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[on:]

I have my arduino grounded with a bunch of wires connnected to the breadboard with 12 pins filled that flow through resistors to leds
a traffic light system where 2 leds of the same colour light on and off
anyway i could provide a pic
but i have an uploaded code that works
how would i test that i shortciruited something

[Reply #1 on:]

1) put power on and watch for the magic smoke  or

2) study EVERY wire, where it comes from, where it goes and compare this to the circuit diagram

There is no short cut to verifying a circuit is wired correctly.  It's either a case of checking and double checking or taking a gamble and switching on the power and accepting the consequences of any errors made

[Reply #2 on:]

1) put power on and watch for the magic smoke  or

The technical term for this is "smoke checking". Although, some new electronics have a different kind of tell sign... they let some interestinc electronicky fragrance in the air. It's quite nice, but don't use it on a date.

Now seriously, excessive heat on resistors or voltage regulators is sometimes a sign that you may have something wrong.

How to see if it's not connected correctly, check the voltages... if you have a short circuit, most likely the voltage is 0 or almost.

[Reply #3 on:]

Before you wire anything up to the pins down load the sketch.
Then connect up the external wires (with the power off)
When first turning on if it doesn't do what you expected immediately turn it off and get the meter out.
Check with a voltmeter that you see 5V, if not turn off immediately and look for shorts or if the power is the wrong way round.
Power it on and feel the chips rapidly n turn, at the slightest sign of heating up turn it off and look for shorts again.

[Reply #4 on:]

You should also check for  shorts between power & ground with your meter before applying power.

If you just have an output or two that is not working, the ATMega may run very warm to the touch, while other outputs may be working fine.

[Reply #5 on:]

You should also check for  shorts between power & ground with your meter before applying power

Make sure you know what polarity the comes out of your resistance meter is. On my analogue AVO meter when measuring resistance the negative lead becomes the positive source of power. Therefore if you measure the resistance between power and ground but the wrong way round a good circuit will look like a short.