7 segment display forward current question

Other Hardware General Electronics
1

Hi there,

Sorry if this is a very basic question...

I'm trying to set up some 7 segment displays with a MAX7219 chip and want to work out what Resistor to use on the Rset pin. I can't find a datasheet for my 7 segment displays but they are listed as having a voltage of 3.2 V and a current of 160mA

here is everything I know about them:

http://www.ebay.co.uk/itm/ws/eBayISAPI.dll?ViewItem&item=260898336740&ssPageName=ADME:L:OU:GB:1123

Obviously this is greater than the 40mA forward current shown on the MAX72XX datasheet - am I right in thinking that the forward current of these displays is actually 20mA (160/8) as the current listed is really that for all LED's lit up together?

Therefore my resistor should be: 24.5kOhms?

Thanks for your help!

2

am I right in thinking that the forward current of these displays is actually 20mA (160/8) as the current listed is really that for all LED's lit up together?

Yes I would say that this is a reasonable assumption. It won't do any harm running it at 20mA anyway even if each segment can take 160mA, which I doubt.

3

Thanks very much for your help! :slight_smile: