Anyone have on of these?

[Andy1845c]

I bought some of these from electronics glodmine
https://www.goldmine-elec-products.com/prodinfo.asp?number=G9987

I got the red to light with my 12v power supply, but I can't figure the green out. Does anyone have one and know how to supply it in order to make it light green? There is a description of the leads on the EG's site, but being a novice, i'm not quite sure what to make of it. I thought white was ground, but it dosn't seem to work that way. any insight would be great

Thanks!!!!

 

[HarveyH42]

Guessing the white wire is common/ground/negetive. Let see red leds - red wire, so the green wire must be for the green leds. The ad says the reds need 13.2 volts, so 12 volts would likely be okay, just not max. brightness. The greens need 19.0 volts, so 12 volts ain't going to get it, sorry.

 

[philba]

I don't have one but the ad text is pretty clear, you need 19V for the green. also, It's kind of wierd in that the text says that its a common anode device (+ leads are connected). Your power supplies need to be negative supplies. so use a 7912 (or LM337 set for 13.2) voltage regulator for the reds and an LM337 set for 19V for the greens. see the datasheet for circuit details. You probably dont need a huge filter cap if that's all you are powering.

As usual, goldmine leaves out important details but I suspect the current draw is 80mA for the greens and 40 mA for the reds

 

[Andy1845c]

Hey, Thanks Harvey. I thought mabey I should have seen them glow dimly with 12v. I'll see if I can figure out a way to get closer to 19v and see what happens. I just don't want to damage them. They look like they are gonna be pretty awsome lol

Thanks again!

 

[1Steveo]

Can You take a picture of the led board? also check out "http://led.linear1.org/led.wiz" !

 

[philba]

one other point. you should verify that the unit has current limiting resistors for the LEDs. I suspect they do but it's a good idea to know. Otherwise, you might burn out the LEDs.

 

[mramos1]

That is a weird unit.

But there are a lot more green LEDs than red. I would think the white is common. I agree with Harvey, I would have made that ground, but as philba says it states anode so it should be the positive on white.

The RED wire I would have made the red LEDs and GREEN the green LEDs. So if you have RED working, move the wire on the RED wire to the GREEN wire and I would think you would see the green LEDs just dimmer.

Glad we are not working for NASA right now . But that is what I would try.

 

[audioguru]

They don't tell you what it is correctly. They don't have a clue how it is wired.
36 green LEDs in series don't work from only 19V. They need about 79V without a current-limiting resistor. 4 strings of 9 in series will work from 19V but without a current-limiting resistor.

14 red LEDs in series don't work from only 13.2V They need about 25V without a current-limiting resistor. Two strings of 7?

 

[zevon8]

First hit in google, search for LT6750 ( Sharp is the brand, as it says in the ad copy )

http://www.datasheetcatalog.com/datasheets_pdf/L/T/6/7/LT6750.shtml

Not all that unusual of a circuit configuration really, low side switching. I do this with all my signs/panels/indicators at work. Makes the controller easier and cheaper to build.

BTW, there are no limiting resistors.

 

[Andy1845c]

Thanks agian for all the replys

I wasn't able to get anything out of the greens with 12v. I was able to get them to light using an 18v cordless drill battery the mesured just under 20v.

As was said, the white needs to be on the positve and the green wire in the negitive.

I never even though to look for a data sheet. I thought they were surplus and figured there wouldn't be a sheet for the unit as a whole. There is no way to get it apart and look at the insides either. Its all molded in one peice.

My next novice question is, the data sheet lists max V as 14 and 20.5v If I limit the supply voltage to that, or slightly under, do I need a current limiting resistor for each of the colors? It seems like anything I add just makes them really dim.

 

[philba]

They don't tell you what it is correctly. They don't have a clue how it is wired.
36 green LEDs in series don't work from only 19V. They need about 79V without a current-limiting resistor. 4 strings of 9 in series will work from 19V but without a current-limiting resistor.

14 red LEDs in series don't work from only 13.2V They need about 25V without a current-limiting resistor. Two strings of 7?

yes, thats exactly what I came up with to get the current rating I suggested.

No current limiting resistors is an issue - I don't quite understand why. Everything I've read about parallel LEDs says that you should have the dropping resistors in the parallel chains since LEDs don't share the current equally. Maybe if the chains are long enough, the differences even out. kind of makes sense.

This certainly means that he will need to put current limiting resistors in series.

On the common anode issue. Here's what I would do - use a 20V supply, put a 110 ohm, 1/2 watt resistor on the red chain and an 8.2 ohm, 1/4 watt on the green one. Feed the common from the +20V side and then you don't need 2 supplies. if you use an NPN to control each chain, add about .7V to the supply.

edit: I missed your last post - yes, you need a current limiting resistor for each branch. see my above point. Your battery boltage probably dropped a volt or 2 when you hooked it up.

 

[Hero999]

If the LEDs were all fabricated at the same time (they're all cut from the same die) then it's perfectly acceptable to connect multiple chains in parallel without separate series resistors because they will have exactly the same foward voltage, but only the manufacturers can do this.

 

[HarveyH42]

How easy would it be to pop the module open? Wouldn't you need to know how the LEDs are wired? Doubt that 36 green are all in the same series. Maybe there is already (doubtful) some sort of driver circuit behind the LEDs.

I've seen these modules on Goldmine for a while, thought about buying a couple when the had them on sale for $5, but figured the come down further in price eventually. Guessed wrong, so far anyway...

 

[Andy1845c]

I don't see any way of opening the housing. It looks as if the leds are molded in. The back is all one peice with a small slot the wires come out. I'd have to wreck one in order to get it open.

Philba - Thanks for the hook up suggestion It helps point me in the right direction, hopfully anyway, lol. I'm not very experianced with electronics, but I have the desire to learn.

 

[HarveyH42]

Just stumbled across an article you have to read.

**broken link removed**

This is all about hooking up and drive this exact module as a light on a bicycle. Has a ripped open view, all kinds of tech stuff. It will save you alot of experimenting.

 

[Andy1845c]

Just stumbled across an article you have to read.

**broken link removed**

This is all about hooking up and drive this exact module as a light on a bicycle. Has a ripped open view, all kinds of tech stuff. It will save you alot of experimenting.

Wow... that was agood stumble

Thanks for posting it

 

[HarveyH42]

I was looking for some examples of using an LM317 as a constant-current driver, and that article uses them. I saved the PDF for future reference, if those modules come down some in price.

 

[Andy1845c]

If they come down in price, i'll certinly buy a few more for furture projects, but i didn't think they were all that bad a value. For what I want them for (warning lights) they will work about perfectly. My original idea was to solder LEDs onto small rectangle breadboards and make my own moduals, but these are cheaper, ready built, and come in a nice plastic housing with a sun shade (somthing I hadn't figured out how I was going to do)

I dunno, i'm pretty happy with them so far. They are certinly very bright. lol