|Re: Woodstock's LED display characteristics|
Message #2 Posted by Andrés C. Rodríguez (Argentina) on 28 Nov 2002, 7:18 a.m.,
in response to message #1 by Vieira, Luiz C. (Brazil)
Luiz: I think I have just some hints for your question.
Almost sure, the displays are common cathode (one cathode per digit), the maximum direct (permanent) current should be 15 to 20mA per segment.
The display is multiplexed and scanned by firmware routines; if you take a look at the HP45 emulator and related patents documentation, which includes some of the code, you will have a reference about software-refreshed displays. By the way, if a hardware segment decoder (like the TTL 7448) had been used, messages like "Error" or "OF" would have not been possible.
Asuming a 1/12 duty cycle (only one digit is turned on at any time); or eventually a 1/8 duty cycle (one segment active at a time), you may obtain a peak current value which will be averaged in time. However, I think it is safe not to exceed 40 or 50 mA for pulsed operation, as this case is.
Please take these just as not confirmed suggestions...
By the way, my trip to Brazil was suspended...