Thread: LED Help

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A few years ago I was given a bunch of LED units. I still have at least 60 of them. I have used them to make mini spots running off a 9 volt battery, but they run even brighter on 12 volts. I suspect they are designed for 12 volts. Unfortunately I have misplaced the original packaging, but I seem to recall they were used for automotive purposes. Just today I hooked one up to my notebook power supply which puts out 19.5 volts. They were intensely bright. Not sure how long they will last at that voltage but I will hook one up to a spare Power supply to find out.

So I decided to unsolder the clear brights and solder in some 3 volt 30 MA LEDS I got from Frys. The intensity is quite less. Plus these LEDS are actually yellow in color.

So what I am trying to do is create some lights to continue the test on the steam based virtual fire.

So since we have some Circuit and LED guru's on this board I would like some help. First. This circuit board appears to have two components on it. One is referenced from the front with 10402 the other larger component has 161 printed on it. I have taken close ups of the unit as is, and the board removed and the yellow LED's soldered on to it.

So if anyone can identify the unit so I can obtain the specs for the existing LED, I am hoping I can purchas narrow beam high intensity colored LEDS to replace them. The other option is to use some kind of lense material.

Thx in advance for any help on this.

That holder breaks the 4 LEDs up into two strings of two LEDs each. The 161 component is a 160 Ohm resistor that both strings share (not the best design practice, BTW). The last component is a diode of some sort. It could either be a Zener, to regulate the max current the LEDs get, or a regular rectifier, to act to protect the LEDs from reverse polarity. If you say it gets a lot brighter when you put 19.5V on it, it's probably not a Zener.

Most LEDs don't want more than 20mA through them. As-is, this circuit will give you approximately the following currents, with the given voltages...
@9V: 6.25mA
@12V: 15.625mA
@19.5V: 39mA

So, you probably don't want to be running these (as-is) with more than 12V. Regarding swapping the LEDs, you can find a lot of components at superbrightleds.com However, if you change the color to red, yellow, or orange, you'll need to change the resistor too, because they have different Vf (forward voltage) than blue, green, or white.

If you're looking for decent power, may I suggest going the route I went with the treasure chest lighting, and pirate spotlight, and use some 1/2W or 1W 10mm LEDs from eBay. A standard 'superbright' red LED is ~12,000mCd - (4) of them would be 48,000. One 1/2W 10mm spot from eBay is 190,000mCd.

Depending on what kind of effect you're looking for, the Medusa board might be able add to your display. Having the lighting dim and flicker might make the fire effect look even more realistic. You can see an example of this on the 'gold coins' lighting in the pirate video.

- Hook

Just the information I needed. I suspected the 161 was a resistor, but just does not look like any resistor I have ever seen. As far as the diode. So LED's can survive being overdriven? I have one of these on the 19.5 volts for 20 minutes and it still is going strong. But I will take your advice and consider different LED's. For right now I was just trying to jerry rig for testing. And I think you are correct that some kind of modulation of the LED's will help the effect.

Thank you so much for the help. This is one area I am really light on, Pun intended. LOL !!!

Overdriving LEDs will shorten their life. The more you overdrive, the shorter the life. If you give a 20mA LED 1000mA, it'll probably only last a second or so (totally guessing). If you drive it at 39mA instead of 20... it'll probably last for a while, but it won't last tens of thousands of hours, the way they're supposed to.

One giveaway that you're overdriving LEDs is that the color will change slightly, while they're being overdriven. Although, that won't really affect white LEDs as much, I'm guessing, because much of the light comes from the yellow phosphor, instead of the (actually blue) LED itself.

I was thinking of doing a tutorial on how to build one of the spotlights like you see in the pirate post. It sounds like that might be along the lines of what you'd be needing. I made mine to have 4 different colors (R,G,B,UV), all of which could be controlled. But you could do it differently, and have all one color, and all on one circuit. Or.... if you were to control them, would maybe be cool to have a pair of red, and a pair of yellow, and flicker between them. Hmm....

- Hook

More good info.

I just bought. 10 1 watt of each Orange and Red.

So I will likely want to dim or flicker in pairs spaced out along the steam line. My goal is to work towards a fire effect of about 5 ft. So the spacing on the LEDs will be 6 inches. I am not sure if the steam nozzles can be spaced that far though. So the LED's will likely cover more than one nozzle each.

I will see if I can figure out the proper circuit, but I can use some help on the flicker and dimming. I am working on a two armed grave grabber and I would like the fire effect to effect this prop. Kind of like escape from hell concept. So this prop will be PIR triggered. I will likely use a picaboo controller. I use my VSA for my skull routine so that is out for now.

Your assistance is much appreciated.