5ma vs 100ma on the 400B.

If you are interested in dimming leds then I would go with the more sensitive triac, 700T.

Brian, What triac are you using to trigger your led mega tree? I'm wondering because I am moving to a led tree this year at 200 led's per channel and I already have boards built with the 400's. How well does yours dim? If it does that is. Thanks for any info.
Jerome

[omzig]

EDITED: Nevermind...Sorry, my comment wasn't really relevant since I was talking about dimming with 12V. That's what happens when you post when you're half asleep. :oops:

[aussiephil]

NOTE for all. (Especially all the new people to electronics)

The recommended resistor values for the SSR's should not be varied without careful evaluation of the data sheets for each triac you may use.
The resistors have been chosen to limit the peak currents through the Optocoupler in worse case.
Most of the optocouplers used have a peak rating of 1A, the 180Ohm @ 110v will limit peak current to around 900mA.

The following is for the techo's amongst us to pick apart......

For 110v with 180Ohm
a 400B will turn on at 50mA
this equates to about 6.5v RMS or 11% of the total voltage range.
a 700T will turn on at 5mA
this equates to about .75v RMS with a 180ohm resistor - the triac actually has a minimum of 3.15v before it conducts though.

From the above figures a "normal" triac used can benefit from a lower value resistor when driving low current loads like a few hundred millamps but this value needs to be carefully worked out.

The sensitive gate triac will be better all round when used with the normal values of resistors in both the ability to turn on and to stay latched.
The gate resistor value could actually be increased in most cases for sensitive gate triacs without affecting the turn on point.

Now for low voltage 24v systems the calculations get interesting and i'm happy to discuss these figures if required.
Based on the datasheets and spreadsheets calcs the Vgt and Vtm are more critical than the gate trigger current.
I need to do some more analysis on this as well as some real world tests.

aussiePhil

[Macrosill]

Brian, What triac are you using to trigger your led mega tree? I'm wondering because I am moving to a led tree this year at 200 led's per channel and I already have boards built with the 400's. How well does yours dim? If it does that is. Thanks for any info.
Jerome

I used the standard triacs on the Ren-24s controlling the Mega Tree. It dimmed fine. Most triacs will dim fine but the issues is the range of dimming. The more sensitive triacs will dim over a larger range and be easier to sych' up with dimming minis.

[omzig]

NOTE for all. (Especially all the new people to electronics)

The recommended resistor values for the SSR's should not be varied without careful evaluation of the data sheets for each triac you may use.
The resistors have been chosen to limit the peak currents through the Optocoupler in worse case.You are, of course, correct on this. I removed my comment about the gate resistors so nobody gets confused...I was referring to dimming with 12V which was really not relevant to this topic. :oops:

[aussiephil]

You are, of course, correct on this. I removed my comment about the gate resistors so nobody gets confused...I was referring to dimming with 12V which was really not relevant to this topic. :oops:

Don

thanks - i wasn't inferring you should remove the post though.

changing the resistor is important for low voltage and also for low currents.

cheers
aussiePhil