mini-transformers

Discussion in 'Landscape Lighting' started by sprinkler guy, Sep 8, 2007.

  1. sprinkler guy

    sprinkler guy LawnSite Member
    Posts: 223

    Have any of you guys ever used any mini-transformers? The little 75 watt or 150 watt units that are about the size of a deck of cards or cigarette box. I have an application where the house has a wall sconce for the patio, but the homeowner built a pergola (patio cover) that now makes the sconce ineffective. I'm only calling out three lights (2 downlights with 18 watt incadescents to soflty light the area, a 20 watt spot over the BBQ) Because of the layout of the hardscape I cannot easily get wire from the existing system.
     
  2. ar-t

    ar-t LawnSite Member
    Posts: 49

    I have a similar job in the wings.

    While I have not used any yet, judging from the few I have encountered, they are what we call in the electronics "bidnis" switching power supplies.

    From my limited experience with them, you may notice that the voltage readings won't seem right. Since the waveform is not the usual sine wave that meters are calibrated to work with, it will read lower. The waveform is closer to a square wave, and most meters will give erroneous readings with such a waveform. In addition, the frequency they probably operate could be above the useful range of the meter.

    I'll know better once I get my hands on hand, and get to futz with it.
     
  3. NightScenes

    NightScenes LawnSite Silver Member
    Posts: 2,207

    I have used them on several occasions. You can purchase them through Terradek, www.terradek.com . I think that they are more of a resistor than a transformer. They work very well and I have not had any problems with them.
     
  4. ar-t

    ar-t LawnSite Member
    Posts: 49

    C'mon...you're joking, right.........you have to be joking.

    I hooked up a 75W LighTech (yep, that really is the name......) unit to my 'scope. Interesting waveform, in case anyone cares. I'll post a picture of that if anyone here is interested.

    But, as I am most likely the only bona fide nerd, here......I'll hold off unless someone asks.

    I can assure you that it is not a resistor.
     
  5. pete scalia

    pete scalia LawnSite Senior Member
    Posts: 960

    art I'd like to see your readings. I also cannot read voltage on my meter from these junky electronic transformers. They are a fire waiting to happen. whoever endorses them is crazy. Your right these are definately not resistors whoever said that doesn't know what they are talking about. cheers!
     
  6. NightScenes

    NightScenes LawnSite Silver Member
    Posts: 2,207

    Main Entry: re·sis·tor
    Pronunciation: ri-'zis-t&r
    Function: noun
    : a device that has electrical resistance and that is used in an electric circuit for protection, operation, or current control

    Main Entry: trans·form·er
    Pronunciation: tran(t)s-'for-m&r
    Function: noun
    : one that transforms; specifically : a device employing the principle of mutual induction to convert variations of current in a primary circuit into variations of voltage and current in a secondary circuit


    Here is a picture of this "mini transformer" or "resistor". I said that it is more like a resistor because it "appears" to be more like a resistor than what most of us are used to calling a transformer. (no core and coil)

    Maybe we should include schematics for everything that we post on these issues? I have been an electrician for over 15 years and know the difference but I didn't think we had to get so technical.

    1.jpg
     
  7. Chris J

    Chris J LawnSite Silver Member
    Posts: 2,829

    Paul,
    These things look pretty cool, and I must admit I have never used them or even seen them. But I'm stumped as to how one would control the few lights powered by these devices within the rest of the lighting scheme. In other words, in a typical situation all of the other lights will be coming off of the trans which is probably being controlled by a simple digital timer. How could you add something like this and easily control it along with the rest of the lighting system?
    By the way, thanks for the great new info. I'm still learning something new every day (I hope I always keep the attitude of the consummate student).
     
  8. NightScenes

    NightScenes LawnSite Silver Member
    Posts: 2,207

    Chris, I use these for for areas that currently have line voltage. I can install a low voltage fixture and operate it along with the low voltage system via CS. Sometimes I'll replace a corner flood with a spot light.
     
  9. ar-t

    ar-t LawnSite Member
    Posts: 49

    "Lighten up." (I know........horrible pun.)

    OK, here are some photos of their output. Sorry for the quality of the pictures, but without a viewing hood for my 'scope, and minimal photography skills.......the best I can do.

    Anyway.........the first is the envelope of the output waveform. Horizontal scale is 1 mSec/div.

    [​IMG]

    The portion of the waveform that is intensified is shown in this photo:

    [​IMG]

    Horizontal scale is 20 uSec/div. Basically, the output is a 20 kHz (or so) square wave, that has its amplitude raised and lowered to approximate a sine wave. As opposed to a typical SMPS that will have a square wave output that has its duty cycle altered. Indeed, when measured on a typical DVM, the voltage read 11.7V. The last electronic supply (designed for LV lighting) that I had my hands on measured around 8V. Operating at around 8 kHz.

    Yes.....you could hear it, and I felt it was annoying.
     
  10. pete scalia

    pete scalia LawnSite Senior Member
    Posts: 960

    art that's what i'm sayin these units should be passed on. look at those puny wires coming out of that box they are just waiting to be overloaded and burned up. just my humble opinion
     

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