Proper Wiring and Selecting a Transformer for LED Backlit House Numbers

Thread Starter

ljmccon

Joined Nov 27, 2015
35
Hello, circuit peeps. I need to install some new numbers on my house, and I came across these very cool LED backlit house numbers. (I'll be using the 5" numbers with white backlight.) I have limited experience with low voltage wiring, and for some reason, I'm having a heck of a time getting the seller or manufacturer to answer my installation questions. So far, here's what I've gotten out of them:

LED Numbers (link):
Contain 6-9 Cree LEDs
Voltage: 6-12V AC or 6-12V DC
Power: .045A @ 12V DC
Recommended LED Driver (link):
Input: 100-265V AC
Output: 12V DC, 1A, 50-60 Hz​

So here are my questions:
  1. Based on the driver they recommended, it looks like these numbers require a constant-voltage driver, correct?
  2. Would I be correct in assuming these numbers should be wired to the driver in parallel?
  3. Is there any way of determining whether or not these LEDs are dimmable with the information I have? (I'm aware I'd have to get a driver that allows dimming -- I'm just wondering if the LEDs themselves are capable of being dimmed.)
  4. I read an article that said you shouldn't have a load of less than 50% of the driver’s maximum wattage (source). The driver recommended by the manufacturer is 1A @ 12V, which makes it a 12W driver; I'll have 5 numbers (presuming in parallel), and at 12V, they're each using 0.54W, for a total load of 2.7W. So, wouldn't this 12W driver be too much? Or do I not need to worry about minimum load, here?
If you can educate me, I'd very much appreciate it!!!
 

Bernard

Joined Aug 7, 2008
5,784
Use a SMPS so that output does not change with load. Probably can dim with PWM from a12 V supply.
Wire in parallel, 4, refers to a transformer power supply where output can change from 2 X rated V to rated V @ rated load..
 

philba

Joined Aug 17, 2017
959
based on the 6-12 AC/DC spec and 6-9 LEDs per letter, I'd say it does not take a constant current supply. My guess is that they have individual light modules, each with one led, that they parallel in the letter assembly.

You can get in-line PWM dimmers for DC. However, it depends on how they power the LEDs. Worth trying.

I'm not sure why you are worrying about the supply. Just use the recommended luxello 6W supply. They spec it to support up to 5 numbers. I would not second guess them. If it fails, they would need to make good on it.
 

Thread Starter

ljmccon

Joined Nov 27, 2015
35
Thanks for the replies! Two reason I'm worrying about the supply: 1. I might want to dim this setup by incorporating a dimmable LED driver rather than the driver they have recommended, and 2. I'm curious. I want to understand exactly what I'm doing and how this all works.

So, I think this is where we are:
  1. Yes, the driver needs to be constant voltage.
  2. Yes, I should wire the numbers in parallel.
  3. Might be able to dim, but not enough info to be sure -- I'd just have to try it.
  4. This is where I'm still fuzzy -- that article I read said you shouldn't load the driver less than 50% of its max wattage, yet the manufacturer is recommending a driver with a max wattage that is over 4x the load. Is the article I read incorrect? Do you not need to worry about underloading an LED driver?
 

philba

Joined Aug 17, 2017
959
Thanks for the replies! Two reason I'm worrying about the supply: 1. I might want to dim this setup by incorporating a dimmable LED driver rather than the driver they have recommended, and 2. I'm curious. I want to understand exactly what I'm doing and how this all works.

So, I think this is where we are:
  1. Yes, the driver needs to be constant voltage.
  2. Yes, I should wire the numbers in parallel.
  3. Might be able to dim, but not enough info to be sure -- I'd just have to try it.
  4. This is where I'm still fuzzy -- that article I read said you shouldn't load the driver less than 50% of its max wattage, yet the manufacturer is recommending a driver with a max wattage that is over 4x the load. Is the article I read incorrect? Do you not need to worry about underloading an LED driver?
1-3, yes.

4. I explained this previously. Why would the manufacturer make recommendations for their products that would clearly fail?

On the 50% loading point - that is pretty much BS. There may be somewhat lower efficiency at low loading but it's not going to break anything. I've never seen a power supply where there were warnings about using a low load. And switch mode power supplies do need some load to start but it's typically not that much, maybe a few percent of rated capacity. You can always just add a resistor in parallel to increase a load at the very worst case but I don't think you will need it.
 

Bernard

Joined Aug 7, 2008
5,784
You need more information on that article driver. Is it transformer based or switch mode. With AC input of 100 to 265 V it will be a SMPS & not dependent on minimum load. The modules probably have a bridge rectifier, resistors, & LEDs, with slight possibility of a filter capacitor. If there is a cap. then it might have no effect on dimming.
 

Colin55

Joined Aug 27, 2015
519
Just use this:

NIGHT LIGHT
This circuit activates a relay when illumination falls below a preset level on the Light Dependent Resistor (Photo Cell).

This circuit will drive 30cm strips to 5m strips. Two 5m strips have been tested with this circuit. NightLight-2.gif

Put a 1k pot in place of 100R to dim the LEDs

 
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