Low voltage lighting transformer

I recently installed some low voltage landscape lights. They use about 75 watts of power (10 LED fixtures) so I purchased the smallest transformer available at Lowe's - a 120 Watt model. The lights look great and everything is working except...
The AC circuit I used is swtiched on at dusk and off at dawn (for other unrelated lights). No other AC circuits are available without running new lines. The transformer has its own timers and light sensors, but I do not need those. I essentially want it on all the time as long as it has AC power. I set it to ON mode which means the lights are on until manually turned off. After AC power is lost and then restored, it powers up indicating it is still in "on" mode but the lights are off. Changing the mode from "on" to "automatic" and then back to "on" fixes it until the next time it looses power. Does anyone have any experience with these things? Am I missing something? I could understand it powering up to auto but it seems to remember it was in "on"mode. It just doesn't power the lights without manual intervention.
Pat
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The mode switch you are describing, is it an old fashioned mechanical Switch or are we talking about an electronic switch.
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On Sunday, May 8, 2016 at 9:26:21 PM UTC-4, snipped-for-privacy@yahoo.com wrote:

Given that it's a new transformer for lights, and also has an auto setting, I'm betting 100% it's an electronic switch. So when it loses power, and then power is restored, it comes up in off mode. Kind of makes sense to me. Though some products, eg TVs remember and if they were powered up some will come back on when power is restored.
OP should just get a transformer with a manual switch.
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On 5/8/2016 6:09 PM, Pat wrote:

Your "transformer" has an electronic control. You're probably pushing a button that toggles an indicator/display between "auto" and "on"? And, the button you are pressing feels like a doorbell button -- i.e., if you closed your eyes and concentrated VERY CAREFULLY on what the button felt like each time you pressed it, you could never differentiate between the "on" and "auto" states... because there is nothing in the BUTTON that "remembers" this information!

Yes. Because the electronics notice the CHANGE from "auto" to "on" and act on that, now. When power fails, the device was designed to power up in the "off" state (this was either an intentional choice on the designer's part or just an oversight). You have to manually put it back into the "on" mode (even though it is IN the on mode!)

I suspect you're SoL -- unless you want to open it up and tinker, a bit.
You might be able to trick it into doing what you want by leaving it in auto mode and setting up a "schedule" that says "on at 12:05A, off at 12:04A". Then, regardless of what time it *thinks* it is (because it will "forget" when powered off?), it will still manage to turn the lights ON for 23 hours and 59 minutes out of every 24 hour period THAT IT HAS POWER.
(This should be easy to test. Put it into AUTO. Program it. Then, trn the light switch on and off a few times to see if it remembers to come back on.)
Alternatively, if it elects to power up OFF regardless of what time it *thinks* it is ("Gee, it's 1:00A, why aren't the lights on?"), you may have to resort to creating multiple schedules to ensure it sees some "event" often enough.
(As with the recovery from "power fail", it might have been designed to only *do* something at 12:04 and 12:05 and ignore the current time, otherwise)
A model number/URL would be helpful...
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On Sun, 08 May 2016 18:54:08 -0700, Don Y

Portfolio model #00740. Thanks to all who responded. Yes, it is an electronic control. They had no mechanical version available. I was worried this would happen when I bought it so I tested it (without lights attached) at the time. I set it to "on" and then unplugged it. When I plugged it back in, it came up with the display indicating "on". I was surprised but impressed that it remembered the state it was in when power was removed. It turns out only the display was on, not the lights.
You said I was SOL unless I wanted to tinker. That is my plan. I will open it up and completely bypass the electronic control. The weight indicates it has a real transformer in it so I will just connect the secondary windings to the output screws directly.
It just occurred to me to try one more thing before opening it up. I will set it to auto mode (controlled by the light sensor) and then cover the light sensor. Maybe it will power up to auto and then turn the lights on after a minute or two. I'll let you know.
Thanks again, Pat
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On 5/9/2016 3:52 AM, Pat wrote:

The display indicates the *mode*.
The problem is, YOU (reasonably) think ON should mean "apply power to load" as if it was a static decision.
It, instead, appears that the device regards the auto-to-on TRANSITION as the "turn on the power" EVENT (it's not a state but, rather, a transition between states)
Likewise, I'd guess that setting an "on at 1:00, off at 2:00" schedule would NOT have it turn on if powered up at 1:10. Rather, it would only turn on as the time changed TO 1:00 from 12:59.

That should work. Note that the display will go dark if you isolate the electronics board from the transformer secondary.

Possible. Surely worth trying!
But, it could also be that it "goes into auto mode" via a transition from some other mode -- in much the same way that it goes into ON mode as a transition from some other mode (i.e., power failed)
"If you want to test the photo eye during the day, plug the power pack and cover the photo eye so the photo eye does not receive any light. Press the setting button to "A", making sure the photo eye is completely covered, and your light fixtures will turn on. Uncover the photo eye and your lighting fixtures will shut off automatically."
This description leaves the actual behavior undefined. It still doesn't indicate how the device will react when powered up -- with the sensor *dark* OR *light*. (I.e., test it in both configurations just to be sure)
We had a similar issue, here. But, our power supplies are driven with a mechanical timer. So, I just removed the PHYSICAL "stops" (that trip the switch on or off as they are encountered on the rotating disc) and manually tripped the switch into the ON position.
Note, also, that you might want to consider replacing the incandescent lamps with LED substitutes. We had 20W incandescents in all of our fixtures (200W supplies for front and back yards). The transformer laminations would hum a good tune! When we swapped the bulbs for LED lamps, the load dropped substantially.
One last tip... to weatherproof any splices in the buried cables, make the splice inside a Rx pill bottle. Then, fill the bottle with silicone caulk (the bottle gives a "shape" to the caulk)
Good luck!
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On Mon, 09 May 2016 04:27:29 -0700, Don Y wrote:

Yabutt, as has been pointed out for similar (motion detector) switches, if the switch does not have a white (neutral) connection, then the light sensor circuit uses the load as a virtual ground, and thus will not function if the load is not purely resistive.
--
http://mduffy.x10host.com/index.htm

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On 5/9/2016 8:43 AM, Mike Duffy wrote:

It;s a "power pack" -- essentially a giant wall wart. It has line, neutral and (no doubt) earth available to it. You can switch the *line* connection (via the wall switch) but unlikely that you'd not have earth and neutral available continuously at the outlet to which the transformer is connected.
A motion detector light typically is designed to be installed in place of a light fixture. In which case, you don't have *guaranteed* access to anything (line, neutral or earth) so have to "make do", electronically.
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On Mon, 09 May 2016 04:27:29 -0700, Don Y

It turns out that it always powers up that same way (indicator "on" with the lights off). I ended up removing the control board but I was able to keep the circuit breaker in the circuit. It works as I want it to now. Thanks for you help.
Pat
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On 5/9/2016 12:24 PM, Pat wrote:

Ah, so it doesn't "remember" -- unless you want it to remember "on"! :>

Great!
Did you notice if they were using a solid state switch to control it? Or, a relay? You might be able to put the board back in and just "jimmy" the control. Then, un-jimmy (Jammy?) it when you want its original behavior back.
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On 5/8/2016 9:54 PM, Don Y wrote:

What I've done is to provide a different 'transformer', one that is actually a 12 volt DC output made for powering a printer, a switching power supply. I'm using standard Malibu lights, but I have replaced the incandescent bulb with LED bulbs. AC to the power supply is controlled by X10 in my case.
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On 5/9/2016 5:18 AM, Art Todesco wrote:

120W is a fairly large "brick" at 12V. Usually, as loads increase, they like to up the output voltage as well. E.g., 19VDC for most laptops -- esp larger ones. (also sort of required by the battery packs in them)

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