Feb 27, 2009 03:41 pm I have no answer, but "?" isn't much of a topic title...
?
Posted on Feb 27, 2009 03:39 pm
Rob Stemple
The Czar of BS
Member Since: Dec 31, 2007
This is something that I am not even trying to funny on. I have a project that I am working on right now.
It's an LED dimmer circuit that has a high current LED. And I need a transistor that will be able to handle the current requirements.
So I was looking at the LM3909 as a possible candidate for my needs. And I came across this article that describes the LM3909 in a high current situation. Or, at least I think I did!?!
www.elecfree.com/electron...rent-by-lm3909/
Can anyone understand what this was translated from to English? I think it was Japaneses. But I am not sure. Any clue as to what the heck it means?
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Feb 27, 2009 03:41 pm I have no answer, but "?" isn't much of a topic title...
Feb 27, 2009 03:45 pm Sorry for that. But my head is still swimming from this.
Quote:
By lamp at have reflect large-sized stay within a darkroom will fine give wink with tall speed That will do see to is actor picture stops something K rumor can shake.
I didn't know what else to put.
Feb 27, 2009 03:50 pm Oh my word. What the hell? Is there a place on that site anywhere to let them know that they sound like either a spam email body or a mentally retarded thesarus author? I sure hope they're not trying to sell anything.
Hey, maybe they should go to work for the IRS and write help documents for tax laws? It'd be an improvement.
? indeed.
Feb 28, 2009 01:08 am Rob, I will try and take a look tomorrow when I get a minute.
How high current are you talking? I know there are a couple circuits that will replace the LM3909 as it has gotten expensive.
Feb 28, 2009 02:41 pm We are not talking a lot of current in general. The LED that I have draws around 800ma @ 3v. Running through a 555 timer. So I am looking for a transistor that the Ib that has an hfe large enough.
If I were using T1 3/4 LED's, this wouldn't be an issue. But, there color temp, and view angles suck. So, I bought the Osram LED's with the thermal backing. I even have Germanium diodes for the potentiometer.
It works well for the little that I am able to test the circuit. That is until the small transistors that I have go up in smoke. Which I knew that they would. I just wanted to see on my bread board that the 555 is behaving the way that it should. I never played with Germanium diodes before. And I wanted to make sure that the square wave was clean.
I don't have a transistor chart yet on my computer. And that is why that I was looking at the LM3909. But the translation on this page is horrendous.
I just may go with an MPSA14, or 65. I just don't feel like the CE junction will last long enough.
Feb 28, 2009 08:19 pm OK, well it looks like your on your way then. I guess seeing the MPSA actually related in English makes it easier to decide.
But either one will handle that kind of current.
Feb 28, 2009 08:26 pm As I read this thread earlier, I couldn't help but wonder what kind of single LED would draw 800mA of current. Most ordinary ones draw less than a tenth of that amount. Probably designed to be seen in bright sunlight over vast distances, eh?
Feb 28, 2009 08:51 pm It's a monster of an LED.
www.mouser.com/Search/Pro...lkey889-W42182T
The guys I work with are looking to convert most of the board lights to LED's. They are getting tired of arriving at a gig with half of the lights burned out.
So, I came up with an adapter that will plug into the consul, then into this box that I am building, and out to an LED littlelite of my design.
It should work. I just got to get the design a little more bullet proff.
Feb 28, 2009 09:00 pm Thanks monmixr. I tried a v-reg, and sadly it wasn't able to handle the high speed switching. When you dim it to 50%, and a large heat sink attached, it still burned up.
That's why I started to look at small signal transistors. But all of them are to small on the Ib, Ic junctions. Since they are for low current.
I'm starting to think that I may have to go the puck buck way. But most of them, require a higher power then +12v.
Feb 28, 2009 09:35 pm I was wondering what you were needing such a huge drawing LED for. I kind of thought it might be for something along those lines.
How close are you to getting it to work without fail?
I might have a different source on the 3909 spec as well in more english. I'll have to look on Monday at work though.
Mar 01, 2009 08:15 am Hmm. This plan uses STP36NF06L
picprojects.org.uk/projects/bigmosfetrgb/index.htm
$0.84 here:
www.google.com/products?h...=1&ct=title
For what it's worth.
Mar 01, 2009 02:05 pm Cool, thanks Herb. I was going to go the MOSFET route. But, I wasn't sure if they could handle the high speed switching. I'll give it a shot.
As for the RGB plan. I have made a similar one to that already. I made it with a different power supply. I wasn't to worried about AC ripple. So, I didn't make the supply as large. Mine has a little over a half volt of ripple. Which the IC doesn't seem to mind all that much.
The one I made was for my wife. She wanted a moon the would light up for a stage effect for Halloween.
What I did was to take a 14" drum head, and paste a picture of the moon on it. Where ever the paper moon wasn't, I painted black. Then I took a piece of wood that was 14" in diameter, spread mylar of on it. And put two different colors of LED's all around it. Amber and White.
Then I made a control box up with two faders, and a pump button. With the power supply built in it.
It works very well. I'll have to take some pictures of it in operation. But, I had to steal some parts from it, to get another piece up and running. I should order the pieces for it soon.
Mar 06, 2009 05:24 pm So, I found a transistor that will work. And I actually had them in my repair shop. Go figure?
Turns out that a ZTX449 has a 1A Ic junction. And will have a hfe of 200 with a 10k base resistor.
Just for right now, I have 30 T1 3/4 LED's drawing a pitiful 160 ma through it. But it's working just fine. With a 14.4v supply, I get from around 10% to 99% dimming.
Next step will be to find a 22w 6.8 ohm power resistor. Believe it or not, that's what I need for the monster LED.
Once I find the resistor, ever board in the shop goes LED for the Littlelite's. No more burned out bulbs!
Mar 06, 2009 06:23 pm May the genie in control of the magic blue smoke forget where you gig.
Mar 06, 2009 06:27 pm One of the better sources for high performance res I have used.
www.caddock.com/Online_catalog/power/Power.html
As well this place can make you anything your little heart desires. I've used them for some rather large water cooled type.
www.milwaukeeresistor.com/index.html
These might be overkill.
www.powerohm.com/
Mar 06, 2009 09:03 pm Nothin much to do on a Friday night is there Herb?
I'm hiding from more furniture moving.
Mar 06, 2009 09:28 pm What? Binford doesn't make resistors?
I don't know Noise.... Powerohm may not make one big enough for this LED.
Ha..... Ha.
Overkill maybe to understated for thous resistors. Hell I just wanted to cut down on the current. Not start my own power plant.
Caddock looks very interesting. I never heard of them. And I'm digging there catalog. Mouser has wire wound ceramic resistors that I need. But, does not have them in stock. And it would take a 5 week lead time for them to order them.
I think I will go with Caddock thank you.
Mar 06, 2009 09:37 pm Ya, Caddock seems to have a pretty good selection in stock. Most times that is. I have had a wait now and then though.
I thought you would get a kick out of the Powerohm link. Funny Herb didn't step in on that one.
Mar 06, 2009 09:44 pm Oh, give him time. He is just thinking of the perfect little quip to throw at us.
I was just going back over the spec's for the LED that I have. And found that it is now obsolete.
Got to love haw fast they are developing the new generations of LED's.
As soon as you purchase a batch, they are already out dated.
Mar 06, 2009 09:49 pm Ya, I bought 3 1 TB Seagate SATA drives about 9 weeks ago and now the 1.5 TB drives are cheaper then I paid for the 1 TB drives. Ain't technology fun?
Mar 06, 2009 10:52 pm [quote]
Oh, give him time. He is just thinking of the perfect little quip to throw at us.[/quote]
"Funny Herb didn't step in on that one."
Lawd, y'all fellers jest need mo practiss.
Mar 06, 2009 11:28 pm Wees sa gettin there. Yousa gotta give us simple folk more time.
Mar 07, 2009 12:09 am www.littlite.com/products.php?category=10
looks like you need to sell this to littlelite, they just switch from red to white...
Mar 07, 2009 12:21 am <disclaimer> All offenses taken from dialectizations written and/or characterized in this thread shall be the sole responsibility of the receiver of said offensive material. </disclaimer>
Ah. Now it's Ravioli in bed. I'll upload photos later. Nitey.
Mar 07, 2009 12:24 am Now I have seen guys put Blue gels on their lights. But Red? I can't imagine why you would want Red?
Littlelite won't make any dimmable LED lights. I had already approached them on the subject. They are too worried about the idiots out there that would try to vary the voltage. By turning the dimmer pot on the board, instead of the PWM dimmer pot.
They are already having issues with the LED line in that respect. People are calling up to tell them how much the new LED's suck. Because they are trying to dim them.
That's why you see the warnings all over their site for this. And why I had to design my own.
Mar 07, 2009 12:29 am Oooh. Ravioli.
Oh great. Now I'm hungry. And it's 1:30 am.
NUTS!
Mar 07, 2009 07:53 pm Ya, I tried one of them in here for over my turntable and it sucked. I returned it.
Mar 08, 2009 03:23 am I really like the idea. Im going to see how beefy the phantom power in my sr6000 PSUs are, since I already have it torn apart, I may try it as a mod to that thing....
Mar 08, 2009 11:12 pm Yeah, it's coming together rather well.
The schematic for the circuit are on a site that you know of already monmixr.
It's from REUK.com
www.reuk.co.uk/LED-Dimmer-Circuit.htm
The only thing that I found that was a mistake, was the fact that the base resistor is wrong. It should be 10k instead of 1k.
I also used a switched potentiometer as well. So that I could turn them on and off right from the project box itself.
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