Need Snubbers?

[Guest guest]

After the great success I had with the wirekat MR-16 LED landscape spots I used this year, I decided to swap all my landscape lights out to their warm white MR16s.

The landscape lighting controller is a 12V unit...the way the landscape lights were installed, its two parallel chains of lights, being fed from the 12V supply.

They look really good, but only one problem...they won't go completely dark when the timer turns them off. I did notice this on one section of lights when I had my display up, and am thinking now it only happened on some, not all, due to the fact that one of the chains had a couple incandescent MR-16s still being used, pretty sure the other was all LED spots.

A snubber would be the first thing I would try..assuming I can put it across the terminals at the lighting transformer, as opposed to the end of the line for each "light string"...but I could also do it in each parallel string, easiest to do it at the transformer end, as opposed to digging up the far end of the lighting chain.

As a test, I may also replace one light on each string with an incandescent and see if that essentially serves as my snubber.

Open to suggestions...

[George Simmons]

DonFL wrote:

As a test, I may also replace one light on each string with an incandescent and see if that essentially serves as my snubber.

I think you're on the right track and this should do the job if you are.

[Guest guest]

So...can add this one to the "duh..maybe that wasn't such a good idea" category.

I created a snubber out of an incan MR-16, soldered wires to the lamp pins, connected it across the lighting transformer output.

I declared the fix a success, as the low level "need a snubber" glow was immediately gone...problem solved, right?

Wrong.

As it got dark last night, I look out the window, landscape lights are on, I once again congratulate myself on a job well done, like I had launched the space shuttle...:cool:

Then..as I watch..the lights go off. Then back on. Then off...etc..etc.

And I realize..that little MR-16 was so damned bright, and so close to the photocell, it was putting the light controller into a cycle of dark-lights on, MR-16 on-photocell illuminated-lights off, dark-lights on...ad infinitum...

So today, we'll go the classic resistor snubber route...like I should have done in the first place..

I thought about extending the leads on the MR-16 several feet and trying to do it that way, but with the heat those things generate, I'd have to suspend it so its not touching anything. Its a definite plan B, but we'll see if the resistor snubber solves the problem first.

[beeiilll]

Well Don, congradulations on automating the landscape lights and sorry to hear that the experiment was a slight failure :shock:.

Isn't science amazing? We can have so much fun keeping ourselves entertained that before long we even forget why we were doing something in the first place!

What was I talking about?

Oh yea, good luck with the snubber on those pesky lights.

Bill

[Guest guest]

so I need a lot less than 47K, like the snubbers I'm seeing described as typical.

Looks like something in the range of 10-50 ohms will work. Since I don't have anything bigger than a 1/4 W in the junk box, will need to pick up a higher wattage resistor..for now, going back to the original MR-16 idea, and "remote mounting"

[Max-Paul]

I would think that a 10-50 ohm resistor would be way to low. How did you come up with this value? Is that the cold ohmage of the ican M16 lamp? With the LED lamps at a much higher ohmage, I would think that maybe a 100 ohm would work. This would lower your wattage of the resistor. A 5 or 10 watt resistor produces a lot of heat too.

[Guest guest]

I think it was actually a 100 that worked. Probably not the highest value I can use, but it was trial and error with visible results. Started with 47k, cut it in half to 22K, then down to 1K...and still no luck. So decided to get drastic, and went with 100. Sorry, not a lot of engineering analysis put to this one.

I do believe I need a relatively (compared to standard snubber values) low resistance, before I head to skycraft next saturday to pick up a few larger wattage resistors, need to lock down the best value.

[-klb-]

I think a 1/4 W 10 ohm probably would have smoked, as it would have been 14 watts.

If this is truly 12V, not 13.8 you get the following:

100 ohms would be 1.44

220 ohms would be 0.65

330 ohms is .43

470 ohms is .306

1K is 0.144

If you really need 100 ohms, a 5W resistor is probably not too tough to get, and only dissipating 1.5W, it should only get warm, not hot.

A 1 watt 220 ohm might be a good choice, if it clears your problem.

If it is 13.8V, the 5W, 100 ohm is still fine, but the 1W 220 will be at 90% of rated power, and I would try to find at least a 2W..

[Guest guest]

No doubt..I would have been roasting marshmallows on a 1/4 resistor..at least for a second or two.

Its a 12V transformer, standard landscape lighting transformer/timer. As I've discovered, there isn't a lot of high tech products out there for landscape lighting..no one seems to be embracing LEDs just yet..or at least, they are not advertising it. We're pondering some major landscape renovation, and I've thought about something a little more high-tech, if I stick with the LEDs. A CMB-16D and PS is cheaper than most landscape units, and, can be standalone. And somewhere outside, I know I ran automation controller cable for "future use", so that is an option also.

Anyway.,..If I get some time today I may step thru a few values and find that minimum value I need. Unfortunately, my friends at Skycraft aren't open on sundays, I and I don't get back from the west coast until 7 AM next saturday morning, so it will be a next weekend effort at earliest.