Attn: GatorCSM
- Thread starter sucram
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gatorcsm
Member
You'll need around a 20 ohm resistor for that setup. You're goal is to get the 4.5 volts to 20-30milliamps per LED. So since you'll have 4 of them in parallel, you'll need to drop it to around a 35 ohm resistor. Don't go less than 35 ohms (this might be pushing the capacity of those LEDs). This will give you a total of 128 milliamps (assuming 35 ohm resistor) and then divide that by 4 for the 4 LEDs, giving you approx 32millamps per LED. That's just .2mA over the rating. But shouldn't be a problem. I have mine slightly over, and it's not a big deal. Been working for a while now.
You'll put the resistor in series with all of the LEDs by connecting it either on the + or - side of your drawing going to the power source. This would make it such that the entire circuit's resistance is being raised (not only for one LED).
Here's the diagram pointing the spot out.
You'll put the resistor in series with all of the LEDs by connecting it either on the + or - side of your drawing going to the power source. This would make it such that the entire circuit's resistance is being raised (not only for one LED).
Here's the diagram pointing the spot out.
sucram
Member
Gator, a couple more questions. I got some 10 ohm and 15 ohm resistors (1/2 watt, 5% tolerance). Are these the right ones? Resistors are additive, right? I figure I'd put 2 15's and 1 10 ohm resistors in a line together. That would give me 40 total, I think. So the number on the LED packaging, 20-30 mA is the required current for the LED, and the 400mA on the power source is the maximum amount I can draw from (ie. I could put 20 20mA LED's in the same circuit)? Just wondering for my own knowledge.
Thanks again.
Thanks again.
gatorcsm
Member
That's correct on current (LED requirement and power supply limit). If adding resistors, put them in series (end to end). So to answer your question, they are cummulative.
You could also use 2 10 ohm and 1 15 ohm (35) ... this would be borderline on the LED high current but would provide maximum output w/o excessively overloading it and significantly shortening it's life.
Hope this helps.
Gator
You could also use 2 10 ohm and 1 15 ohm (35) ... this would be borderline on the LED high current but would provide maximum output w/o excessively overloading it and significantly shortening it's life.
Hope this helps.
Gator
hookedonreefs
Member
This weekend I bought 5 2600 MCD blue LEDs. They're rated 20 - 30 mA. I also bought a 4.5 V power supply which produces 700 mA. Then I bought a 440 Ohm resistor. I put the LEDs in parallel, and the resistor on the positive wire of the system. The LEDs work, but they're dim. I took the resistor out and the setup still worked. (much brighter) My question is: without the resistor, am I supplying too much current? I get lost in the Ohm/volt/mA relation so I couldn't figure it out. I've read the DIY moonlighting posts and get a little lost there as well. Can anyone explain it in Laman's (sp?) terms please? Thanks.
gatorcsm
Member
hooked--
Gator is in the Navy and is out to sea. This is Mandy, his wife, and I am going to be forwarding anything I see that might need his specific help (electrical stuff). I don't know that anyone else will look at this post at this point, so I am going to email him your question. He is on a submarine, so it may take a bit for a response. Email is sparadic from a sub. You might want to start a new thread and see if there is anyone else who might be able to get you on the right track before he can respond. I will post his response here as soon as I get it. If you have already gotten what you need by the time there is a response here, disregard. Hopefully won't be long, I would like to hear from him too!
Caio,
Mandy
Gator is in the Navy and is out to sea. This is Mandy, his wife, and I am going to be forwarding anything I see that might need his specific help (electrical stuff). I don't know that anyone else will look at this post at this point, so I am going to email him your question. He is on a submarine, so it may take a bit for a response. Email is sparadic from a sub. You might want to start a new thread and see if there is anyone else who might be able to get you on the right track before he can respond. I will post his response here as soon as I get it. If you have already gotten what you need by the time there is a response here, disregard. Hopefully won't be long, I would like to hear from him too!
Caio,
Mandy
hookedonreefs
Member
Thanks for the heads-up Mandy. I really appreciate what you're doing, but I don't want to bother a person that is busy defending our country. I'm sure other people on the board will help, and I'll start a new thread. Thanks again, I hope gator returns soon and in great health.
sucram
Member
I think I can help you out. Mine works and yours is very similar to the setup Gator helped me with. (Volts=CurrentxResistance). I have 4 of the same LED's that you have, the math isn't that different from what is above.The relationship is V=IR.
If you want to supply each LED with 30mA, figure 5x30mA=150mA
You need to drop the current to 150mA (or .15A)
4.5V=.15A x R
R=30
With 5 LED's you need a 30ohm resistor. The 440ohm didn't allow enough current to get to the LED's.
If you wire the LED's in parallel, and add 30ohms of resistance, it should run well. If you can't find a 30ohm resistor, you can wire lesser ohm resistors in series to produce the same resistance (ie 3 10 ohms resistors, 2 15's...)
Hope this helps. It should look pretty cool.
Here's mine.
If you want to supply each LED with 30mA, figure 5x30mA=150mA
You need to drop the current to 150mA (or .15A)
4.5V=.15A x R
R=30
With 5 LED's you need a 30ohm resistor. The 440ohm didn't allow enough current to get to the LED's.
If you wire the LED's in parallel, and add 30ohms of resistance, it should run well. If you can't find a 30ohm resistor, you can wire lesser ohm resistors in series to produce the same resistance (ie 3 10 ohms resistors, 2 15's...)
Hope this helps. It should look pretty cool.
Here's mine.
hookedonreefs
Member
Thanks sucram. I had seem that same picture of your tank on your webpage, and it inspired me to create moonlighting as well. I went a Radio Shack and had a well educated man help me with the problem. I didn't like his answer because he asserted that the onlly correct way to wire this was to install 44ohm resistors on each LED and have each LED run to a separate groud.
I don't think he realized what he was saying. I bought the 44 ohmers anyway, and will replace my 440 with the 44. That should still do the trick and give me some nice lighting. Thanks again for the reply.
I don't think he realized what he was saying. I bought the 44 ohmers anyway, and will replace my 440 with the 44. That should still do the trick and give me some nice lighting. Thanks again for the reply.