We are getting into concepts beyond 1st year electronics. While we're not going to make you into an electronic tech you will have a practical understanding of a lot of concepts. A good thing, no?Thanks again for the help I checked the voltage across the resistors it was around 1.22v. I have a couple more questions though. The 25v I can use does that include the 1.22 from the resistors or do I use 25v in leds? One string of leds that I set up have 25.20v is anything over 25 a no no? One more question kinda two parts on the PS there is a hook up for a fan but there is no power at the pins do you know what turns the power on to the fan? I would like to run a small fan for the power supply off of the hook up for the fan on the PS. My last question would be I would like to run one or two fans to cool the light what fans would you recommend and how would I wire them in. Thanks again for the help.
OK, the LM317 data sheet actually says it will output 1.25V ± .05V. So 1.22V is good. It does have some practical ramifications however. It will affect the real current flowing though the LEDs.
We are also going to have start drawing real schematics of what you are using, to prevent misunderstandings. You are going to have to try your hand at it to some extent. You don't have to do this on a computer screen, you can hand draw it and either take a picture of it or scan it in using a flat bed scanner.
I am beginning to loose track do to number of entries in this thread, and length of time between them. This is another reason to pin down the exact schematics we are talking about.
I am assuming you are following the concepts I'm explaining so far, but I don't know if you are unless you can give me some definite feedback.
So you have 0.7A through the LEDs, with a 25.2V regulated power supply. Lets pin down every chain you have, numbers of LEDs and their colors.
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You are wanting to add a fan, per earlier recommendations. If I read you correctly your power supply is 25V. You can do this three ways.
- You can buy a small 5V or 12V wall wart (whatever the fan uses) to provide the power.
- You can put the fans in series with your existing power supply (probably the cheapest option, but not necessarily the best).
- You can build a voltage regulator to tap off the existing power supply for the fans (LM317s are programmable).
Computer fans are cheap, it is usually what I go for. If you can't find a local source (such as Fry's or a local computer store) I can point you to other online sources. You should not spend much over $3 each over them, though $5 is acceptable. If you have a choice look for ones marked as having ball bearings, they last longer. Fans are also noisy, no way around it.
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It sounds like we are at the end game for your project. A lot of what I was explaining above is the measure twice cut once principle. Better to go over something several times than to burn out any expensive components.