Current Draw in Parallel circuits

So I have been playing around with a INA169 tonight and thought up a question I cannot answer. So here goes...

If you have a simple circuit with a DC power source, 1 LED, and a resistor you are going to have a set current consumption in the circuit. If you add another LED in parallel with the first the INA169 will still read the exact same current consumption as with one LED. Why is that? In the end you are using more current to power both LED's, correct?. A battery will drain faster at least so that would lead me to believe that the circuit is using more current.

If you add resistors in parallel is lowers the resistance value and therefore cause's a measurable changed in current draw in reference to the INA169. So why not with LED's. Thanks for answering my questions in advance. I will have alot of them! :slight_smile:

LEDs are not resistors.

LEDs conduct at a specific voltage. Below that voltage they do not conduct and raising the current you pass through them does not cause a very substantial increase in the voltage at which they conduct. That is precisely the reason you use a current limiting resistor - the current will be defined by the voltage across the resistor which is the supply voltage minus the relatively constant voltage drop of the LED.

So if you connect two essentially identical LEDs in parallel, the voltage drop will still be the same so the total current in the circuit will be the same. Depending on their exact characteristics, they will share the current between them in some manner.

If you add another LED in parallel with the first the INA169 will still read the exact same current consumption as with one LED.

It seems to me, two leds in parallel need twice as much current as one led.

michinyon:
It seems to me, two leds in parallel need twice as much current as one led.

"Need" was not the question. The question was in regard to the behaviour of a circuit consisting of a resistor and LED in series when a second LED is put in parallel, and that is what I explained here.

OK so that is why LED's will burn out when you do not have a resistor with them. I understand that better now thank you!

I think the point (not really explained yet) is the OP put a second led in parallel with the first but didn't change the current limiting resistor so the current that originally powered the one led through the resistor
was split between the two leds and of course didn't change because the resistor hasn't changed. (sorry to
be so verbose but some newbies might not get it otherwise)

jtroutt19:
OK so that is why LED's will burn out when you do not have a resistor with them.

Well this is why:-
http://www.thebox.myzen.co.uk/Tutorial/LEDs.html

Grumpy_Mike:
Well this is why:-
LEDs

That is by far one of the best answers to one of my questions I have ever got. Thank you for the link. I now understand "why". I have always been the type of person that has to understand the "why" to really learn something. I cannot just take it as "it is because it is". Thank you again!