[JRTame]

Was wondering how many people have experience with Lutron LUT-LBX. Tech support told me today not to use these on an output of a remote power module BUT I'm calling BS on this one as it states in the tech guide these are compatible.


I was also told in the past that this device - when installed in line between the module output and say an LED load - helps to prevent voltage leakage (resulting in LED loads either turning on themselves OR not turning off at all). Anyone have experience with this?

 

[duvetyne]



Quote:
Tech support told me today not to use these on an output of a remote power module BUT I'm calling BS on this one as it states in the tech guide these are compatible.

It's not required on a remote power module because the RPM doesn't use the load as a neutral connection in order to power the dimmer.

When the RPM output is 'off', no voltage is available so the LEDs will not turn on.

When a two wire dimmer is 'off' there is still a trickle current through the load, required to power the microprocessor in the dimmer. this trickle current is what prevents the LEDs from extinguishing.

 

[JRTame]

Hmmm - ok but I've experienced situations where though the output controlling an LED load was off it still remained on. Was told this was due to voltage leakage as a result of any one of the other 3 module outputs being "on" controlling a different zone. I was told by tech support that there is always a small amount of voltage leakage occurring on any module output that might be switched off IF any one of the other module outputs are on.


Crestron modules on the other hand do not appear to have this issue - again based on what I've witnessed as well as what tech support as told me.

 

[duvetyne]



Quote:
I was told by tech support that there is always a small amount of voltage leakage occurring on any module output that might be switched off IF any one of the other module outputs are on.

Sounds like a poor design, there's no reason for this to happen....specially when it involves a different load.

Try the LUT-LBX...it's just a resistor on a heatsink.

 

[joatmonjf]



Quote:
It's not required on a remote power module because the RPM doesn't use the load as a neutral connection in order to power the dimmer.

When the RPM output is 'off', no voltage is available so the LEDs will not turn on.

I believe that there is a leakage current through the output thyristors. As I understand it, Lutron RPMs are isolated from power by one relay at the feed circuit. The relay opens to isolate the outputs only when all circuits are commanded off. If the relay contacts are not open, a high impedance load could be energized by leakage current even if that channel is commanded off.. Crestron CLX modules employ isolation relays on the ass end of each output circuit. If a channel is commanded off, the load is mechanically isolated from module power.

Regardless, the LUT-LBX is a low impedance device used to provide a minimum load for dimmers. Even dimmers that have a neutral connection, and do not complete their control electronics power path through the load have minimum load specs.

LUT-LBX is recommended for use with LEDs because it provides enough of a load to swamp out the leakage current, so "none" flows through the high impedance LED load.

If Lutron tech support says they shouldn't be used with RPMs, maybe they have had some sort of issue with them, even though they are spec'd for RPM use. I'd prod Lutron for more information.

Worse case, you could wire an isolation relay into the circuit. A 120V AC coil is probably low impedance enough not to be picked up by the leakage current, but also might drop out before the low end of a dim is reached.

 

[duvetyne]



Quote:
I believe that there is a leakage current through the output thyristors.

This is surprising, it's really not that hard to build a triac based dimmer that doesn't leak current.

Controlling LEDs with a triac based dimmer isn't ideal anyway.

 

[joatmonjf]

Even with circuitry for squeaky clean, noise free gates, a triac is a single substrate, imperfect semiconductor device. There is always going to be leakage through the junctions.

It is easy to build leakage free dimmers. Put an air gap closure on the output.


You are correct about standard incandescent lamp dimmers not being correct for LEDs. I don't know the technology yet (perhaps PWM and IGBTs), but we are going to be seeing more, and more of it in the near future, no doubt.

 

[duvetyne]



Quote:
There is always going to be leakage through the junctions.

Most dimmers used in entertainment lighting do not have any leakage current.

Most of these are triac based dimmers, with a few IGBT's available.

Since LED's are DC devices, PWM of a DC source is usually used to vary intensity.

 

[wags_1]

Who makes the LED's and how do they need to be controlled? Some LED's can not use a forward phase or revers phase control. Lutron has a matrix that list all the LED companies that they work well with along with how to control them. I would suggest looking there to see what if the LED's you are using are listed.