# Will this circuit work?

Discussion in 'The Projects Forum' started by Evie, Mar 11, 2015.

Mar 11, 2015
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2. ### tshuck Well-Known Member

Oct 18, 2012
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If you are only attempting to light the first LED, yes, but you'll likely burn it out after a short while.

Otherwise, you can stack 2 or 3 LEDs in series (a string of components) with a single resistor across the battery.

Either way, a single LED and a single 270 ohm resistor will take 23mA - exceeding the max current for some LEDs.

3. ### Dodgydave Distinguished Member

Jun 22, 2012
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NO, as all the leds are wired reversed.

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4. ### tshuck Well-Known Member

Oct 18, 2012
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Good catch, I missed that.

5. ### Evie Thread Starter New Member

Mar 11, 2015
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Could expand upon your answer? I'm not sure what you mean by "all the LEDs are veversed"

Jul 18, 2013
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Actually the battery is shown the right way around, it is the +- notation that is wrong.
The +ve terminal is actually connected to the black wire.
Max.

7. ### Evie Thread Starter New Member

Mar 11, 2015
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Do I need to change the side that the resistors are on?

Jul 18, 2013
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You have just coloured the conductors wrong if the battery is connected as shown.
Max.

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Mar 11, 2015
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10. ### Evie Thread Starter New Member

Mar 11, 2015
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Ah, so will the circuit work?

Jul 18, 2013
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IOW, the circuit should work as shown, the Red conductor customarily goes to the +ve battery terminal.
You have the battery +ve drawn in Black which tends to throw a viewer off at first.
Max.

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12. ### Evie Thread Starter New Member

Mar 11, 2015
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AAhh okay, thanks so so much

13. ### ScottWang Moderator

Aug 23, 2012
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What's reason to make you to do the circuit like that, it is not a regular method, you should use led in series with resistor and in parallel all of five leds and resistors strings.

Jul 18, 2013
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Good catch, I missed that one.
Max.

15. ### Evie Thread Starter New Member

Mar 11, 2015
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would a 9v battery give enough power?

16. ### Evie Thread Starter New Member

Mar 11, 2015
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the LEDs im going to be using are 2.5v. I will be using 5 of the them which so they will need 12.5 v, but the battery is only 9v?

17. ### tshuck Well-Known Member

Oct 18, 2012
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They don't all have to be in series, you can make a series-parallel circuit. See post #2.

18. ### ScottWang Moderator

Aug 23, 2012
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Using 80% of 25mA for brightness and led life, it will be 20mA.
R=(9V-2.5V)/20mA=325Ω, yous can choosing 330Ω.
You can have 5 strings or two strings as two leds in series with one resistor and three leds in series with one resistor.

You can calculate the R values for two and three led strings.

19. ### ScottWang Moderator

Aug 23, 2012
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Haha, never mind.
I have been missed some over here and missed some over there ...

Jan 15, 2015
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Here is what the members are getting at using a series parallel configuration.

I would also do as Scott suggest and calculate the series resistors based on 20 mA. My numbers were based on 25 mA. So slightly higher value resistors that conform to off the shelf values.

Ron

Last edited: Mar 11, 2015
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