Hi,
I have a question about the experiment titled "7 segment display" on the site (url : http://www.allaboutcircuits.com/vol_6/chpt_7/9.html ). I was curious about the use of 470 Ohms resistors for the display and went on to check its characteristics on the Radio Shack website. It uses 20mA and 1.7V as an input for each led.
My question is: as the output of the 4511 CMOS component, when it is fed 6V, is about 4.84 volts (assuming output voltage raises linearly when input voltage raises); I should only need to put a resistor that lowers the voltage to 1.7 volt, and according to Ohm's law that would be about 160 Ohm. This is quite different from 470 Ohms.
So, can anyone point out what where I am making a mistake? This is very puzzling...
Thanks,
-mat
I have a question about the experiment titled "7 segment display" on the site (url : http://www.allaboutcircuits.com/vol_6/chpt_7/9.html ). I was curious about the use of 470 Ohms resistors for the display and went on to check its characteristics on the Radio Shack website. It uses 20mA and 1.7V as an input for each led.
My question is: as the output of the 4511 CMOS component, when it is fed 6V, is about 4.84 volts (assuming output voltage raises linearly when input voltage raises); I should only need to put a resistor that lowers the voltage to 1.7 volt, and according to Ohm's law that would be about 160 Ohm. This is quite different from 470 Ohms.
So, can anyone point out what where I am making a mistake? This is very puzzling...
Thanks,
-mat