330 ohm resistors are chosen in order to limit the current flowing through the LEDs to 10mA. The LEDs have a voltage drop of 1.8v.

Therefore there is 3.2v across the resistor (5 - 1.8 = 3.2).

V = IR, which can be rewritten as R = V/I.

Plugging in 10maA as 0.01 gives 3.2 / 0.01 which is 320 ohm. 330 is a close enough value.


Component Description Image
0.01uF Cap (2x) Bypass caps for level shifters Image
LED (2x) Battery / Status LEDs Image
330 ohm Resistor (2x) Current limiting resistors for LEDs Image
Reset Button Momentary Switch Image
50 Pin Connector Female Connector to Main Board Image