Jump to content
Light-O-Rama Forums
Sign in to follow this  
Randy

A question about LOR and powering LEDs

Recommended Posts

Alan C wrote:

There seem to be two separate solutions here. The first is to use an additional load of a 33kohm resistor (120v) or 66kohm resistor (240v) across the controller output, to ensure that the triacs always have a load. In most cases, this will ensure that the triacs turn fully off. The second point is that of using a "snubber" across the triac (from supply to output), to ensure that the triac fires correctly with small loads (typically those using LED strings). The recommendation for this is a 100 ohm resistor in series with a 100nF high voltage capacitor.

In addition, there are changes when using the controllers on 240v, such as the UK. There is a link on the board for its own dc power supply that sets either 120v or 240v, but the "kit version" of the CTB16K includes two different values of resistor that are used in series with the triac "gate" connection. The values supplied are 220 ohm for use with a 120v supply, and 330 ohm for use ith a 240v supply.

Your other point, there is no reason why a transformer would not work on the output side of the controller, as long as it is a true "wound" transformer, rather than the electronic "switched mode" type (which would only work correctly with on & off commands only). Some of the australian users (who also have 240v) are using wound transformers.

Regards,

Alan.


Fantastic, Thanks for your help.

I am so tired of leds at the moment! This past week I must have soldered over 500 together!

They all got to be tested before they go in because 1 in every 50 is shorted out! :X

but it will be something else when its all finnished.

Ill have to post a pic of my hobby room, (it looks like Clark Griswold`s house in a small room!

Thanks for your your help Alan.

Kind Regards.

Trevor.

Share this post


Link to post
Share on other sites

Max-Paul wrote:

I wonder if you and Richard have the same load besides these 33K 1/2W resistors. Richard was is the smallest load you have along with these resistors. Same for you stachows?

Max, I have various sizes of loads. Some channels use only a single string of 70 leds, and some channels use multiple strings. The same size resistor will work regardless of the number of strings (up to the limit of the triac of course). In the 1602 controllers I have, I believe the rated output is 8 amps per channel (120vac) up to a maximum draw of 30 amps per unit. In my setup with LEDs, the max I ever draw per channel is about 1/2 amp.

Share this post


Link to post
Share on other sites

Hello Trev.

Iam also a newbie here comming from the Netherlands. Same as with you we use 240V / 50Hz. only we have different wallsockets.

You mensioned the resistor of 66 K. I think this is incorrect. The outcom if you will use a resistor of 0,5 W will be as follow:

P=UxI=0,5 W:240 V=2,1 mA. maximum trough the resistor.

R=U:I=240 V:0,0021 A=114285 Ohm =115 K

So for the europeen voltage you have to use 115K resistor. Any lower resistor will burn out because of the power above the 0,5 Wattof the resistor itself.

By the way. Iam gone make a 48 channel christmasdisplay for 2009. Five minitrees with 3 channels each, and 3 arches 8 channels each and some spotlights. For me this will be the first time doing a christmaslight display. Probably I'm going to use one AC controller (CTB16PC kit) and two dc Controllers (CMB16D) for my lights. For the dc controler I want to use a 24Vdc power supply that will be used for the power of my total 32 channels of led strings. The rest are minilights and 240Vac rope lights. In the case of the dc controler I won't need the all of the separed transformers with the ledstrings.

What I want to know is do the dc controlers with ledstrings need a resistor also for dimming the leds? If this is the case when i made the right calculation I will need an resistor of 0,5 Ohm 0,5 W because of the 24Vdc.

But at this time I don't know where to order led strings for europe (24V)and minilights (not yet the season). I don't have the time to make them by myself, so I have to search the internet.

I would like to hear more about the using the LOR controles in the europeen country's.

Share this post


Link to post
Share on other sites

Hi

I'm in Australia - also a 240V 50Hz supply country. I've been using LOR for 5 years now, initially using the 240V boards to switch the individual transformers that are supplied with our lights (mostly 24V AC outputs), and then last year for the first time, using the DC boards to control low voltage LED strings directly. There is an Australian LOR discussion group at http://groups.google.com/group/Aussie-LOR-Users where there have been many threads about use of transformers, disabling multi-function controllers, and use of DC boards with LEDs.

With the increasing availability of LED Christmas lights, their better reliability and the improvements in the string construction techniques, I am moving more to the use of LEDs directly connected to the DC boards. We do find however, that it is often necessary to add resistors to strings and to operate from a higher DC voltage than might be expected; eg a lot of strings operating from a nominal 24V AC power pack will need around 30V DC to get an appropriate string brightness.

Have a look at our discussions at the above link. Hope this helps

Regards Geoff

Share this post


Link to post
Share on other sites
Guest
This topic is now closed to further replies.
Sign in to follow this  

×
×
  • Create New...