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| rwhip41:
The IPAC from Ultimarc recommends using a 220 ohm resistor ro 5V LEDs. Here is a schematic involving a 5V input (scroll down 2/3 of the page)... http://www.ultimarc.com/ipac2.html |
| Sinner:
--- Quote from: whammoed on February 06, 2006, 01:53:00 pm ---A single led is likely not meant for 5 volts, so you need a resistor for it. Those 12volt automotive leds already have a resistor built into them, so you just plug them in to any 12 volt source. --- End quote --- The singles I bought were actually 5V LEDs, so I don't think the actual voltage was an issue... I got them from Electrosonic and the specs were on the bag... The automotive LEDs have resistors in them, but a car's electrical system outputs a certain amount of current...I assume those resistors are calculated for that amperage... A PC powersupply puts out a certain amount of current and voltage...I guess what I'm trying to figure out, is the difference between a car's output (which I can't find) and a PCs (on the power supply)...That way I can determine if a resistor is needed, and then what size it should be... |
| Sinner:
--- Quote from: rwhip41 on February 06, 2006, 01:57:13 pm ---The IPAC from Ultimarc recommends using a 220 ohm resistor ro 5V LEDs. Here is a schematic involving a 5V input (scroll down 2/3 of the page)... http://www.ultimarc.com/ipac2.html --- End quote --- Thank you. |
| whammoed:
You don't have to worry about what your power source is rated for unless you will be exceeding its rating with whatever device you are using. (a few leds certainly won't exceed any power supplies rating.) Look at ohms law: I = V/R where I = current V = volts R = resistance a 12 volt car bulb will draw the same amps it does from a 2 amp power supply as it does from a 200 amp supply. |
| Sinner:
--- Quote from: whammoed on February 06, 2006, 02:47:42 pm ---You don't have to worry about what your power source is rated for unless you will be exceeding its rating with whatever device you are using. (a few leds certainly won't exceed any power supplies rating.) Look at ohms law: I = V/R where I = current V = volts R = resistance a 12 volt car bulb will draw the same amps it does from a 2 amp power supply as it does from a 200 amp supply. --- End quote --- Then if some LEDs are connected to a powersupply, why do they need a resistor? They have to be drawing more, or are they being driven? Is the power supply putting out 12V+ at 26A, or will the bulb only draw 12V+ at 3A? If it's the second, then there would be no need for a resistor, but if it's the first, then I would need to regulate how much current is going through the LED... This is where I'm confused... |
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