spooky Posted September 20, 2004 Report Share Posted September 20, 2004 Ira, your electronics is confused. When any electronic devices are strung in series the voltage is split between and if they are all the same then it is split evenly. You may also be having vague memories of a common high-school electronics problem about whether to wire light bulbs in series of parallel. Light bulbs are not the same as LEDs and the result is different. So here is the complete, but long-winded (and hopefully understandable) explanation: First remember the the brightness is roughly proportional to both current and voltage. Secondly remember that a light bulb is just a glorified resistor and as the voltage increases so does the current. (Ohm's Law for those who haven't blacked out their memory of high-school science). This is not true for LEDs. An ideal LED doesn't let any current flow beneath it's threshold voltage and lets any current flow at the threshold voltage. So, ideally, the voltage is limited to that threshold voltage, no matter how much more current you put in. Obviously this isn't true, however the voltage increases a lot more slowly than the current and it's easiest to just think that the voltage is at the threshold voltage when it is glowing. Ohm's Law does not apply to LEDs, so we won't mention Ohm's law again. In a string of light bulbs in series the current through them all is identical (it flows from one to the next) but the voltage is spread across all of them. In parallel you have the same (but higher) voltage across each of them, but the current is split. It turns out though that the increase in current from having a lower resistance beats the decrease from splitting it up. This is a common high-school electricity problem that you are possibly remembering from you dim dark past. So for a given voltage you want to run light bulbs in parallel. For LEDs in parallel you only have the fixed voltage drop across the LED (the rest is used up across the resistor) and the current is still split. Whereas is series you use up the voltage a bit at a time as it goes across each LED and they all get the same full current (the last little bit of power is dropped across the resistor). So you end up with more brightness from LEDs in series, although you can only keep stringing them together while you have enough voltage for them all. Furthermore, in parallel (assuming a common resistor) the LED's voltage is limited to just above the threshold voltage of the LED with the lowest threshold. This means that an LED with a high threshold won't turn on properly and will be dim. Quote Link to comment Share on other sites More sharing options...
Brianemone Posted September 20, 2004 Author Report Share Posted September 20, 2004 ira dont listen to him get a 9v battery, stick out your tounge and if you feel a tingle wire the led to it Quote Link to comment Share on other sites More sharing options...
spooky Posted September 20, 2004 Report Share Posted September 20, 2004 One of those two statements is good advice. Quote Link to comment Share on other sites More sharing options...
Brianemone Posted September 20, 2004 Author Report Share Posted September 20, 2004 and i think we both know which :lol: Quote Link to comment Share on other sites More sharing options...
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