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I am usinf a processor here. Im testing this clock for months now still no error. There are no resistors for displays because I limit the current using the software instead of using resistors.
More info about Zero-error 1 second Timer you can see if you search.
I will post pictures and schematics later for you.
The no resistor LED drive is a very common trick. but its normally PWM not current limiting.
So hes gotta be controlling the average power to the LED with direct PWM. Generally, average power is the limiting factor to driving common LEDs. Peak pulse current current may be very high as in the case of pulsed IR used in remote controls.
It may be common, but you are driving the uC waaaaaay outside the limits speciied in the datasheet.
so, now we have another 'trick', at least, this one does not put the 'developer' in danger.
Erik
Not necessarily
The forward voltage of a LED is relatively high; therefore, if the LED is connected directly to the 8051's open-drain driver, that doesn't leave very much to be dropped across the driver - so the driver might not be stressed too much...
But it's the on-resistance of the driver that limits the current - not "the software"!
The forward voltage of a LED is relatively high; grabbing one at random www.lumex.com/.../LDS-A512RI.pdf about 2V2
therefore, if the LED is connected directly to the 8051's open-drain driver, that doesn't leave very much to be dropped across the driver - so the driver might not be stressed too much... 2v7 (definitely not saturation) across the driver in a 5V system could stress quite much
But it's the on-resistance of the driver that limits the current - not "the software"! a value I have not seen in any datasheet, thus this must be "design by luck"
or that the LEDs are fed from 5V...?
"thus this must be 'design (sic) by luck'"
Indeed it is; but I gather it is quite common where "Cheap" is the overriding requirement - this was discussed on 8052.com a while back...
can mister pasan lariNski plz post the schemantics.
i have been working for the 512 led SIGN BOARD nopw and have problems.
plz post teh code too as well. is it messy? how did you work that as you have given in the photos and too in the video plz. Also share the final working files here. this is important.
if you've already "got problems", you don't want to compound them by adding questionable design practices...