Newbie with problems with Knight rider (4/8 leds work) (SOLVED)


I am a newbie with an arduino uno, using the starting kit of oomlout.

I have done the blinking led project and no problem with the variations (fading etc.) But I have problems with the second project, the knight rider with 8 leds. I think everything is Ok, but only 4 leds that are nearest to the ground wire work, and if I change the ground wire to the other side the other four leds start working and the first four don't work. You can see it here:

After this try, I have tried putting a wire next to the "- to ground" wire, "from + to 5v" with the same result. I have put pinheads in the corners too, and the same result.

I have done those last changes because the diagram of oomlout is that way but I have seen some other tutorials for the same Knight rider and they don't use the pinheads and the 5v wire. Besides, I am using 560 Ohm resistors, but in other webs I have seen that they are using 200 Ohms resistors. Maybe the reason is that 560 Ohm is the smallest resistor of the kit?

And one last question I have seen this other diagram: If I understood well, the resistor must be between the anode of the led and the ground, but here the resistor goes to the pin (?).

Any ideas, please?

cheers, danelu

The resistor value isn't the issue.

It looks like the power rails of your breadboard are split half way through the board.

Jumper the ground rail like #1 in this article:

I assume James solved it.

Butr, If you are going to be playing around with electronics, I recommend that you get a multimeter. It would have helped you find yoru missing connection. You don't need an expensive one... If you live in the U.S., you can order one from Jameco for around $10 USD.

With a multimeter you can check voltages, or switch to Ohms to check your connections.

A meter isn't too good at looking at signals that change quickly such as PWM-dimmed LED outputs. For that, it can be handy to make a tester by wiring an LED in series with a resistor, with a clip on one end and a probe on the other. I made one with two LEDs. The red LED lights-up with positive voltage, the green comes on with negative voltage, and with AC, they both come-on. (But, it's only for low-voltage AC... 120 or 240VAC would fry it. ;) )

And, it wouldn't hurt to study-up on basic electronics. Learn Ohms Law, or learn about Ohm's Law so you can look it up if you need to calculate a resistor value or something like that. Then, study about current and voltage in series and parallel circuits.


@James: Thank you very much, your advice was very helpful.

@DVDdoug: I have asked for a mutimeter :-) I have tons of documentation to start to learn about electronics and programming, and will start with the basics of electronics as you say. Thanks for your advice too.

Best, danelu