Hi all,
I just bought my fist arduino board, and am trying out different things [smiley=2vrolijk_08.gif]. I bought a Kingbright SC23-12 SGWA large led display and I am not sure how to wire it properly.
I made a diagram of how I think it should be wired - basiclly what I am asking is: is the diagram correct and if not where did I go wrong.
datasheet of the display:http://www.farnell.com/datasheets/46331.pdf
No, pin 8 should be grounded, NOT connected to 5V.
Each segment has 4 LEDs in series, but it doesn't make it clear whether the voltage drop is for each LED, or each segment. If it's for each LED, the arduino will not be able to source enough voltage to directly drive the segments, and you'll need to use transistors to switch a higher voltage.
To add to trialex's comment, the words "common cathode" mean that all of the lamps share their negative pole, and each input is to be independently drawn high to activate that lamp. There's no pin that needs to be high all the time, the pins 3 and 8 are the common cathodes. (An anode is a pin that should be at the +V end of your circuit.)
Thanks for the quick answer -will ground it!
In the datasheet the maximum forward voltage is 2,5 V - I thought that was the voltage needed to drive one segment of the Led display, that is why all the resistors are 144 Ohm.
but it doesn't make it clear whether the voltage drop is for each LED
It's physics the voltage drop is for each LED therefore you need 4 * 2.5 = 10V to get the segments to turn on. This will involve an external supply and transistor or FET to do the switching.
As it is common cathode then the best bet is to use a p-channel FET pulling up. However as this is going to be sitting at in excess of 10V you need something else to drive the gate from the 0 - 5v output of the arduino. Probably an NPN transistor.
To use a transistor you need a PNP pulling up and still need an NPN to drive it.
You would have been better off with common anode display.