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Topic: Need help with 7-Segment Display (Read 2 times) previous topic - next topic

demonic_crow

I'm still learning stuff right now so bare with me.  I just wanted to know if I needed to add any resistor when I hook the digital display up to my arduino.  I have 8 anode which I figure would all go to a pin on the arduino and 2 cathode which would hook up to the ground pin.  Let me know if I'm doing it right so far.  Also don't know if this stuff will help since I have no idea how to read it:

Maximum ratings
Forward current:   30mA
Forward voltage:   2V
Reverse voltage:   5V
Power dissipation:   100mW

Typical characteristics
Forward current:   20mA
Forward voltae:    1.7V
Peak wavelength:  655nm

Thanks alot for explaining stuff.

darudude

do you have a picture of the display or a link to a website where you bought it from?

the device i used had 8 pins. 1 for each led and 1 common ground. I connected each led pin a digital out on the arduino and the ground to ground.

Grumpy_Mike

Yes you always need a resistor with an LED (unless you have a current controlled source which you don't). It should be between 150 and 470 ohms, the smaller the value the brighter it will be.

darudude

oh yeah, im an idiot, forgot to mention the resistors!!

if you don't have any resistors available you can try connecting one of the segments to pin 13 and ground. pin 13 has a 1k pull up resistor which should be enough to get you a dim light going.

demonic_crow

http://www.radioshack.com/product/index.jsp?productId=2062557
thats what I have.
Can I connect it like this:

anode F to 13
anode G to 12
anode E to 11
anode D to 10
anode C to 9
anode RHDP to 8
anode B to 7
anode A to 6

then connect the two cathode to ground.  

Also where would I need the resistor at if it safe to connect it like that, and how would I figure out what size to use.

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