mwtheplumber
New Member
Hi Everyone,
I am in the process of designing a scoreboard for my cricket club. We will need to display runs scored (3 digits), wickets (1 digit) and overs (2 digits).
So far I have made a single digit prototype using a BCD thumbwheel switch to input to a CD4543 IC which drives a 0.5" 7 segment display. I have used 470R resistors on the outputs to the led segments. This works fine with an 8V supply. My next step was to substitute the 0.5" display for a 5" (125mm) display from futurlec. I have increased the supply to 15.75V and this works, but the display is very dim and only passing 0.33mA per segment. The data sheet for the display gives Vf 9.25, If 20mA. By my calculations this should give me a resistor value to use of 275R. By using 2 x 470R resistors in parallel, giving me 235R I still only get 0.38mA. Obviously I am doing something wrong here and would appreciate any help.
Many Thanks in advance,
Mike
I am in the process of designing a scoreboard for my cricket club. We will need to display runs scored (3 digits), wickets (1 digit) and overs (2 digits).
So far I have made a single digit prototype using a BCD thumbwheel switch to input to a CD4543 IC which drives a 0.5" 7 segment display. I have used 470R resistors on the outputs to the led segments. This works fine with an 8V supply. My next step was to substitute the 0.5" display for a 5" (125mm) display from futurlec. I have increased the supply to 15.75V and this works, but the display is very dim and only passing 0.33mA per segment. The data sheet for the display gives Vf 9.25, If 20mA. By my calculations this should give me a resistor value to use of 275R. By using 2 x 470R resistors in parallel, giving me 235R I still only get 0.38mA. Obviously I am doing something wrong here and would appreciate any help.
Many Thanks in advance,
Mike
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