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### Topic: General series circuit question (noob) (Read 1 time)previous topic - next topic

#### Ampix0

##### Sep 25, 2012, 12:18 am
I bought a kit online for the arduino uno. I just set up my first project ever with a potentiometer controlling the delay on blinking pin 13. I had an LED in there, and then decided to try to hook up a buzzer and LED in series and the brightness of the LED DROPPED. How am I supposed to do this?

#### RPCoyle

#1
##### Sep 25, 2012, 12:33 am
You can't do that. The buzzer robs too much current ( amps) from a LED in series. You will probably have to wire them in parallel and use an external voltage source... if you are not already doing that.

It is not good to hook anything up between the pins and ground without a resistor of some kind.  For an LED probably around 300 ohms is OK. for the buzzer it's hard to say. It might not buzz if you have a resistance in series. The pins might burn out if you push more than 40 or 50 mil-amps through them.

If you are going to do much more than just blink LED's, then you need to learn a little bit of electronics.

Google "Ohms law"  for a start. Also you probably need to buy at least a cheap multimeter to know what is going on in your circuits.

#### Grumpy_Mike

#2
##### Sep 25, 2012, 12:53 am
Quote
The buzzer robs too much current ( amps) from a LED in series.

No.
If the LED and buzzer are in seriese then by definition the same current will flow in both.

The problem is that your buzzer has a higher resistance than your resistor and so there is less current.

#### cottewmi

#3
##### Sep 25, 2012, 12:59 am
fellow n00b! perhaps if you wired the buzzer to another pin, you could power them with greater ease, that or it would burn out the chip... hm. only one way to find out! experiment on!

also, is it a straight buzzer, or does it require pwm?

#### oric_dan

#4
##### Sep 25, 2012, 01:14 amLast Edit: Sep 25, 2012, 01:23 am by oric_dan(333) Reason: 1
You can run an Led and a buzzer off the same I/O pin if they are
wired in "parallel" rather than in series. Of course, the Led should
have its own current-limiting resistor wired in series with itself,
and separate from the buzzer.

This works ok if the buzzer is a piezo. However, if the buzzer is a
magnetic buzzer, then it needs a capacitor [10uF or so] in series
with it.

Basically, this all works because the I/O pin is essentially a "voltage-
source" [within limits], and you can wire separate loads in parallel
to a voltage-source, and they will work essentially without affecting
each other.

#### Ampix0

#5
##### Sep 25, 2012, 01:51 am
Ok I was wrong guys! I was actually trying this in parallel. I did try it in series and it killed my LED (dunno why).

Also pin 13 has a resistor in it doesn't it?

#### cottewmi

#6
##### Sep 25, 2012, 03:56 am
Mmm I think only the LED that's on the board has a resistor. I'd still use one.

#### stoopkid

#7
##### Sep 25, 2012, 07:13 am
If you aren't using the on board LED, you need a resistor. You first post sounds like you plugged an LED into it, rather than using the on board. If that's what you did, that's why your LED died.

#### Grumpy_Mike

#8
##### Sep 25, 2012, 09:58 am
Quote
Also pin 13 has a resistor in it doesn't it?

If you arduino was made after 2006 then no you don't have a resistor on pin 13.
You always need something to limit the current with an LED.

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