Newbie : Converting Landscape lights to LED's

Thread Starter

misfit0138

Joined Jan 4, 2015
15
Newbie here with a few question.

Being a Machinist I manufactured new landscape lights out of some 3 x 3 x 1/4 wall aluminum tube(pic attached) a few years ago. I was tired of spending a ton of money on c**p that would only last a year or two before they fell apart, and the kids with balls etc.So i figured a nice simple newbie project. Ive

It is a 12 volt system, i think the power supply is rated for like 200 watts or so. not 100% sure.

I was thinking of a small board with im thinking between 4 and 8 LED's (id like them pretty bright as i have no street lights by the house) my resistors and some sort of plug to attach to main line. Im guessing i should seal the board and all with silicon or something( any ideas on that) or will silicon work?

Also i know that negitive and positive really dose not matter with the standard landscape bulb so how would that work.Do i need to put some other component like diode or compositor etc?

Do i need to build something at the beginning by the power supply?

Also any anyone suggest some good books for a newbie.

Thanks for your help.
 

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wayneh

Joined Sep 9, 2010
17,153
One thing to resolve is the bulbs you want to use. This will dictate some of the other design choices.

Personally, I would go with hard-wired LEDs because of their longevity and efficiency. Regular landscape bulbs are another choice. They are available everywhere. In my limited experience, though, they often fail due to weathering and corrosion at the socket terminals. LEDs sometimes fail due to corrosion of the leads as well, but with attention to moisture control I think the LEDs would be more solid and less work to maintain over the long haul. But even with LEDs, you have to choose the type, color, spread angle and so on. The big box stores are starting to have good displays showing the differences.

Those lights look great, by the way.
 

#12

Joined Nov 30, 2010
18,223
I was thinking of a small board with between 4 and 8 LED's (id like them pretty bright as i have no street lights by the house)
Therein lies our problem. You say, "4 to 8 LEDs" and I think, "You couldn't possibly be aware of the improvements available lately".

Do what wayneh said. Go exploring. Look at the CREE website. It's weak giving you an idea about brightness, but that's what the big box stores are for. Think, "brightness per watt" and try to scale your imagination up.

Personally, I installed 20 foot poles with HPS bulbs on them, but that has nothing to do with looking good. It's merely functional.
 

wayneh

Joined Sep 9, 2010
17,153
You should also be aware of things like this. They're designed for cars, so presumably are fine for a 12V landscape light. The thing is, you won't have to fool around with individual LEDs. Buy a complete solution, one you can easily fix down the road.

I only just now realized your thread title. I guess we're going with LEDs.
 

ebeowulf17

Joined Aug 12, 2014
3,282
I'm pretty sure your system is AC right now, and the LEDs will only produce light for a portion of each positive cycle if powered directly from it.

Here's an interesting discussion from another forum that touches on many of the decisions you have to make:
1) to rectify or not
2) if rectifying, to do it system-wide or per-fixture
3) what optics to use to spread/diffuse the LED output, which tends to be in narrow beams, at least compared to incandescent lighting

http://www.candlepowerforums.com/vb/showthread.php?260026-Low-voltage-power-transmission-AC-or-DC
 

Thread Starter

misfit0138

Joined Jan 4, 2015
15
Thanks for all the replys. Looks like i have some more reading to do.

It is a 12o volt transformer down to 12 volts.
Ive been playing around with 5mm high brightness white LED from radio shack. PN 276-0017. the intensity is 7000mcd, viewing angle 30 deg(which doset matter as i have some reflective material in the top abd bottom), FW current 25Ma and FW supply 3.3 to 3.6 max. Not to sure if thats what im going with but thats what i have right now, and its a start and what i have been playing with on my test breadboard learning.

Im not looking to be able to land planes with the lights but enough to see where your walking.

I have 5 lights total installed outside along driveway and up to door, each bulb i believe is 12 or 15 watts and thats pretty good light.

Im also not looking for perfection on the first run, theres always room for improvment, plus its a learning curve. I can only learn so much from reading, and not that i have money to throw away, i know mistakes happen, and sometimes thats the only way to learn.

I was told a long time ago. And have tried to go by this. Theres noting impossible in life, just tricky. And you need to find the right trick to get it done.
 

Brevor

Joined Apr 9, 2011
297
I assume you are planning to use "white" LED's, be aware there are 2 types of white LED's, warm white and cool white. Warm white looks like the color of an incandesent lamp and cool white has the color of a flourecesent lamp.
 

ronv

Joined Nov 12, 2008
3,770
Leds are about 10 times more efficient that incandescent lights. So if you have a 12 watt bulb now and like it you will need about 1.2 watts of LEDs for the same light. Looking at your picture (very nice) I would think 3 110 degree ones like this:
http://www.mouser.com/ds/2/90/C535A WJN 877-474272.pdf
A little bridge rectifier like this to turn the AC into DC.
http://www.mouser.com/ds/2/345/db101-107-32844.pdf
and a 332 ohm resistor like this for each 3 in series:
http://www.koaspeer.com/catimages/Products/MF-MFS-RK/MF-MFS-RK.pdf
Since your a machinist you could probably make a perf board box to mount them on.
See what you think and we can make you a picture if you like it.
Capacitor
http://www.mouser.com/ds/2/293/e-pw-364183.pdf
 
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Alec_t

Joined Sep 17, 2013
12,249
viewing angle 30 deg(which doset matter as i have some reflective material in the top abd bottom)
Unfortunately, in a limited size enclosure, the 30 deg beam won't reach the reflector unless you deliberately aim it there.
 

Thread Starter

misfit0138

Joined Jan 4, 2015
15
Thank you for all the reply's. I appreciate all the help and new web pages to surf. Really like that cree site.

Yes i though about buying them already done from somewhere and just drop them in. But whats the fun in that. lol

@ronv thats pretty much what im looking for. I have never used mouser. How are they. Any thing i ever need I usually use MSC Direct, McMaster Carr, And Newark electronics.

Also the bridge rectifier changes AC to DC? I beleive it is already converted to dc being that its 12 volts? Its one of those Home Depot transformers. I will check though. And I really havent done much with bridge rectifies before. I really am a newbie to all this.

I Have A 2 1/2 x 2 1/2 piece of reflective aluminum in the top of all lights now. Was sort of thinking of doing the same in the bottom. Shouldnt be too bad.

In my 20+ years of R & D, machining, welding, manufacturing and more, Make a prototype (or 10) and keep working it till your satisfied.
 

ronv

Joined Nov 12, 2008
3,770
Yes i though about buying them already done from somewhere and just drop them in. But whats the fun in that. lol
Now your in trouble. They will start calling you sparky instead of tin bender. :eek:

thats pretty much what im looking for. I have never used mouser. How are they. Any thing i ever need I usually use MSC Direct, McMaster Carr, And Newark electronics.
I like Mouser. They send me a catalog about the size of the Denver phone book. Sometimes it makes it easier to find parts than the online search. They also have a neat feature where I can make you a parts list and you can just click it and order all the parts. If you want to PM me your e-mail I'll send one to you for this project.

Also the bridge rectifier changes AC to DC? I beleive it is already converted to dc being that its 12 volts? Its one of those Home Depot transformers. I will check though. And I really havent done much with bridge rectifies before. I really am a newbie to all this.
Usually they are AC since the regular bulbs don't care. You could use one larger bridge at the transformer but it's another modification and if the kids put a tent stake thru the wires it would probably blow. :(

I Have A 2 1/2 x 2 1/2 piece of reflective aluminum in the top of all lights now. Was sort of thinking of doing the same in the bottom. Shouldnt be too bad.
I modified the circuit a little so we can run four in series - a little over a watt of led light.

In my 20+ years of R & D, machining, welding, manufacturing and more, Make a prototype (or 10) and keep working it till your satisfied.
My concern is if it will be bright enough. I think it will be ok.
 

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ronv

Joined Nov 12, 2008
3,770
Here are a few pictures to help with the wiring.
For the bridge most have 2 pins marked with ~. These get the two wires from the transformer. The other 2 pins will be marked + and -.
The capacitors usually have ---- down the side that goes to -.
The short lead and the flat on the led are the cathode and go to -.
When calculating the resistors you need to know the output of the transformer is 12 volts RMS. The peak voltage will be 1.41 times higher or around 17 volts.
The voltage drop across the bridge rectifier will be about 1.1 volts, so you have about 16 volts to work with.
Most white LEDs drop about 3.2 to 3.5 volts. So to calculate the resistor for 1 LED you can use ohms law - R = E / I. or 16 -3.2/.020 = 640 ohms. Nearest standard value is 680 I think.
For 4 LEDs in series. 16 - 12.8 / .020 = 160. Use 150.
 

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Thread Starter

misfit0138

Joined Jan 4, 2015
15
So please help me under stand something. Im going to go to radio shack tomorrow and just pick up some different leds to play around with and see what i like. And then order what i need from mouser or someplace else.

I know i need a bridge rectifier. A 1a 400v should do if i am using only a few led's. the amp draw should be way under 250Ma and im using 12 volt.

I know i need corisponding resistors for led's.

But Why the cap? just not sure. I may be wrong but they store energy? correct. Can someone please explain why.
 

ebeowulf17

Joined Aug 12, 2014
3,282
I believe it's there to make the DC smoother. You start with AC, which looks like a sine wave. Running that through a bridge rectifier turns it into a series of positive arches, with no negative component, but still with dramatic valleys in between rounded peaks. The cap stores energy from peak times to fill in the valley times so that the peaks and valleys at the output are much closer to one another. The image below is from this very website, at http://www.allaboutcircuits.com/vol_6/chpt_5/6.html. Click through and read on if you want a much better explanation of all this than the one I just gave...

 

wayneh

Joined Sep 9, 2010
17,153
Im going to go to radio shack tomorrow and just pick up some different leds to play around with ...
In my opinion, that's nearly a waste of time. The range of things offered at the Shack is too narrow and just won't show you the type of things that are available. For instance a cheap blue LED I bought on E-Bay was 10 times brighter than the similar LED I bought at the Shack, and I'd guess I got a bag of 50 for the price of one single LED at the Shack.

A more thorough way of trying different things might be to seek out different LED types. The hardware store can show you the difference between cool white and soft white. At Mouser you should also be able to find wide angle LEDs to compare with focused-beam LEDs.
 

Thread Starter

misfit0138

Joined Jan 4, 2015
15
I recently bought from Amazon 100 leds with resistors for like 8 bucks. Seems like good deal to play around d and do some learning. I have a few questions. But here are some specs.

Landscape transformer is pushing out 15 volts ac, and so through the bridge rectifier and cap I have approx 12.4 volts dc

Leds are 5mm 3.2 volts and 24 MA. They are very bright and push out some really nice light.

I have total 18 leds. I made 6 groups of 3 leds in a group with a 100ohm resistor. A radio shack single phase bridge rectifier at 400 vdc and 1.5 amps. Pm 276-0268. Also have 16volt 100uf compasitor.

Does any one see a problem with this set up. If so please explain.

Here is a pic of1 done. It's in the r and d stage. I think I may add a few more leds to each set up. Also is there something out there to aid in the drawing of schematics. So I can attach a pic of that.
 

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Bernard

Joined Aug 7, 2008
5,788
You might have a measuring error or a wiring error, output V should be around 19 V DC. Capacitor V rating should be about 25 V, C 500 to 1000 uF.
How many fixtures? 3 or 4 faces?
 

wayneh

Joined Sep 9, 2010
17,153
... is there something out there to aid in the drawing of schematics.
There are many. One that is useful LTspice. It's free, lots of folks here use it, and you get a simulation of your circuit to boot. The interface takes some getting used to, but it's not to bad.

The answer depends on what you need and what you are comfortable with. I have a long history with 2D drawing programs so when I started drawing circuits, it was easy for me to use that familiar tool. Others use dedicated circuit-drawing programs such as Eagle and DipTrace because those can produce a drawing suitable for producing a finished printed circuit board. But for a noob unlikely to use that feature, they can be overkill.
 
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