Help with LEDdriver

Hi there,

I am new to Arduino, and I am also trying to complete this example:

I have the circuit breadboarded, but the circuit simply will not work.

The circuit is complete, except for what I am assuming are diodes (?) between the current and the LEDs.

Are these crucial to the circuits operation?

The TX light also blinks, and I'm not sure what that means exactly.

I have posted photos here:

Any help would be greatly appreciated,


This is driving me crazy!!! I mean... I've checked it a couple dozen times...

I'm pretty sure the wiring is correct, apart from the diodes.

I've used the diagram presented here:

Anyone know if those diodes are what's missing? Are they in fact diodes?

Those aren't diodes, they are resistors. probably around 220 ohms or so. They are needed to prevent too much current burning out the LEDs.

Not sure those LEDs will now work but try something simpel like the blink skecth with an LED and a series resistor on a digital pin other than 13.

Alright, well, I have since gotten the circuit 'working'.

I have the LEDs lighting, and I have (with a couple modifications to the program) gotten every LED to light.

At this point, I am mostly confused as to the code.

I have written code before, that's one area I know what I'm doing.

But I can't seem to figure out how to, say, light each LED individually.

I don't understand the how to write code to control them basically.

Can anyone describe this?


You turn an LED on with a digitalWrite(pin, HIGH); Where pin has a value of the pin you have wired up the LED to. The variable pin can be replaced with a constant. But I suspect you know that. When you say:-

But I can't seem to figure out how to, say, light each LED individually

What exactly do you mean. Please explain what you are trying to do then we can point you in the right direction.

I ended up figuring it all out.

I had to read up on translating binary numbers, and I wrote a little function to convert the number (1 through 8) of the LED I wanted to light, to a binary number to send to the 4794 chip.

It works! Kickass!!!