# Circuit diagram help

#### j0npae

May 22, 2012
8
Hey, this is a circuit diagram from instructables. I wanted to know how the circuit in the attachment works. I just started learning the basics of electronics and circuits, so I'm not 100% certain what I'm thinking is correct. So at the top of the image, it says source 220V. Is there a positive/negative to this circuit diagram? if so, which is which? I always thought resistors were near the source of the circuit, but from what I read about capacitors it seems they too are suppose to be near the source of the circuit.

Another question, what parts do I need to power this thing with AC? Is there an alternative to a AC receptacle?

EDIT: So using the LED wiz calculator, it seems the resistor is connected towards the ground, why is this? When, let's say 9v, flows through the circuit it would burn out the LED and then go through the resistor?

Thanks for bearing with me, I hope you can help.

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#### donkey

Feb 26, 2011
1,301
ok first of all I can't think of any reason this shouldn't work on 220volts BUT I would not play with at a beginners level.

If you are trying to figure out AC voltage get a starter motor from a car(these things hurt too but are a bit safer) or even a hand dynamo (they range from 1.5v up to 24) but they both need motion. without a rectifier bridge they will produce an AC voltage at a level that is slighlty better for your health and insurance.

just an addition can you link us to the page with the instructable?

#### CocaCola

Apr 7, 2012
3,635
just an addition can you link us to the page with the instructable?

I can...

http://www.instructables.com/id/LED-CLOCK-cum-NIGHT-LAMP/

I wanted to know how the circuit in the attachment works.

http://www.marcspages.co.uk/tech/6103.htm

Is there a positive/negative to this circuit diagram?

No such thing on the incoming AC current, but yes there is once it's rectified by the diodes, the LEDs are a dead giveaway on the polarity...

I always thought resistors were near the source of the circuit, but from what I read about capacitors it seems they too are suppose to be near the source of the circuit.

If you are using resistors to limit current in to an LED it doesn't matter where it is on the negative or positive side works equality well...

But, this circuit is operating on a different principle... Read above...

As donkey has stated, not the best thing to be messing with mains power when you don't understand it, it can be lethal... You can easily convert this design to run off a low voltage wall wart and thus avoid many potential safety concerns...

#### j0npae

May 22, 2012
8
I just finished my first year of college and in my very first programming class our teacher made us build a robot with two servos controlled by an arduino. However, I don't think I learned much from the hardware aspect of that project. During my last quarter, I tried modifying an RC car to use an arduino. I was overwhelmed. I'm not going to lie. There were so many parts to consider and understand. And the fact that I didn't have the proper tools to proceed did not help. That's why I thought a led project with a few parts would help. This project only has a resistor, capacitor, LEDs, and two diodes. Anyways, the link is http://www.instructables.com/id/LED-CLOCK-cum-NIGHT-LAMP/?ALLSTEPS

#### donkey

Feb 26, 2011
1,301
personally I would downgrade this to a 12volt application. the maths side is not my strong suit so will leave that to others.
as for overwhelming.... well it can be. I found the easiest way of doing things is finding people in the know with a few minutes and ask them questions, show them what I have done and listen for advice..... and here you are. you are doing better than most.

as for simplicity, if you want really easy circuit try 1 resistor and 1 LED to a battery. then upgrade. then try my favourite project for kids, get a DPDT switch(centre of is best for this) a motor and a battery. try to make the motor go in both directions when you switch the switch. understanding the nature of the current is MASSIVE for beginners. after that try to figure out components and what they do.
If you read the forums you will find people with YEARS of experience, ask the dumb questions, if you don't know then its not a dumb question.
good luck with your projects and as always let us know where you need help, and be SAFE

#### CDRIVE

##### Hauling 10' pipe on a Trek Shift3
May 8, 2012
4,960
I'm sure that many folks can't imagine a time when Wallwarts didn't exist but it really wasn't that long ago. Up until wallwarts became available nearly every electronics project, that wasn't battery powered, involved building a power supply.

I'm not a Nanny State Drone so I don't preach about projects that are connected directly to the Mains. That said, Mains projects should be left to those with experience. A wallwart is dirt cheap and most of us have accumulated copious amounts of them over the years. Do yourself a favor and build your circuit based on wallwart power.

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