Hi, noob here, just finishing my first project...
I have an Arduino Nano connected by I2C to a 1602 Display via a 3x4 keypad. Also connected are 3 74HC595 shift registers in series, each controlling 8 LEDs, for a total of 24. Each LED has an inline resistor.
My code is used to switch on a single LED. After a certain idle time, the code randomises 1 LED from each shift register to switch on, and this randomises continually after 2 seconds. So far so good.
There's also a password which turns on ALL LEDs at once, and waits for a key press to turn them off again. It is while all the LEDs are on that the contrast on the Display reduces significantly. The backlight looks to be unaffected.
Is this to be expected, or does there seem to be a fault? Also, as this is a prototype, my intention is for the system to handle several more shift registers populated with LEDs. Should I assume that this will decrease the contrast even more?
Thank you for any help.