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???
05/02/08 10:18
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 		 #154291 - excellente Senor one comment
Responding to: ???'s previous message
An excellent summary.
:
4. The eye's response to PWM is very non linear. So to get 8 relatively even steps of brightness use the following PWM schemes:
7: 100.0% (brightest)
6: 50.0%
5: 25.0%
4: 12.5%
3: 6.3%
2: 3.1%
1: 1.7%
0: 0.0% (off)
the above is true, HOWEVER

you are not regulating to "the eye" but to sign intensity vs ambient light which is linear.

Re the ST2221A:
it is available as a ST2221C which is a 16 LED driver, beware. The 16 LED drivers "tend to get hot" and some have had problems with that. Also Allegro and Rohm have similar chips.

Erik



List of 31 messages in thread
TopicAuthorDate
outdoor display            01/01/70 00:00      
   LED sign summary            01/01/70 00:00      
      excellente Senor one comment            01/01/70 00:00      
         LEDs arrangement on PCB            01/01/70 00:00      
            The big tradeoff            01/01/70 00:00      
               Reverse engineering            01/01/70 00:00      
                  once color get involved ...            01/01/70 00:00      
      Human perception of luminance            01/01/70 00:00      
         nice, correct, but irrelevant in this respect            01/01/70 00:00      
   Ambient Light Sensor            01/01/70 00:00      
      anything you can read that is ...            01/01/70 00:00      
         TSL250R            01/01/70 00:00      
            maybe not, maybe so            01/01/70 00:00      
               Late Question            01/01/70 00:00      
                  l/f l/v            01/01/70 00:00      
                  i thought those common            01/01/70 00:00      
   LED Panel Fonts            01/01/70 00:00      
      go to the PC            01/01/70 00:00      
      http://www.8052.com/users/bahrio/            01/01/70 00:00      
      Here is a 9Wx7H Font            01/01/70 00:00      
      8x8 char font            01/01/70 00:00      
         go for a proportional font            01/01/70 00:00      
   I Agree; Go Proportional            01/01/70 00:00      
      that's the one            01/01/70 00:00      
         Rotating....            01/01/70 00:00      
            so do I            01/01/70 00:00      
               Luxury?            01/01/70 00:00      
                  no, no squirt            01/01/70 00:00      
      thats exactly the one I was looking for            01/01/70 00:00      
   LED Panel FAQ            01/01/70 00:00      
      LED Panel FAQ does not match what I 'know'            01/01/70 00:00      

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