Schematic Help!

[SpinnerBait_Nut]

Re: Schematic Help!

Wow!!!! My head is spinning from all that. I now know why I stuck to automobile repair instead of electronics.

 

[petryshyn]

Re: Schematic Help!

You guys are on the right track.....except for the current. Most high intensity LED's utilize .050 amps. That is why it is important to know the LED specs. The forward bias voltage drop also varies with different models. I wouldn't connect them in series for the simple reason that if one fails open, they all go out. Each LED should have its own resistor. At 5 cents apiece, its cost effective.<br /><br />As I said before, let us know what you are using....we then can calculate the resistance required (rather than guessing).

 

[JB]

Re: Schematic Help!

Hi, Schematic.<br /><br />I hadn't thought about the question of one of the diodes going out. Your suggestion to parallel them makes good sense. <br /><br />Maybe you missed the link to the spec sheet.<br /><br />It lists Ifmax as 30 ma and typical as 20ma.<br /><br />Therefore a single diode limiter resistor for Vmax of 16V to get Ifmax of 30ma would calculate to 413 ohms, which you can't buy, but you can buy 470 ohms which would supply a safety margin. Half watt should be big enough.<br /><br />Now, Trollhole, don't let the difference between Scoop's calculations for 1 diode and mine confuse you. He calculated for average current, I calculated for maximum current. Either resistor, or one somewhere between will work well.<br /><br />Good luck.

 

[trollhole]

Re: Schematic Help!

Thanks guys so 1/2 WATT resistor it is. I'll post some pics of my setup when I get done.

 

[trollhole]

Re: Schematic Help!

Got the LEDs today. Man are they bright. I'd say a pack of 25 will really light my boat up. If I can get this resistor thing to work I might be replacing all my light in everything I own.<br /><br />Hey is it possible to use LEDs on 120v house current.<br /><br />I can see these things replacing christmas light bulbs. Wouldn't it be nice to never have to worry about burned out bulbs!

 

[jee70611]

Re: Schematic Help!

You sure can, just get a 120 to 12 volt step down transformer from Radio Shack, couple it to a bridge rectifier, add some capacitors. That would get you to 12 volts. I don't know if you would need a regulator since house current is pretty stable anyway. Schematic and the others can probrably get you the values and other info for making your power supply. Or, you could just buy one already built from Radio Shack. Unless of course, you wanna shady it from old radio parts. Just hook up the power supply in place of your battery and you should be good to go. Good Luck!

 

[Scoop]

Re: Schematic Help!

Jee70611 is on the right track. You would have to have more than just a rectifier to use them on AC. A rectifier just turns the AC sine wave to the positive. You still have a fluxuating voltage from 0V to 115V. While you could make this, it is easier to just buy a DC power supply. They have everything built in and are relatively cheap. 12 volt AC to DC adapter 1500mA<br /><br />Another thing you may want to look at is the low voltage transformers for Undercabinet Halogen lights. they sell thes ein most hardware and other home improvment stores. Not sure what voltage, but it should be around 12. Just keep in mind current limitations for each of these options.

 

[trollhole]

Re: Schematic Help!

Problem Radio Shack doesn't have the exact resistor I need. I bought a 1k ohm 1/2watt and a 470ohm 1/2watt resistor but am not sure either of these two will work. Anybody know what part number from radio shack I should buy that will work the best? I'd hate to experiment since the bulbs cost $1.25 a piece. Thanks guys.

 

[JB]

Re: Schematic Help!

Either the 1K or the 470 will work, Trollhole. you will probably get a bit more light with the 470.<br /><br />Neither one will cause damage to the diode. try them both and go with the result you like better.

 

[trollhole]

Re: Schematic Help!

Thanks JB.

 

[Scoop]

Re: Schematic Help!

Sorry Trollhole, I should have mentioned that the calculions were theory and that resistors come in standard sizes.