Calculate Current

[Jerry]

Hi... I just started embedde3d C at uni and the prelim work had this question... i dont remeber much from my first year at uni so would appreciate the help.... These are the 2 questions....

1. How much current will the LEDs draw?
2. How do we make the Z8 supply this current from these pins?

 

 

[Jerry]

OK, to calculate the current in your circuit, I am making a couple of assumptions.

1. To light your LED, you are placing ground or zero volts on the cathode of the LED
2. The voltage drop across the LED is approximately 2 volts

 

With that in mind we can find the current for each LED by calculating the current through the Led resistor:

So each LED draws about 4.5 mA, just multiply that times the number of LED that you will have on at the same time.

I’m not sure about your second question.  I need to know what Z8 refers to.